path: root/0008-add-zstd-kernel-compression.patch

diff -uNr linux-5.4/arch/arm/boot/compressed/decompress.c linux-5.4-zstd/arch/arm/boot/compressed/decompress.c
--- linux-5.4/arch/arm/boot/compressed/decompress.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/boot/compressed/decompress.c	2019-12-15 15:07:01.242285193 -0800
@@ -42,10 +42,6 @@
 #include "../../../../lib/decompress_unlzo.c"
 #endif
 
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 #ifdef CONFIG_KERNEL_XZ
 #define memmove memmove
 #define memcpy memcpy
diff -uNr linux-5.4/arch/arm/boot/compressed/Makefile linux-5.4-zstd/arch/arm/boot/compressed/Makefile
--- linux-5.4/arch/arm/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/boot/compressed/Makefile	2019-12-15 15:07:01.242285193 -0800
@@ -72,7 +72,6 @@
 
 compress-$(CONFIG_KERNEL_GZIP) = gzip
 compress-$(CONFIG_KERNEL_LZO)  = lzo
-compress-$(CONFIG_KERNEL_LZMA) = lzma
 compress-$(CONFIG_KERNEL_XZ)   = xzkern
 compress-$(CONFIG_KERNEL_LZ4)  = lz4
 
diff -uNr linux-5.4/arch/arm/configs/aspeed_g4_defconfig linux-5.4-zstd/arch/arm/configs/aspeed_g4_defconfig
--- linux-5.4/arch/arm/configs/aspeed_g4_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/aspeed_g4_defconfig	2019-12-15 15:07:01.382282352 -0800
@@ -8,7 +8,6 @@
 CONFIG_LOG_BUF_SHIFT=16
 CONFIG_CGROUPS=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
 # CONFIG_UID16 is not set
diff -uNr linux-5.4/arch/arm/configs/aspeed_g5_defconfig linux-5.4-zstd/arch/arm/configs/aspeed_g5_defconfig
--- linux-5.4/arch/arm/configs/aspeed_g5_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/aspeed_g5_defconfig	2019-12-15 15:07:01.422281540 -0800
@@ -8,7 +8,6 @@
 CONFIG_LOG_BUF_SHIFT=16
 CONFIG_CGROUPS=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
 # CONFIG_UID16 is not set
diff -uNr linux-5.4/arch/arm/configs/clps711x_defconfig linux-5.4-zstd/arch/arm/configs/clps711x_defconfig
--- linux-5.4/arch/arm/configs/clps711x_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/clps711x_defconfig	2019-12-15 15:07:01.445614399 -0800
@@ -2,7 +2,6 @@
 CONFIG_SYSVIPC=y
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_BLK_DEV_INITRD=y
-CONFIG_RD_LZMA=y
 CONFIG_EMBEDDED=y
 CONFIG_SLOB=y
 CONFIG_JUMP_LABEL=y
diff -uNr linux-5.4/arch/arm/configs/ezx_defconfig linux-5.4-zstd/arch/arm/configs/ezx_defconfig
--- linux-5.4/arch/arm/configs/ezx_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/ezx_defconfig	2019-12-15 15:07:01.462280728 -0800
@@ -4,8 +4,6 @@
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_SYSFS_DEPRECATED_V2=y
 CONFIG_BLK_DEV_INITRD=y
-CONFIG_RD_BZIP2=y
-CONFIG_RD_LZMA=y
 CONFIG_EXPERT=y
 # CONFIG_COMPAT_BRK is not set
 CONFIG_SLAB=y
diff -uNr linux-5.4/arch/arm/configs/hisi_defconfig linux-5.4-zstd/arch/arm/configs/hisi_defconfig
--- linux-5.4/arch/arm/configs/hisi_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/hisi_defconfig	2019-12-15 15:07:01.505613182 -0800
@@ -1,7 +1,6 @@
 CONFIG_NO_HZ=y
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_BLK_DEV_INITRD=y
-CONFIG_RD_LZMA=y
 CONFIG_ARCH_HISI=y
 CONFIG_ARCH_HI3xxx=y
 CONFIG_PARTITION_ADVANCED=y
diff -uNr linux-5.4/arch/arm/configs/imote2_defconfig linux-5.4-zstd/arch/arm/configs/imote2_defconfig
--- linux-5.4/arch/arm/configs/imote2_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/imote2_defconfig	2019-12-15 15:07:01.505613182 -0800
@@ -3,8 +3,6 @@
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_SYSFS_DEPRECATED_V2=y
 CONFIG_BLK_DEV_INITRD=y
-CONFIG_RD_BZIP2=y
-CONFIG_RD_LZMA=y
 CONFIG_EXPERT=y
 # CONFIG_COMPAT_BRK is not set
 CONFIG_SLAB=y
diff -uNr linux-5.4/arch/arm/configs/lpc18xx_defconfig linux-5.4-zstd/arch/arm/configs/lpc18xx_defconfig
--- linux-5.4/arch/arm/configs/lpc18xx_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/lpc18xx_defconfig	2019-12-15 15:07:01.545612370 -0800
@@ -2,8 +2,6 @@
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_PREEMPT=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/arch/arm/configs/vf610m4_defconfig linux-5.4-zstd/arch/arm/configs/vf610m4_defconfig
--- linux-5.4/arch/arm/configs/vf610m4_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/configs/vf610m4_defconfig	2019-12-15 15:07:01.568945230 -0800
@@ -1,7 +1,5 @@
 CONFIG_NAMESPACES=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZ4 is not set
 CONFIG_KALLSYMS_ALL=y
diff -uNr linux-5.4/arch/arm/Kconfig linux-5.4-zstd/arch/arm/Kconfig
--- linux-5.4/arch/arm/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/arm/Kconfig	2019-12-15 15:07:01.155620285 -0800
@@ -90,7 +90,6 @@
 	select HAVE_IRQ_TIME_ACCOUNTING
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_LZ4
-	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
 	select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M
diff -uNr linux-5.4/arch/m68k/configs/stmark2_defconfig linux-5.4-zstd/arch/m68k/configs/stmark2_defconfig
--- linux-5.4/arch/m68k/configs/stmark2_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/m68k/configs/stmark2_defconfig	2019-12-15 15:07:01.592278090 -0800
@@ -5,8 +5,6 @@
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_NAMESPACES=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/arch/mips/boot/compressed/decompress.c linux-5.4-zstd/arch/mips/boot/compressed/decompress.c
--- linux-5.4/arch/mips/boot/compressed/decompress.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/mips/boot/compressed/decompress.c	2019-12-15 15:07:00.468967555 -0800
@@ -52,18 +52,10 @@
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-#include "../../../../lib/decompress_bunzip2.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZ4
 #include "../../../../lib/decompress_unlz4.c"
 #endif
 
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZO
 #include "../../../../lib/decompress_unlzo.c"
 #endif
diff -uNr linux-5.4/arch/mips/boot/compressed/Makefile linux-5.4-zstd/arch/mips/boot/compressed/Makefile
--- linux-5.4/arch/mips/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/mips/boot/compressed/Makefile	2019-12-15 15:07:00.462301024 -0800
@@ -62,9 +62,7 @@
 	$(call if_changed,objcopy)
 
 tool_$(CONFIG_KERNEL_GZIP)    = gzip
-tool_$(CONFIG_KERNEL_BZIP2)   = bzip2
 tool_$(CONFIG_KERNEL_LZ4)     = lz4
-tool_$(CONFIG_KERNEL_LZMA)    = lzma
 tool_$(CONFIG_KERNEL_LZO)     = lzo
 tool_$(CONFIG_KERNEL_XZ)      = xzkern
 
diff -uNr linux-5.4/arch/mips/boot/Makefile linux-5.4-zstd/arch/mips/boot/Makefile
--- linux-5.4/arch/mips/boot/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/mips/boot/Makefile	2019-12-15 15:07:00.398968976 -0800
@@ -24,9 +24,7 @@
 hostprogs-y := elf2ecoff
 
 suffix-y			:= bin
-suffix-$(CONFIG_KERNEL_BZIP2)	:= bz2
 suffix-$(CONFIG_KERNEL_GZIP)	:= gz
-suffix-$(CONFIG_KERNEL_LZMA)	:= lzma
 suffix-$(CONFIG_KERNEL_LZO)	:= lzo
 
 targets := vmlinux.ecoff
@@ -54,20 +52,12 @@
 # Compressed vmlinux images
 #
 
-extra-y += vmlinux.bin.bz2
 extra-y += vmlinux.bin.gz
-extra-y += vmlinux.bin.lzma
 extra-y += vmlinux.bin.lzo
 
-$(obj)/vmlinux.bin.bz2: $(obj)/vmlinux.bin FORCE
-	$(call if_changed,bzip2)
-
 $(obj)/vmlinux.bin.gz: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,gzip)
 
-$(obj)/vmlinux.bin.lzma: $(obj)/vmlinux.bin FORCE
-	$(call if_changed,lzma)
-
 $(obj)/vmlinux.bin.lzo: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,lzo)
 
@@ -77,23 +67,15 @@
 
 targets += uImage
 targets += uImage.bin
-targets += uImage.bz2
 targets += uImage.gz
-targets += uImage.lzma
 targets += uImage.lzo
 
 $(obj)/uImage.bin: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,uimage,none)
 
-$(obj)/uImage.bz2: $(obj)/vmlinux.bin.bz2 FORCE
-	$(call if_changed,uimage,bzip2)
-
 $(obj)/uImage.gz: $(obj)/vmlinux.bin.gz FORCE
 	$(call if_changed,uimage,gzip)
 
-$(obj)/uImage.lzma: $(obj)/vmlinux.bin.lzma FORCE
-	$(call if_changed,uimage,lzma)
-
 $(obj)/uImage.lzo: $(obj)/vmlinux.bin.lzo FORCE
 	$(call if_changed,uimage,lzo)
 
@@ -122,7 +104,6 @@
 
 targets += vmlinux.its
 targets += vmlinux.gz.its
-targets += vmlinux.bz2.its
 targets += vmlinux.lzmo.its
 targets += vmlinux.lzo.its
 
@@ -142,19 +123,11 @@
 $(obj)/vmlinux.gz.its: $(obj)/vmlinux.its.S $(VMLINUX) FORCE
 	$(call if_changed,cpp_its_S,gzip,vmlinux.bin.gz)
 
-$(obj)/vmlinux.bz2.its: $(obj)/vmlinux.its.S $(VMLINUX)  FORCE
-	$(call if_changed,cpp_its_S,bzip2,vmlinux.bin.bz2)
-
-$(obj)/vmlinux.lzma.its: $(obj)/vmlinux.its.S $(VMLINUX) FORCE
-	$(call if_changed,cpp_its_S,lzma,vmlinux.bin.lzma)
-
 $(obj)/vmlinux.lzo.its: $(obj)/vmlinux.its.S $(VMLINUX) FORCE
 	$(call if_changed,cpp_its_S,lzo,vmlinux.bin.lzo)
 
 targets += vmlinux.itb
 targets += vmlinux.gz.itb
-targets += vmlinux.bz2.itb
-targets += vmlinux.lzma.itb
 targets += vmlinux.lzo.itb
 
 quiet_cmd_itb-image = ITB     $@
diff -uNr linux-5.4/arch/mips/configs/ath25_defconfig linux-5.4-zstd/arch/mips/configs/ath25_defconfig
--- linux-5.4/arch/mips/configs/ath25_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/mips/configs/ath25_defconfig	2019-12-15 15:07:01.595611355 -0800
@@ -4,7 +4,6 @@
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_BLK_DEV_INITRD=y
 # CONFIG_RD_GZIP is not set
-# CONFIG_RD_BZIP2 is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/arch/mips/configs/pistachio_defconfig linux-5.4-zstd/arch/mips/configs/pistachio_defconfig
--- linux-5.4/arch/mips/configs/pistachio_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/mips/configs/pistachio_defconfig	2019-12-15 15:07:01.678942997 -0800
@@ -14,8 +14,6 @@
 CONFIG_NAMESPACES=y
 CONFIG_USER_NS=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
 CONFIG_CC_OPTIMIZE_FOR_SIZE=y
diff -uNr linux-5.4/arch/mips/Kconfig linux-5.4-zstd/arch/mips/Kconfig
--- linux-5.4/arch/mips/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/mips/Kconfig	2019-12-15 15:07:00.365636320 -0800
@@ -1843,9 +1843,7 @@
 config SYS_SUPPORTS_ZBOOT
 	bool
 	select HAVE_KERNEL_GZIP
-	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_LZ4
-	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
 
diff -uNr linux-5.4/arch/openrisc/configs/simple_smp_defconfig linux-5.4-zstd/arch/openrisc/configs/simple_smp_defconfig
--- linux-5.4/arch/openrisc/configs/simple_smp_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/openrisc/configs/simple_smp_defconfig	2019-12-15 15:07:01.725608717 -0800
@@ -4,8 +4,6 @@
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_BLK_DEV_INITRD=y
 # CONFIG_RD_GZIP is not set
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/arch/parisc/boot/compressed/Makefile linux-5.4-zstd/arch/parisc/boot/compressed/Makefile
--- linux-5.4/arch/parisc/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/parisc/boot/compressed/Makefile	2019-12-15 15:07:00.692296356 -0800
@@ -9,8 +9,8 @@
 GCOV_PROFILE := n
 UBSAN_SANITIZE := n
 
-targets := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2
-targets += vmlinux.bin.xz vmlinux.bin.lzma vmlinux.bin.lzo vmlinux.bin.lz4
+targets := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz
+targets += vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4
 targets += misc.o piggy.o sizes.h head.o real2.o firmware.o
 targets += real2.S firmware.c
 
@@ -63,20 +63,14 @@
 vmlinux.bin.all-y := $(obj)/vmlinux.bin
 
 suffix-$(CONFIG_KERNEL_GZIP)  := gz
-suffix-$(CONFIG_KERNEL_BZIP2) := bz2
 suffix-$(CONFIG_KERNEL_LZ4)  := lz4
-suffix-$(CONFIG_KERNEL_LZMA)  := lzma
 suffix-$(CONFIG_KERNEL_LZO)  := lzo
 suffix-$(CONFIG_KERNEL_XZ)  := xz
 
 $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y)
 	$(call if_changed,gzip)
-$(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y)
-	$(call if_changed,bzip2)
 $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y)
 	$(call if_changed,lz4)
-$(obj)/vmlinux.bin.lzma: $(vmlinux.bin.all-y)
-	$(call if_changed,lzma)
 $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y)
 	$(call if_changed,lzo)
 $(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y)
diff -uNr linux-5.4/arch/parisc/boot/compressed/misc.c linux-5.4-zstd/arch/parisc/boot/compressed/misc.c
--- linux-5.4/arch/parisc/boot/compressed/misc.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/parisc/boot/compressed/misc.c	2019-12-15 15:07:00.692296356 -0800
@@ -42,18 +42,10 @@
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-#include "../../../../lib/decompress_bunzip2.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZ4
 #include "../../../../lib/decompress_unlz4.c"
 #endif
 
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZO
 #include "../../../../lib/decompress_unlzo.c"
 #endif
diff -uNr linux-5.4/arch/parisc/Kconfig linux-5.4-zstd/arch/parisc/Kconfig
--- linux-5.4/arch/parisc/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/parisc/Kconfig	2019-12-15 15:07:00.652297168 -0800
@@ -21,10 +21,8 @@
 	select BUILDTIME_EXTABLE_SORT
 	select HAVE_PCI
 	select HAVE_PERF_EVENTS
-	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_LZ4
-	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
 	select GENERIC_ATOMIC64 if !64BIT
diff -uNr linux-5.4/arch/powerpc/configs/44x/fsp2_defconfig linux-5.4-zstd/arch/powerpc/configs/44x/fsp2_defconfig
--- linux-5.4/arch/powerpc/configs/44x/fsp2_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/powerpc/configs/44x/fsp2_defconfig	2019-12-15 15:07:01.845606281 -0800
@@ -9,7 +9,6 @@
 CONFIG_IKCONFIG_PROC=y
 CONFIG_LOG_BUF_SHIFT=16
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/arch/powerpc/configs/skiroot_defconfig linux-5.4-zstd/arch/powerpc/configs/skiroot_defconfig
--- linux-5.4/arch/powerpc/configs/skiroot_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/powerpc/configs/skiroot_defconfig	2019-12-15 15:07:01.895605266 -0800
@@ -16,8 +16,6 @@
 CONFIG_LOG_BUF_SHIFT=20
 CONFIG_BLK_DEV_INITRD=y
 # CONFIG_RD_GZIP is not set
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
 CONFIG_CC_OPTIMIZE_FOR_SIZE=y
diff -uNr linux-5.4/arch/s390/boot/compressed/decompressor.c linux-5.4-zstd/arch/s390/boot/compressed/decompressor.c
--- linux-5.4/arch/s390/boot/compressed/decompressor.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/s390/boot/compressed/decompressor.c	2019-12-15 15:07:00.768961466 -0800
@@ -42,18 +42,10 @@
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-#include "../../../../lib/decompress_bunzip2.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZ4
 #include "../../../../lib/decompress_unlz4.c"
 #endif
 
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZO
 #include "../../../../lib/decompress_unlzo.c"
 #endif
diff -uNr linux-5.4/arch/s390/boot/compressed/Makefile linux-5.4-zstd/arch/s390/boot/compressed/Makefile
--- linux-5.4/arch/s390/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/s390/boot/compressed/Makefile	2019-12-15 15:07:00.768961466 -0800
@@ -11,7 +11,7 @@
 KASAN_SANITIZE := n
 
 obj-y	:= $(if $(CONFIG_KERNEL_UNCOMPRESSED),,decompressor.o) piggy.o info.o
-targets	:= vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2
+targets	:= vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz
 targets += vmlinux.bin.xz vmlinux.bin.lzma vmlinux.bin.lzo vmlinux.bin.lz4
 targets += info.bin $(obj-y)
 
diff -uNr linux-5.4/arch/s390/Kconfig linux-5.4-zstd/arch/s390/Kconfig
--- linux-5.4/arch/s390/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/s390/Kconfig	2019-12-15 15:07:00.765628201 -0800
@@ -147,10 +147,8 @@
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUTEX_CMPXCHG if FUTEX
 	select HAVE_GCC_PLUGINS
-	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_LZ4
-	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_UNCOMPRESSED
 	select HAVE_KERNEL_XZ
diff -uNr linux-5.4/arch/sh/boot/compressed/Makefile linux-5.4-zstd/arch/sh/boot/compressed/Makefile
--- linux-5.4/arch/sh/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/sh/boot/compressed/Makefile	2019-12-15 15:07:00.872292703 -0800
@@ -6,7 +6,6 @@
 #
 
 targets		:= vmlinux vmlinux.bin vmlinux.bin.gz \
-		   vmlinux.bin.bz2 vmlinux.bin.lzma \
 		   vmlinux.bin.xz vmlinux.bin.lzo \
 		   head_$(BITS).o misc.o piggy.o
 
@@ -64,10 +63,6 @@
 
 $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,gzip)
-$(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE
-	$(call if_changed,bzip2)
-$(obj)/vmlinux.bin.lzma: $(vmlinux.bin.all-y) FORCE
-	$(call if_changed,lzma)
 $(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,xzkern)
 $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
diff -uNr linux-5.4/arch/sh/boot/compressed/misc.c linux-5.4-zstd/arch/sh/boot/compressed/misc.c
--- linux-5.4/arch/sh/boot/compressed/misc.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/sh/boot/compressed/misc.c	2019-12-15 15:07:00.942291282 -0800
@@ -44,24 +44,12 @@
 static unsigned long free_mem_ptr;
 static unsigned long free_mem_end_ptr;
 
-#ifdef CONFIG_HAVE_KERNEL_BZIP2
-#define HEAP_SIZE	0x400000
-#else
 #define HEAP_SIZE	0x10000
-#endif
 
 #ifdef CONFIG_KERNEL_GZIP
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-#include "../../../../lib/decompress_bunzip2.c"
-#endif
-
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 #ifdef CONFIG_KERNEL_XZ
 #include "../../../../lib/decompress_unxz.c"
 #endif
diff -uNr linux-5.4/arch/sh/boot/Makefile linux-5.4-zstd/arch/sh/boot/Makefile
--- linux-5.4/arch/sh/boot/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/sh/boot/Makefile	2019-12-15 15:07:00.852293109 -0800
@@ -21,15 +21,12 @@
 
 suffix-y := bin
 suffix-$(CONFIG_KERNEL_GZIP)	:= gz
-suffix-$(CONFIG_KERNEL_BZIP2)	:= bz2
-suffix-$(CONFIG_KERNEL_LZMA)	:= lzma
 suffix-$(CONFIG_KERNEL_XZ)	:= xz
 suffix-$(CONFIG_KERNEL_LZO)	:= lzo
 
 targets := zImage vmlinux.srec romImage uImage uImage.srec uImage.gz \
-	   uImage.bz2 uImage.lzma uImage.xz uImage.lzo uImage.bin
-extra-y += vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
-	   vmlinux.bin.xz vmlinux.bin.lzo
+	   uImage.xz uImage.lzo uImage.bin
+extra-y += vmlinux.bin vmlinux.bin.gz vmlinux.bin.xz vmlinux.bin.lzo
 subdir- := compressed romimage
 
 $(obj)/zImage: $(obj)/compressed/vmlinux FORCE
@@ -68,27 +65,15 @@
 $(obj)/vmlinux.bin.gz: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,gzip)
 
-$(obj)/vmlinux.bin.bz2: $(obj)/vmlinux.bin FORCE
-	$(call if_changed,bzip2)
-
-$(obj)/vmlinux.bin.lzma: $(obj)/vmlinux.bin FORCE
-	$(call if_changed,lzma)
-
 $(obj)/vmlinux.bin.xz: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,xzkern)
 
 $(obj)/vmlinux.bin.lzo: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,lzo)
 
-$(obj)/uImage.bz2: $(obj)/vmlinux.bin.bz2
-	$(call if_changed,uimage,bzip2)
-
 $(obj)/uImage.gz: $(obj)/vmlinux.bin.gz
 	$(call if_changed,uimage,gzip)
 
-$(obj)/uImage.lzma: $(obj)/vmlinux.bin.lzma
-	$(call if_changed,uimage,lzma)
-
 $(obj)/uImage.xz: $(obj)/vmlinux.bin.xz
 	$(call if_changed,uimage,xz)
 
diff -uNr linux-5.4/arch/sh/configs/sdk7786_defconfig linux-5.4-zstd/arch/sh/configs/sdk7786_defconfig
--- linux-5.4/arch/sh/configs/sdk7786_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/sh/configs/sdk7786_defconfig	2019-12-15 15:07:01.908938329 -0800
@@ -29,8 +29,6 @@
 CONFIG_PID_NS=y
 CONFIG_NET_NS=y
 CONFIG_BLK_DEV_INITRD=y
-CONFIG_RD_BZIP2=y
-CONFIG_RD_LZMA=y
 CONFIG_RD_LZO=y
 # CONFIG_COMPAT_BRK is not set
 CONFIG_SLAB=y
diff -uNr linux-5.4/arch/sh/Kconfig linux-5.4-zstd/arch/sh/Kconfig
--- linux-5.4/arch/sh/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/sh/Kconfig	2019-12-15 15:07:00.842293312 -0800
@@ -22,8 +22,6 @@
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_KERNEL_GZIP
 	select CPU_NO_EFFICIENT_FFS
-	select HAVE_KERNEL_BZIP2
-	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_LZO
 	select HAVE_UID16
diff -uNr linux-5.4/arch/sh/Makefile linux-5.4-zstd/arch/sh/Makefile
--- linux-5.4/arch/sh/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/sh/Makefile	2019-12-15 15:07:00.842293312 -0800
@@ -209,7 +209,7 @@
 libs-$(CONFIG_SUPERH32)		:= arch/sh/lib/	$(libs-y)
 libs-$(CONFIG_SUPERH64)		:= arch/sh/lib64/ $(libs-y)
 
-BOOT_TARGETS = uImage uImage.bz2 uImage.gz uImage.lzma uImage.xz uImage.lzo \
+BOOT_TARGETS = uImage uImage.bz2 uImage.gz uImage.xz uImage.lzo \
 	       uImage.srec uImage.bin zImage vmlinux.bin vmlinux.srec \
 	       romImage
 PHONY += $(BOOT_TARGETS)
@@ -240,8 +240,6 @@
 	@echo '  uImage.srec	           - Create an S-record for U-Boot'
 	@echo '  uImage.bin	           - Kernel-only image for U-Boot (bin)'
 	@echo '* uImage.gz	           - Kernel-only image for U-Boot (gzip)'
-	@echo '  uImage.bz2	           - Kernel-only image for U-Boot (bzip2)'
-	@echo '  uImage.lzma	           - Kernel-only image for U-Boot (lzma)'
 	@echo '  uImage.xz	           - Kernel-only image for U-Boot (xz)'
 	@echo '  uImage.lzo	           - Kernel-only image for U-Boot (lzo)'
 endef
diff -uNr linux-5.4/arch/unicore32/boot/compressed/Makefile linux-5.4-zstd/arch/unicore32/boot/compressed/Makefile
--- linux-5.4/arch/unicore32/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/unicore32/boot/compressed/Makefile	2019-12-15 15:07:01.092288237 -0800
@@ -22,9 +22,7 @@
 
 # piggy.S and piggy.o
 suffix_$(CONFIG_KERNEL_GZIP)	:= gzip
-suffix_$(CONFIG_KERNEL_BZIP2)	:= bz2
 suffix_$(CONFIG_KERNEL_LZO)	:= lzo
-suffix_$(CONFIG_KERNEL_LZMA)	:= lzma
 
 $(obj)/piggy.$(suffix_y): $(obj)/../Image FORCE
 	$(call if_changed,$(suffix_y))
@@ -39,7 +37,7 @@
 			piggy.$(suffix_y) piggy.o piggy.S \
 
 # Make sure files are removed during clean
-extra-y		+= piggy.gzip piggy.bz2 piggy.lzo piggy.lzma
+extra-y		+= piggy.gzip piggy.lzo
 
 # ?
 LDFLAGS_vmlinux += -p
diff -uNr linux-5.4/arch/unicore32/boot/compressed/misc.c linux-5.4-zstd/arch/unicore32/boot/compressed/misc.c
--- linux-5.4/arch/unicore32/boot/compressed/misc.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/unicore32/boot/compressed/misc.c	2019-12-15 15:07:01.095621503 -0800
@@ -88,18 +88,10 @@
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-#include "../../../../lib/decompress_bunzip2.c"
-#endif
-
 #ifdef CONFIG_KERNEL_LZO
 #include "../../../../lib/decompress_unlzo.c"
 #endif
 
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 unsigned long decompress_kernel(unsigned long output_start,
 		unsigned long free_mem_ptr_p,
 		unsigned long free_mem_ptr_end_p)
diff -uNr linux-5.4/arch/x86/boot/compressed/Makefile linux-5.4-zstd/arch/x86/boot/compressed/Makefile
--- linux-5.4/arch/x86/boot/compressed/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/x86/boot/compressed/Makefile	2019-12-15 15:07:00.308970803 -0800
@@ -7,13 +7,13 @@
 # vmlinuz is:
 #	decompression code (*.o)
 #	asm globals (piggy.S), including:
-#		vmlinux.bin.(gz|bz2|lzma|...)
+#		vmlinux.bin.(gz|zst|xz|...)
 #
 # vmlinux.bin is:
 #	vmlinux stripped of debugging and comments
 # vmlinux.bin.all is:
 #	vmlinux.bin + vmlinux.relocs
-# vmlinux.bin.(gz|bz2|lzma|...) is:
+# vmlinux.bin.(gz|zst|xz|...) is:
 #	(see scripts/Makefile.lib size_append)
 #	compressed vmlinux.bin.all + u32 size of vmlinux.bin.all
 
@@ -23,8 +23,8 @@
 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
 KCOV_INSTRUMENT		:= n
 
-targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
-	vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4
+targets := vmlinux vmlinux.bin vmlinux.bin.gz \
+	vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 vmlinux.bin.zst
 
 KBUILD_CFLAGS := -m$(BITS) -O2
 KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC)
@@ -134,23 +134,20 @@
 
 $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,gzip)
-$(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE
-	$(call if_changed,bzip2)
-$(obj)/vmlinux.bin.lzma: $(vmlinux.bin.all-y) FORCE
-	$(call if_changed,lzma)
 $(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,xzkern)
 $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,lzo)
 $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,lz4)
+$(obj)/vmlinux.bin.zst: $(vmlinux.bin.all-y) FORCE
+	$(call if_changed,zstd)
 
 suffix-$(CONFIG_KERNEL_GZIP)	:= gz
-suffix-$(CONFIG_KERNEL_BZIP2)	:= bz2
-suffix-$(CONFIG_KERNEL_LZMA)	:= lzma
 suffix-$(CONFIG_KERNEL_XZ)	:= xz
 suffix-$(CONFIG_KERNEL_LZO) 	:= lzo
 suffix-$(CONFIG_KERNEL_LZ4) 	:= lz4
+suffix-$(CONFIG_KERNEL_ZSTD)	:= zst
 
 quiet_cmd_mkpiggy = MKPIGGY $@
       cmd_mkpiggy = $(obj)/mkpiggy $< > $@
diff -uNr linux-5.4/arch/x86/boot/compressed/misc.c linux-5.4-zstd/arch/x86/boot/compressed/misc.c
--- linux-5.4/arch/x86/boot/compressed/misc.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/x86/boot/compressed/misc.c	2019-12-15 15:07:00.308970803 -0800
@@ -58,14 +58,6 @@
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-#include "../../../../lib/decompress_bunzip2.c"
-#endif
-
-#ifdef CONFIG_KERNEL_LZMA
-#include "../../../../lib/decompress_unlzma.c"
-#endif
-
 #ifdef CONFIG_KERNEL_XZ
 #include "../../../../lib/decompress_unxz.c"
 #endif
@@ -77,6 +69,10 @@
 #ifdef CONFIG_KERNEL_LZ4
 #include "../../../../lib/decompress_unlz4.c"
 #endif
+
+#ifdef CONFIG_KERNEL_ZSTD
+#include "../../../../lib/decompress_unzstd.c"
+#endif
 /*
  * NOTE: When adding a new decompressor, please update the analysis in
  * ../header.S.
diff -uNr linux-5.4/arch/x86/boot/header.S linux-5.4-zstd/arch/x86/boot/header.S
--- linux-5.4/arch/x86/boot/header.S	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/x86/boot/header.S	2019-12-15 15:07:00.302304271 -0800
@@ -536,8 +536,14 @@
 # the size-dependent part now grows so fast.
 #
 # extra_bytes = (uncompressed_size >> 8) + 65536
+#
+# ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
+# byte fixed overhead but has a maximum block size of 128K, so it needs a
+# larger margin.
+#
+# extra_bytes = (uncompressed_size >> 8) + 131072
 
-#define ZO_z_extra_bytes	((ZO_z_output_len >> 8) + 65536)
+#define ZO_z_extra_bytes	((ZO_z_output_len >> 8) + 131072)
 #if ZO_z_output_len > ZO_z_input_len
 # define ZO_z_extract_offset	(ZO_z_output_len + ZO_z_extra_bytes - \
 				 ZO_z_input_len)
diff -uNr linux-5.4/arch/x86/include/asm/boot.h linux-5.4-zstd/arch/x86/include/asm/boot.h
--- linux-5.4/arch/x86/include/asm/boot.h	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/x86/include/asm/boot.h	2019-12-15 15:07:00.308970803 -0800
@@ -24,9 +24,9 @@
 # error "Invalid value for CONFIG_PHYSICAL_ALIGN"
 #endif
 
-#ifdef CONFIG_KERNEL_BZIP2
-# define BOOT_HEAP_SIZE		0x400000
-#else /* !CONFIG_KERNEL_BZIP2 */
+#if defined(CONFIG_KERNEL_ZSTD)
+# define BOOT_HEAP_SIZE		 0x30000
+#else
 # define BOOT_HEAP_SIZE		 0x10000
 #endif
 
diff -uNr linux-5.4/arch/x86/Kconfig linux-5.4-zstd/arch/x86/Kconfig
--- linux-5.4/arch/x86/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/x86/Kconfig	2019-12-15 15:07:00.308970803 -0800
@@ -173,12 +173,11 @@
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK	if X86_64
 	select HAVE_IRQ_TIME_ACCOUNTING
-	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_LZ4
-	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
+	select HAVE_KERNEL_ZSTD
 	select HAVE_KPROBES
 	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_FUNCTION_ERROR_INJECTION
diff -uNr linux-5.4/arch/xtensa/configs/cadence_csp_defconfig linux-5.4-zstd/arch/xtensa/configs/cadence_csp_defconfig
--- linux-5.4/arch/xtensa/configs/cadence_csp_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/xtensa/configs/cadence_csp_defconfig	2019-12-15 15:07:01.948937517 -0800
@@ -15,8 +15,6 @@
 CONFIG_RELAY=y
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_INITRAMFS_SOURCE="$$KERNEL_INITRAMFS_SOURCE"
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/arch/xtensa/configs/nommu_kc705_defconfig linux-5.4-zstd/arch/xtensa/configs/nommu_kc705_defconfig
--- linux-5.4/arch/xtensa/configs/nommu_kc705_defconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/arch/xtensa/configs/nommu_kc705_defconfig	2019-12-15 15:07:01.958937314 -0800
@@ -15,8 +15,6 @@
 CONFIG_SCHED_AUTOGROUP=y
 CONFIG_RELAY=y
 CONFIG_BLK_DEV_INITRD=y
-# CONFIG_RD_BZIP2 is not set
-# CONFIG_RD_LZMA is not set
 # CONFIG_RD_XZ is not set
 # CONFIG_RD_LZO is not set
 # CONFIG_RD_LZ4 is not set
diff -uNr linux-5.4/.gitignore linux-5.4-zstd/.gitignore
--- linux-5.4/.gitignore	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/.gitignore	2019-12-15 15:07:00.305637537 -0800
@@ -44,6 +44,7 @@
 *.tab.[ch]
 *.tar
 *.xz
+*.zst
 Module.symvers
 modules.builtin
 modules.order
diff -uNr linux-5.4/include/linux/decompress/unlzma.h linux-5.4-zstd/include/linux/decompress/unlzma.h
--- linux-5.4/include/linux/decompress/unlzma.h	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/include/linux/decompress/unlzma.h	1969-12-31 16:00:00.000000000 -0800
@@ -1,13 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef DECOMPRESS_UNLZMA_H
-#define DECOMPRESS_UNLZMA_H
-
-int unlzma(unsigned char *, long,
-	   long (*fill)(void*, unsigned long),
-	   long (*flush)(void*, unsigned long),
-	   unsigned char *output,
-	   long *posp,
-	   void(*error)(char *x)
-	);
-
-#endif
diff -uNr linux-5.4/include/linux/decompress/unzstd.h linux-5.4-zstd/include/linux/decompress/unzstd.h
--- linux-5.4/include/linux/decompress/unzstd.h	1969-12-31 16:00:00.000000000 -0800
+++ linux-5.4-zstd/include/linux/decompress/unzstd.h	2019-12-15 15:06:59.968977703 -0800
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef LINUX_DECOMPRESS_UNZSTD_H
+#define LINUX_DECOMPRESS_UNZSTD_H
+
+int unzstd(unsigned char *inbuf, long len,
+	   long (*fill)(void*, unsigned long),
+	   long (*flush)(void*, unsigned long),
+	   unsigned char *output,
+	   long *pos,
+	   void (*error_fn)(char *x));
+#endif
diff -uNr linux-5.4/init/do_mounts_rd.c linux-5.4-zstd/init/do_mounts_rd.c
--- linux-5.4/init/do_mounts_rd.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/init/do_mounts_rd.c	2019-12-15 15:07:01.265618053 -0800
@@ -48,7 +48,6 @@
  *	cramfs
  *	squashfs
  *	gzip
- *	bzip2
  *	lzma
  *	xz
  *	lzo
diff -uNr linux-5.4/init/Kconfig linux-5.4-zstd/init/Kconfig
--- linux-5.4/init/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/init/Kconfig	2019-12-15 15:07:02.112267535 -0800
@@ -177,9 +177,6 @@
 config HAVE_KERNEL_GZIP
 	bool
 
-config HAVE_KERNEL_BZIP2
-	bool
-
 config HAVE_KERNEL_LZMA
 	bool
 
@@ -192,13 +189,16 @@
 config HAVE_KERNEL_LZ4
 	bool
 
+config HAVE_KERNEL_ZSTD
+	bool
+
 config HAVE_KERNEL_UNCOMPRESSED
 	bool
 
 choice
 	prompt "Kernel compression mode"
 	default KERNEL_GZIP
-	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
+	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
 	help
 	  The linux kernel is a kind of self-extracting executable.
 	  Several compression algorithms are available, which differ
@@ -206,41 +206,32 @@
 	  Compression speed is only relevant when building a kernel.
 	  Decompression speed is relevant at each boot.
 
-	  If you have any problems with bzip2 or lzma compressed
+	  If you have any problems with lzma compressed
 	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 	  version of this functionality (bzip2 only), for 2.4, was
 	  supplied by Christian Ludwig)
 
-	  High compression options are mostly useful for users, who
-	  are low on disk space (embedded systems), but for whom ram
-	  size matters less.
+	  High compression options tend to be more useful in most cases,
+	  as bootloaders are often egregiously slow to read the kernel
+	  from the disk/SD card/network/etc, overcoming any boot time
+	  savings you would get from faster decompression.
 
-	  If in doubt, select 'gzip'
+	  If in doubt, select 'xz'
 
 config KERNEL_GZIP
 	bool "Gzip"
 	depends on HAVE_KERNEL_GZIP
 	help
-	  The old and tried gzip compression. It provides a good balance
-	  between compression ratio and decompression speed.
-
-config KERNEL_BZIP2
-	bool "Bzip2"
-	depends on HAVE_KERNEL_BZIP2
-	help
-	  Its compression ratio and speed is intermediate.
-	  Decompression speed is slowest among the choices.  The kernel
-	  size is about 10% smaller with bzip2, in comparison to gzip.
-	  Bzip2 uses a large amount of memory. For modern kernels you
-	  will need at least 8MB RAM or more for booting.
+	  The old and tried gzip compression. You generally want it if
+	  some tool you use doesn't support more modern compressors.
 
 config KERNEL_LZMA
 	bool "LZMA"
 	depends on HAVE_KERNEL_LZMA
 	help
-	  This compression algorithm's ratio is best.  Decompression speed
-	  is between gzip and bzip2.  Compression is slowest.
-	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
+	  An old version of xz, like it providing strong compression at slow
+	  speed. It lacks a header and support for filters or uncompressed
+	  blocks, thus it's usually better to pick xz.
 
 config KERNEL_XZ
 	bool "XZ"
@@ -261,9 +252,9 @@
 	bool "LZO"
 	depends on HAVE_KERNEL_LZO
 	help
-	  Its compression ratio is the poorest among the choices. The kernel
-	  size is about 10% bigger than gzip; however its speed
-	  (both compression and decompression) is the fastest.
+	  Its compression ratio is pretty poor (but still better than
+	  LZ4). You want to pick ZSTD (similar speed but much better
+	  compression) or LZ4 (much better speed) instead.
 
 config KERNEL_LZ4
 	bool "LZ4"
@@ -277,6 +268,15 @@
 	  is about 8% bigger than LZO. But the decompression speed is
 	  faster than LZO.
 
+config KERNEL_ZSTD
+	bool "ZSTD"
+	depends on HAVE_KERNEL_ZSTD
+	help
+	  ZSTD is a compression algorithm targeting intermediate compression
+	  with fast decompression speed. It will compress better than GZIP and
+	  decompress around the same speed as LZO, but slower than LZ4. You
+	  will need at least 192 KB RAM or more for booting.
+
 config KERNEL_UNCOMPRESSED
 	bool "None"
 	depends on HAVE_KERNEL_UNCOMPRESSED
diff -uNr linux-5.4/kernel/configs/tiny.config linux-5.4-zstd/kernel/configs/tiny.config
--- linux-5.4/kernel/configs/tiny.config	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/kernel/configs/tiny.config	2019-12-15 15:07:01.265618053 -0800
@@ -1,7 +1,6 @@
 # CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
 CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 # CONFIG_KERNEL_GZIP is not set
-# CONFIG_KERNEL_BZIP2 is not set
 # CONFIG_KERNEL_LZMA is not set
 CONFIG_KERNEL_XZ=y
 # CONFIG_KERNEL_LZO is not set
diff -uNr linux-5.4/lib/decompress_bunzip2.c linux-5.4-zstd/lib/decompress_bunzip2.c
--- linux-5.4/lib/decompress_bunzip2.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/decompress_bunzip2.c	1969-12-31 16:00:00.000000000 -0800
@@ -1,756 +0,0 @@
-/*	Small bzip2 deflate implementation, by Rob Landley (rob@landley.net).
-
-	Based on bzip2 decompression code by Julian R Seward (jseward@acm.org),
-	which also acknowledges contributions by Mike Burrows, David Wheeler,
-	Peter Fenwick, Alistair Moffat, Radford Neal, Ian H. Witten,
-	Robert Sedgewick, and Jon L. Bentley.
-
-	This code is licensed under the LGPLv2:
-		LGPL (http://www.gnu.org/copyleft/lgpl.html
-*/
-
-/*
-	Size and speed optimizations by Manuel Novoa III  (mjn3@codepoet.org).
-
-	More efficient reading of Huffman codes, a streamlined read_bunzip()
-	function, and various other tweaks.  In (limited) tests, approximately
-	20% faster than bzcat on x86 and about 10% faster on arm.
-
-	Note that about 2/3 of the time is spent in read_unzip() reversing
-	the Burrows-Wheeler transformation.  Much of that time is delay
-	resulting from cache misses.
-
-	I would ask that anyone benefiting from this work, especially those
-	using it in commercial products, consider making a donation to my local
-	non-profit hospice organization in the name of the woman I loved, who
-	passed away Feb. 12, 2003.
-
-		In memory of Toni W. Hagan
-
-		Hospice of Acadiana, Inc.
-		2600 Johnston St., Suite 200
-		Lafayette, LA 70503-3240
-
-		Phone (337) 232-1234 or 1-800-738-2226
-		Fax   (337) 232-1297
-
-		http://www.hospiceacadiana.com/
-
-	Manuel
- */
-
-/*
-	Made it fit for running in Linux Kernel by Alain Knaff (alain@knaff.lu)
-*/
-
-
-#ifdef STATIC
-#define PREBOOT
-#else
-#include <linux/decompress/bunzip2.h>
-#endif /* STATIC */
-
-#include <linux/decompress/mm.h>
-#include <linux/crc32poly.h>
-
-#ifndef INT_MAX
-#define INT_MAX 0x7fffffff
-#endif
-
-/* Constants for Huffman coding */
-#define MAX_GROUPS		6
-#define GROUP_SIZE   		50	/* 64 would have been more efficient */
-#define MAX_HUFCODE_BITS 	20	/* Longest Huffman code allowed */
-#define MAX_SYMBOLS 		258	/* 256 literals + RUNA + RUNB */
-#define SYMBOL_RUNA		0
-#define SYMBOL_RUNB		1
-
-/* Status return values */
-#define RETVAL_OK			0
-#define RETVAL_LAST_BLOCK		(-1)
-#define RETVAL_NOT_BZIP_DATA		(-2)
-#define RETVAL_UNEXPECTED_INPUT_EOF	(-3)
-#define RETVAL_UNEXPECTED_OUTPUT_EOF	(-4)
-#define RETVAL_DATA_ERROR		(-5)
-#define RETVAL_OUT_OF_MEMORY		(-6)
-#define RETVAL_OBSOLETE_INPUT		(-7)
-
-/* Other housekeeping constants */
-#define BZIP2_IOBUF_SIZE		4096
-
-/* This is what we know about each Huffman coding group */
-struct group_data {
-	/* We have an extra slot at the end of limit[] for a sentinal value. */
-	int limit[MAX_HUFCODE_BITS+1];
-	int base[MAX_HUFCODE_BITS];
-	int permute[MAX_SYMBOLS];
-	int minLen, maxLen;
-};
-
-/* Structure holding all the housekeeping data, including IO buffers and
-   memory that persists between calls to bunzip */
-struct bunzip_data {
-	/* State for interrupting output loop */
-	int writeCopies, writePos, writeRunCountdown, writeCount, writeCurrent;
-	/* I/O tracking data (file handles, buffers, positions, etc.) */
-	long (*fill)(void*, unsigned long);
-	long inbufCount, inbufPos /*, outbufPos*/;
-	unsigned char *inbuf /*,*outbuf*/;
-	unsigned int inbufBitCount, inbufBits;
-	/* The CRC values stored in the block header and calculated from the
-	data */
-	unsigned int crc32Table[256], headerCRC, totalCRC, writeCRC;
-	/* Intermediate buffer and its size (in bytes) */
-	unsigned int *dbuf, dbufSize;
-	/* These things are a bit too big to go on the stack */
-	unsigned char selectors[32768];		/* nSelectors = 15 bits */
-	struct group_data groups[MAX_GROUPS];	/* Huffman coding tables */
-	int io_error;			/* non-zero if we have IO error */
-	int byteCount[256];
-	unsigned char symToByte[256], mtfSymbol[256];
-};
-
-
-/* Return the next nnn bits of input.  All reads from the compressed input
-   are done through this function.  All reads are big endian */
-static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
-{
-	unsigned int bits = 0;
-
-	/* If we need to get more data from the byte buffer, do so.
-	   (Loop getting one byte at a time to enforce endianness and avoid
-	   unaligned access.) */
-	while (bd->inbufBitCount < bits_wanted) {
-		/* If we need to read more data from file into byte buffer, do
-		   so */
-		if (bd->inbufPos == bd->inbufCount) {
-			if (bd->io_error)
-				return 0;
-			bd->inbufCount = bd->fill(bd->inbuf, BZIP2_IOBUF_SIZE);
-			if (bd->inbufCount <= 0) {
-				bd->io_error = RETVAL_UNEXPECTED_INPUT_EOF;
-				return 0;
-			}
-			bd->inbufPos = 0;
-		}
-		/* Avoid 32-bit overflow (dump bit buffer to top of output) */
-		if (bd->inbufBitCount >= 24) {
-			bits = bd->inbufBits&((1 << bd->inbufBitCount)-1);
-			bits_wanted -= bd->inbufBitCount;
-			bits <<= bits_wanted;
-			bd->inbufBitCount = 0;
-		}
-		/* Grab next 8 bits of input from buffer. */
-		bd->inbufBits = (bd->inbufBits << 8)|bd->inbuf[bd->inbufPos++];
-		bd->inbufBitCount += 8;
-	}
-	/* Calculate result */
-	bd->inbufBitCount -= bits_wanted;
-	bits |= (bd->inbufBits >> bd->inbufBitCount)&((1 << bits_wanted)-1);
-
-	return bits;
-}
-
-/* Unpacks the next block and sets up for the inverse burrows-wheeler step. */
-
-static int INIT get_next_block(struct bunzip_data *bd)
-{
-	struct group_data *hufGroup = NULL;
-	int *base = NULL;
-	int *limit = NULL;
-	int dbufCount, nextSym, dbufSize, groupCount, selector,
-		i, j, k, t, runPos, symCount, symTotal, nSelectors, *byteCount;
-	unsigned char uc, *symToByte, *mtfSymbol, *selectors;
-	unsigned int *dbuf, origPtr;
-
-	dbuf = bd->dbuf;
-	dbufSize = bd->dbufSize;
-	selectors = bd->selectors;
-	byteCount = bd->byteCount;
-	symToByte = bd->symToByte;
-	mtfSymbol = bd->mtfSymbol;
-
-	/* Read in header signature and CRC, then validate signature.
-	   (last block signature means CRC is for whole file, return now) */
-	i = get_bits(bd, 24);
-	j = get_bits(bd, 24);
-	bd->headerCRC = get_bits(bd, 32);
-	if ((i == 0x177245) && (j == 0x385090))
-		return RETVAL_LAST_BLOCK;
-	if ((i != 0x314159) || (j != 0x265359))
-		return RETVAL_NOT_BZIP_DATA;
-	/* We can add support for blockRandomised if anybody complains.
-	   There was some code for this in busybox 1.0.0-pre3, but nobody ever
-	   noticed that it didn't actually work. */
-	if (get_bits(bd, 1))
-		return RETVAL_OBSOLETE_INPUT;
-	origPtr = get_bits(bd, 24);
-	if (origPtr >= dbufSize)
-		return RETVAL_DATA_ERROR;
-	/* mapping table: if some byte values are never used (encoding things
-	   like ascii text), the compression code removes the gaps to have fewer
-	   symbols to deal with, and writes a sparse bitfield indicating which
-	   values were present.  We make a translation table to convert the
-	   symbols back to the corresponding bytes. */
-	t = get_bits(bd, 16);
-	symTotal = 0;
-	for (i = 0; i < 16; i++) {
-		if (t&(1 << (15-i))) {
-			k = get_bits(bd, 16);
-			for (j = 0; j < 16; j++)
-				if (k&(1 << (15-j)))
-					symToByte[symTotal++] = (16*i)+j;
-		}
-	}
-	/* How many different Huffman coding groups does this block use? */
-	groupCount = get_bits(bd, 3);
-	if (groupCount < 2 || groupCount > MAX_GROUPS)
-		return RETVAL_DATA_ERROR;
-	/* nSelectors: Every GROUP_SIZE many symbols we select a new
-	   Huffman coding group.  Read in the group selector list,
-	   which is stored as MTF encoded bit runs.  (MTF = Move To
-	   Front, as each value is used it's moved to the start of the
-	   list.) */
-	nSelectors = get_bits(bd, 15);
-	if (!nSelectors)
-		return RETVAL_DATA_ERROR;
-	for (i = 0; i < groupCount; i++)
-		mtfSymbol[i] = i;
-	for (i = 0; i < nSelectors; i++) {
-		/* Get next value */
-		for (j = 0; get_bits(bd, 1); j++)
-			if (j >= groupCount)
-				return RETVAL_DATA_ERROR;
-		/* Decode MTF to get the next selector */
-		uc = mtfSymbol[j];
-		for (; j; j--)
-			mtfSymbol[j] = mtfSymbol[j-1];
-		mtfSymbol[0] = selectors[i] = uc;
-	}
-	/* Read the Huffman coding tables for each group, which code
-	   for symTotal literal symbols, plus two run symbols (RUNA,
-	   RUNB) */
-	symCount = symTotal+2;
-	for (j = 0; j < groupCount; j++) {
-		unsigned char length[MAX_SYMBOLS], temp[MAX_HUFCODE_BITS+1];
-		int	minLen,	maxLen, pp;
-		/* Read Huffman code lengths for each symbol.  They're
-		   stored in a way similar to mtf; record a starting
-		   value for the first symbol, and an offset from the
-		   previous value for everys symbol after that.
-		   (Subtracting 1 before the loop and then adding it
-		   back at the end is an optimization that makes the
-		   test inside the loop simpler: symbol length 0
-		   becomes negative, so an unsigned inequality catches
-		   it.) */
-		t = get_bits(bd, 5)-1;
-		for (i = 0; i < symCount; i++) {
-			for (;;) {
-				if (((unsigned)t) > (MAX_HUFCODE_BITS-1))
-					return RETVAL_DATA_ERROR;
-
-				/* If first bit is 0, stop.  Else
-				   second bit indicates whether to
-				   increment or decrement the value.
-				   Optimization: grab 2 bits and unget
-				   the second if the first was 0. */
-
-				k = get_bits(bd, 2);
-				if (k < 2) {
-					bd->inbufBitCount++;
-					break;
-				}
-				/* Add one if second bit 1, else
-				 * subtract 1.  Avoids if/else */
-				t += (((k+1)&2)-1);
-			}
-			/* Correct for the initial -1, to get the
-			 * final symbol length */
-			length[i] = t+1;
-		}
-		/* Find largest and smallest lengths in this group */
-		minLen = maxLen = length[0];
-
-		for (i = 1; i < symCount; i++) {
-			if (length[i] > maxLen)
-				maxLen = length[i];
-			else if (length[i] < minLen)
-				minLen = length[i];
-		}
-
-		/* Calculate permute[], base[], and limit[] tables from
-		 * length[].
-		 *
-		 * permute[] is the lookup table for converting
-		 * Huffman coded symbols into decoded symbols.  base[]
-		 * is the amount to subtract from the value of a
-		 * Huffman symbol of a given length when using
-		 * permute[].
-		 *
-		 * limit[] indicates the largest numerical value a
-		 * symbol with a given number of bits can have.  This
-		 * is how the Huffman codes can vary in length: each
-		 * code with a value > limit[length] needs another
-		 * bit.
-		 */
-		hufGroup = bd->groups+j;
-		hufGroup->minLen = minLen;
-		hufGroup->maxLen = maxLen;
-		/* Note that minLen can't be smaller than 1, so we
-		   adjust the base and limit array pointers so we're
-		   not always wasting the first entry.  We do this
-		   again when using them (during symbol decoding).*/
-		base = hufGroup->base-1;
-		limit = hufGroup->limit-1;
-		/* Calculate permute[].  Concurrently, initialize
-		 * temp[] and limit[]. */
-		pp = 0;
-		for (i = minLen; i <= maxLen; i++) {
-			temp[i] = limit[i] = 0;
-			for (t = 0; t < symCount; t++)
-				if (length[t] == i)
-					hufGroup->permute[pp++] = t;
-		}
-		/* Count symbols coded for at each bit length */
-		for (i = 0; i < symCount; i++)
-			temp[length[i]]++;
-		/* Calculate limit[] (the largest symbol-coding value
-		 *at each bit length, which is (previous limit <<
-		 *1)+symbols at this level), and base[] (number of
-		 *symbols to ignore at each bit length, which is limit
-		 *minus the cumulative count of symbols coded for
-		 *already). */
-		pp = t = 0;
-		for (i = minLen; i < maxLen; i++) {
-			pp += temp[i];
-			/* We read the largest possible symbol size
-			   and then unget bits after determining how
-			   many we need, and those extra bits could be
-			   set to anything.  (They're noise from
-			   future symbols.)  At each level we're
-			   really only interested in the first few
-			   bits, so here we set all the trailing
-			   to-be-ignored bits to 1 so they don't
-			   affect the value > limit[length]
-			   comparison. */
-			limit[i] = (pp << (maxLen - i)) - 1;
-			pp <<= 1;
-			base[i+1] = pp-(t += temp[i]);
-		}
-		limit[maxLen+1] = INT_MAX; /* Sentinal value for
-					    * reading next sym. */
-		limit[maxLen] = pp+temp[maxLen]-1;
-		base[minLen] = 0;
-	}
-	/* We've finished reading and digesting the block header.  Now
-	   read this block's Huffman coded symbols from the file and
-	   undo the Huffman coding and run length encoding, saving the
-	   result into dbuf[dbufCount++] = uc */
-
-	/* Initialize symbol occurrence counters and symbol Move To
-	 * Front table */
-	for (i = 0; i < 256; i++) {
-		byteCount[i] = 0;
-		mtfSymbol[i] = (unsigned char)i;
-	}
-	/* Loop through compressed symbols. */
-	runPos = dbufCount = symCount = selector = 0;
-	for (;;) {
-		/* Determine which Huffman coding group to use. */
-		if (!(symCount--)) {
-			symCount = GROUP_SIZE-1;
-			if (selector >= nSelectors)
-				return RETVAL_DATA_ERROR;
-			hufGroup = bd->groups+selectors[selector++];
-			base = hufGroup->base-1;
-			limit = hufGroup->limit-1;
-		}
-		/* Read next Huffman-coded symbol. */
-		/* Note: It is far cheaper to read maxLen bits and
-		   back up than it is to read minLen bits and then an
-		   additional bit at a time, testing as we go.
-		   Because there is a trailing last block (with file
-		   CRC), there is no danger of the overread causing an
-		   unexpected EOF for a valid compressed file.  As a
-		   further optimization, we do the read inline
-		   (falling back to a call to get_bits if the buffer
-		   runs dry).  The following (up to got_huff_bits:) is
-		   equivalent to j = get_bits(bd, hufGroup->maxLen);
-		 */
-		while (bd->inbufBitCount < hufGroup->maxLen) {
-			if (bd->inbufPos == bd->inbufCount) {
-				j = get_bits(bd, hufGroup->maxLen);
-				goto got_huff_bits;
-			}
-			bd->inbufBits =
-				(bd->inbufBits << 8)|bd->inbuf[bd->inbufPos++];
-			bd->inbufBitCount += 8;
-		};
-		bd->inbufBitCount -= hufGroup->maxLen;
-		j = (bd->inbufBits >> bd->inbufBitCount)&
-			((1 << hufGroup->maxLen)-1);
-got_huff_bits:
-		/* Figure how how many bits are in next symbol and
-		 * unget extras */
-		i = hufGroup->minLen;
-		while (j > limit[i])
-			++i;
-		bd->inbufBitCount += (hufGroup->maxLen - i);
-		/* Huffman decode value to get nextSym (with bounds checking) */
-		if ((i > hufGroup->maxLen)
-			|| (((unsigned)(j = (j>>(hufGroup->maxLen-i))-base[i]))
-				>= MAX_SYMBOLS))
-			return RETVAL_DATA_ERROR;
-		nextSym = hufGroup->permute[j];
-		/* We have now decoded the symbol, which indicates
-		   either a new literal byte, or a repeated run of the
-		   most recent literal byte.  First, check if nextSym
-		   indicates a repeated run, and if so loop collecting
-		   how many times to repeat the last literal. */
-		if (((unsigned)nextSym) <= SYMBOL_RUNB) { /* RUNA or RUNB */
-			/* If this is the start of a new run, zero out
-			 * counter */
-			if (!runPos) {
-				runPos = 1;
-				t = 0;
-			}
-			/* Neat trick that saves 1 symbol: instead of
-			   or-ing 0 or 1 at each bit position, add 1
-			   or 2 instead.  For example, 1011 is 1 << 0
-			   + 1 << 1 + 2 << 2.  1010 is 2 << 0 + 2 << 1
-			   + 1 << 2.  You can make any bit pattern
-			   that way using 1 less symbol than the basic
-			   or 0/1 method (except all bits 0, which
-			   would use no symbols, but a run of length 0
-			   doesn't mean anything in this context).
-			   Thus space is saved. */
-			t += (runPos << nextSym);
-			/* +runPos if RUNA; +2*runPos if RUNB */
-
-			runPos <<= 1;
-			continue;
-		}
-		/* When we hit the first non-run symbol after a run,
-		   we now know how many times to repeat the last
-		   literal, so append that many copies to our buffer
-		   of decoded symbols (dbuf) now.  (The last literal
-		   used is the one at the head of the mtfSymbol
-		   array.) */
-		if (runPos) {
-			runPos = 0;
-			if (dbufCount+t >= dbufSize)
-				return RETVAL_DATA_ERROR;
-
-			uc = symToByte[mtfSymbol[0]];
-			byteCount[uc] += t;
-			while (t--)
-				dbuf[dbufCount++] = uc;
-		}
-		/* Is this the terminating symbol? */
-		if (nextSym > symTotal)
-			break;
-		/* At this point, nextSym indicates a new literal
-		   character.  Subtract one to get the position in the
-		   MTF array at which this literal is currently to be
-		   found.  (Note that the result can't be -1 or 0,
-		   because 0 and 1 are RUNA and RUNB.  But another
-		   instance of the first symbol in the mtf array,
-		   position 0, would have been handled as part of a
-		   run above.  Therefore 1 unused mtf position minus 2
-		   non-literal nextSym values equals -1.) */
-		if (dbufCount >= dbufSize)
-			return RETVAL_DATA_ERROR;
-		i = nextSym - 1;
-		uc = mtfSymbol[i];
-		/* Adjust the MTF array.  Since we typically expect to
-		 *move only a small number of symbols, and are bound
-		 *by 256 in any case, using memmove here would
-		 *typically be bigger and slower due to function call
-		 *overhead and other assorted setup costs. */
-		do {
-			mtfSymbol[i] = mtfSymbol[i-1];
-		} while (--i);
-		mtfSymbol[0] = uc;
-		uc = symToByte[uc];
-		/* We have our literal byte.  Save it into dbuf. */
-		byteCount[uc]++;
-		dbuf[dbufCount++] = (unsigned int)uc;
-	}
-	/* At this point, we've read all the Huffman-coded symbols
-	   (and repeated runs) for this block from the input stream,
-	   and decoded them into the intermediate buffer.  There are
-	   dbufCount many decoded bytes in dbuf[].  Now undo the
-	   Burrows-Wheeler transform on dbuf.  See
-	   http://dogma.net/markn/articles/bwt/bwt.htm
-	 */
-	/* Turn byteCount into cumulative occurrence counts of 0 to n-1. */
-	j = 0;
-	for (i = 0; i < 256; i++) {
-		k = j+byteCount[i];
-		byteCount[i] = j;
-		j = k;
-	}
-	/* Figure out what order dbuf would be in if we sorted it. */
-	for (i = 0; i < dbufCount; i++) {
-		uc = (unsigned char)(dbuf[i] & 0xff);
-		dbuf[byteCount[uc]] |= (i << 8);
-		byteCount[uc]++;
-	}
-	/* Decode first byte by hand to initialize "previous" byte.
-	   Note that it doesn't get output, and if the first three
-	   characters are identical it doesn't qualify as a run (hence
-	   writeRunCountdown = 5). */
-	if (dbufCount) {
-		if (origPtr >= dbufCount)
-			return RETVAL_DATA_ERROR;
-		bd->writePos = dbuf[origPtr];
-		bd->writeCurrent = (unsigned char)(bd->writePos&0xff);
-		bd->writePos >>= 8;
-		bd->writeRunCountdown = 5;
-	}
-	bd->writeCount = dbufCount;
-
-	return RETVAL_OK;
-}
-
-/* Undo burrows-wheeler transform on intermediate buffer to produce output.
-   If start_bunzip was initialized with out_fd =-1, then up to len bytes of
-   data are written to outbuf.  Return value is number of bytes written or
-   error (all errors are negative numbers).  If out_fd!=-1, outbuf and len
-   are ignored, data is written to out_fd and return is RETVAL_OK or error.
-*/
-
-static int INIT read_bunzip(struct bunzip_data *bd, char *outbuf, int len)
-{
-	const unsigned int *dbuf;
-	int pos, xcurrent, previous, gotcount;
-
-	/* If last read was short due to end of file, return last block now */
-	if (bd->writeCount < 0)
-		return bd->writeCount;
-
-	gotcount = 0;
-	dbuf = bd->dbuf;
-	pos = bd->writePos;
-	xcurrent = bd->writeCurrent;
-
-	/* We will always have pending decoded data to write into the output
-	   buffer unless this is the very first call (in which case we haven't
-	   Huffman-decoded a block into the intermediate buffer yet). */
-
-	if (bd->writeCopies) {
-		/* Inside the loop, writeCopies means extra copies (beyond 1) */
-		--bd->writeCopies;
-		/* Loop outputting bytes */
-		for (;;) {
-			/* If the output buffer is full, snapshot
-			 * state and return */
-			if (gotcount >= len) {
-				bd->writePos = pos;
-				bd->writeCurrent = xcurrent;
-				bd->writeCopies++;
-				return len;
-			}
-			/* Write next byte into output buffer, updating CRC */
-			outbuf[gotcount++] = xcurrent;
-			bd->writeCRC = (((bd->writeCRC) << 8)
-				^bd->crc32Table[((bd->writeCRC) >> 24)
-				^xcurrent]);
-			/* Loop now if we're outputting multiple
-			 * copies of this byte */
-			if (bd->writeCopies) {
-				--bd->writeCopies;
-				continue;
-			}
-decode_next_byte:
-			if (!bd->writeCount--)
-				break;
-			/* Follow sequence vector to undo
-			 * Burrows-Wheeler transform */
-			previous = xcurrent;
-			pos = dbuf[pos];
-			xcurrent = pos&0xff;
-			pos >>= 8;
-			/* After 3 consecutive copies of the same
-			   byte, the 4th is a repeat count.  We count
-			   down from 4 instead *of counting up because
-			   testing for non-zero is faster */
-			if (--bd->writeRunCountdown) {
-				if (xcurrent != previous)
-					bd->writeRunCountdown = 4;
-			} else {
-				/* We have a repeated run, this byte
-				 * indicates the count */
-				bd->writeCopies = xcurrent;
-				xcurrent = previous;
-				bd->writeRunCountdown = 5;
-				/* Sometimes there are just 3 bytes
-				 * (run length 0) */
-				if (!bd->writeCopies)
-					goto decode_next_byte;
-				/* Subtract the 1 copy we'd output
-				 * anyway to get extras */
-				--bd->writeCopies;
-			}
-		}
-		/* Decompression of this block completed successfully */
-		bd->writeCRC = ~bd->writeCRC;
-		bd->totalCRC = ((bd->totalCRC << 1) |
-				(bd->totalCRC >> 31)) ^ bd->writeCRC;
-		/* If this block had a CRC error, force file level CRC error. */
-		if (bd->writeCRC != bd->headerCRC) {
-			bd->totalCRC = bd->headerCRC+1;
-			return RETVAL_LAST_BLOCK;
-		}
-	}
-
-	/* Refill the intermediate buffer by Huffman-decoding next
-	 * block of input */
-	/* (previous is just a convenient unused temp variable here) */
-	previous = get_next_block(bd);
-	if (previous) {
-		bd->writeCount = previous;
-		return (previous != RETVAL_LAST_BLOCK) ? previous : gotcount;
-	}
-	bd->writeCRC = 0xffffffffUL;
-	pos = bd->writePos;
-	xcurrent = bd->writeCurrent;
-	goto decode_next_byte;
-}
-
-static long INIT nofill(void *buf, unsigned long len)
-{
-	return -1;
-}
-
-/* Allocate the structure, read file header.  If in_fd ==-1, inbuf must contain
-   a complete bunzip file (len bytes long).  If in_fd!=-1, inbuf and len are
-   ignored, and data is read from file handle into temporary buffer. */
-static int INIT start_bunzip(struct bunzip_data **bdp, void *inbuf, long len,
-			     long (*fill)(void*, unsigned long))
-{
-	struct bunzip_data *bd;
-	unsigned int i, j, c;
-	const unsigned int BZh0 =
-		(((unsigned int)'B') << 24)+(((unsigned int)'Z') << 16)
-		+(((unsigned int)'h') << 8)+(unsigned int)'0';
-
-	/* Figure out how much data to allocate */
-	i = sizeof(struct bunzip_data);
-
-	/* Allocate bunzip_data.  Most fields initialize to zero. */
-	bd = *bdp = malloc(i);
-	if (!bd)
-		return RETVAL_OUT_OF_MEMORY;
-	memset(bd, 0, sizeof(struct bunzip_data));
-	/* Setup input buffer */
-	bd->inbuf = inbuf;
-	bd->inbufCount = len;
-	if (fill != NULL)
-		bd->fill = fill;
-	else
-		bd->fill = nofill;
-
-	/* Init the CRC32 table (big endian) */
-	for (i = 0; i < 256; i++) {
-		c = i << 24;
-		for (j = 8; j; j--)
-			c = c&0x80000000 ? (c << 1)^(CRC32_POLY_BE) : (c << 1);
-		bd->crc32Table[i] = c;
-	}
-
-	/* Ensure that file starts with "BZh['1'-'9']." */
-	i = get_bits(bd, 32);
-	if (((unsigned int)(i-BZh0-1)) >= 9)
-		return RETVAL_NOT_BZIP_DATA;
-
-	/* Fourth byte (ascii '1'-'9'), indicates block size in units of 100k of
-	   uncompressed data.  Allocate intermediate buffer for block. */
-	bd->dbufSize = 100000*(i-BZh0);
-
-	bd->dbuf = large_malloc(bd->dbufSize * sizeof(int));
-	if (!bd->dbuf)
-		return RETVAL_OUT_OF_MEMORY;
-	return RETVAL_OK;
-}
-
-/* Example usage: decompress src_fd to dst_fd.  (Stops at end of bzip2 data,
-   not end of file.) */
-STATIC int INIT bunzip2(unsigned char *buf, long len,
-			long (*fill)(void*, unsigned long),
-			long (*flush)(void*, unsigned long),
-			unsigned char *outbuf,
-			long *pos,
-			void(*error)(char *x))
-{
-	struct bunzip_data *bd;
-	int i = -1;
-	unsigned char *inbuf;
-
-	if (flush)
-		outbuf = malloc(BZIP2_IOBUF_SIZE);
-
-	if (!outbuf) {
-		error("Could not allocate output buffer");
-		return RETVAL_OUT_OF_MEMORY;
-	}
-	if (buf)
-		inbuf = buf;
-	else
-		inbuf = malloc(BZIP2_IOBUF_SIZE);
-	if (!inbuf) {
-		error("Could not allocate input buffer");
-		i = RETVAL_OUT_OF_MEMORY;
-		goto exit_0;
-	}
-	i = start_bunzip(&bd, inbuf, len, fill);
-	if (!i) {
-		for (;;) {
-			i = read_bunzip(bd, outbuf, BZIP2_IOBUF_SIZE);
-			if (i <= 0)
-				break;
-			if (!flush)
-				outbuf += i;
-			else
-				if (i != flush(outbuf, i)) {
-					i = RETVAL_UNEXPECTED_OUTPUT_EOF;
-					break;
-				}
-		}
-	}
-	/* Check CRC and release memory */
-	if (i == RETVAL_LAST_BLOCK) {
-		if (bd->headerCRC != bd->totalCRC)
-			error("Data integrity error when decompressing.");
-		else
-			i = RETVAL_OK;
-	} else if (i == RETVAL_UNEXPECTED_OUTPUT_EOF) {
-		error("Compressed file ends unexpectedly");
-	}
-	if (!bd)
-		goto exit_1;
-	if (bd->dbuf)
-		large_free(bd->dbuf);
-	if (pos)
-		*pos = bd->inbufPos;
-	free(bd);
-exit_1:
-	if (!buf)
-		free(inbuf);
-exit_0:
-	if (flush)
-		free(outbuf);
-	return i;
-}
-
-#ifdef PREBOOT
-STATIC int INIT __decompress(unsigned char *buf, long len,
-			long (*fill)(void*, unsigned long),
-			long (*flush)(void*, unsigned long),
-			unsigned char *outbuf, long olen,
-			long *pos,
-			void (*error)(char *x))
-{
-	return bunzip2(buf, len - 4, fill, flush, outbuf, pos, error);
-}
-#endif
diff -uNr linux-5.4/lib/decompress.c linux-5.4-zstd/lib/decompress.c
--- linux-5.4/lib/decompress.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/decompress.c	2019-12-15 15:07:02.115600801 -0800
@@ -8,11 +8,11 @@
 #include <linux/decompress/generic.h>
 
 #include <linux/decompress/bunzip2.h>
-#include <linux/decompress/unlzma.h>
 #include <linux/decompress/unxz.h>
 #include <linux/decompress/inflate.h>
 #include <linux/decompress/unlzo.h>
 #include <linux/decompress/unlz4.h>
+#include <linux/decompress/unzstd.h>
 
 #include <linux/types.h>
 #include <linux/string.h>
@@ -22,12 +22,6 @@
 #ifndef CONFIG_DECOMPRESS_GZIP
 # define gunzip NULL
 #endif
-#ifndef CONFIG_DECOMPRESS_BZIP2
-# define bunzip2 NULL
-#endif
-#ifndef CONFIG_DECOMPRESS_LZMA
-# define unlzma NULL
-#endif
 #ifndef CONFIG_DECOMPRESS_XZ
 # define unxz NULL
 #endif
@@ -37,6 +31,9 @@
 #ifndef CONFIG_DECOMPRESS_LZ4
 # define unlz4 NULL
 #endif
+#ifndef CONFIG_DECOMPRESS_ZSTD
+# define unzstd NULL
+#endif
 
 struct compress_format {
 	unsigned char magic[2];
@@ -47,11 +44,10 @@
 static const struct compress_format compressed_formats[] __initconst = {
 	{ {0x1f, 0x8b}, "gzip", gunzip },
 	{ {0x1f, 0x9e}, "gzip", gunzip },
-	{ {0x42, 0x5a}, "bzip2", bunzip2 },
-	{ {0x5d, 0x00}, "lzma", unlzma },
 	{ {0xfd, 0x37}, "xz", unxz },
 	{ {0x89, 0x4c}, "lzo", unlzo },
 	{ {0x02, 0x21}, "lz4", unlz4 },
+	{ {0x28, 0xb5}, "zstd", unzstd },
 	{ {0, 0}, NULL, NULL }
 };
 
@@ -73,7 +69,9 @@
 			break;
 
 	}
-	if (name)
+	if (name) {
 		*name = cf->name;
+		printk("Decompressing using %s.\n", *name);
+	}
 	return cf->decompressor;
 }
diff -uNr linux-5.4/lib/decompress_unlzma.c linux-5.4-zstd/lib/decompress_unlzma.c
--- linux-5.4/lib/decompress_unlzma.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/decompress_unlzma.c	1969-12-31 16:00:00.000000000 -0800
@@ -1,679 +0,0 @@
-/* Lzma decompressor for Linux kernel. Shamelessly snarfed
- *from busybox 1.1.1
- *
- *Linux kernel adaptation
- *Copyright (C) 2006  Alain < alain@knaff.lu >
- *
- *Based on small lzma deflate implementation/Small range coder
- *implementation for lzma.
- *Copyright (C) 2006  Aurelien Jacobs < aurel@gnuage.org >
- *
- *Based on LzmaDecode.c from the LZMA SDK 4.22 (http://www.7-zip.org/)
- *Copyright (C) 1999-2005  Igor Pavlov
- *
- *Copyrights of the parts, see headers below.
- *
- *
- *This program is free software; you can redistribute it and/or
- *modify it under the terms of the GNU Lesser General Public
- *License as published by the Free Software Foundation; either
- *version 2.1 of the License, or (at your option) any later version.
- *
- *This program is distributed in the hope that it will be useful,
- *but WITHOUT ANY WARRANTY; without even the implied warranty of
- *MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- *Lesser General Public License for more details.
- *
- *You should have received a copy of the GNU Lesser General Public
- *License along with this library; if not, write to the Free Software
- *Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- */
-
-#ifdef STATIC
-#define PREBOOT
-#else
-#include <linux/decompress/unlzma.h>
-#endif /* STATIC */
-
-#include <linux/decompress/mm.h>
-
-#define	MIN(a, b) (((a) < (b)) ? (a) : (b))
-
-static long long INIT read_int(unsigned char *ptr, int size)
-{
-	int i;
-	long long ret = 0;
-
-	for (i = 0; i < size; i++)
-		ret = (ret << 8) | ptr[size-i-1];
-	return ret;
-}
-
-#define ENDIAN_CONVERT(x) \
-  x = (typeof(x))read_int((unsigned char *)&x, sizeof(x))
-
-
-/* Small range coder implementation for lzma.
- *Copyright (C) 2006  Aurelien Jacobs < aurel@gnuage.org >
- *
- *Based on LzmaDecode.c from the LZMA SDK 4.22 (http://www.7-zip.org/)
- *Copyright (c) 1999-2005  Igor Pavlov
- */
-
-#include <linux/compiler.h>
-
-#define LZMA_IOBUF_SIZE	0x10000
-
-struct rc {
-	long (*fill)(void*, unsigned long);
-	uint8_t *ptr;
-	uint8_t *buffer;
-	uint8_t *buffer_end;
-	long buffer_size;
-	uint32_t code;
-	uint32_t range;
-	uint32_t bound;
-	void (*error)(char *);
-};
-
-
-#define RC_TOP_BITS 24
-#define RC_MOVE_BITS 5
-#define RC_MODEL_TOTAL_BITS 11
-
-
-static long INIT nofill(void *buffer, unsigned long len)
-{
-	return -1;
-}
-
-/* Called twice: once at startup and once in rc_normalize() */
-static void INIT rc_read(struct rc *rc)
-{
-	rc->buffer_size = rc->fill((char *)rc->buffer, LZMA_IOBUF_SIZE);
-	if (rc->buffer_size <= 0)
-		rc->error("unexpected EOF");
-	rc->ptr = rc->buffer;
-	rc->buffer_end = rc->buffer + rc->buffer_size;
-}
-
-/* Called once */
-static inline void INIT rc_init(struct rc *rc,
-				       long (*fill)(void*, unsigned long),
-				       char *buffer, long buffer_size)
-{
-	if (fill)
-		rc->fill = fill;
-	else
-		rc->fill = nofill;
-	rc->buffer = (uint8_t *)buffer;
-	rc->buffer_size = buffer_size;
-	rc->buffer_end = rc->buffer + rc->buffer_size;
-	rc->ptr = rc->buffer;
-
-	rc->code = 0;
-	rc->range = 0xFFFFFFFF;
-}
-
-static inline void INIT rc_init_code(struct rc *rc)
-{
-	int i;
-
-	for (i = 0; i < 5; i++) {
-		if (rc->ptr >= rc->buffer_end)
-			rc_read(rc);
-		rc->code = (rc->code << 8) | *rc->ptr++;
-	}
-}
-
-
-/* Called twice, but one callsite is in inline'd rc_is_bit_0_helper() */
-static void INIT rc_do_normalize(struct rc *rc)
-{
-	if (rc->ptr >= rc->buffer_end)
-		rc_read(rc);
-	rc->range <<= 8;
-	rc->code = (rc->code << 8) | *rc->ptr++;
-}
-static inline void INIT rc_normalize(struct rc *rc)
-{
-	if (rc->range < (1 << RC_TOP_BITS))
-		rc_do_normalize(rc);
-}
-
-/* Called 9 times */
-/* Why rc_is_bit_0_helper exists?
- *Because we want to always expose (rc->code < rc->bound) to optimizer
- */
-static inline uint32_t INIT rc_is_bit_0_helper(struct rc *rc, uint16_t *p)
-{
-	rc_normalize(rc);
-	rc->bound = *p * (rc->range >> RC_MODEL_TOTAL_BITS);
-	return rc->bound;
-}
-static inline int INIT rc_is_bit_0(struct rc *rc, uint16_t *p)
-{
-	uint32_t t = rc_is_bit_0_helper(rc, p);
-	return rc->code < t;
-}
-
-/* Called ~10 times, but very small, thus inlined */
-static inline void INIT rc_update_bit_0(struct rc *rc, uint16_t *p)
-{
-	rc->range = rc->bound;
-	*p += ((1 << RC_MODEL_TOTAL_BITS) - *p) >> RC_MOVE_BITS;
-}
-static inline void INIT rc_update_bit_1(struct rc *rc, uint16_t *p)
-{
-	rc->range -= rc->bound;
-	rc->code -= rc->bound;
-	*p -= *p >> RC_MOVE_BITS;
-}
-
-/* Called 4 times in unlzma loop */
-static int INIT rc_get_bit(struct rc *rc, uint16_t *p, int *symbol)
-{
-	if (rc_is_bit_0(rc, p)) {
-		rc_update_bit_0(rc, p);
-		*symbol *= 2;
-		return 0;
-	} else {
-		rc_update_bit_1(rc, p);
-		*symbol = *symbol * 2 + 1;
-		return 1;
-	}
-}
-
-/* Called once */
-static inline int INIT rc_direct_bit(struct rc *rc)
-{
-	rc_normalize(rc);
-	rc->range >>= 1;
-	if (rc->code >= rc->range) {
-		rc->code -= rc->range;
-		return 1;
-	}
-	return 0;
-}
-
-/* Called twice */
-static inline void INIT
-rc_bit_tree_decode(struct rc *rc, uint16_t *p, int num_levels, int *symbol)
-{
-	int i = num_levels;
-
-	*symbol = 1;
-	while (i--)
-		rc_get_bit(rc, p + *symbol, symbol);
-	*symbol -= 1 << num_levels;
-}
-
-
-/*
- * Small lzma deflate implementation.
- * Copyright (C) 2006  Aurelien Jacobs < aurel@gnuage.org >
- *
- * Based on LzmaDecode.c from the LZMA SDK 4.22 (http://www.7-zip.org/)
- * Copyright (C) 1999-2005  Igor Pavlov
- */
-
-
-struct lzma_header {
-	uint8_t pos;
-	uint32_t dict_size;
-	uint64_t dst_size;
-} __attribute__ ((packed)) ;
-
-
-#define LZMA_BASE_SIZE 1846
-#define LZMA_LIT_SIZE 768
-
-#define LZMA_NUM_POS_BITS_MAX 4
-
-#define LZMA_LEN_NUM_LOW_BITS 3
-#define LZMA_LEN_NUM_MID_BITS 3
-#define LZMA_LEN_NUM_HIGH_BITS 8
-
-#define LZMA_LEN_CHOICE 0
-#define LZMA_LEN_CHOICE_2 (LZMA_LEN_CHOICE + 1)
-#define LZMA_LEN_LOW (LZMA_LEN_CHOICE_2 + 1)
-#define LZMA_LEN_MID (LZMA_LEN_LOW \
-		      + (1 << (LZMA_NUM_POS_BITS_MAX + LZMA_LEN_NUM_LOW_BITS)))
-#define LZMA_LEN_HIGH (LZMA_LEN_MID \
-		       +(1 << (LZMA_NUM_POS_BITS_MAX + LZMA_LEN_NUM_MID_BITS)))
-#define LZMA_NUM_LEN_PROBS (LZMA_LEN_HIGH + (1 << LZMA_LEN_NUM_HIGH_BITS))
-
-#define LZMA_NUM_STATES 12
-#define LZMA_NUM_LIT_STATES 7
-
-#define LZMA_START_POS_MODEL_INDEX 4
-#define LZMA_END_POS_MODEL_INDEX 14
-#define LZMA_NUM_FULL_DISTANCES (1 << (LZMA_END_POS_MODEL_INDEX >> 1))
-
-#define LZMA_NUM_POS_SLOT_BITS 6
-#define LZMA_NUM_LEN_TO_POS_STATES 4
-
-#define LZMA_NUM_ALIGN_BITS 4
-
-#define LZMA_MATCH_MIN_LEN 2
-
-#define LZMA_IS_MATCH 0
-#define LZMA_IS_REP (LZMA_IS_MATCH + (LZMA_NUM_STATES << LZMA_NUM_POS_BITS_MAX))
-#define LZMA_IS_REP_G0 (LZMA_IS_REP + LZMA_NUM_STATES)
-#define LZMA_IS_REP_G1 (LZMA_IS_REP_G0 + LZMA_NUM_STATES)
-#define LZMA_IS_REP_G2 (LZMA_IS_REP_G1 + LZMA_NUM_STATES)
-#define LZMA_IS_REP_0_LONG (LZMA_IS_REP_G2 + LZMA_NUM_STATES)
-#define LZMA_POS_SLOT (LZMA_IS_REP_0_LONG \
-		       + (LZMA_NUM_STATES << LZMA_NUM_POS_BITS_MAX))
-#define LZMA_SPEC_POS (LZMA_POS_SLOT \
-		       +(LZMA_NUM_LEN_TO_POS_STATES << LZMA_NUM_POS_SLOT_BITS))
-#define LZMA_ALIGN (LZMA_SPEC_POS \
-		    + LZMA_NUM_FULL_DISTANCES - LZMA_END_POS_MODEL_INDEX)
-#define LZMA_LEN_CODER (LZMA_ALIGN + (1 << LZMA_NUM_ALIGN_BITS))
-#define LZMA_REP_LEN_CODER (LZMA_LEN_CODER + LZMA_NUM_LEN_PROBS)
-#define LZMA_LITERAL (LZMA_REP_LEN_CODER + LZMA_NUM_LEN_PROBS)
-
-
-struct writer {
-	uint8_t *buffer;
-	uint8_t previous_byte;
-	size_t buffer_pos;
-	int bufsize;
-	size_t global_pos;
-	long (*flush)(void*, unsigned long);
-	struct lzma_header *header;
-};
-
-struct cstate {
-	int state;
-	uint32_t rep0, rep1, rep2, rep3;
-};
-
-static inline size_t INIT get_pos(struct writer *wr)
-{
-	return
-		wr->global_pos + wr->buffer_pos;
-}
-
-static inline uint8_t INIT peek_old_byte(struct writer *wr,
-						uint32_t offs)
-{
-	if (!wr->flush) {
-		int32_t pos;
-		while (offs > wr->header->dict_size)
-			offs -= wr->header->dict_size;
-		pos = wr->buffer_pos - offs;
-		return wr->buffer[pos];
-	} else {
-		uint32_t pos = wr->buffer_pos - offs;
-		while (pos >= wr->header->dict_size)
-			pos += wr->header->dict_size;
-		return wr->buffer[pos];
-	}
-
-}
-
-static inline int INIT write_byte(struct writer *wr, uint8_t byte)
-{
-	wr->buffer[wr->buffer_pos++] = wr->previous_byte = byte;
-	if (wr->flush && wr->buffer_pos == wr->header->dict_size) {
-		wr->buffer_pos = 0;
-		wr->global_pos += wr->header->dict_size;
-		if (wr->flush((char *)wr->buffer, wr->header->dict_size)
-				!= wr->header->dict_size)
-			return -1;
-	}
-	return 0;
-}
-
-
-static inline int INIT copy_byte(struct writer *wr, uint32_t offs)
-{
-	return write_byte(wr, peek_old_byte(wr, offs));
-}
-
-static inline int INIT copy_bytes(struct writer *wr,
-					 uint32_t rep0, int len)
-{
-	do {
-		if (copy_byte(wr, rep0))
-			return -1;
-		len--;
-	} while (len != 0 && wr->buffer_pos < wr->header->dst_size);
-
-	return len;
-}
-
-static inline int INIT process_bit0(struct writer *wr, struct rc *rc,
-				     struct cstate *cst, uint16_t *p,
-				     int pos_state, uint16_t *prob,
-				     int lc, uint32_t literal_pos_mask) {
-	int mi = 1;
-	rc_update_bit_0(rc, prob);
-	prob = (p + LZMA_LITERAL +
-		(LZMA_LIT_SIZE
-		 * (((get_pos(wr) & literal_pos_mask) << lc)
-		    + (wr->previous_byte >> (8 - lc))))
-		);
-
-	if (cst->state >= LZMA_NUM_LIT_STATES) {
-		int match_byte = peek_old_byte(wr, cst->rep0);
-		do {
-			int bit;
-			uint16_t *prob_lit;
-
-			match_byte <<= 1;
-			bit = match_byte & 0x100;
-			prob_lit = prob + 0x100 + bit + mi;
-			if (rc_get_bit(rc, prob_lit, &mi)) {
-				if (!bit)
-					break;
-			} else {
-				if (bit)
-					break;
-			}
-		} while (mi < 0x100);
-	}
-	while (mi < 0x100) {
-		uint16_t *prob_lit = prob + mi;
-		rc_get_bit(rc, prob_lit, &mi);
-	}
-	if (cst->state < 4)
-		cst->state = 0;
-	else if (cst->state < 10)
-		cst->state -= 3;
-	else
-		cst->state -= 6;
-
-	return write_byte(wr, mi);
-}
-
-static inline int INIT process_bit1(struct writer *wr, struct rc *rc,
-					    struct cstate *cst, uint16_t *p,
-					    int pos_state, uint16_t *prob) {
-  int offset;
-	uint16_t *prob_len;
-	int num_bits;
-	int len;
-
-	rc_update_bit_1(rc, prob);
-	prob = p + LZMA_IS_REP + cst->state;
-	if (rc_is_bit_0(rc, prob)) {
-		rc_update_bit_0(rc, prob);
-		cst->rep3 = cst->rep2;
-		cst->rep2 = cst->rep1;
-		cst->rep1 = cst->rep0;
-		cst->state = cst->state < LZMA_NUM_LIT_STATES ? 0 : 3;
-		prob = p + LZMA_LEN_CODER;
-	} else {
-		rc_update_bit_1(rc, prob);
-		prob = p + LZMA_IS_REP_G0 + cst->state;
-		if (rc_is_bit_0(rc, prob)) {
-			rc_update_bit_0(rc, prob);
-			prob = (p + LZMA_IS_REP_0_LONG
-				+ (cst->state <<
-				   LZMA_NUM_POS_BITS_MAX) +
-				pos_state);
-			if (rc_is_bit_0(rc, prob)) {
-				rc_update_bit_0(rc, prob);
-
-				cst->state = cst->state < LZMA_NUM_LIT_STATES ?
-					9 : 11;
-				return copy_byte(wr, cst->rep0);
-			} else {
-				rc_update_bit_1(rc, prob);
-			}
-		} else {
-			uint32_t distance;
-
-			rc_update_bit_1(rc, prob);
-			prob = p + LZMA_IS_REP_G1 + cst->state;
-			if (rc_is_bit_0(rc, prob)) {
-				rc_update_bit_0(rc, prob);
-				distance = cst->rep1;
-			} else {
-				rc_update_bit_1(rc, prob);
-				prob = p + LZMA_IS_REP_G2 + cst->state;
-				if (rc_is_bit_0(rc, prob)) {
-					rc_update_bit_0(rc, prob);
-					distance = cst->rep2;
-				} else {
-					rc_update_bit_1(rc, prob);
-					distance = cst->rep3;
-					cst->rep3 = cst->rep2;
-				}
-				cst->rep2 = cst->rep1;
-			}
-			cst->rep1 = cst->rep0;
-			cst->rep0 = distance;
-		}
-		cst->state = cst->state < LZMA_NUM_LIT_STATES ? 8 : 11;
-		prob = p + LZMA_REP_LEN_CODER;
-	}
-
-	prob_len = prob + LZMA_LEN_CHOICE;
-	if (rc_is_bit_0(rc, prob_len)) {
-		rc_update_bit_0(rc, prob_len);
-		prob_len = (prob + LZMA_LEN_LOW
-			    + (pos_state <<
-			       LZMA_LEN_NUM_LOW_BITS));
-		offset = 0;
-		num_bits = LZMA_LEN_NUM_LOW_BITS;
-	} else {
-		rc_update_bit_1(rc, prob_len);
-		prob_len = prob + LZMA_LEN_CHOICE_2;
-		if (rc_is_bit_0(rc, prob_len)) {
-			rc_update_bit_0(rc, prob_len);
-			prob_len = (prob + LZMA_LEN_MID
-				    + (pos_state <<
-				       LZMA_LEN_NUM_MID_BITS));
-			offset = 1 << LZMA_LEN_NUM_LOW_BITS;
-			num_bits = LZMA_LEN_NUM_MID_BITS;
-		} else {
-			rc_update_bit_1(rc, prob_len);
-			prob_len = prob + LZMA_LEN_HIGH;
-			offset = ((1 << LZMA_LEN_NUM_LOW_BITS)
-				  + (1 << LZMA_LEN_NUM_MID_BITS));
-			num_bits = LZMA_LEN_NUM_HIGH_BITS;
-		}
-	}
-
-	rc_bit_tree_decode(rc, prob_len, num_bits, &len);
-	len += offset;
-
-	if (cst->state < 4) {
-		int pos_slot;
-
-		cst->state += LZMA_NUM_LIT_STATES;
-		prob =
-			p + LZMA_POS_SLOT +
-			((len <
-			  LZMA_NUM_LEN_TO_POS_STATES ? len :
-			  LZMA_NUM_LEN_TO_POS_STATES - 1)
-			 << LZMA_NUM_POS_SLOT_BITS);
-		rc_bit_tree_decode(rc, prob,
-				   LZMA_NUM_POS_SLOT_BITS,
-				   &pos_slot);
-		if (pos_slot >= LZMA_START_POS_MODEL_INDEX) {
-			int i, mi;
-			num_bits = (pos_slot >> 1) - 1;
-			cst->rep0 = 2 | (pos_slot & 1);
-			if (pos_slot < LZMA_END_POS_MODEL_INDEX) {
-				cst->rep0 <<= num_bits;
-				prob = p + LZMA_SPEC_POS +
-					cst->rep0 - pos_slot - 1;
-			} else {
-				num_bits -= LZMA_NUM_ALIGN_BITS;
-				while (num_bits--)
-					cst->rep0 = (cst->rep0 << 1) |
-						rc_direct_bit(rc);
-				prob = p + LZMA_ALIGN;
-				cst->rep0 <<= LZMA_NUM_ALIGN_BITS;
-				num_bits = LZMA_NUM_ALIGN_BITS;
-			}
-			i = 1;
-			mi = 1;
-			while (num_bits--) {
-				if (rc_get_bit(rc, prob + mi, &mi))
-					cst->rep0 |= i;
-				i <<= 1;
-			}
-		} else
-			cst->rep0 = pos_slot;
-		if (++(cst->rep0) == 0)
-			return 0;
-		if (cst->rep0 > wr->header->dict_size
-				|| cst->rep0 > get_pos(wr))
-			return -1;
-	}
-
-	len += LZMA_MATCH_MIN_LEN;
-
-	return copy_bytes(wr, cst->rep0, len);
-}
-
-
-
-STATIC inline int INIT unlzma(unsigned char *buf, long in_len,
-			      long (*fill)(void*, unsigned long),
-			      long (*flush)(void*, unsigned long),
-			      unsigned char *output,
-			      long *posp,
-			      void(*error)(char *x)
-	)
-{
-	struct lzma_header header;
-	int lc, pb, lp;
-	uint32_t pos_state_mask;
-	uint32_t literal_pos_mask;
-	uint16_t *p;
-	int num_probs;
-	struct rc rc;
-	int i, mi;
-	struct writer wr;
-	struct cstate cst;
-	unsigned char *inbuf;
-	int ret = -1;
-
-	rc.error = error;
-
-	if (buf)
-		inbuf = buf;
-	else
-		inbuf = malloc(LZMA_IOBUF_SIZE);
-	if (!inbuf) {
-		error("Could not allocate input buffer");
-		goto exit_0;
-	}
-
-	cst.state = 0;
-	cst.rep0 = cst.rep1 = cst.rep2 = cst.rep3 = 1;
-
-	wr.header = &header;
-	wr.flush = flush;
-	wr.global_pos = 0;
-	wr.previous_byte = 0;
-	wr.buffer_pos = 0;
-
-	rc_init(&rc, fill, inbuf, in_len);
-
-	for (i = 0; i < sizeof(header); i++) {
-		if (rc.ptr >= rc.buffer_end)
-			rc_read(&rc);
-		((unsigned char *)&header)[i] = *rc.ptr++;
-	}
-
-	if (header.pos >= (9 * 5 * 5)) {
-		error("bad header");
-		goto exit_1;
-	}
-
-	mi = 0;
-	lc = header.pos;
-	while (lc >= 9) {
-		mi++;
-		lc -= 9;
-	}
-	pb = 0;
-	lp = mi;
-	while (lp >= 5) {
-		pb++;
-		lp -= 5;
-	}
-	pos_state_mask = (1 << pb) - 1;
-	literal_pos_mask = (1 << lp) - 1;
-
-	ENDIAN_CONVERT(header.dict_size);
-	ENDIAN_CONVERT(header.dst_size);
-
-	if (header.dict_size == 0)
-		header.dict_size = 1;
-
-	if (output)
-		wr.buffer = output;
-	else {
-		wr.bufsize = MIN(header.dst_size, header.dict_size);
-		wr.buffer = large_malloc(wr.bufsize);
-	}
-	if (wr.buffer == NULL)
-		goto exit_1;
-
-	num_probs = LZMA_BASE_SIZE + (LZMA_LIT_SIZE << (lc + lp));
-	p = (uint16_t *) large_malloc(num_probs * sizeof(*p));
-	if (p == NULL)
-		goto exit_2;
-	num_probs = LZMA_LITERAL + (LZMA_LIT_SIZE << (lc + lp));
-	for (i = 0; i < num_probs; i++)
-		p[i] = (1 << RC_MODEL_TOTAL_BITS) >> 1;
-
-	rc_init_code(&rc);
-
-	while (get_pos(&wr) < header.dst_size) {
-		int pos_state =	get_pos(&wr) & pos_state_mask;
-		uint16_t *prob = p + LZMA_IS_MATCH +
-			(cst.state << LZMA_NUM_POS_BITS_MAX) + pos_state;
-		if (rc_is_bit_0(&rc, prob)) {
-			if (process_bit0(&wr, &rc, &cst, p, pos_state, prob,
-					lc, literal_pos_mask)) {
-				error("LZMA data is corrupt");
-				goto exit_3;
-			}
-		} else {
-			if (process_bit1(&wr, &rc, &cst, p, pos_state, prob)) {
-				error("LZMA data is corrupt");
-				goto exit_3;
-			}
-			if (cst.rep0 == 0)
-				break;
-		}
-		if (rc.buffer_size <= 0)
-			goto exit_3;
-	}
-
-	if (posp)
-		*posp = rc.ptr-rc.buffer;
-	if (!wr.flush || wr.flush(wr.buffer, wr.buffer_pos) == wr.buffer_pos)
-		ret = 0;
-exit_3:
-	large_free(p);
-exit_2:
-	if (!output)
-		large_free(wr.buffer);
-exit_1:
-	if (!buf)
-		free(inbuf);
-exit_0:
-	return ret;
-}
-
-#ifdef PREBOOT
-STATIC int INIT __decompress(unsigned char *buf, long in_len,
-			      long (*fill)(void*, unsigned long),
-			      long (*flush)(void*, unsigned long),
-			      unsigned char *output, long out_len,
-			      long *posp,
-			      void (*error)(char *x))
-{
-	return unlzma(buf, in_len - 4, fill, flush, output, posp, error);
-}
-#endif
diff -uNr linux-5.4/lib/decompress_unzstd.c linux-5.4-zstd/lib/decompress_unzstd.c
--- linux-5.4/lib/decompress_unzstd.c	1969-12-31 16:00:00.000000000 -0800
+++ linux-5.4-zstd/lib/decompress_unzstd.c	2019-12-15 15:06:59.972310969 -0800
@@ -0,0 +1,341 @@
+/*
+ * Copyright (C) 2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * Important notes about in-place decompression
+ *
+ * At least on x86, the kernel is decompressed in place: the compressed data
+ * is placed to the end of the output buffer, and the decompressor overwrites
+ * most of the compressed data. There must be enough safety margin to
+ * guarantee that the write position is always behind the read position.
+ *
+ * The safety margin for ZSTD with a 128 KB block size is calculated below.
+ * Note that the margin with ZSTD is bigger than with GZIP or XZ!
+ *
+ * The worst case for in-place decompression is that the beginning of
+ * the file is compressed extremely well, and the rest of the file is
+ * uncompressible. Thus, we must look for worst-case expansion when the
+ * compressor is encoding uncompressible data.
+ *
+ * The structure of the .zst file in case of a compresed kernel is as follows.
+ * Maximum sizes (as bytes) of the fields are in parenthesis.
+ *
+ *    Frame Header: (18)
+ *    Blocks: (N)
+ *    Checksum: (4)
+ *
+ * The frame header and checksum overhead is at most 22 bytes.
+ *
+ * ZSTD stores the data in blocks. Each block has a header whose size is
+ * a 3 bytes. After the block header, there is up to 128 KB of payload.
+ * The maximum uncompressed size of the payload is 128 KB. The minimum
+ * uncompressed size of the payload is never less than the payload size
+ * (excluding the block header).
+ *
+ * The assumption, that the uncompressed size of the payload is never
+ * smaller than the payload itself, is valid only when talking about
+ * the payload as a whole. It is possible that the payload has parts where
+ * the decompressor consumes more input than it produces output. Calculating
+ * the worst case for this would be tricky. Instead of trying to do that,
+ * let's simply make sure that the decompressor never overwrites any bytes
+ * of the payload which it is currently reading.
+ *
+ * Now we have enough information to calculate the safety margin. We need
+ *   - 22 bytes for the .zst file format headers;
+ *   - 3 bytes per every 128 KiB of uncompressed size (one block header per
+ *     block); and
+ *   - 128 KiB (biggest possible zstd block size) to make sure that the
+ *     decompressor never overwrites anything from the block it is currently
+ *     reading.
+ *
+ * We get the following formula:
+ *
+ *    safety_margin = 22 + uncompressed_size * 3 / 131072 + 131072
+ *                 <= 22 + (uncompressed_size >> 15) + 131072
+ */
+
+#ifdef STATIC
+	/* Preboot environments #include "path/to/decompress_unzstd.c".
+	 * All of the source files we depend on must be #included.
+	 * zstd's only source dependeny is xxhash, which has no source
+	 * dependencies.
+	 *
+	 * zstd and xxhash both avoid declaring themselves as modules
+	 * when PREBOOT is defined.
+	 */
+#	define PREBOOT
+#	include "xxhash.c"
+#	include "zstd/entropy_common.c"
+#	include "zstd/fse_decompress.c"
+#	include "zstd/huf_decompress.c"
+#	include "zstd/zstd_common.c"
+#	include "zstd/decompress.c"
+#endif
+
+#include <linux/decompress/mm.h>
+#include <linux/kernel.h>
+#include <linux/zstd.h>
+
+/* 8 MB maximum window size */
+#define ZSTD_WINDOWSIZE_MAX	(1 << 23)
+/* Size of the input and output buffers in multi-call mdoe */
+#define ZSTD_IOBUF_SIZE		4096
+
+static int INIT handle_zstd_error(size_t ret, void (*error)(char *x))
+{
+	const int err = ZSTD_getErrorCode(ret);
+
+	if (!ZSTD_isError(ret))
+		return 0;
+
+	switch (err) {
+	case ZSTD_error_memory_allocation:
+		error("ZSTD decompressor ran out of memory");
+		break;
+	case ZSTD_error_prefix_unknown:
+		error("Input is not in the ZSTD format (wrong magic bytes)");
+		break;
+	case ZSTD_error_dstSize_tooSmall:
+	case ZSTD_error_corruption_detected:
+	case ZSTD_error_checksum_wrong:
+		error("ZSTD-compressed data is corrupt");
+		break;
+	default:
+		error("ZSTD-compressed data is probably corrupt");
+		break;
+	}
+	return -1;
+}
+
+/* Handle the case where we have the entire input and output in one segment.
+ * We can allocate less memory (no circular buffer for the sliding window),
+ * and avoid some memcpy() calls.
+ */
+static int INIT decompress_single(const u8 *in_buf, long in_len, u8 *out_buf,
+				  long out_len, long *in_pos,
+				  void (*error)(char *x))
+{
+	const size_t wksp_size = ZSTD_DCtxWorkspaceBound();
+	void *wksp = large_malloc(wksp_size);
+	ZSTD_DCtx *dctx = ZSTD_initDCtx(wksp, wksp_size);
+	int err;
+	size_t ret;
+
+	if (dctx == NULL) {
+		error("Out of memory while allocating ZSTD_DCtx");
+		err = -1;
+		goto out;
+	}
+	/* Find out how large the frame actually is, there may be junk at
+	 * the end of the frame that ZSTD_decompressDCtx() can't handle.
+	 */
+	ret = ZSTD_findFrameCompressedSize(in_buf, in_len);
+	err = handle_zstd_error(ret, error);
+	if (err)
+		goto out;
+	in_len = (long)ret;
+
+	ret = ZSTD_decompressDCtx(dctx, out_buf, out_len, in_buf, in_len);
+	err = handle_zstd_error(ret, error);
+	if (err)
+		goto out;
+
+	if (in_pos != NULL)
+		*in_pos = in_len;
+
+	err = 0;
+out:
+	if (wksp != NULL)
+		large_free(wksp);
+	return err;
+}
+
+static int INIT __unzstd(unsigned char *in_buf, long in_len,
+			 long (*fill)(void*, unsigned long),
+			 long (*flush)(void*, unsigned long),
+			 unsigned char *out_buf, long out_len,
+			 long *in_pos,
+			 void (*error)(char *x))
+{
+	ZSTD_inBuffer in;
+	ZSTD_outBuffer out;
+	ZSTD_frameParams params;
+	void *in_allocated = NULL;
+	void *out_allocated = NULL;
+	void *wksp = NULL;
+	size_t wksp_size;
+	ZSTD_DStream *dstream;
+	int err;
+	size_t ret;
+
+	if (out_len == 0)
+		out_len = LONG_MAX; /* no limit */
+
+	if (fill == NULL && flush == NULL)
+		/* We can decompress faster and with less memory when we have a
+		 * single chunk.
+		 */
+		return decompress_single(in_buf, in_len, out_buf, out_len,
+					 in_pos, error);
+
+	/* If in_buf is not provided, we must be using fill(), so allocate
+	 * a large enough buffer. If it is provided, it must be at least
+	 * ZSTD_IOBUF_SIZE large.
+	 */
+	if (in_buf == NULL) {
+		in_allocated = malloc(ZSTD_IOBUF_SIZE);
+		if (in_allocated == NULL) {
+			error("Out of memory while allocating input buffer");
+			err = -1;
+			goto out;
+		}
+		in_buf = in_allocated;
+		in_len = 0;
+	}
+	/* Read the first chunk, since we need to decode the frame header */
+	if (fill != NULL)
+		in_len = fill(in_buf, ZSTD_IOBUF_SIZE);
+	if (in_len < 0) {
+		error("ZSTD-compressed data is truncated");
+		err = -1;
+		goto out;
+	}
+	/* Set the first non-empty input buffer */
+	in.src = in_buf;
+	in.pos = 0;
+	in.size = in_len;
+	/* Allocate the output buffer if we are using flush(). */
+	if (flush != NULL) {
+		out_allocated = malloc(ZSTD_IOBUF_SIZE);
+		if (out_allocated == NULL) {
+			error("Out of memory while allocating output buffer");
+			err = -1;
+			goto out;
+		}
+		out_buf = out_allocated;
+		out_len = ZSTD_IOBUF_SIZE;
+	}
+	/* Set the output buffer */
+	out.dst = out_buf;
+	out.pos = 0;
+	out.size = out_len;
+
+	/* We need to know the window size to allocate the ZSTD_DStream.
+	 * Since we are streaming, we need to allocate a buffer for the sliding
+	 * window. The window size varies from 1 KB to ZSTD_WINDOWSIZE_MAX
+	 * (8 MB), so it is important to use the actual value so as not to
+	 * waste memory when it is smaller.
+	 */
+	ret = ZSTD_getFrameParams(&params, in.src, in.size);
+	err = handle_zstd_error(ret, error);
+	if (err)
+		goto out;
+	if (ret != 0) {
+		error("ZSTD-compressed data has an incomplete frame header");
+		err = -1;
+		goto out;
+	}
+	if (params.windowSize > ZSTD_WINDOWSIZE_MAX) {
+		error("ZSTD-compressed data has too large a window size");
+		err = -1;
+		goto out;
+	}
+
+	/* Allocate the ZSTD_DStream now that we know how much memory is
+	 * required.
+	 */
+	wksp_size = ZSTD_DStreamWorkspaceBound(params.windowSize);
+	wksp = large_malloc(wksp_size);
+	dstream = ZSTD_initDStream(params.windowSize, wksp, wksp_size);
+	if (dstream == NULL) {
+		error("Out of memory while allocating ZSTD_DStream");
+		err = -1;
+		goto out;
+	}
+	/* Decompression loop:
+	 * Read more data if necessary (error if no more data can be read).
+	 * Call the decompression function, which returns 0 when finished.
+	 * Flush any data produced if using flush().
+	 */
+	if (in_pos != NULL)
+		*in_pos = 0;
+	do {
+		/* If we need to reload data, either we have fill() and can
+		 * try to get more data, or we don't and the input is truncated.
+		 */
+		if (in.pos == in.size) {
+			if (in_pos != NULL)
+				*in_pos += in.pos;
+			in_len = fill ? fill(in_buf, ZSTD_IOBUF_SIZE) : -1;
+			if (in_len < 0) {
+				error("ZSTD-compressed data is truncated");
+				err = -1;
+				goto out;
+			}
+			in.pos = 0;
+			in.size = in_len;
+		}
+		/* Returns zero when the frame is complete */
+		ret = ZSTD_decompressStream(dstream, &out, &in);
+		err = handle_zstd_error(ret, error);
+		if (err)
+			goto out;
+		/* Flush all of the data produced if using flush() */
+		if (flush != NULL && out.pos > 0) {
+			if (out.pos != flush(out.dst, out.pos)) {
+				error("Failed to flush()");
+				err = -1;
+				goto out;
+			}
+			out.pos = 0;
+		}
+	} while (ret != 0);
+
+	if (in_pos != NULL)
+		*in_pos += in.pos;
+
+	err = 0;
+out:
+	if (in_allocated != NULL)
+		free(in_allocated);
+	if (out_allocated != NULL)
+		free(out_allocated);
+	if (wksp != NULL)
+		large_free(wksp);
+	return err;
+}
+
+#ifndef PREBOOT
+STATIC int INIT unzstd(unsigned char *buf, long len,
+		       long (*fill)(void*, unsigned long),
+		       long (*flush)(void*, unsigned long),
+		       unsigned char *out_buf,
+		       long *pos,
+		       void (*error)(char *x))
+{
+	return __unzstd(buf, len, fill, flush, out_buf, 0, pos, error);
+}
+#else
+STATIC int INIT __decompress(unsigned char *buf, long len,
+			     long (*fill)(void*, unsigned long),
+			     long (*flush)(void*, unsigned long),
+			     unsigned char *out_buf, long out_len,
+			     long *pos,
+			     void (*error)(char *x))
+{
+	return __unzstd(buf, len, fill, flush, out_buf, out_len, pos, error);
+}
+#endif
diff -uNr linux-5.4/lib/Kconfig linux-5.4-zstd/lib/Kconfig
--- linux-5.4/lib/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/Kconfig	2019-12-15 15:07:02.042268956 -0800
@@ -311,9 +311,6 @@
 	select ZLIB_INFLATE
 	tristate
 
-config DECOMPRESS_BZIP2
-	tristate
-
 config DECOMPRESS_LZMA
 	tristate
 
@@ -329,6 +326,10 @@
 	select LZ4_DECOMPRESS
 	tristate
 
+config DECOMPRESS_ZSTD
+	select ZSTD_DECOMPRESS
+	tristate
+
 #
 # Generic allocator support is selected if needed
 #
diff -uNr linux-5.4/lib/Makefile linux-5.4-zstd/lib/Makefile
--- linux-5.4/lib/Makefile	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/Makefile	2019-12-15 15:07:02.065601816 -0800
@@ -152,11 +152,10 @@
 obj-$(CONFIG_RAID6_PQ) += raid6/
 
 lib-$(CONFIG_DECOMPRESS_GZIP) += decompress_inflate.o
-lib-$(CONFIG_DECOMPRESS_BZIP2) += decompress_bunzip2.o
-lib-$(CONFIG_DECOMPRESS_LZMA) += decompress_unlzma.o
 lib-$(CONFIG_DECOMPRESS_XZ) += decompress_unxz.o
 lib-$(CONFIG_DECOMPRESS_LZO) += decompress_unlzo.o
 lib-$(CONFIG_DECOMPRESS_LZ4) += decompress_unlz4.o
+lib-$(CONFIG_DECOMPRESS_ZSTD) += decompress_unzstd.o
 
 obj-$(CONFIG_TEXTSEARCH) += textsearch.o
 obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o
diff -uNr linux-5.4/lib/xxhash.c linux-5.4-zstd/lib/xxhash.c
--- linux-5.4/lib/xxhash.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/xxhash.c	2019-12-15 15:06:59.988977298 -0800
@@ -80,13 +80,11 @@
 {
 	memcpy(dst, src, sizeof(*dst));
 }
-EXPORT_SYMBOL(xxh32_copy_state);
 
 void xxh64_copy_state(struct xxh64_state *dst, const struct xxh64_state *src)
 {
 	memcpy(dst, src, sizeof(*dst));
 }
-EXPORT_SYMBOL(xxh64_copy_state);
 
 /*-***************************
  * Simple Hash Functions
@@ -151,7 +149,6 @@
 
 	return h32;
 }
-EXPORT_SYMBOL(xxh32);
 
 static uint64_t xxh64_round(uint64_t acc, const uint64_t input)
 {
@@ -234,7 +231,6 @@
 
 	return h64;
 }
-EXPORT_SYMBOL(xxh64);
 
 /*-**************************************************
  * Advanced Hash Functions
@@ -251,7 +247,6 @@
 	state.v4 = seed - PRIME32_1;
 	memcpy(statePtr, &state, sizeof(state));
 }
-EXPORT_SYMBOL(xxh32_reset);
 
 void xxh64_reset(struct xxh64_state *statePtr, const uint64_t seed)
 {
@@ -265,7 +260,6 @@
 	state.v4 = seed - PRIME64_1;
 	memcpy(statePtr, &state, sizeof(state));
 }
-EXPORT_SYMBOL(xxh64_reset);
 
 int xxh32_update(struct xxh32_state *state, const void *input, const size_t len)
 {
@@ -334,7 +328,6 @@
 
 	return 0;
 }
-EXPORT_SYMBOL(xxh32_update);
 
 uint32_t xxh32_digest(const struct xxh32_state *state)
 {
@@ -372,7 +365,6 @@
 
 	return h32;
 }
-EXPORT_SYMBOL(xxh32_digest);
 
 int xxh64_update(struct xxh64_state *state, const void *input, const size_t len)
 {
@@ -439,7 +431,6 @@
 
 	return 0;
 }
-EXPORT_SYMBOL(xxh64_update);
 
 uint64_t xxh64_digest(const struct xxh64_state *state)
 {
@@ -494,7 +485,19 @@
 
 	return h64;
 }
+
+#ifndef PREBOOT
+EXPORT_SYMBOL(xxh32_copy_state);
+EXPORT_SYMBOL(xxh64_copy_state);
+EXPORT_SYMBOL(xxh32);
+EXPORT_SYMBOL(xxh64);
+EXPORT_SYMBOL(xxh32_reset);
+EXPORT_SYMBOL(xxh64_reset);
+EXPORT_SYMBOL(xxh32_update);
+EXPORT_SYMBOL(xxh32_digest);
+EXPORT_SYMBOL(xxh64_update);
 EXPORT_SYMBOL(xxh64_digest);
 
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("xxHash");
+#endif
diff -uNr linux-5.4/lib/zstd/decompress.c linux-5.4-zstd/lib/zstd/decompress.c
--- linux-5.4/lib/zstd/decompress.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/zstd/decompress.c	2019-12-15 15:06:59.988977298 -0800
@@ -2490,6 +2490,7 @@
 	}
 }
 
+#ifndef PREBOOT
 EXPORT_SYMBOL(ZSTD_DCtxWorkspaceBound);
 EXPORT_SYMBOL(ZSTD_initDCtx);
 EXPORT_SYMBOL(ZSTD_decompressDCtx);
@@ -2529,3 +2530,4 @@
 
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("Zstd Decompressor");
+#endif
diff -uNr linux-5.4/lib/zstd/fse_decompress.c linux-5.4-zstd/lib/zstd/fse_decompress.c
--- linux-5.4/lib/zstd/fse_decompress.c	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/zstd/fse_decompress.c	2019-12-15 15:06:59.992310563 -0800
@@ -47,6 +47,7 @@
 ****************************************************************/
 #include "bitstream.h"
 #include "fse.h"
+#include "zstd_internal.h"
 #include <linux/compiler.h>
 #include <linux/kernel.h>
 #include <linux/string.h> /* memcpy, memset */
@@ -60,14 +61,6 @@
 		enum { FSE_static_assert = 1 / (int)(!!(c)) }; \
 	} /* use only *after* variable declarations */
 
-/* check and forward error code */
-#define CHECK_F(f)                  \
-	{                           \
-		size_t const e = f; \
-		if (FSE_isError(e)) \
-			return e;   \
-	}
-
 /* **************************************************************
 *  Templates
 ****************************************************************/
diff -uNr linux-5.4/lib/zstd/zstd_internal.h linux-5.4-zstd/lib/zstd/zstd_internal.h
--- linux-5.4/lib/zstd/zstd_internal.h	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/lib/zstd/zstd_internal.h	2019-12-15 15:06:59.992310563 -0800
@@ -127,7 +127,13 @@
 *  Shared functions to include for inlining
 *********************************************/
 ZSTD_STATIC void ZSTD_copy8(void *dst, const void *src) {
-	memcpy(dst, src, 8);
+	/* zstd relies heavily on gcc being able to analyze and inline this
+	 * memcpy() call, since it is called in a tight loop. Preboot mode
+	 * is compiled in freestanding mode, which stops gcc from analyzing
+	 * memcpy(). Use __builtin_memcpy() to tell gcc to analyze this as a
+	 * regular memcpy().
+	 */
+	__builtin_memcpy(dst, src, 8);
 }
 /*! ZSTD_wildcopy() :
 *   custom version of memcpy(), can copy up to 7 bytes too many (8 bytes if length==0) */
@@ -137,6 +143,7 @@
 	const BYTE* ip = (const BYTE*)src;
 	BYTE* op = (BYTE*)dst;
 	BYTE* const oend = op + length;
+#if GCC_VERSION >= 70000 && GCC_VERSION < 70200
 	/* Work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388.
 	 * Avoid the bad case where the loop only runs once by handling the
 	 * special case separately. This doesn't trigger the bug because it
@@ -144,6 +151,7 @@
 	 */
 	if (length <= 8)
 		return ZSTD_copy8(dst, src);
+#endif
 	do {
 		ZSTD_copy8(op, ip);
 		op += 8;
diff -uNr linux-5.4/scripts/Makefile.lib linux-5.4-zstd/scripts/Makefile.lib
--- linux-5.4/scripts/Makefile.lib	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/scripts/Makefile.lib	2019-12-15 15:07:02.065601816 -0800
@@ -315,10 +315,10 @@
 
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
 
-# Bzip2
+# Lzma
 # ---------------------------------------------------------------------------
 
-# Bzip2 and LZMA do not include size in file... so we have to fake that;
+# LZMA does not include size in file... so we have to fake that;
 # append the size as a 32-bit littleendian number as gzip does.
 size_append = printf $(shell						\
 dec_size=0;								\
@@ -397,6 +397,21 @@
 quiet_cmd_xzmisc = XZMISC  $@
       cmd_xzmisc = cat $(real-prereqs) | xz --check=crc32 --lzma2=dict=1MiB > $@
 
+# ZSTD
+# ---------------------------------------------------------------------------
+# Appends the uncompressed size of the data using size_append. The .zst
+# format has the size information available at the beginning of the file too,
+# but it's in a more complex format and it's good to avoid changing the part
+# of the boot code that reads the uncompressed size.
+# Note that the bytes added by size_append will make the zstd tool think that
+# the file is corrupt. This is expected.
+
+quiet_cmd_zstd = ZSTD    $@
+cmd_zstd = (cat $(filter-out FORCE,$^) | \
+	zstd -19 && \
+        $(call size_append, $(filter-out FORCE,$^))) > $@ || \
+	(rm -f $@ ; false)
+
 # ASM offsets
 # ---------------------------------------------------------------------------
 
diff -uNr linux-5.4/usr/Kconfig linux-5.4-zstd/usr/Kconfig
--- linux-5.4/usr/Kconfig	2019-11-24 16:32:01.000000000 -0800
+++ linux-5.4-zstd/usr/Kconfig	2019-12-15 15:07:02.112267535 -0800
@@ -61,24 +61,6 @@
 	  Support loading of a gzip encoded initial ramdisk or cpio buffer.
 	  If unsure, say Y.
 
-config RD_BZIP2
-	bool "Support initial ramdisk/ramfs compressed using bzip2"
-	default y
-	depends on BLK_DEV_INITRD
-	select DECOMPRESS_BZIP2
-	help
-	  Support loading of a bzip2 encoded initial ramdisk or cpio buffer
-	  If unsure, say N.
-
-config RD_LZMA
-	bool "Support initial ramdisk/ramfs compressed using LZMA"
-	default y
-	depends on BLK_DEV_INITRD
-	select DECOMPRESS_LZMA
-	help
-	  Support loading of a LZMA encoded initial ramdisk or cpio buffer
-	  If unsure, say N.
-
 config RD_XZ
 	bool "Support initial ramdisk/ramfs compressed using XZ"
 	depends on BLK_DEV_INITRD
@@ -106,6 +88,15 @@
 	  Support loading of a LZ4 encoded initial ramdisk or cpio buffer
 	  If unsure, say N.
 
+config RD_ZSTD
+	bool "Support initial ramdisk/ramfs compressed using ZSTD"
+	default y
+	depends on BLK_DEV_INITRD
+	select DECOMPRESS_ZSTD
+	help
+	  Support loading of a ZSTD encoded initial ramdisk or cpio buffer.
+	  If unsure, say N.
+
 choice
 	prompt "Built-in initramfs compression mode"
 	depends on INITRAMFS_SOURCE!=""
@@ -118,8 +109,8 @@
 	  when building a kernel.  Decompression speed is relevant at
 	  each boot. Also the memory usage during decompression may become
 	  relevant on memory constrained systems. This is usually based on the
-	  dictionary size of the algorithm with algorithms like XZ and LZMA
-	  featuring large dictionary sizes.
+	  dictionary size of the algorithm with algorithms like XZ featuring
+	  large dictionary sizes.
 
 	  High compression options are mostly useful for users who are
 	  low on RAM, since it reduces the memory consumption during
@@ -140,43 +131,15 @@
 	  on those architectures that support this. However, not compressing the
 	  initramfs may lead to slightly higher memory consumption during a
 	  short time at boot, while both the cpio image and the unpacked
-	  filesystem image will be present in memory simultaneously
+	  filesystem image will be present in memory simultaneously.
 
 config INITRAMFS_COMPRESSION_GZIP
 	bool "Gzip"
 	depends on RD_GZIP
 	help
-	  Use the old and well tested gzip compression algorithm. Gzip provides
-	  a good balance between compression ratio and decompression speed and
-	  has a reasonable compression speed. It is also more likely to be
-	  supported by your build system as the gzip tool is present by default
-	  on most distros.
-
-config INITRAMFS_COMPRESSION_BZIP2
-	bool "Bzip2"
-	depends on RD_BZIP2
-	help
-	  It's compression ratio and speed is intermediate. Decompression speed
-	  is slowest among the choices. The initramfs size is about 10% smaller
-	  with bzip2, in comparison to gzip. Bzip2 uses a large amount of
-	  memory. For modern kernels you will need at least 8MB RAM or more for
-	  booting.
-
-	  If you choose this, keep in mind that you need to have the bzip2 tool
-	  available to be able to compress the initram.
-
-config INITRAMFS_COMPRESSION_LZMA
-	bool "LZMA"
-	depends on RD_LZMA
-	help
-	  This algorithm's compression ratio is best but has a large dictionary
-	  size which might cause issues in memory constrained systems.
-	  Decompression speed is between the other choices. Compression is
-	  slowest. The initramfs size is about 33% smaller with LZMA in
-	  comparison to gzip.
-
-	  If you choose this, keep in mind that you may need to install the xz
-	  or lzma tools to be able to compress the initram.
+	  Use the old and well tested gzip compression algorithm. Gzip doesn't
+	  provide very good compression nor speed, but it's the safest choice,
+	  with wide support.
 
 config INITRAMFS_COMPRESSION_XZ
 	bool "XZ"
@@ -185,20 +148,20 @@
 	  XZ uses the LZMA2 algorithm and has a large dictionary which may cause
 	  problems on memory constrained systems. The initramfs size is about
 	  30% smaller with XZ in comparison to gzip. Decompression speed is
-	  better than that of bzip2 but worse than gzip and LZO. Compression is
-	  slow.
+	  okayish but still slowest of all currently available algorithms.
+	  Compression is slow.
 
-	  If you choose this, keep in mind that you may need to install the xz
-	  tool to be able to compress the initram.
+	  Any modern distro provides xz in its default install, but on
+	  minimal build systems you might need to install xz-utils to be
+	  able to compress the initram.
 
 config INITRAMFS_COMPRESSION_LZO
 	bool "LZO"
 	depends on RD_LZO
 	help
 	  It's compression ratio is the second poorest amongst the choices. The
-	  kernel size is about 10% bigger than gzip. Despite that, it's
-	  decompression speed is the second fastest and it's compression speed
-	  is quite fast too.
+	  kernel size is about 10% bigger than gzip. Pick ZSTD instead, or LZ4
+	  if speed is paramount.
 
 	  If you choose this, keep in mind that you may need to install the lzop
 	  tool to be able to compress the initram.
@@ -214,6 +177,17 @@
 	  If you choose this, keep in mind that most distros don't provide lz4
 	  by default which could cause a build failure.
 
+config INITRAMFS_COMPRESSION_ZSTD
+	bool "ZSTD"
+	depends on RD_ZSTD
+	help
+	  ZSTD is a compression algorithm targeting intermediate compression
+	  with fast decompression speed. It will compress better than GZIP and
+	  decompress around the same speed as LZO, but slower than LZ4.
+
+	  If you choose this, keep in mind that you may need to install the zstd
+	  tool to be able to compress the initram.
+
 endchoice
 
 config INITRAMFS_COMPRESSION
@@ -221,15 +195,13 @@
 	string
 	default ""      if INITRAMFS_COMPRESSION_NONE
 	default ".gz"   if INITRAMFS_COMPRESSION_GZIP
-	default ".bz2"  if INITRAMFS_COMPRESSION_BZIP2
-	default ".lzma" if INITRAMFS_COMPRESSION_LZMA
 	default ".xz"   if INITRAMFS_COMPRESSION_XZ
 	default ".lzo"  if INITRAMFS_COMPRESSION_LZO
 	default ".lz4"  if INITRAMFS_COMPRESSION_LZ4
+	default ".zst"  if INITRAMFS_COMPRESSION_ZSTD
 	default ".gz"   if RD_GZIP
 	default ".lz4"  if RD_LZ4
 	default ".lzo"  if RD_LZO
 	default ".xz"   if RD_XZ
-	default ".lzma" if RD_LZMA
-	default ".bz2"  if RD_BZIP2
+	default ".zst"  if RD_ZSTD
 	default ""