diff options
Diffstat (limited to '0004-x86-xen-init-gs-very-early-to-avoid-page-faults-with.patch')
| -rw-r--r-- | 0004-x86-xen-init-gs-very-early-to-avoid-page-faults-with.patch | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/0004-x86-xen-init-gs-very-early-to-avoid-page-faults-with.patch b/0004-x86-xen-init-gs-very-early-to-avoid-page-faults-with.patch new file mode 100644 index 000000000000..688462359503 --- /dev/null +++ b/0004-x86-xen-init-gs-very-early-to-avoid-page-faults-with.patch @@ -0,0 +1,80 @@ +From 782e9c805d19610d5821d1f75a3854ac587e2dac Mon Sep 17 00:00:00 2001 +Message-Id: <782e9c805d19610d5821d1f75a3854ac587e2dac.1518653356.git.jan.steffens@gmail.com> +In-Reply-To: <44c5097b2711429f0d49d138681f67157982e729.1518653356.git.jan.steffens@gmail.com> +References: <44c5097b2711429f0d49d138681f67157982e729.1518653356.git.jan.steffens@gmail.com> +From: Juergen Gross <jgross@suse.com> +Date: Thu, 1 Feb 2018 13:40:19 +0100 +Subject: [PATCH 4/4] x86/xen: init %gs very early to avoid page faults with + stack protector + +When running as Xen pv guest %gs is initialized some time after +C code is started. Depending on stack protector usage this might be +too late, resulting in page faults. + +So setup %gs and MSR_GS_BASE in assembly code already. + +Cc: stable@vger.kernel.org +Signed-off-by: Juergen Gross <jgross@suse.com> +Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> +Tested-by: Chris Patterson <cjp256@gmail.com> +Signed-off-by: Juergen Gross <jgross@suse.com> +--- + arch/x86/xen/xen-head.S | 16 ++++++++++++++++ + 1 file changed, 16 insertions(+) + +diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S +index 497cc55a0c16..96f26e026783 100644 +--- a/arch/x86/xen/xen-head.S ++++ b/arch/x86/xen/xen-head.S +@@ -9,32 +9,48 @@ + + #include <asm/boot.h> + #include <asm/asm.h> ++#include <asm/msr.h> + #include <asm/page_types.h> ++#include <asm/percpu.h> + #include <asm/unwind_hints.h> + + #include <xen/interface/elfnote.h> + #include <xen/interface/features.h> + #include <xen/interface/xen.h> + #include <xen/interface/xen-mca.h> + #include <asm/xen/interface.h> + + #ifdef CONFIG_XEN_PV + __INIT + ENTRY(startup_xen) + UNWIND_HINT_EMPTY + cld + + /* Clear .bss */ + xor %eax,%eax + mov $__bss_start, %_ASM_DI + mov $__bss_stop, %_ASM_CX + sub %_ASM_DI, %_ASM_CX + shr $__ASM_SEL(2, 3), %_ASM_CX + rep __ASM_SIZE(stos) + + mov %_ASM_SI, xen_start_info + mov $init_thread_union+THREAD_SIZE, %_ASM_SP + ++#ifdef CONFIG_X86_64 ++ /* Set up %gs. ++ * ++ * The base of %gs always points to the bottom of the irqstack ++ * union. If the stack protector canary is enabled, it is ++ * located at %gs:40. Note that, on SMP, the boot cpu uses ++ * init data section till per cpu areas are set up. ++ */ ++ movl $MSR_GS_BASE,%ecx ++ movq $INIT_PER_CPU_VAR(irq_stack_union),%rax ++ cdq ++ wrmsr ++#endif ++ + jmp xen_start_kernel + END(startup_xen) + __FINIT +-- +2.16.1 + |