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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@kernel.org>
Date: Fri, 3 Jun 2022 08:04:44 -0700
Subject: [PATCH] x86/ftrace: Remove OBJECT_FILES_NON_STANDARD usage
[ Upstream commit 7b6c7a877cc616bc7dc9cd39646fe454acbed48b ]
The file-wide OBJECT_FILES_NON_STANDARD annotation is used with
CONFIG_FRAME_POINTER to tell objtool to skip the entire file when frame
pointers are enabled. However that annotation is now deprecated because
it doesn't work with IBT, where objtool runs on vmlinux.o instead of
individual translation units.
Instead, use more fine-grained function-specific annotations:
- The 'save_mcount_regs' macro does funny things with the frame pointer.
Use STACK_FRAME_NON_STANDARD_FP to tell objtool to ignore the
functions using it.
- The return_to_handler() "function" isn't actually a callable function.
Instead of being called, it's returned to. The real return address
isn't on the stack, so unwinding is already doomed no matter which
unwinder is used. So just remove the STT_FUNC annotation, telling
objtool to ignore it. That also removes the implicit
ANNOTATE_NOENDBR, which now needs to be made explicit.
Fixes the following warning:
vmlinux.o: warning: objtool: __fentry__+0x16: return with modified stack frame
Fixes: ed53a0d97192 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/b7a7a42fe306aca37826043dac89e113a1acdbac.1654268610.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/Makefile | 4 ----
arch/x86/kernel/ftrace_64.S | 11 ++++++++---
include/linux/objtool.h | 6 ++++++
tools/include/linux/objtool.h | 6 ++++++
4 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index c41ef42adbe8a3b13d10442b3d3b590b1ac40836..25828e4c62375007b3efd2fa392604b8c85636a4 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -36,10 +36,6 @@ KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD_test_nx.o := y
-ifdef CONFIG_FRAME_POINTER
-OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o := y
-endif
-
# If instrumentation of this dir is enabled, boot hangs during first second.
# Probably could be more selective here, but note that files related to irqs,
# boot, dumpstack/stacktrace, etc are either non-interesting or can lead to
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 4ec13608d3c62bd8acae0d897b264cde3eb41e14..dfeb227de5617c6d55ad6ace1f321b7ac87b6a70 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -175,6 +175,7 @@ SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL)
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_caller);
+STACK_FRAME_NON_STANDARD_FP(ftrace_caller)
SYM_FUNC_START(ftrace_epilogue)
/*
@@ -282,6 +283,7 @@ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_regs_caller)
+STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller)
#else /* ! CONFIG_DYNAMIC_FTRACE */
@@ -311,10 +313,14 @@ trace:
jmp ftrace_stub
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)
+STACK_FRAME_NON_STANDARD_FP(__fentry__)
+
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-SYM_FUNC_START(return_to_handler)
+SYM_CODE_START(return_to_handler)
+ UNWIND_HINT_EMPTY
+ ANNOTATE_NOENDBR
subq $16, %rsp
/* Save the return values */
@@ -339,7 +345,6 @@ SYM_FUNC_START(return_to_handler)
int3
.Ldo_rop:
mov %rdi, (%rsp)
- UNWIND_HINT_FUNC
RET
-SYM_FUNC_END(return_to_handler)
+SYM_CODE_END(return_to_handler)
#endif
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 586d35720f135f62b9d7434beccacb2e22a5bd2d..c81ea2264ad8a74b765f5649f81ee1198d7704dd 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -141,6 +141,12 @@ struct unwind_hint {
.popsection
.endm
+.macro STACK_FRAME_NON_STANDARD_FP func:req
+#ifdef CONFIG_FRAME_POINTER
+ STACK_FRAME_NON_STANDARD \func
+#endif
+.endm
+
.macro ANNOTATE_NOENDBR
.Lhere_\@:
.pushsection .discard.noendbr
diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
index 586d35720f135f62b9d7434beccacb2e22a5bd2d..c81ea2264ad8a74b765f5649f81ee1198d7704dd 100644
--- a/tools/include/linux/objtool.h
+++ b/tools/include/linux/objtool.h
@@ -141,6 +141,12 @@ struct unwind_hint {
.popsection
.endm
+.macro STACK_FRAME_NON_STANDARD_FP func:req
+#ifdef CONFIG_FRAME_POINTER
+ STACK_FRAME_NON_STANDARD \func
+#endif
+.endm
+
.macro ANNOTATE_NOENDBR
.Lhere_\@:
.pushsection .discard.noendbr
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