linux-kernel - [PATCH v2 1/9] x86/asm: Mark all top level asm statements as .text

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Date:   Fri, 29 Mar 2019 17:47:35 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v2 1/9] x86/asm: Mark all top level asm statements as .text

From: Andi Kleen <ak@...ux.intel.com>

With gcc toplevel assembler statements that do not mark themselves
as .text may end up in other sections. I had LTO boot crashes because
various assembler statements ended up in the middle of the initcall
section. It's also a latent problem without LTO, although it's
currently not known to cause any real problems.

According to the gcc team it's expected behavior.

Always mark all the top level assembler statements as text
so that they switch to the right section.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/kernel/cpu/amd.c      | 3 ++-
 arch/x86/kernel/kprobes/core.c | 1 +
 arch/x86/lib/error-inject.c    | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 01004bfb1a1b..1bcb489e07e7 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -83,7 +83,8 @@ static inline int wrmsrl_amd_safe(unsigned msr, unsigned long long val)
  */
 
 extern __visible void vide(void);
-__asm__(".globl vide\n"
+__asm__(".text\n"
+	".globl vide\n"
 	".type vide, @function\n"
 	".align 4\n"
 	"vide: ret\n");
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index a034cb808e7e..31ab91c9c4e9 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -715,6 +715,7 @@ NOKPROBE_SYMBOL(kprobe_int3_handler);
  * calls trampoline_handler() runs, which calls the kretprobe's handler.
  */
 asm(
+	".text\n"
 	".global kretprobe_trampoline\n"
 	".type kretprobe_trampoline, @function\n"
 	"kretprobe_trampoline:\n"
diff --git a/arch/x86/lib/error-inject.c b/arch/x86/lib/error-inject.c
index 3cdf06128d13..be5b5fb1598b 100644
--- a/arch/x86/lib/error-inject.c
+++ b/arch/x86/lib/error-inject.c
@@ -6,6 +6,7 @@
 asmlinkage void just_return_func(void);
 
 asm(
+	".text\n"
 	".type just_return_func, @function\n"
 	".globl just_return_func\n"
 	"just_return_func:\n"
-- 
2.20.1