linux-kernel - [PATCH AUTOSEL 5.8 019/101] x86/mce: Annotate mce

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Date:   Sun, 18 Oct 2020 15:19:04 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Borislav Petkov <bp@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.8 019/101] x86/mce: Annotate mce_rd/wrmsrl() with noinstr

From: Borislav Petkov <bp@...e.de>

[ Upstream commit e100777016fdf6ec3a9d7c1773b15a2b5eca6c55 ]

They do get called from the #MC handler which is already marked
"noinstr".

Commit

  e2def7d49d08 ("x86/mce: Make mce_rdmsrl() panic on an inaccessible MSR")

already got rid of the instrumentation in the MSR accessors, fix the
annotation now too, in order to get rid of:

  vmlinux.o: warning: objtool: do_machine_check()+0x4a: call to mce_rdmsrl() leaves .noinstr.text section

Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20200915194020.28807-1-bp@alien8.de
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/cpu/mce/core.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 14e4b4d17ee5b..d8dca24feccbe 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -371,16 +371,25 @@ static int msr_to_offset(u32 msr)
 }
 
 /* MSR access wrappers used for error injection */
-static u64 mce_rdmsrl(u32 msr)
+static noinstr u64 mce_rdmsrl(u32 msr)
 {
 	u64 v;
 
 	if (__this_cpu_read(injectm.finished)) {
-		int offset = msr_to_offset(msr);
+		int offset;
+		u64 ret;
 
+		instrumentation_begin();
+
+		offset = msr_to_offset(msr);
 		if (offset < 0)
-			return 0;
-		return *(u64 *)((char *)this_cpu_ptr(&injectm) + offset);
+			ret = 0;
+		else
+			ret = *(u64 *)((char *)this_cpu_ptr(&injectm) + offset);
+
+		instrumentation_end();
+
+		return ret;
 	}
 
 	if (rdmsrl_safe(msr, &v)) {
@@ -396,13 +405,19 @@ static u64 mce_rdmsrl(u32 msr)
 	return v;
 }
 
-static void mce_wrmsrl(u32 msr, u64 v)
+static noinstr void mce_wrmsrl(u32 msr, u64 v)
 {
 	if (__this_cpu_read(injectm.finished)) {
-		int offset = msr_to_offset(msr);
+		int offset;
 
+		instrumentation_begin();
+
+		offset = msr_to_offset(msr);
 		if (offset >= 0)
 			*(u64 *)((char *)this_cpu_ptr(&injectm) + offset) = v;
+
+		instrumentation_end();
+
 		return;
 	}
 	wrmsrl(msr, v);
-- 
2.25.1