linux-kernel - [PATCH] x86/mce: Annotate mce

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Message-Id: <20200915194020.28807-1-bp@alien8.de>
Date:   Tue, 15 Sep 2020 21:40:20 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tony Luck <tony.luck@...el.com>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/mce: Annotate mce_rd/wrmsrl() with noinstr

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

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>
---
 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 a697baee9aa0..1ed14f67d13f 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -392,16 +392,25 @@ __visible bool ex_handler_rdmsr_fault(const struct exception_table_entry *fixup,
 }
 
 /* MSR access wrappers used for error injection */
-static u64 mce_rdmsrl(u32 msr)
+static noinstr u64 mce_rdmsrl(u32 msr)
 {
 	DECLARE_ARGS(val, low, high);
 
 	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;
 	}
 
 	/*
@@ -437,15 +446,21 @@ __visible bool ex_handler_wrmsr_fault(const struct exception_table_entry *fixup,
 	return true;
 }
 
-static void mce_wrmsrl(u32 msr, u64 v)
+static noinstr void mce_wrmsrl(u32 msr, u64 v)
 {
 	u32 low, high;
 
 	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;
 	}
 
-- 
2.21.0