[PATCH] x86/mce: Annotate mce_rd/wrmsrl() with noinstr

[PATCH] x86/mce: Annotate mce_rd/wrmsrl() with noinstr

[Borislav Petkov]

From: Borislav Petkov <bp@suse.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@suse.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

[tip: ras/core] x86/mce: Annotate mce_rd/wrmsrl() with noinstr

[tip-bot2 for Borislav Petkov]

The following commit has been merged into the ras/core branch of tip:

Commit-ID:     e100777016fdf6ec3a9d7c1773b15a2b5eca6c55
Gitweb:        https://git.kernel.org/tip/e100777016fdf6ec3a9d7c1773b15a2b5eca6c55
Author:        Borislav Petkov <bp@suse.de>
AuthorDate:    Mon, 14 Sep 2020 19:21:28 +02:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 18 Sep 2020 15:21:11 +02:00

x86/mce: Annotate mce_rd/wrmsrl() with noinstr

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@suse.de>
Link: https://lkml.kernel.org/r/20200915194020.28807-1-bp@alien8.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 5b1d5f3..11b6697 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;
 	}