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

1 files changed, 21 insertions, 6 deletions

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 5b1d5f33d60b..11b6697be010 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;
 	}