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