Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 08970fc4 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86: msr: fix bogus return values from rdmsr_safe/wrmsr_safe 



Impact: bogus error codes (+other?) on x86-64

The rdmsr_safe/wrmsr_safe routines have macros for the handling of the
edx:eax arguments.  Those macros take a variable number of assembly
arguments.  This is rather inherently incompatible with using
%digit-style escapes in the inline assembly; replace those with
%[name]-style escapes.

This fixes miscompilation on x86-64, which at the very least caused
bogus return values.  It is possible that this could also corrupt the
return value; I am not sure.

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 9ea2b82e

include/asm-x86/msr.h

+8 −8
Original line number Diff line number Diff line
@@ -52,14 +52,14 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr, 
{

	DECLARE_ARGS(val, low, high);



	asm volatile("2: rdmsr ; xor %0,%0\n"

	asm volatile("2: rdmsr ; xor %[err],%[err]\n"

		     "1:\n\t"

		     ".section .fixup,\"ax\"\n\t"

		     "3:  mov %3,%0 ; jmp 1b\n\t"

		     "3:  mov %[fault],%[err] ; jmp 1b\n\t"

		     ".previous\n\t"

		     _ASM_EXTABLE(2b, 3b)

		     : "=r" (*err), EAX_EDX_RET(val, low, high)

		     : "c" (msr), "i" (-EFAULT));

		     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)

		     : "c" (msr), [fault] "i" (-EFAULT));

	return EAX_EDX_VAL(val, low, high);

}
@@ -73,15 +73,15 @@ static inline int native_write_msr_safe(unsigned int msr, 
					unsigned low, unsigned high)

{

	int err;

	asm volatile("2: wrmsr ; xor %0,%0\n"

	asm volatile("2: wrmsr ; xor %[err],%[err]\n"

		     "1:\n\t"

		     ".section .fixup,\"ax\"\n\t"

		     "3:  mov %4,%0 ; jmp 1b\n\t"

		     "3:  mov %[fault],%[err] ; jmp 1b\n\t"

		     ".previous\n\t"

		     _ASM_EXTABLE(2b, 3b)

		     : "=a" (err)

		     : [err] "=a" (err)

		     : "c" (msr), "0" (low), "d" (high),

		       "i" (-EFAULT)

		       [fault] "i" (-EFAULT)

		     : "memory");

	return err;

}