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

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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: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2008-08-25 22:39:15 -07:00
parent 9ea2b82ed6
commit 08970fc4e0
1 changed files with 8 additions and 8 deletions
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16
include/asm-x86/msr.h
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@ -52,14 +52,14 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
{ {
DECLARE_ARGS(val, low, high); DECLARE_ARGS(val, low, high);
asm volatile("2: rdmsr ; xor %0,%0\n" asm volatile("2: rdmsr ; xor %[err],%[err]\n"
"1:\n\t" "1:\n\t"
".section .fixup,\"ax\"\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" ".previous\n\t"
_ASM_EXTABLE(2b, 3b) _ASM_EXTABLE(2b, 3b)
: "=r" (*err), EAX_EDX_RET(val, low, high) : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
: "c" (msr), "i" (-EFAULT)); : "c" (msr), [fault] "i" (-EFAULT));
return EAX_EDX_VAL(val, low, high); 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) unsigned low, unsigned high)
{ {
int err; int err;
asm volatile("2: wrmsr ; xor %0,%0\n" asm volatile("2: wrmsr ; xor %[err],%[err]\n"
"1:\n\t" "1:\n\t"
".section .fixup,\"ax\"\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" ".previous\n\t"
_ASM_EXTABLE(2b, 3b) _ASM_EXTABLE(2b, 3b)
: "=a" (err) : [err] "=a" (err)
: "c" (msr), "0" (low), "d" (high), : "c" (msr), "0" (low), "d" (high),
"i" (-EFAULT) [fault] "i" (-EFAULT)
: "memory"); : "memory");
return err; return err;
} }