Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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: H. Peter Anvin <hpa@zytor.com>
+8
-8
include/asm-x86/msr.h
+8
-8
include/asm-x86/msr.h
···
52
{
53
DECLARE_ARGS(val, low, high);
54
55
-
asm volatile("2: rdmsr ; xor %0,%0\n"
56
"1:\n\t"
57
".section .fixup,\"ax\"\n\t"
58
-
"3: mov %3,%0 ; jmp 1b\n\t"
59
".previous\n\t"
60
_ASM_EXTABLE(2b, 3b)
61
-
: "=r" (*err), EAX_EDX_RET(val, low, high)
62
-
: "c" (msr), "i" (-EFAULT));
63
return EAX_EDX_VAL(val, low, high);
64
}
65
···
73
unsigned low, unsigned high)
74
{
75
int err;
76
-
asm volatile("2: wrmsr ; xor %0,%0\n"
77
"1:\n\t"
78
".section .fixup,\"ax\"\n\t"
79
-
"3: mov %4,%0 ; jmp 1b\n\t"
80
".previous\n\t"
81
_ASM_EXTABLE(2b, 3b)
82
-
: "=a" (err)
83
: "c" (msr), "0" (low), "d" (high),
84
-
"i" (-EFAULT)
85
: "memory");
86
return err;
87
}
···
52
{
53
DECLARE_ARGS(val, low, high);
54
55
+
asm volatile("2: rdmsr ; xor %[err],%[err]\n"
56
"1:\n\t"
57
".section .fixup,\"ax\"\n\t"
58
+
"3: mov %[fault],%[err] ; jmp 1b\n\t"
59
".previous\n\t"
60
_ASM_EXTABLE(2b, 3b)
61
+
: [err] "=r" (*err), EAX_EDX_RET(val, low, high)
62
+
: "c" (msr), [fault] "i" (-EFAULT));
63
return EAX_EDX_VAL(val, low, high);
64
}
65
···
73
unsigned low, unsigned high)
74
{
75
int err;
76
+
asm volatile("2: wrmsr ; xor %[err],%[err]\n"
77
"1:\n\t"
78
".section .fixup,\"ax\"\n\t"
79
+
"3: mov %[fault],%[err] ; jmp 1b\n\t"
80
".previous\n\t"
81
_ASM_EXTABLE(2b, 3b)
82
+
: [err] "=a" (err)
83
: "c" (msr), "0" (low), "d" (high),
84
+
[fault] "i" (-EFAULT)
85
: "memory");
86
return err;
87
}