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>

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>
H. Peter Anvin
1 parent 9ea2b82ed6
Showing 1 changed file with 8 additions and 8 deletions Side-by-side Diff
include/asm-x86/msr.h
@@ -52,14 +52,14 @@
 {
 	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 @@
 					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;
 }
...	...	@@ -52,14 +52,14 @@
52	52	{
53	53	DECLARE_ARGS(val, low, high);
54	54
55		- asm volatile("2: rdmsr ; xor %0,%0\n"
	55	+ asm volatile("2: rdmsr ; xor %[err],%[err]\n"
56	56	"1:\n\t"
57	57	".section .fixup,\"ax\"\n\t"
58		- "3: mov %3,%0 ; jmp 1b\n\t"
	58	+ "3: mov %[fault],%[err] ; jmp 1b\n\t"
59	59	".previous\n\t"
60	60	_ASM_EXTABLE(2b, 3b)
61		- : "=r" (*err), EAX_EDX_RET(val, low, high)
62		- : "c" (msr), "i" (-EFAULT));
	61	+ : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
	62	+ : "c" (msr), [fault] "i" (-EFAULT));
63	63	return EAX_EDX_VAL(val, low, high);
64	64	}
65	65
66	66
67	67
68	68
...	...	@@ -73,15 +73,15 @@
73	73	unsigned low, unsigned high)
74	74	{
75	75	int err;
76		- asm volatile("2: wrmsr ; xor %0,%0\n"
	76	+ asm volatile("2: wrmsr ; xor %[err],%[err]\n"
77	77	"1:\n\t"
78	78	".section .fixup,\"ax\"\n\t"
79		- "3: mov %4,%0 ; jmp 1b\n\t"
	79	+ "3: mov %[fault],%[err] ; jmp 1b\n\t"
80	80	".previous\n\t"
81	81	_ASM_EXTABLE(2b, 3b)
82		- : "=a" (err)
	82	+ : [err] "=a" (err)
83	83	: "c" (msr), "0" (low), "d" (high),
84		- "i" (-EFAULT)
	84	+ [fault] "i" (-EFAULT)
85	85	: "memory");
86	86	return err;
87	87	}