percpu: Omit segment prefix in the UP case for cmpxchg_double
Omit the segment prefix in the UP case. GS is not used then
and we will generate segfaults if cmpxchg16b is used otherwise.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index a09e1f0..d475b43 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -45,7 +45,7 @@
#include <linux/stringify.h>
#ifdef CONFIG_SMP
-#define __percpu_arg(x) "%%"__stringify(__percpu_seg)":%P" #x
+#define __percpu_prefix "%%"__stringify(__percpu_seg)":"
#define __my_cpu_offset percpu_read(this_cpu_off)
/*
@@ -62,9 +62,11 @@
(typeof(*(ptr)) __kernel __force *)tcp_ptr__; \
})
#else
-#define __percpu_arg(x) "%P" #x
+#define __percpu_prefix ""
#endif
+#define __percpu_arg(x) __percpu_prefix "%P" #x
+
/*
* Initialized pointers to per-cpu variables needed for the boot
* processor need to use these macros to get the proper address
@@ -516,11 +518,11 @@
typeof(o2) __n2 = n2; \
typeof(o2) __dummy; \
alternative_io("call this_cpu_cmpxchg16b_emu\n\t" P6_NOP4, \
- "cmpxchg16b %%gs:(%%rsi)\n\tsetz %0\n\t", \
+ "cmpxchg16b " __percpu_prefix "(%%rsi)\n\tsetz %0\n\t", \
X86_FEATURE_CX16, \
ASM_OUTPUT2("=a"(__ret), "=d"(__dummy)), \
"S" (&pcp1), "b"(__n1), "c"(__n2), \
- "a"(__o1), "d"(__o2)); \
+ "a"(__o1), "d"(__o2) : "memory"); \
__ret; \
})
diff --git a/arch/x86/lib/cmpxchg16b_emu.S b/arch/x86/lib/cmpxchg16b_emu.S
index 3e8b08a..1e572c5 100644
--- a/arch/x86/lib/cmpxchg16b_emu.S
+++ b/arch/x86/lib/cmpxchg16b_emu.S
@@ -10,6 +10,12 @@
#include <asm/frame.h>
#include <asm/dwarf2.h>
+#ifdef CONFIG_SMP
+#define SEG_PREFIX %gs:
+#else
+#define SEG_PREFIX
+#endif
+
.text
/*
@@ -37,13 +43,13 @@
pushf
cli
- cmpq %gs:(%rsi), %rax
+ cmpq SEG_PREFIX(%rsi), %rax
jne not_same
- cmpq %gs:8(%rsi), %rdx
+ cmpq SEG_PREFIX 8(%rsi), %rdx
jne not_same
- movq %rbx, %gs:(%rsi)
- movq %rcx, %gs:8(%rsi)
+ movq %rbx, SEG_PREFIX(%rsi)
+ movq %rcx, SEG_PREFIX 8(%rsi)
popf
mov $1, %al