Skip to content

Commit

Permalink
x86: Generate cmpxchg build failures
Browse files Browse the repository at this point in the history 
Rework the x86 cmpxchg() implementation to generate build failures
when used on improper types.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1254771187.21044.22.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
  • Loading branch information
Peter Zijlstra authored and Ingo Molnar committed Oct 9, 2009
1 parent 63312b6 commit f3834b9
Show file tree
Hide file tree
Showing 2 changed files with 177 additions and 275 deletions.
218 changes: 86 additions & 132 deletions arch/x86/include/asm/cmpxchg_32.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,14 +8,50 @@
* you need to test for the feature in boot_cpu_data.
*/

#define xchg(ptr, v) \
((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), sizeof(*(ptr))))
extern void __xchg_wrong_size(void);

/*
* Note: no "lock" prefix even on SMP: xchg always implies lock anyway
* Note 2: xchg has side effect, so that attribute volatile is necessary,
* but generally the primitive is invalid, *ptr is output argument. --ANK
*/

struct __xchg_dummy {
unsigned long a[100];
};
#define __xg(x) ((struct __xchg_dummy *)(x))

#define __xchg(x, ptr, size) \
({ \
__typeof(*(ptr)) __x = (x); \
switch (size) { \
case 1: \
asm volatile("xchgb %b0,%1" \
: "=q" (__x) \
: "m" (*__xg(ptr)), "0" (__x) \
: "memory"); \
break; \
case 2: \
asm volatile("xchgw %w0,%1" \
: "=r" (__x) \
: "m" (*__xg(ptr)), "0" (__x) \
: "memory"); \
break; \
case 4: \
asm volatile("xchgl %0,%1" \
: "=r" (__x) \
: "m" (*__xg(ptr)), "0" (__x) \
: "memory"); \
break; \
default: \
__xchg_wrong_size(); \
} \
__x; \
})

#define xchg(ptr, v) \
__xchg((v), (ptr), sizeof(*ptr))

/*
* The semantics of XCHGCMP8B are a bit strange, this is why
* there is a loop and the loading of %%eax and %%edx has to
Expand Down Expand Up @@ -71,57 +107,63 @@ static inline void __set_64bit_var(unsigned long long *ptr,
(unsigned int)((value) >> 32)) \
: __set_64bit(ptr, ll_low((value)), ll_high((value))))

/*
* Note: no "lock" prefix even on SMP: xchg always implies lock anyway
* Note 2: xchg has side effect, so that attribute volatile is necessary,
* but generally the primitive is invalid, *ptr is output argument. --ANK
*/
static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
int size)
{
switch (size) {
case 1:
asm volatile("xchgb %b0,%1"
: "=q" (x)
: "m" (*__xg(ptr)), "0" (x)
: "memory");
break;
case 2:
asm volatile("xchgw %w0,%1"
: "=r" (x)
: "m" (*__xg(ptr)), "0" (x)
: "memory");
break;
case 4:
asm volatile("xchgl %0,%1"
: "=r" (x)
: "m" (*__xg(ptr)), "0" (x)
: "memory");
break;
}
return x;
}
extern void __cmpxchg_wrong_size(void);

/*
* Atomic compare and exchange. Compare OLD with MEM, if identical,
* store NEW in MEM. Return the initial value in MEM. Success is
* indicated by comparing RETURN with OLD.
*/
#define __raw_cmpxchg(ptr, old, new, size, lock) \
({ \
__typeof__(*(ptr)) __ret; \
__typeof__(*(ptr)) __old = (old); \
__typeof__(*(ptr)) __new = (new); \
switch (size) { \
case 1: \
asm volatile(lock "cmpxchgb %b1,%2" \
: "=a"(__ret) \
: "q"(__new), "m"(*__xg(ptr)), "0"(__old) \
: "memory"); \
break; \
case 2: \
asm volatile(lock "cmpxchgw %w1,%2" \
: "=a"(__ret) \
: "r"(__new), "m"(*__xg(ptr)), "0"(__old) \
: "memory"); \
break; \
case 4: \
asm volatile(lock "cmpxchgl %1,%2" \
: "=a"(__ret) \
: "r"(__new), "m"(*__xg(ptr)), "0"(__old) \
: "memory"); \
break; \
default: \
__cmpxchg_wrong_size(); \
} \
__ret; \
})

#define __cmpxchg(ptr, old, new, size) \
__raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)

#define __sync_cmpxchg(ptr, old, new, size) \
__raw_cmpxchg((ptr), (old), (new), (size), "lock; ")

#define __cmpxchg_local(ptr, old, new, size) \
__raw_cmpxchg((ptr), (old), (new), (size), "")

#ifdef CONFIG_X86_CMPXCHG
#define __HAVE_ARCH_CMPXCHG 1
#define cmpxchg(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o), \
(unsigned long)(n), \
sizeof(*(ptr))))
#define sync_cmpxchg(ptr, o, n) \
((__typeof__(*(ptr)))__sync_cmpxchg((ptr), (unsigned long)(o), \
(unsigned long)(n), \
sizeof(*(ptr))))
#define cmpxchg_local(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o), \
(unsigned long)(n), \
sizeof(*(ptr))))

#define cmpxchg(ptr, old, new) \
__cmpxchg((ptr), (old), (new), sizeof(*ptr))

#define sync_cmpxchg(ptr, old, new) \
__sync_cmpxchg((ptr), (old), (new), sizeof(*ptr))

#define cmpxchg_local(ptr, old, new) \
__cmpxchg_local((ptr), (old), (new), sizeof(*ptr))
#endif

#ifdef CONFIG_X86_CMPXCHG64
Expand All @@ -133,94 +175,6 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
(unsigned long long)(n)))
#endif

static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
unsigned long new, int size)
{
unsigned long prev;
switch (size) {
case 1:
asm volatile(LOCK_PREFIX "cmpxchgb %b1,%2"
: "=a"(prev)
: "q"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 2:
asm volatile(LOCK_PREFIX "cmpxchgw %w1,%2"
: "=a"(prev)
: "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 4:
asm volatile(LOCK_PREFIX "cmpxchgl %1,%2"
: "=a"(prev)
: "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
}
return old;
}

/*
* Always use locked operations when touching memory shared with a
* hypervisor, since the system may be SMP even if the guest kernel
* isn't.
*/
static inline unsigned long __sync_cmpxchg(volatile void *ptr,
unsigned long old,
unsigned long new, int size)
{
unsigned long prev;
switch (size) {
case 1:
asm volatile("lock; cmpxchgb %b1,%2"
: "=a"(prev)
: "q"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 2:
asm volatile("lock; cmpxchgw %w1,%2"
: "=a"(prev)
: "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 4:
asm volatile("lock; cmpxchgl %1,%2"
: "=a"(prev)
: "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
}
return old;
}

static inline unsigned long __cmpxchg_local(volatile void *ptr,
unsigned long old,
unsigned long new, int size)
{
unsigned long prev;
switch (size) {
case 1:
asm volatile("cmpxchgb %b1,%2"
: "=a"(prev)
: "q"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 2:
asm volatile("cmpxchgw %w1,%2"
: "=a"(prev)
: "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 4:
asm volatile("cmpxchgl %1,%2"
: "=a"(prev)
: "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
}
return old;
}

static inline unsigned long long __cmpxchg64(volatile void *ptr,
unsigned long long old,
unsigned long long new)
Expand Down
Loading

0 comments on commit f3834b9

Please sign in to comment.