diff options
Diffstat (limited to 'include/asm-x86_64/futex.h')
| -rw-r--r-- | include/asm-x86_64/futex.h | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/include/asm-x86_64/futex.h b/include/asm-x86_64/futex.h index 4f4cb3410d06..7d9eb1a84546 100644 --- a/include/asm-x86_64/futex.h +++ b/include/asm-x86_64/futex.h @@ -97,7 +97,28 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr) static inline int futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval) { - return -ENOSYS; + if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) + return -EFAULT; + + __asm__ __volatile__( + "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n" + + "2: .section .fixup, \"ax\" \n" + "3: mov %2, %0 \n" + " jmp 2b \n" + " .previous \n" + + " .section __ex_table, \"a\" \n" + " .align 8 \n" + " .quad 1b,3b \n" + " .previous \n" + + : "=a" (oldval), "=m" (*uaddr) + : "i" (-EFAULT), "r" (newval), "0" (oldval) + : "memory" + ); + + return oldval; } #endif |