From 882a95ae0a4f8fc303257acf5c6ff305df34d04b Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Thu, 6 Aug 2015 17:03:17 +0530 Subject: [PATCH] ARC: make futex_atomic_cmpxchg_inatomic() return bimodal Callers of cmpxchg_futex_value_locked() in futex code expect bimodal return value: !0 (essentially -EFAULT as failure) 0 (success) Before this patch, the success return value was old value of futex, which could very well be non zero, causing caller to possibly take the failure path erroneously. Fix that by returning 0 for success (This fix was done back in 2011 for all upstream arches, which ARC obviously missed) Cc: Peter Zijlstra (Intel) Cc: Thomas Gleixner Cc: Michel Lespinasse Signed-off-by: Vineet Gupta --- arch/arc/include/asm/futex.h | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/arch/arc/include/asm/futex.h b/arch/arc/include/asm/futex.h index 14b1c9aaf455..0ea8bcc7b846 100644 --- a/arch/arc/include/asm/futex.h +++ b/arch/arc/include/asm/futex.h @@ -141,11 +141,13 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr) /* * cmpxchg of futex (pagefaults disabled by caller) + * Return 0 for success, -EFAULT otherwise */ static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, u32 newval) { + int ret = 0; u32 existval; if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))) @@ -155,18 +157,18 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, __asm__ __volatile__( #ifdef CONFIG_ARC_HAS_LLSC - "1: llock %0, [%3] \n" - " brne %0, %1, 3f \n" - "2: scond %2, [%3] \n" + "1: llock %1, [%4] \n" + " brne %1, %2, 3f \n" + "2: scond %3, [%4] \n" " bnz 1b \n" #else - "1: ld %0, [%3] \n" - " brne %0, %1, 3f \n" - "2: st %2, [%3] \n" + "1: ld %1, [%4] \n" + " brne %1, %2, 3f \n" + "2: st %3, [%4] \n" #endif "3: \n" " .section .fixup,\"ax\" \n" - "4: mov %0, %4 \n" + "4: mov %0, %5 \n" " b 3b \n" " .previous \n" " .section __ex_table,\"a\" \n" @@ -174,14 +176,14 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, " .word 1b, 4b \n" " .word 2b, 4b \n" " .previous\n" - : "=&r"(existval) + : "+&r"(ret), "=&r"(existval) : "r"(expval), "r"(newval), "r"(uaddr), "ir"(-EFAULT) : "cc", "memory"); smp_mb(); *uval = existval; - return existval; + return ret; } #endif -- 2.34.1