diff options
| author | Michel Lespinasse <walken@google.com> | 2011-03-10 18:48:51 -0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-03-11 12:23:08 +0100 |
| commit | 37a9d912b24f96a0591773e6e6c3642991ae5a70 (patch) | |
| tree | 5c4d5b9a52e2c533269e589115afbd25b6c8534b /arch/mips | |
| parent | 522d7decc0370070448a8c28982c8dfd8970489e (diff) | |
futex: Sanitize cmpxchg_futex_value_locked API
The cmpxchg_futex_value_locked API was funny in that it returned either
the original, user-exposed futex value OR an error code such as -EFAULT.
This was confusing at best, and could be a source of livelocks in places
that retry the cmpxchg_futex_value_locked after trying to fix the issue
by running fault_in_user_writeable().
This change makes the cmpxchg_futex_value_locked API more similar to the
get_futex_value_locked one, returning an error code and updating the
original value through a reference argument.
Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Chris Metcalf <cmetcalf@tilera.com> [tile]
Acked-by: Tony Luck <tony.luck@intel.com> [ia64]
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michal Simek <monstr@monstr.eu> [microblaze]
Acked-by: David Howells <dhowells@redhat.com> [frv]
Cc: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20110311024851.GC26122@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/mips')
| -rw-r--r-- | arch/mips/include/asm/futex.h | 32 |
1 files changed, 17 insertions, 15 deletions
diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h index b9cce90346cf..692a24bd83b7 100644 --- a/arch/mips/include/asm/futex.h +++ b/arch/mips/include/asm/futex.h @@ -132,9 +132,10 @@ futex_atomic_op_inuser(int encoded_op, int __user *uaddr) } static inline int -futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) +futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr, + int oldval, int newval) { - int retval; + int ret = 0, val; if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; @@ -145,25 +146,25 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) " .set push \n" " .set noat \n" " .set mips3 \n" - "1: ll %0, %2 \n" - " bne %0, %z3, 3f \n" + "1: ll %1, %3 \n" + " bne %1, %z4, 3f \n" " .set mips0 \n" - " move $1, %z4 \n" + " move $1, %z5 \n" " .set mips3 \n" - "2: sc $1, %1 \n" + "2: sc $1, %2 \n" " beqzl $1, 1b \n" __WEAK_LLSC_MB "3: \n" " .set pop \n" " .section .fixup,\"ax\" \n" - "4: li %0, %5 \n" + "4: li %0, %6 \n" " j 3b \n" " .previous \n" " .section __ex_table,\"a\" \n" " "__UA_ADDR "\t1b, 4b \n" " "__UA_ADDR "\t2b, 4b \n" " .previous \n" - : "=&r" (retval), "=R" (*uaddr) + : "+r" (ret), "=&r" (val), "=R" (*uaddr) : "R" (*uaddr), "Jr" (oldval), "Jr" (newval), "i" (-EFAULT) : "memory"); } else if (cpu_has_llsc) { @@ -172,31 +173,32 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) " .set push \n" " .set noat \n" " .set mips3 \n" - "1: ll %0, %2 \n" - " bne %0, %z3, 3f \n" + "1: ll %1, %3 \n" + " bne %1, %z4, 3f \n" " .set mips0 \n" - " move $1, %z4 \n" + " move $1, %z5 \n" " .set mips3 \n" - "2: sc $1, %1 \n" + "2: sc $1, %2 \n" " beqz $1, 1b \n" __WEAK_LLSC_MB "3: \n" " .set pop \n" " .section .fixup,\"ax\" \n" - "4: li %0, %5 \n" + "4: li %0, %6 \n" " j 3b \n" " .previous \n" " .section __ex_table,\"a\" \n" " "__UA_ADDR "\t1b, 4b \n" " "__UA_ADDR "\t2b, 4b \n" " .previous \n" - : "=&r" (retval), "=R" (*uaddr) + : "+r" (ret), "=&r" (val), "=R" (*uaddr) : "R" (*uaddr), "Jr" (oldval), "Jr" (newval), "i" (-EFAULT) : "memory"); } else return -ENOSYS; - return retval; + *uval = val; + return ret; } #endif |