diff options
| author | Michel Lespinasse <walken@google.com> | 2011-03-11 05:48:51 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-03-11 14:23:08 +0300 |
| commit | 37a9d912b24f96a0591773e6e6c3642991ae5a70 (patch) | |
| tree | 5c4d5b9a52e2c533269e589115afbd25b6c8534b /arch/microblaze | |
| parent | 522d7decc0370070448a8c28982c8dfd8970489e (diff) | |
| download | linux-37a9d912b24f96a0591773e6e6c3642991ae5a70.tar.xz | |
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/microblaze')
| -rw-r--r-- | arch/microblaze/include/asm/futex.h | 24 |
1 files changed, 13 insertions, 11 deletions
diff --git a/arch/microblaze/include/asm/futex.h b/arch/microblaze/include/asm/futex.h index ad3fd61b2fe7..fa019ed65dfb 100644 --- a/arch/microblaze/include/asm/futex.h +++ b/arch/microblaze/include/asm/futex.h @@ -94,31 +94,33 @@ 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 prev, cmp; + int ret = 0, prev, cmp; if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; - __asm__ __volatile__ ("1: lwx %0, %2, r0; \ - cmp %1, %0, %3; \ - beqi %1, 3f; \ - 2: swx %4, %2, r0; \ - addic %1, r0, 0; \ - bnei %1, 1b; \ + __asm__ __volatile__ ("1: lwx %1, %3, r0; \ + cmp %2, %1, %4; \ + beqi %2, 3f; \ + 2: swx %5, %3, r0; \ + addic %2, r0, 0; \ + bnei %2, 1b; \ 3: \ .section .fixup,\"ax\"; \ 4: brid 3b; \ - addik %0, r0, %5; \ + addik %0, r0, %6; \ .previous; \ .section __ex_table,\"a\"; \ .word 1b,4b,2b,4b; \ .previous;" \ - : "=&r" (prev), "=&r"(cmp) \ + : "+r" (ret), "=&r" (prev), "=&r"(cmp) \ : "r" (uaddr), "r" (oldval), "r" (newval), "i" (-EFAULT)); - return prev; + *uval = prev; + return ret; } #endif /* __KERNEL__ */ |