From 37a9d912b24f96a0591773e6e6c3642991ae5a70 Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Thu, 10 Mar 2011 18:48:51 -0800 Subject: 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 Acked-by: Chris Metcalf [tile] Acked-by: Tony Luck [ia64] Acked-by: Thomas Gleixner Tested-by: Michal Simek [microblaze] Acked-by: David Howells [frv] Cc: Darren Hart Cc: Peter Zijlstra Cc: Matt Turner Cc: Russell King Cc: Ralf Baechle Cc: "James E.J. Bottomley" Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: Paul Mundt Cc: "David S. Miller" Cc: Linus Torvalds LKML-Reference: <20110311024851.GC26122@google.com> Signed-off-by: Thomas Gleixner --- arch/microblaze/include/asm/futex.h | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) (limited to 'arch/microblaze') diff --git a/arch/microblaze/include/asm/futex.h b/arch/microblaze/include/asm/futex.h index ad3fd61..fa019ed 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__ */ -- cgit v1.1