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/sparc/include/asm/futex_64.h | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'arch/sparc/include/asm/futex_64.h') diff --git a/arch/sparc/include/asm/futex_64.h b/arch/sparc/include/asm/futex_64.h index 47f95839dc69..e0862200d6a1 100644 --- a/arch/sparc/include/asm/futex_64.h +++ b/arch/sparc/include/asm/futex_64.h @@ -85,26 +85,30 @@ static inline int 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 ret = 0; + __asm__ __volatile__( - "\n1: casa [%3] %%asi, %2, %0\n" + "\n1: casa [%4] %%asi, %3, %1\n" "2:\n" " .section .fixup,#alloc,#execinstr\n" " .align 4\n" "3: sethi %%hi(2b), %0\n" " jmpl %0 + %%lo(2b), %%g0\n" - " mov %4, %0\n" + " mov %5, %0\n" " .previous\n" " .section __ex_table,\"a\"\n" " .align 4\n" " .word 1b, 3b\n" " .previous\n" - : "=r" (newval) - : "0" (newval), "r" (oldval), "r" (uaddr), "i" (-EFAULT) + : "+r" (ret), "=r" (newval) + : "1" (newval), "r" (oldval), "r" (uaddr), "i" (-EFAULT) : "memory"); - return newval; + *uval = newval; + return ret; } #endif /* !(_SPARC64_FUTEX_H) */ -- cgit v1.2.3