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authorMichel Lespinasse <walken@google.com>2011-03-10 18:48:51 -0800
committerThomas Gleixner <tglx@linutronix.de>2011-03-11 12:23:08 +0100
commit37a9d912b24f96a0591773e6e6c3642991ae5a70 (patch)
tree5c4d5b9a52e2c533269e589115afbd25b6c8534b /arch/mips
parent522d7decc0370070448a8c28982c8dfd8970489e (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.h32
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