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Subject[223/244] ARM: 7099/1: futex: preserve oldval in SMP __futex_atomic_op
3.0-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Will Deacon <will.deacon@arm.com>

commit df77abcafc8dc881b6c9347548651777088e4b27 upstream.

The SMP implementation of __futex_atomic_op clobbers oldval with the
status flag from the exclusive store. This causes it to always read as
zero when performing the FUTEX_OP_CMP_* operation.

This patch updates the ARM __futex_atomic_op implementations to take a
tmp argument, allowing us to store the strex status flag without
overwriting the register containing oldval.

Reported-by: Minho Ban <mhban@samsung.com>
Reviewed-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/arm/include/asm/futex.h | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -25,17 +25,17 @@

#ifdef CONFIG_SMP

-#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
+#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \
smp_mb(); \
__asm__ __volatile__( \
- "1: ldrex %1, [%2]\n" \
+ "1: ldrex %1, [%3]\n" \
" " insn "\n" \
- "2: strex %1, %0, [%2]\n" \
- " teq %1, #0\n" \
+ "2: strex %2, %0, [%3]\n" \
+ " teq %2, #0\n" \
" bne 1b\n" \
" mov %0, #0\n" \
- __futex_atomic_ex_table("%4") \
- : "=&r" (ret), "=&r" (oldval) \
+ __futex_atomic_ex_table("%5") \
+ : "=&r" (ret), "=&r" (oldval), "=&r" (tmp) \
: "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
: "cc", "memory")

@@ -73,14 +73,14 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
#include <linux/preempt.h>
#include <asm/domain.h>

-#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
+#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \
__asm__ __volatile__( \
- "1: " T(ldr) " %1, [%2]\n" \
+ "1: " T(ldr) " %1, [%3]\n" \
" " insn "\n" \
- "2: " T(str) " %0, [%2]\n" \
+ "2: " T(str) " %0, [%3]\n" \
" mov %0, #0\n" \
- __futex_atomic_ex_table("%4") \
- : "=&r" (ret), "=&r" (oldval) \
+ __futex_atomic_ex_table("%5") \
+ : "=&r" (ret), "=&r" (oldval), "=&r" (tmp) \
: "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
: "cc", "memory")

@@ -117,7 +117,7 @@ futex_atomic_op_inuser (int encoded_op,
int cmp = (encoded_op >> 24) & 15;
int oparg = (encoded_op << 8) >> 20;
int cmparg = (encoded_op << 20) >> 20;
- int oldval = 0, ret;
+ int oldval = 0, ret, tmp;

if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
oparg = 1 << oparg;
@@ -129,19 +129,19 @@ futex_atomic_op_inuser (int encoded_op,

switch (op) {
case FUTEX_OP_SET:
- __futex_atomic_op("mov %0, %3", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("mov %0, %4", ret, oldval, tmp, uaddr, oparg);
break;
case FUTEX_OP_ADD:
- __futex_atomic_op("add %0, %1, %3", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("add %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
break;
case FUTEX_OP_OR:
- __futex_atomic_op("orr %0, %1, %3", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("orr %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
break;
case FUTEX_OP_ANDN:
- __futex_atomic_op("and %0, %1, %3", ret, oldval, uaddr, ~oparg);
+ __futex_atomic_op("and %0, %1, %4", ret, oldval, tmp, uaddr, ~oparg);
break;
case FUTEX_OP_XOR:
- __futex_atomic_op("eor %0, %1, %3", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("eor %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
break;
default:
ret = -ENOSYS;



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