linux/arch/alpha/include/asm/futex.h
Andrew Morton 62aca40365 alpha: fix 32/64-bit bug in futex support
Michael Cree said:

: : I have noticed some user space problems (pulseaudio crashes in pthread
: : code, glibc/nptl test suite failures, java compiler freezes on SMP alpha
: : systems) that arise when using a 2.6.39 or later kernel on Alpha.
: : Bisecting between 2.6.38 and 2.6.39 (using glibc/nptl test suite as
: : criterion for good/bad kernel) eventually leads to:
: :
: : 8d7718aa08 is the first bad commit
: : commit 8d7718aa08
: : Author: Michel Lespinasse <walken@google.com>
: : Date:   Thu Mar 10 18:50:58 2011 -0800
: :
: :     futex: Sanitize futex ops argument types
: :
: :     Change futex_atomic_op_inuser and futex_atomic_cmpxchg_inatomic
: :     prototypes to use u32 types for the futex as this is the data type the
: :     futex core code uses all over the place.
: :
: : Looking at the commit I see there is a change of the uaddr argument in
: : the Alpha architecture specific code for futexes from int to u32, but I
: : don't see why this should cause a problem.

Richard Henderson said:

: futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
:                               u32 oldval, u32 newval)
: ...
:         :       "r"(uaddr), "r"((long)oldval), "r"(newval)
:
:
: There is no 32-bit compare instruction.  These are implemented by
: consistently extending the values to a 64-bit type.  Since the
: load instruction sign-extends, we want to sign-extend the other
: quantity as well (despite the fact it's logically unsigned).
:
: So:
:
: -        :       "r"(uaddr), "r"((long)oldval), "r"(newval)
: +        :       "r"(uaddr), "r"((long)(int)oldval), "r"(newval)
:
: should do the trick.

Michael said:

: This fixes the glibc test suite failures and the pulseaudio related
: crashes, but it does not fix the java compiiler lockups that I was (and
: are still) observing.  That is some other problem.

Reported-by: Michael Cree <mcree@orcon.net.nz>
Tested-by: Michael Cree <mcree@orcon.net.nz>
Acked-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-05 15:49:43 -08:00

120 lines
2.8 KiB
C

#ifndef _ASM_ALPHA_FUTEX_H
#define _ASM_ALPHA_FUTEX_H
#ifdef __KERNEL__
#include <linux/futex.h>
#include <linux/uaccess.h>
#include <asm/errno.h>
#include <asm/barrier.h>
#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
__asm__ __volatile__( \
__ASM_SMP_MB \
"1: ldl_l %0,0(%2)\n" \
insn \
"2: stl_c %1,0(%2)\n" \
" beq %1,4f\n" \
" mov $31,%1\n" \
"3: .subsection 2\n" \
"4: br 1b\n" \
" .previous\n" \
" .section __ex_table,\"a\"\n" \
" .long 1b-.\n" \
" lda $31,3b-1b(%1)\n" \
" .long 2b-.\n" \
" lda $31,3b-2b(%1)\n" \
" .previous\n" \
: "=&r" (oldval), "=&r"(ret) \
: "r" (uaddr), "r"(oparg) \
: "memory")
static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
{
int op = (encoded_op >> 28) & 7;
int cmp = (encoded_op >> 24) & 15;
int oparg = (encoded_op << 8) >> 20;
int cmparg = (encoded_op << 20) >> 20;
int oldval = 0, ret;
if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
oparg = 1 << oparg;
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
pagefault_disable();
switch (op) {
case FUTEX_OP_SET:
__futex_atomic_op("mov %3,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ADD:
__futex_atomic_op("addl %0,%3,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_OR:
__futex_atomic_op("or %0,%3,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ANDN:
__futex_atomic_op("andnot %0,%3,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_XOR:
__futex_atomic_op("xor %0,%3,%1\n", ret, oldval, uaddr, oparg);
break;
default:
ret = -ENOSYS;
}
pagefault_enable();
if (!ret) {
switch (cmp) {
case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
default: ret = -ENOSYS;
}
}
return ret;
}
static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
u32 oldval, u32 newval)
{
int ret = 0, cmp;
u32 prev;
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
__asm__ __volatile__ (
__ASM_SMP_MB
"1: ldl_l %1,0(%3)\n"
" cmpeq %1,%4,%2\n"
" beq %2,3f\n"
" mov %5,%2\n"
"2: stl_c %2,0(%3)\n"
" beq %2,4f\n"
"3: .subsection 2\n"
"4: br 1b\n"
" .previous\n"
" .section __ex_table,\"a\"\n"
" .long 1b-.\n"
" lda $31,3b-1b(%0)\n"
" .long 2b-.\n"
" lda $31,3b-2b(%0)\n"
" .previous\n"
: "+r"(ret), "=&r"(prev), "=&r"(cmp)
: "r"(uaddr), "r"((long)(int)oldval), "r"(newval)
: "memory");
*uval = prev;
return ret;
}
#endif /* __KERNEL__ */
#endif /* _ASM_ALPHA_FUTEX_H */