37a9d912b2
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>
114 lines
2.8 KiB
C
114 lines
2.8 KiB
C
#ifndef _SPARC64_FUTEX_H
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#define _SPARC64_FUTEX_H
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#include <linux/futex.h>
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#include <linux/uaccess.h>
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#include <asm/errno.h>
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#include <asm/system.h>
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#define __futex_cas_op(insn, ret, oldval, uaddr, oparg) \
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__asm__ __volatile__( \
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"\n1: lduwa [%3] %%asi, %2\n" \
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" " insn "\n" \
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"2: casa [%3] %%asi, %2, %1\n" \
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" cmp %2, %1\n" \
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" bne,pn %%icc, 1b\n" \
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" mov 0, %0\n" \
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"3:\n" \
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" .section .fixup,#alloc,#execinstr\n" \
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" .align 4\n" \
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"4: sethi %%hi(3b), %0\n" \
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" jmpl %0 + %%lo(3b), %%g0\n" \
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" mov %5, %0\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .word 1b, 4b\n" \
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" .word 2b, 4b\n" \
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" .previous\n" \
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: "=&r" (ret), "=&r" (oldval), "=&r" (tem) \
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: "r" (uaddr), "r" (oparg), "i" (-EFAULT) \
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: "memory")
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static inline int futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
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{
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int op = (encoded_op >> 28) & 7;
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int cmp = (encoded_op >> 24) & 15;
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int oparg = (encoded_op << 8) >> 20;
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int cmparg = (encoded_op << 20) >> 20;
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int oldval = 0, ret, tem;
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if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(int))))
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return -EFAULT;
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if (unlikely((((unsigned long) uaddr) & 0x3UL)))
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return -EINVAL;
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if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
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oparg = 1 << oparg;
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pagefault_disable();
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switch (op) {
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case FUTEX_OP_SET:
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__futex_cas_op("mov\t%4, %1", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ADD:
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__futex_cas_op("add\t%2, %4, %1", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_OR:
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__futex_cas_op("or\t%2, %4, %1", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ANDN:
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__futex_cas_op("andn\t%2, %4, %1", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_XOR:
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__futex_cas_op("xor\t%2, %4, %1", ret, oldval, uaddr, oparg);
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break;
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default:
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ret = -ENOSYS;
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}
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pagefault_enable();
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if (!ret) {
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switch (cmp) {
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case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
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case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
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case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
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case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
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case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
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case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
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default: ret = -ENOSYS;
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}
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}
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return ret;
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}
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static inline int
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futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr,
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int oldval, int newval)
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{
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int ret = 0;
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__asm__ __volatile__(
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"\n1: casa [%4] %%asi, %3, %1\n"
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"2:\n"
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" .section .fixup,#alloc,#execinstr\n"
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" .align 4\n"
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"3: sethi %%hi(2b), %0\n"
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" jmpl %0 + %%lo(2b), %%g0\n"
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" mov %5, %0\n"
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" .previous\n"
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" .section __ex_table,\"a\"\n"
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" .align 4\n"
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" .word 1b, 3b\n"
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" .previous\n"
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: "+r" (ret), "=r" (newval)
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: "1" (newval), "r" (oldval), "r" (uaddr), "i" (-EFAULT)
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: "memory");
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*uval = newval;
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return ret;
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}
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#endif /* !(_SPARC64_FUTEX_H) */
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