882a95ae0a
Callers of cmpxchg_futex_value_locked() in futex code expect bimodal return value: !0 (essentially -EFAULT as failure) 0 (success) Before this patch, the success return value was old value of futex, which could very well be non zero, causing caller to possibly take the failure path erroneously. Fix that by returning 0 for success (This fix was done back in 2011 for all upstream arches, which ARC obviously missed) Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Michel Lespinasse <walken@google.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
190 lines
4.0 KiB
C
190 lines
4.0 KiB
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Vineetg: August 2010: From Android kernel work
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*/
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#ifndef _ASM_FUTEX_H
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#define _ASM_FUTEX_H
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#include <linux/futex.h>
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#include <linux/preempt.h>
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#include <linux/uaccess.h>
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#include <asm/errno.h>
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#ifdef CONFIG_ARC_HAS_LLSC
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#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)\
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\
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smp_mb(); \
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__asm__ __volatile__( \
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"1: llock %1, [%2] \n" \
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insn "\n" \
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"2: scond %0, [%2] \n" \
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" bnz 1b \n" \
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" mov %0, 0 \n" \
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"3: \n" \
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" .section .fixup,\"ax\" \n" \
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" .align 4 \n" \
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"4: mov %0, %4 \n" \
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" b 3b \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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\
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: "=&r" (ret), "=&r" (oldval) \
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: "r" (uaddr), "r" (oparg), "ir" (-EFAULT) \
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: "cc", "memory"); \
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smp_mb() \
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#else /* !CONFIG_ARC_HAS_LLSC */
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#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)\
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\
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smp_mb(); \
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__asm__ __volatile__( \
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"1: ld %1, [%2] \n" \
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insn "\n" \
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"2: st %0, [%2] \n" \
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" mov %0, 0 \n" \
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"3: \n" \
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" .section .fixup,\"ax\" \n" \
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" .align 4 \n" \
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"4: mov %0, %4 \n" \
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" b 3b \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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\
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: "=&r" (ret), "=&r" (oldval) \
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: "r" (uaddr), "r" (oparg), "ir" (-EFAULT) \
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: "cc", "memory"); \
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smp_mb() \
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#endif
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static inline int futex_atomic_op_inuser(int encoded_op, u32 __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;
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if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
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oparg = 1 << oparg;
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if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
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return -EFAULT;
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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_atomic_op("mov %0, %3", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ADD:
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/* oldval = *uaddr; *uaddr += oparg ; ret = *uaddr */
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__futex_atomic_op("add %0, %1, %3", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_OR:
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__futex_atomic_op("or %0, %1, %3", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ANDN:
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__futex_atomic_op("bic %0, %1, %3", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_XOR:
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__futex_atomic_op("xor %0, %1, %3", 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:
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ret = (oldval == cmparg);
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break;
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case FUTEX_OP_CMP_NE:
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ret = (oldval != cmparg);
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break;
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case FUTEX_OP_CMP_LT:
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ret = (oldval < cmparg);
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break;
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case FUTEX_OP_CMP_GE:
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ret = (oldval >= cmparg);
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break;
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case FUTEX_OP_CMP_LE:
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ret = (oldval <= cmparg);
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break;
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case FUTEX_OP_CMP_GT:
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ret = (oldval > cmparg);
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break;
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default:
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ret = -ENOSYS;
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}
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}
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return ret;
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}
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/*
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* cmpxchg of futex (pagefaults disabled by caller)
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* Return 0 for success, -EFAULT otherwise
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*/
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static inline int
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futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval,
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u32 newval)
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{
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int ret = 0;
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u32 existval;
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if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
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return -EFAULT;
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smp_mb();
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__asm__ __volatile__(
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#ifdef CONFIG_ARC_HAS_LLSC
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"1: llock %1, [%4] \n"
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" brne %1, %2, 3f \n"
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"2: scond %3, [%4] \n"
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" bnz 1b \n"
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#else
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"1: ld %1, [%4] \n"
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" brne %1, %2, 3f \n"
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"2: st %3, [%4] \n"
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#endif
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"3: \n"
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" .section .fixup,\"ax\" \n"
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"4: mov %0, %5 \n"
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" b 3b \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"(existval)
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: "r"(expval), "r"(newval), "r"(uaddr), "ir"(-EFAULT)
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: "cc", "memory");
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smp_mb();
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*uval = existval;
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return ret;
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}
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#endif
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