arc-linux-uclibc/usr/include/asm/futex.h

/*
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Vineetg: August 2010: From Android kernel work
 */

#ifndef _ASM_FUTEX_H
#define _ASM_FUTEX_H

#include <linux/futex.h>
#include <linux/preempt.h>
#include <linux/uaccess.h>
#include <asm/errno.h>

#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)  \
                                            \
    __asm__ __volatile__(                   \
    "1:     ld  %1, [%2]            \n"     \
            insn                   "\n"     \
    "2:     st  %0, [%2]            \n"     \
    "       mov %0, 0               \n"     \
    "3:                             \n"     \
    "   .section .fixup,\"ax\"      \n"     \
    "   .align  4                   \n"     \
    "4:     mov %0, %4              \n"     \
    "       b   3b                  \n"     \
    "   .previous                   \n"     \
    "   .section __ex_table,\"a\"   \n"     \
    "   .align  4                   \n"     \
    "       .word   1b, 4b          \n"     \
    "       .word   2b, 4b          \n"     \
    "   .previous                   \n"     \
                                            \
    : "=&r" (ret), "=&r" (oldval)           \
    : "r" (uaddr), "r" (oparg), "ir" (-EFAULT)      \
    : "cc", "memory")

static inline int
futex_atomic_op_inuser (int encoded_op, int __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(int)))
        return -EFAULT;

    pagefault_disable();    /* implies preempt_disable() */

    switch (op) {
    case FUTEX_OP_SET:
        __futex_atomic_op("mov  %0, %3", ret, oldval, uaddr, oparg);
        break;
    case FUTEX_OP_ADD:
        __futex_atomic_op("add  %0, %1, %3", ret, oldval, uaddr, oparg);
        break;
    case FUTEX_OP_OR:
        __futex_atomic_op("or   %0, %1, %3", ret, oldval, uaddr, oparg);
        break;
    case FUTEX_OP_ANDN:
        __futex_atomic_op("bic  %0, %1, %3", ret, oldval, uaddr, oparg);
        break;
    case FUTEX_OP_XOR:
        __futex_atomic_op("xor  %0, %1, %3", ret, oldval, uaddr, oparg);
        break;
    default:
        ret = -ENOSYS;
    }

    pagefault_enable(); /* subsumes preempt_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;
}

/* Compare-xchg with preemption disabled.
 *  Notes:
 *      -Best-Effort: Exchg happens only if compare succeeds.
 *          If compare fails, returns; leaving retry/looping to upper layers
 *      -successful cmp-xchg: return orig value in @addr (same as cmp val)
 *      -Compare fails: return orig value in @addr
 *      -user access r/w fails: return -EFAULT
 */
static inline int
futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
{
    int val;

    if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
        return -EFAULT;

    pagefault_disable();    /* implies preempt_disable() */

    __asm__ __volatile__(

    "1:     ld    %0, [%3]          \n"
    "       brne  %0, %1, 3f        \n"
    "2:     st    %2, [%3]          \n"
    "3:                             \n"
    "   .section .fixup,\"ax\"      \n"
    "4:     mov %0, %4              \n"
    "       b   3b                  \n"
    "   .previous                   \n"
    "   .section __ex_table,\"a\"   \n"
    "   .align  4                   \n"
    "       .word   1b, 4b          \n"
    "       .word   2b, 4b          \n"
    "   .previous\n"

    : "=&r" (val)
    : "r" (oldval), "r" (newval), "r" (uaddr), "ir" (-EFAULT)
    : "cc", "memory");

    pagefault_enable(); /* subsumes preempt_enable() */

    return val;
}

#endif