futex.h

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#ifndef _ASM_X86_FUTEX_H
#define _ASM_X86_FUTEX_H

#ifdef __KERNEL__

#include <linux/futex.h>
#include <linux/uaccess.h>

#include <asm/asm.h>
#include <asm/errno.h>
#include <asm/processor.h>
#include <asm/smap.h>

#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg) \
    asm volatile("\t" ASM_STAC "\n"             \
             "1:\t" insn "\n"               \
             "2:\t" ASM_CLAC "\n"           \
             "\t.section .fixup,\"ax\"\n"       \
             "3:\tmov\t%3, %1\n"            \
             "\tjmp\t2b\n"              \
             "\t.previous\n"                \
             _ASM_EXTABLE(1b, 3b)           \
             : "=r" (oldval), "=r" (ret), "+m" (*uaddr) \
             : "i" (-EFAULT), "0" (oparg), "1" (0))

#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
    asm volatile("\t" ASM_STAC "\n"             \
             "1:\tmovl  %2, %0\n"           \
             "\tmovl\t%0, %3\n"             \
             "\t" insn "\n"             \
             "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
             "\tjnz\t1b\n"              \
             "3:\t" ASM_CLAC "\n"           \
             "\t.section .fixup,\"ax\"\n"       \
             "4:\tmov\t%5, %1\n"            \
             "\tjmp\t3b\n"              \
             "\t.previous\n"                \
             _ASM_EXTABLE(1b, 4b)           \
             _ASM_EXTABLE(2b, 4b)           \
             : "=&a" (oldval), "=&r" (ret),     \
               "+m" (*uaddr), "=&r" (tem)       \
             : "r" (oparg), "i" (-EFAULT), "1" (0))

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, tem;

    if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
        oparg = 1 << oparg;

    if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
        return -EFAULT;

#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_BSWAP)
    /* Real i386 machines can only support FUTEX_OP_SET */
    if (op != FUTEX_OP_SET && boot_cpu_data.x86 == 3)
        return -ENOSYS;
#endif

    pagefault_disable();

    switch (op) {
    case FUTEX_OP_SET:
        __futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
        break;
    case FUTEX_OP_ADD:
        __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
                   uaddr, oparg);
        break;
    case FUTEX_OP_OR:
        __futex_atomic_op2("orl %4, %3", ret, oldval, uaddr, oparg);
        break;
    case FUTEX_OP_ANDN:
        __futex_atomic_op2("andl %4, %3", ret, oldval, uaddr, ~oparg);
        break;
    case FUTEX_OP_XOR:
        __futex_atomic_op2("xorl %4, %3", 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;

#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_BSWAP)
    /* Real i386 machines have no cmpxchg instruction */
    if (boot_cpu_data.x86 == 3)
        return -ENOSYS;
#endif

    if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
        return -EFAULT;

    asm volatile("\t" ASM_STAC "\n"
             "1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"
             "2:\t" ASM_CLAC "\n"
             "\t.section .fixup, \"ax\"\n"
             "3:\tmov     %3, %0\n"
             "\tjmp     2b\n"
             "\t.previous\n"
             _ASM_EXTABLE(1b, 3b)
             : "+r" (ret), "=a" (oldval), "+m" (*uaddr)
             : "i" (-EFAULT), "r" (newval), "1" (oldval)
             : "memory"
    );

    *uval = oldval;
    return ret;
}

#endif
#endif /* _ASM_X86_FUTEX_H */