usercopy_64.c

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/* 
 * User address space access functions.
 *
 * Copyright 1997 Andi Kleen <[email protected]>
 * Copyright 1997 Linus Torvalds
 * Copyright 2002 Andi Kleen <[email protected]>
 */
#include <linux/module.h>
#include <asm/uaccess.h>

/*
 * Zero Userspace
 */

unsigned long __clear_user(void __user *addr, unsigned long size)
{
    long __d0;
    might_fault();
    /* no memory constraint because it doesn't change any memory gcc knows
       about */
    stac();
    asm volatile(
        "   testq  %[size8],%[size8]\n"
        "   jz     4f\n"
        "0: movq %[zero],(%[dst])\n"
        "   addq   %[eight],%[dst]\n"
        "   decl %%ecx ; jnz   0b\n"
        "4: movq  %[size1],%%rcx\n"
        "   testl %%ecx,%%ecx\n"
        "   jz     2f\n"
        "1: movb   %b[zero],(%[dst])\n"
        "   incq   %[dst]\n"
        "   decl %%ecx ; jnz  1b\n"
        "2:\n"
        ".section .fixup,\"ax\"\n"
        "3: lea 0(%[size1],%[size8],8),%[size8]\n"
        "   jmp 2b\n"
        ".previous\n"
        _ASM_EXTABLE(0b,3b)
        _ASM_EXTABLE(1b,2b)
        : [size8] "=&c"(size), [dst] "=&D" (__d0)
        : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
          [zero] "r" (0UL), [eight] "r" (8UL));
    clac();
    return size;
}
EXPORT_SYMBOL(__clear_user);

unsigned long clear_user(void __user *to, unsigned long n)
{
    if (access_ok(VERIFY_WRITE, to, n))
        return __clear_user(to, n);
    return n;
}
EXPORT_SYMBOL(clear_user);

unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len)
{
    if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) { 
        return copy_user_generic((__force void *)to, (__force void *)from, len);
    } 
    return len;     
}
EXPORT_SYMBOL(copy_in_user);

/*
 * Try to copy last bytes and clear the rest if needed.
 * Since protection fault in copy_from/to_user is not a normal situation,
 * it is not necessary to optimize tail handling.
 */
unsigned long
copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
{
    char c;
    unsigned zero_len;

    for (; len; --len) {
        if (__get_user_nocheck(c, from++, sizeof(char)))
            break;
        if (__put_user_nocheck(c, to++, sizeof(char)))
            break;
    }

    for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
        if (__put_user_nocheck(c, to++, sizeof(char)))
            break;
    clac();
    return len;
}