usercopy.c

来自「是关于linux2.5.1的完全源码」· C语言 代码 · 共 148 行

/* 
 * User address space access functions.
 * The non inlined parts of asm-i386/uaccess.h are here.
 *
 * Copyright 1997 Andi Kleen <[e-mail]>
 * Copyright 1997 Linus Torvalds
 */
#include <linux/config.h>
#include <asm/uaccess.h>
#include <asm/mmx.h>

unsigned long
__generic_copy_to_user(void *to, const void *from, unsigned long n)
{
	prefetch(from);
	if (access_ok(VERIFY_WRITE, to, n))
		__copy_user(to,from,n);
	return n;
}

unsigned long
__generic_copy_from_user(void *to, const void *from, unsigned long n)
{
	prefetchw(to);
	if (access_ok(VERIFY_READ, from, n))
		__copy_user_zeroing(to,from,n);
	else
		memset(to, 0, n);
	return n;
}

/*
 * Copy a null terminated string from userspace.
 */

#define __do_strncpy_from_user(dst,src,count,res)			   \
do {									   \
	long __d0, __d1, __d2;						   \
	__asm__ __volatile__(						   \
		"	testq %1,%1\n"					   \
		"	jz 2f\n"					   \
		"0:	lodsb\n"					   \
		"	stosb\n"					   \
		"	testb %%al,%%al\n"				   \
		"	jz 1f\n"					   \
		"	decq %1\n"					   \
		"	jnz 0b\n"					   \
		"1:	subq %1,%0\n"					   \
		"2:\n"							   \
		".section .fixup,\"ax\"\n"				   \
		"3:	movq %5,%0\n"					   \
		"	jmp 2b\n"					   \
		".previous\n"						   \
		".section __ex_table,\"a\"\n"				   \
		"	.align 4\n"					   \
		"	.quad 0b,3b\n"					   \
		".previous"						   \
		: "=r"(res), "=c"(count), "=&a" (__d0), "=&S" (__d1),	   \
		  "=&D" (__d2)						   \
		: "i"(-EFAULT), "0"(count), "1"(count), "3"(src), "4"(dst) \
		: "memory");						   \
} while (0)

long
__strncpy_from_user(char *dst, const char *src, long count)
{
	long res;
	__do_strncpy_from_user(dst, src, count, res);
	return res;
}

long
strncpy_from_user(char *dst, const char *src, long count)
{
	long res = -EFAULT;
	if (access_ok(VERIFY_READ, src, 1))
		__do_strncpy_from_user(dst, src, count, res);
	return res;
}


/*
 * Zero Userspace
 */

#define __do_clear_user(addr,size)					\
do {									\
	long __d0;							\
  	__asm__ __volatile__(						\
		"cld\n" \
		"0:	rep; stosl\n"					\
		"	movq %2,%0\n"					\
		"1:	rep; stosb\n"					\
		"2:\n"							\
		".section .fixup,\"ax\"\n"				\
		"3:	lea 0(%2,%0,4),%0\n"				\
		"	jmp 2b\n"					\
		".previous\n"						\
		".section __ex_table,\"a\"\n"				\
		"	.align 4\n"					\
		"	.quad 0b,3b\n"					\
		"	.quad 1b,2b\n"					\
		".previous"						\
		: "=&c"(size), "=&D" (__d0)				\
		: "r"(size & 3), "0"(size / 4), "1"(addr), "a"(0));	\
} while (0)

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

unsigned long
__clear_user(void *to, unsigned long n)
{
	__do_clear_user(to, n);
	return n;
}

/*
 * Return the size of a string (including the ending 0)
 *
 * Return 0 on exception, a value greater than N if too long
 */

long strnlen_user(const char *s, long n)
{
	unsigned long res = 0;
	char c;

	if (!access_ok(VERIFY_READ, s, n))
		return 0;

	while (1) {
		if (get_user(c, s))
			return 0;
		if (!c)
			return res+1;
		if (res>n)
			return n+1;
		res++;
		s++;
	}
}