getuser.s

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

/*
 * __get_user functions.
 *
 * (C) Copyright 1998 Linus Torvalds
 *
 * These functions have a non-standard call interface
 * to make them more efficient, especially as they
 * return an error value in addition to the "real"
 * return value.
 */

/*
 * __get_user_X
 *
 * Inputs:	%eax contains the address
 *
 * Outputs:	%eax is error code (0 or -EFAULT)
 *		%edx contains zero-extended value
 *
 * These functions should not modify any other registers,
 * as they get called from within inline assembly.
 */

addr_limit = 12

.text
.align 4
.globl __get_user_1
__get_user_1:
	movl %esp,%edx
	andl $0xffffe000,%edx
	cmpl addr_limit(%edx),%eax
	jae bad_get_user
1:	movzbl (%eax),%edx
	xorl %eax,%eax
	ret

.align 4
.globl __get_user_2
__get_user_2:
	addl $1,%eax
	movl %esp,%edx
	jc bad_get_user
	andl $0xffffe000,%edx
	cmpl addr_limit(%edx),%eax
	jae bad_get_user
2:	movzwl -1(%eax),%edx
	xorl %eax,%eax
	ret

.align 4
.globl __get_user_4
__get_user_4:
	addl $3,%eax
	movl %esp,%edx
	jc bad_get_user
	andl $0xffffe000,%edx
	cmpl addr_limit(%edx),%eax
	jae bad_get_user
3:	movl -3(%eax),%edx
	xorl %eax,%eax
	ret

bad_get_user:
	xorl %edx,%edx
	movl $-14,%eax
	ret

.section __ex_table,"a"
	.long 1b,bad_get_user
	.long 2b,bad_get_user
	.long 3b,bad_get_user
.previous