/* * __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_user1:	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_user2:	movzwl -1(%eax),%edx	xorl %eax,%eax	ret.align 4.globl __get_user_4__get_user_4:	addl $3,%eax    #ptr +3  堆棧向下生長	movl %esp,%edx  #edx=esp用來計算task_struct的地址，esp為內核堆棧指針	jc bad_get_user	andl $0xffffe000,%edx  得到task_struct地址	cmpl addr_limit(%edx),%eax  #比較是否超出了用戶空間地址	jae bad_get_user3:	movl -3(%eax),%edx  #ptr-3 =>%edx	xorl %eax,%eax  #%eax=0	retbad_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