linux/arch/x86/lib/getuser_32.S

/*
 * __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.
 */
#include <linux/linkage.h>
#include <asm/dwarf2.h>
#include <asm/thread_info.h>


/*
 * __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.
 */

.text
ENTRY(__get_user_1)
	CFI_STARTPROC
	GET_THREAD_INFO(%edx)
	cmpl TI_addr_limit(%edx),%eax
	jae bad_get_user
1:	movzbl (%eax),%edx
	xorl %eax,%eax
	ret
	CFI_ENDPROC
ENDPROC(__get_user_1)

ENTRY(__get_user_2)
	CFI_STARTPROC
	addl $1,%eax
	jc bad_get_user
	GET_THREAD_INFO(%edx)
	cmpl TI_addr_limit(%edx),%eax
	jae bad_get_user
2:	movzwl -1(%eax),%edx
	xorl %eax,%eax
	ret
	CFI_ENDPROC
ENDPROC(__get_user_2)

ENTRY(__get_user_4)
	CFI_STARTPROC
	addl $3,%eax
	jc bad_get_user
	GET_THREAD_INFO(%edx)
	cmpl TI_addr_limit(%edx),%eax
	jae bad_get_user
3:	movl -3(%eax),%edx
	xorl %eax,%eax
	ret
	CFI_ENDPROC
ENDPROC(__get_user_4)

bad_get_user:
	CFI_STARTPROC
	xorl %edx,%edx
	movl $-14,%eax
	ret
	CFI_ENDPROC
END(bad_get_user)

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