linux/arch/arm26/lib/uaccess-user.S

/*
 *  linux/arch/arm26/lib/uaccess-user.S
 *
 *  Copyright (C) 1995, 1996,1997,1998 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  Routines to block copy data to/from user memory
 *   These are highly optimised both for the 4k page size
 *   and for various alignments.
 */
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/errno.h>
#include <asm/page.h>

		.text

//FIXME - surely this can be done in C not asm, removing the problem of keeping C and asm in sync? (this is a struct uaccess_t)
                .globl  uaccess_user
uaccess_user:
                .word   uaccess_user_put_byte
                .word   uaccess_user_get_byte
                .word   uaccess_user_put_half
                .word   uaccess_user_get_half
                .word   uaccess_user_put_word
                .word   uaccess_user_get_word
		.word   uaccess_user_put_dword
                .word   uaccess_user_copy_from_user
                .word   uaccess_user_copy_to_user
                .word   uaccess_user_clear_user
                .word   uaccess_user_strncpy_from_user
                .word   uaccess_user_strnlen_user


@ In : r0 = x, r1 = addr, r2 = error
@ Out: r2 = error
uaccess_user_put_byte:
                stmfd   sp!, {lr}
USER(           strbt   r0, [r1])
                ldmfd   sp!, {pc}^

@ In : r0 = x, r1 = addr, r2 = error
@ Out: r2 = error
uaccess_user_put_half:
                stmfd   sp!, {lr}
USER(           strbt   r0, [r1], #1)
                mov     r0, r0, lsr #8
USER(           strbt   r0, [r1])
                ldmfd   sp!, {pc}^

@ In : r0 = x, r1 = addr, r2 = error
@ Out: r2 = error
uaccess_user_put_word:
                stmfd   sp!, {lr}
USER(           strt    r0, [r1])
                ldmfd   sp!, {pc}^

@ In : r0 = x, r1 = addr, r2 = error
@ Out: r2 = error
uaccess_user_put_dword:
                stmfd   sp!, {lr}
USER(           strt    r0, [r1], #4)
USER(           strt    r0, [r1], #0)
                ldmfd   sp!, {pc}^

9001:           mov     r2, #-EFAULT
                ldmfd   sp!, {pc}^


@ In : r0 = addr, r1 = error
@ Out: r0 = x, r1 = error
uaccess_user_get_byte:
                stmfd   sp!, {lr}
USER(           ldrbt   r0, [r0])
                ldmfd   sp!, {pc}^

@ In : r0 = addr, r1 = error
@ Out: r0 = x, r1 = error
uaccess_user_get_half:
                stmfd   sp!, {lr}
USER(           ldrt    r0, [r0])
                mov     r0, r0, lsl #16
                mov     r0, r0, lsr #16
                ldmfd   sp!, {pc}^

@ In : r0 = addr, r1 = error
@ Out: r0 = x, r1 = error
uaccess_user_get_word:
                stmfd   sp!, {lr}
USER(           ldrt    r0, [r0])
                ldmfd   sp!, {pc}^

9001:           mov     r1, #-EFAULT
                ldmfd   sp!, {pc}^

/* Prototype: int uaccess_user_copy_to_user(void *to, const char *from, size_t n)
 * Purpose  : copy a block to user memory from kernel memory
 * Params   : to   - user memory
 *          : from - kernel memory
 *          : n    - number of bytes to copy
 * Returns  : Number of bytes NOT copied.
 */

.c2u_dest_not_aligned:
		rsb	ip, ip, #4
		cmp	ip, #2
		ldrb	r3, [r1], #1
USER(		strbt	r3, [r0], #1)			@ May fault
		ldrgeb	r3, [r1], #1
USER(		strgebt	r3, [r0], #1)			@ May fault
		ldrgtb	r3, [r1], #1
USER(		strgtbt	r3, [r0], #1)			@ May fault
		sub	r2, r2, ip
		b	.c2u_dest_aligned

ENTRY(uaccess_user_copy_to_user)
		stmfd	sp!, {r2, r4 - r7, lr}
		cmp	r2, #4
		blt	.c2u_not_enough
		ands	ip, r0, #3
		bne	.c2u_dest_not_aligned
.c2u_dest_aligned:

		ands	ip, r1, #3
		bne	.c2u_src_not_aligned
/*
 * Seeing as there has to be at least 8 bytes to copy, we can
 * copy one word, and force a user-mode page fault...
 */

.c2u_0fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.c2u_0nowords
		ldr	r3, [r1], #4
USER(		strt	r3, [r0], #4)			@ May fault
		mov	ip, r0, lsl #32 - PAGE_SHIFT	@ On each page, use a ld/st??t instruction
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.c2u_0fupi
/*
 * ip = max no. of bytes to copy before needing another "strt" insn
 */
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #32
		blt	.c2u_0rem8lp

.c2u_0cpy8lp:	ldmia	r1!, {r3 - r6}
		stmia	r0!, {r3 - r6}			@ Shouldnt fault
		ldmia	r1!, {r3 - r6}
		stmia	r0!, {r3 - r6}			@ Shouldnt fault
		subs	ip, ip, #32
		bpl	.c2u_0cpy8lp
.c2u_0rem8lp:	cmn	ip, #16
		ldmgeia	r1!, {r3 - r6}
		stmgeia	r0!, {r3 - r6}			@ Shouldnt fault
		tst	ip, #8
		ldmneia	r1!, {r3 - r4}
		stmneia	r0!, {r3 - r4}			@ Shouldnt fault
		tst	ip, #4
		ldrne	r3, [r1], #4
		strnet	r3, [r0], #4			@ Shouldnt fault
		ands	ip, ip, #3
		beq	.c2u_0fupi
.c2u_0nowords:	teq	ip, #0
		beq	.c2u_finished
.c2u_nowords:	cmp	ip, #2
		ldrb	r3, [r1], #1
USER(		strbt	r3, [r0], #1)			@ May fault
		ldrgeb	r3, [r1], #1
USER(		strgebt	r3, [r0], #1)			@ May fault
		ldrgtb	r3, [r1], #1
USER(		strgtbt	r3, [r0], #1)			@ May fault
		b	.c2u_finished

.c2u_not_enough:
		movs	ip, r2
		bne	.c2u_nowords
.c2u_finished:	mov	r0, #0
		LOADREGS(fd,sp!,{r2, r4 - r7, pc})

.c2u_src_not_aligned:
		bic	r1, r1, #3
		ldr	r7, [r1], #4
		cmp	ip, #2
		bgt	.c2u_3fupi
		beq	.c2u_2fupi
.c2u_1fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.c2u_1nowords
		mov	r3, r7, pull #8
		ldr	r7, [r1], #4
		orr	r3, r3, r7, push #24
USER(		strt	r3, [r0], #4)			@ May fault
		mov	ip, r0, lsl #32 - PAGE_SHIFT
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.c2u_1fupi
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #16
		blt	.c2u_1rem8lp

.c2u_1cpy8lp:	mov	r3, r7, pull #8
		ldmia	r1!, {r4 - r7}
		orr	r3, r3, r4, push #24
		mov	r4, r4, pull #8
		orr	r4, r4, r5, push #24
		mov	r5, r5, pull #8
		orr	r5, r5, r6, push #24
		mov	r6, r6, pull #8
		orr	r6, r6, r7, push #24
		stmia	r0!, {r3 - r6}			@ Shouldnt fault
		subs	ip, ip, #16
		bpl	.c2u_1cpy8lp
.c2u_1rem8lp:	tst	ip, #8
		movne	r3, r7, pull #8
		ldmneia	r1!, {r4, r7}
		orrne	r3, r3, r4, push #24
		movne	r4, r4, pull #8
		orrne	r4, r4, r7, push #24
		stmneia	r0!, {r3 - r4}			@ Shouldnt fault
		tst	ip, #4
		movne	r3, r7, pull #8
		ldrne	r7, [r1], #4
		orrne	r3, r3, r7, push #24
		strnet	r3, [r0], #4			@ Shouldnt fault
		ands	ip, ip, #3
		beq	.c2u_1fupi
.c2u_1nowords:	mov	r3, r7, lsr #byte(1)
		teq	ip, #0
		beq	.c2u_finished
		cmp	ip, #2
USER(		strbt	r3, [r0], #1)			@ May fault
		movge	r3, r7, lsr #byte(2)
USER(		strgebt	r3, [r0], #1)			@ May fault
		movgt	r3, r7, lsr #byte(3)
USER(		strgtbt	r3, [r0], #1)			@ May fault
		b	.c2u_finished

.c2u_2fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.c2u_2nowords
		mov	r3, r7, pull #16
		ldr	r7, [r1], #4
		orr	r3, r3, r7, push #16
USER(		strt	r3, [r0], #4)			@ May fault
		mov	ip, r0, lsl #32 - PAGE_SHIFT
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.c2u_2fupi
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #16
		blt	.c2u_2rem8lp

.c2u_2cpy8lp:	mov	r3, r7, pull #16
		ldmia	r1!, {r4 - r7}
		orr	r3, r3, r4, push #16
		mov	r4, r4, pull #16
		orr	r4, r4, r5, push #16
		mov	r5, r5, pull #16
		orr	r5, r5, r6, push #16
		mov	r6, r6, pull #16
		orr	r6, r6, r7, push #16
		stmia	r0!, {r3 - r6}			@ Shouldnt fault
		subs	ip, ip, #16
		bpl	.c2u_2cpy8lp
.c2u_2rem8lp:	tst	ip, #8
		movne	r3, r7, pull #16
		ldmneia	r1!, {r4, r7}
		orrne	r3, r3, r4, push #16
		movne	r4, r4, pull #16
		orrne	r4, r4, r7, push #16
		stmneia	r0!, {r3 - r4}			@ Shouldnt fault
		tst	ip, #4
		movne	r3, r7, pull #16
		ldrne	r7, [r1], #4
		orrne	r3, r3, r7, push #16
		strnet	r3, [r0], #4			@ Shouldnt fault
		ands	ip, ip, #3
		beq	.c2u_2fupi
.c2u_2nowords:	mov	r3, r7, lsr #byte(2)
		teq	ip, #0
		beq	.c2u_finished
		cmp	ip, #2
USER(		strbt	r3, [r0], #1)			@ May fault
		movge	r3, r7, lsr #byte(3)
USER(		strgebt	r3, [r0], #1)			@ May fault
		ldrgtb	r3, [r1], #0
USER(		strgtbt	r3, [r0], #1)			@ May fault
		b	.c2u_finished

.c2u_3fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.c2u_3nowords
		mov	r3, r7, pull #24
		ldr	r7, [r1], #4
		orr	r3, r3, r7, push #8
USER(		strt	r3, [r0], #4)			@ May fault
		mov	ip, r0, lsl #32 - PAGE_SHIFT
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.c2u_3fupi
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #16
		blt	.c2u_3rem8lp

.c2u_3cpy8lp:	mov	r3, r7, pull #24
		ldmia	r1!, {r4 - r7}
		orr	r3, r3, r4, push #8
		mov	r4, r4, pull #24
		orr	r4, r4, r5, push #8
		mov	r5, r5, pull #24
		orr	r5, r5, r6, push #8
		mov	r6, r6, pull #24
		orr	r6, r6, r7, push #8
		stmia	r0!, {r3 - r6}			@ Shouldnt fault
		subs	ip, ip, #16
		bpl	.c2u_3cpy8lp
.c2u_3rem8lp:	tst	ip, #8
		movne	r3, r7, pull #24
		ldmneia	r1!, {r4, r7}
		orrne	r3, r3, r4, push #8
		movne	r4, r4, pull #24
		orrne	r4, r4, r7, push #8
		stmneia	r0!, {r3 - r4}			@ Shouldnt fault
		tst	ip, #4
		movne	r3, r7, pull #24
		ldrne	r7, [r1], #4
		orrne	r3, r3, r7, push #8
		strnet	r3, [r0], #4			@ Shouldnt fault
		ands	ip, ip, #3
		beq	.c2u_3fupi
.c2u_3nowords:	mov	r3, r7, lsr #byte(3)
		teq	ip, #0
		beq	.c2u_finished
		cmp	ip, #2
USER(		strbt	r3, [r0], #1)			@ May fault
		ldrgeb	r3, [r1], #1
USER(		strgebt	r3, [r0], #1)			@ May fault
		ldrgtb	r3, [r1], #0
USER(		strgtbt	r3, [r0], #1)			@ May fault
		b	.c2u_finished

		.section .fixup,"ax"
		.align	0
9001:		LOADREGS(fd,sp!, {r0, r4 - r7, pc})
		.previous

/* Prototype: unsigned long uaccess_user_copy_from_user(void *to,const void *from,unsigned long n);
 * Purpose  : copy a block from user memory to kernel memory
 * Params   : to   - kernel memory
 *          : from - user memory
 *          : n    - number of bytes to copy
 * Returns  : Number of bytes NOT copied.
 */
.cfu_dest_not_aligned:
		rsb	ip, ip, #4
		cmp	ip, #2
USER(		ldrbt	r3, [r1], #1)			@ May fault
		strb	r3, [r0], #1
USER(		ldrgebt	r3, [r1], #1)			@ May fault
		strgeb	r3, [r0], #1
USER(		ldrgtbt	r3, [r1], #1)			@ May fault
		strgtb	r3, [r0], #1
		sub	r2, r2, ip
		b	.cfu_dest_aligned

ENTRY(uaccess_user_copy_from_user)
		stmfd	sp!, {r0, r2, r4 - r7, lr}
		cmp	r2, #4
		blt	.cfu_not_enough
		ands	ip, r0, #3
		bne	.cfu_dest_not_aligned
.cfu_dest_aligned:
		ands	ip, r1, #3
		bne	.cfu_src_not_aligned
/*
 * Seeing as there has to be at least 8 bytes to copy, we can
 * copy one word, and force a user-mode page fault...
 */

.cfu_0fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.cfu_0nowords
USER(		ldrt	r3, [r1], #4)
		str	r3, [r0], #4
		mov	ip, r1, lsl #32 - PAGE_SHIFT	@ On each page, use a ld/st??t instruction
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.cfu_0fupi
/*
 * ip = max no. of bytes to copy before needing another "strt" insn
 */
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #32
		blt	.cfu_0rem8lp

.cfu_0cpy8lp:	ldmia	r1!, {r3 - r6}			@ Shouldnt fault
		stmia	r0!, {r3 - r6}
		ldmia	r1!, {r3 - r6}			@ Shouldnt fault
		stmia	r0!, {r3 - r6}
		subs	ip, ip, #32
		bpl	.cfu_0cpy8lp
.cfu_0rem8lp:	cmn	ip, #16
		ldmgeia	r1!, {r3 - r6}			@ Shouldnt fault
		stmgeia	r0!, {r3 - r6}
		tst	ip, #8
		ldmneia	r1!, {r3 - r4}			@ Shouldnt fault
		stmneia	r0!, {r3 - r4}
		tst	ip, #4
		ldrnet	r3, [r1], #4			@ Shouldnt fault
		strne	r3, [r0], #4
		ands	ip, ip, #3
		beq	.cfu_0fupi
.cfu_0nowords:	teq	ip, #0
		beq	.cfu_finished
.cfu_nowords:	cmp	ip, #2
USER(		ldrbt	r3, [r1], #1)			@ May fault
		strb	r3, [r0], #1
USER(		ldrgebt	r3, [r1], #1)			@ May fault
		strgeb	r3, [r0], #1
USER(		ldrgtbt	r3, [r1], #1)			@ May fault
		strgtb	r3, [r0], #1
		b	.cfu_finished

.cfu_not_enough:
		movs	ip, r2
		bne	.cfu_nowords
.cfu_finished:	mov	r0, #0
		add	sp, sp, #8
		LOADREGS(fd,sp!,{r4 - r7, pc})

.cfu_src_not_aligned:
		bic	r1, r1, #3
USER(		ldrt	r7, [r1], #4)			@ May fault
		cmp	ip, #2
		bgt	.cfu_3fupi
		beq	.cfu_2fupi
.cfu_1fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.cfu_1nowords
		mov	r3, r7, pull #8
USER(		ldrt	r7, [r1], #4)			@ May fault
		orr	r3, r3, r7, push #24
		str	r3, [r0], #4
		mov	ip, r1, lsl #32 - PAGE_SHIFT
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.cfu_1fupi
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #16
		blt	.cfu_1rem8lp

.cfu_1cpy8lp:	mov	r3, r7, pull #8
		ldmia	r1!, {r4 - r7}			@ Shouldnt fault
		orr	r3, r3, r4, push #24
		mov	r4, r4, pull #8
		orr	r4, r4, r5, push #24
		mov	r5, r5, pull #8
		orr	r5, r5, r6, push #24
		mov	r6, r6, pull #8
		orr	r6, r6, r7, push #24
		stmia	r0!, {r3 - r6}
		subs	ip, ip, #16
		bpl	.cfu_1cpy8lp
.cfu_1rem8lp:	tst	ip, #8
		movne	r3, r7, pull #8
		ldmneia	r1!, {r4, r7}			@ Shouldnt fault
		orrne	r3, r3, r4, push #24
		movne	r4, r4, pull #8
		orrne	r4, r4, r7, push #24
		stmneia	r0!, {r3 - r4}
		tst	ip, #4
		movne	r3, r7, pull #8
USER(		ldrnet	r7, [r1], #4)			@ May fault
		orrne	r3, r3, r7, push #24
		strne	r3, [r0], #4
		ands	ip, ip, #3
		beq	.cfu_1fupi
.cfu_1nowords:	mov	r3, r7, lsr #byte(1)
		teq	ip, #0
		beq	.cfu_finished
		cmp	ip, #2
		strb	r3, [r0], #1
		movge	r3, r7, lsr #byte(2)
		strgeb	r3, [r0], #1
		movgt	r3, r7, lsr #byte(3)
		strgtb	r3, [r0], #1
		b	.cfu_finished

.cfu_2fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.cfu_2nowords
		mov	r3, r7, pull #16
USER(		ldrt	r7, [r1], #4)			@ May fault
		orr	r3, r3, r7, push #16
		str	r3, [r0], #4
		mov	ip, r1, lsl #32 - PAGE_SHIFT
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.cfu_2fupi
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #16
		blt	.cfu_2rem8lp

.cfu_2cpy8lp:	mov	r3, r7, pull #16
		ldmia	r1!, {r4 - r7}			@ Shouldnt fault
		orr	r3, r3, r4, push #16
		mov	r4, r4, pull #16
		orr	r4, r4, r5, push #16
		mov	r5, r5, pull #16
		orr	r5, r5, r6, push #16
		mov	r6, r6, pull #16
		orr	r6, r6, r7, push #16
		stmia	r0!, {r3 - r6}
		subs	ip, ip, #16
		bpl	.cfu_2cpy8lp
.cfu_2rem8lp:	tst	ip, #8
		movne	r3, r7, pull #16
		ldmneia	r1!, {r4, r7}			@ Shouldnt fault
		orrne	r3, r3, r4, push #16
		movne	r4, r4, pull #16
		orrne	r4, r4, r7, push #16
		stmneia	r0!, {r3 - r4}
		tst	ip, #4
		movne	r3, r7, pull #16
USER(		ldrnet	r7, [r1], #4)			@ May fault
		orrne	r3, r3, r7, push #16
		strne	r3, [r0], #4
		ands	ip, ip, #3
		beq	.cfu_2fupi
.cfu_2nowords:	mov	r3, r7, lsr #byte(2)
		teq	ip, #0
		beq	.cfu_finished
		cmp	ip, #2
		strb	r3, [r0], #1
		movge	r3, r7, lsr #byte(3)
		strgeb	r3, [r0], #1
USER(		ldrgtbt	r3, [r1], #0)			@ May fault
		strgtb	r3, [r0], #1
		b	.cfu_finished

.cfu_3fupi:	subs	r2, r2, #4
		addmi	ip, r2, #4
		bmi	.cfu_3nowords
		mov	r3, r7, pull #24
USER(		ldrt	r7, [r1], #4)			@ May fault
		orr	r3, r3, r7, push #8
		str	r3, [r0], #4
		mov	ip, r1, lsl #32 - PAGE_SHIFT
		rsb	ip, ip, #0
		movs	ip, ip, lsr #32 - PAGE_SHIFT
		beq	.cfu_3fupi
		cmp	r2, ip
		movlt	ip, r2
		sub	r2, r2, ip
		subs	ip, ip, #16
		blt	.cfu_3rem8lp

.cfu_3cpy8lp:	mov	r3, r7, pull #24
		ldmia	r1!, {r4 - r7}			@ Shouldnt fault
		orr	r3, r3, r4, push #8
		mov	r4, r4, pull #24
		orr	r4, r4, r5, push #8
		mov	r5, r5, pull #24
		orr	r5, r5, r6, push #8
		mov	r6, r6, pull #24
		orr	r6, r6, r7, push #8
		stmia	r0!, {r3 - r6}
		subs	ip, ip, #16
		bpl	.cfu_3cpy8lp
.cfu_3rem8lp:	tst	ip, #8
		movne	r3, r7, pull #24
		ldmneia	r1!, {r4, r7}			@ Shouldnt fault
		orrne	r3, r3, r4, push #8
		movne	r4, r4, pull #24
		orrne	r4, r4, r7, push #8
		stmneia	r0!, {r3 - r4}
		tst	ip, #4
		movne	r3, r7, pull #24
USER(		ldrnet	r7, [r1], #4)			@ May fault
		orrne	r3, r3, r7, push #8
		strne	r3, [r0], #4
		ands	ip, ip, #3
		beq	.cfu_3fupi
.cfu_3nowords:	mov	r3, r7, lsr #byte(3)
		teq	ip, #0
		beq	.cfu_finished
		cmp	ip, #2
		strb	r3, [r0], #1
USER(		ldrgebt	r3, [r1], #1)			@ May fault
		strgeb	r3, [r0], #1
USER(		ldrgtbt	r3, [r1], #1)			@ May fault
		strgtb	r3, [r0], #1
		b	.cfu_finished

		.section .fixup,"ax"
		.align	0
		/*
		 * We took an exception.  r0 contains a pointer to
		 * the byte not copied.
		 */
9001:		ldr	r2, [sp], #4			@ void *to
		sub	r2, r0, r2			@ bytes copied
		ldr	r1, [sp], #4			@ unsigned long count
		subs	r4, r1, r2			@ bytes left to copy
		movne	r1, r4
		blne	__memzero
		mov	r0, r4
		LOADREGS(fd,sp!, {r4 - r7, pc})
		.previous

/* Prototype: int uaccess_user_clear_user(void *addr, size_t sz)
 * Purpose  : clear some user memory
 * Params   : addr - user memory address to clear
 *          : sz   - number of bytes to clear
 * Returns  : number of bytes NOT cleared
 */
ENTRY(uaccess_user_clear_user)
		stmfd	sp!, {r1, lr}
		mov	r2, #0
		cmp	r1, #4
		blt	2f
		ands	ip, r0, #3
		beq	1f
		cmp	ip, #2
USER(		strbt	r2, [r0], #1)
USER(		strlebt	r2, [r0], #1)
USER(		strltbt	r2, [r0], #1)
		rsb	ip, ip, #4
		sub	r1, r1, ip		@  7  6  5  4  3  2  1
1:		subs	r1, r1, #8		@ -1 -2 -3 -4 -5 -6 -7
USER(		strplt	r2, [r0], #4)
USER(		strplt	r2, [r0], #4)
		bpl	1b
		adds	r1, r1, #4		@  3  2  1  0 -1 -2 -3
USER(		strplt	r2, [r0], #4)
2:		tst	r1, #2			@ 1x 1x 0x 0x 1x 1x 0x
USER(		strnebt	r2, [r0], #1)
USER(		strnebt	r2, [r0], #1)
		tst	r1, #1			@ x1 x0 x1 x0 x1 x0 x1
USER(		strnebt	r2, [r0], #1)
		mov	r0, #0
		LOADREGS(fd,sp!, {r1, pc})

		.section .fixup,"ax"
		.align	0
9001:		LOADREGS(fd,sp!, {r0, pc})
		.previous

/*
 * Copy a string from user space to kernel space.
 *  r0 = dst, r1 = src, r2 = byte length
 * returns the number of characters copied (strlen of copied string),
 *  -EFAULT on exception, or "len" if we fill the whole buffer
 */
ENTRY(uaccess_user_strncpy_from_user)
        save_lr
        mov     ip, r1
1:      subs    r2, r2, #1
USER(   ldrplbt r3, [r1], #1)
        bmi     2f
        strb    r3, [r0], #1
        teq     r3, #0
        bne     1b
        sub     r1, r1, #1      @ take NUL character out of count
2:      sub     r0, r1, ip
        restore_pc

        .section .fixup,"ax"
        .align  0
9001:   mov     r3, #0
        strb    r3, [r0, #0]    @ null terminate
        mov     r0, #-EFAULT
        restore_pc
        .previous

/* Prototype: unsigned long uaccess_user_strnlen_user(const char *str, long n)
 * Purpose  : get length of a string in user memory
 * Params   : str - address of string in user memory
 * Returns  : length of string *including terminator*
 *            or zero on exception, or n + 1 if too long
 */
ENTRY(uaccess_user_strnlen_user)
        save_lr
        mov     r2, r0
1:
USER(   ldrbt   r3, [r0], #1)
        teq     r3, #0
        beq     2f
        subs    r1, r1, #1
        bne     1b
        add     r0, r0, #1
2:      sub     r0, r0, r2
        restore_pc

        .section .fixup,"ax"
        .align  0
9001:   mov     r0, #0
        restore_pc
        .previous