Merge ../linux-2.6
[linux-2.6] / arch / arm / lib / uaccess.S
1 /*
2  *  linux/arch/arm/lib/uaccess.S
3  *
4  *  Copyright (C) 1995, 1996,1997,1998 Russell King
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  *  Routines to block copy data to/from user memory
11  *   These are highly optimised both for the 4k page size
12  *   and for various alignments.
13  */
14 #include <linux/linkage.h>
15 #include <asm/assembler.h>
16 #include <asm/errno.h>
17
18                 .text
19
20 #define PAGE_SHIFT 12
21
22 /* Prototype: int __arch_copy_to_user(void *to, const char *from, size_t n)
23  * Purpose  : copy a block to user memory from kernel memory
24  * Params   : to   - user memory
25  *          : from - kernel memory
26  *          : n    - number of bytes to copy
27  * Returns  : Number of bytes NOT copied.
28  */
29
30 .Lc2u_dest_not_aligned:
31                 rsb     ip, ip, #4
32                 cmp     ip, #2
33                 ldrb    r3, [r1], #1
34 USER(           strbt   r3, [r0], #1)                   @ May fault
35                 ldrgeb  r3, [r1], #1
36 USER(           strgebt r3, [r0], #1)                   @ May fault
37                 ldrgtb  r3, [r1], #1
38 USER(           strgtbt r3, [r0], #1)                   @ May fault
39                 sub     r2, r2, ip
40                 b       .Lc2u_dest_aligned
41
42 ENTRY(__arch_copy_to_user)
43                 stmfd   sp!, {r2, r4 - r7, lr}
44                 cmp     r2, #4
45                 blt     .Lc2u_not_enough
46                 ands    ip, r0, #3
47                 bne     .Lc2u_dest_not_aligned
48 .Lc2u_dest_aligned:
49
50                 ands    ip, r1, #3
51                 bne     .Lc2u_src_not_aligned
52 /*
53  * Seeing as there has to be at least 8 bytes to copy, we can
54  * copy one word, and force a user-mode page fault...
55  */
56
57 .Lc2u_0fupi:    subs    r2, r2, #4
58                 addmi   ip, r2, #4
59                 bmi     .Lc2u_0nowords
60                 ldr     r3, [r1], #4
61 USER(           strt    r3, [r0], #4)                   @ May fault
62                 mov     ip, r0, lsl #32 - PAGE_SHIFT    @ On each page, use a ld/st??t instruction
63                 rsb     ip, ip, #0
64                 movs    ip, ip, lsr #32 - PAGE_SHIFT
65                 beq     .Lc2u_0fupi
66 /*
67  * ip = max no. of bytes to copy before needing another "strt" insn
68  */
69                 cmp     r2, ip
70                 movlt   ip, r2
71                 sub     r2, r2, ip
72                 subs    ip, ip, #32
73                 blt     .Lc2u_0rem8lp
74
75 .Lc2u_0cpy8lp:  ldmia   r1!, {r3 - r6}
76                 stmia   r0!, {r3 - r6}                  @ Shouldnt fault
77                 ldmia   r1!, {r3 - r6}
78                 subs    ip, ip, #32
79                 stmia   r0!, {r3 - r6}                  @ Shouldnt fault
80                 bpl     .Lc2u_0cpy8lp
81
82 .Lc2u_0rem8lp:  cmn     ip, #16
83                 ldmgeia r1!, {r3 - r6}
84                 stmgeia r0!, {r3 - r6}                  @ Shouldnt fault
85                 tst     ip, #8
86                 ldmneia r1!, {r3 - r4}
87                 stmneia r0!, {r3 - r4}                  @ Shouldnt fault
88                 tst     ip, #4
89                 ldrne   r3, [r1], #4
90                 strnet  r3, [r0], #4                    @ Shouldnt fault
91                 ands    ip, ip, #3
92                 beq     .Lc2u_0fupi
93 .Lc2u_0nowords: teq     ip, #0
94                 beq     .Lc2u_finished
95 .Lc2u_nowords:  cmp     ip, #2
96                 ldrb    r3, [r1], #1
97 USER(           strbt   r3, [r0], #1)                   @ May fault
98                 ldrgeb  r3, [r1], #1
99 USER(           strgebt r3, [r0], #1)                   @ May fault
100                 ldrgtb  r3, [r1], #1
101 USER(           strgtbt r3, [r0], #1)                   @ May fault
102                 b       .Lc2u_finished
103
104 .Lc2u_not_enough:
105                 movs    ip, r2
106                 bne     .Lc2u_nowords
107 .Lc2u_finished: mov     r0, #0
108                 LOADREGS(fd,sp!,{r2, r4 - r7, pc})
109
110 .Lc2u_src_not_aligned:
111                 bic     r1, r1, #3
112                 ldr     r7, [r1], #4
113                 cmp     ip, #2
114                 bgt     .Lc2u_3fupi
115                 beq     .Lc2u_2fupi
116 .Lc2u_1fupi:    subs    r2, r2, #4
117                 addmi   ip, r2, #4
118                 bmi     .Lc2u_1nowords
119                 mov     r3, r7, pull #8
120                 ldr     r7, [r1], #4
121                 orr     r3, r3, r7, push #24
122 USER(           strt    r3, [r0], #4)                   @ May fault
123                 mov     ip, r0, lsl #32 - PAGE_SHIFT
124                 rsb     ip, ip, #0
125                 movs    ip, ip, lsr #32 - PAGE_SHIFT
126                 beq     .Lc2u_1fupi
127                 cmp     r2, ip
128                 movlt   ip, r2
129                 sub     r2, r2, ip
130                 subs    ip, ip, #16
131                 blt     .Lc2u_1rem8lp
132
133 .Lc2u_1cpy8lp:  mov     r3, r7, pull #8
134                 ldmia   r1!, {r4 - r7}
135                 subs    ip, ip, #16
136                 orr     r3, r3, r4, push #24
137                 mov     r4, r4, pull #8
138                 orr     r4, r4, r5, push #24
139                 mov     r5, r5, pull #8
140                 orr     r5, r5, r6, push #24
141                 mov     r6, r6, pull #8
142                 orr     r6, r6, r7, push #24
143                 stmia   r0!, {r3 - r6}                  @ Shouldnt fault
144                 bpl     .Lc2u_1cpy8lp
145
146 .Lc2u_1rem8lp:  tst     ip, #8
147                 movne   r3, r7, pull #8
148                 ldmneia r1!, {r4, r7}
149                 orrne   r3, r3, r4, push #24
150                 movne   r4, r4, pull #8
151                 orrne   r4, r4, r7, push #24
152                 stmneia r0!, {r3 - r4}                  @ Shouldnt fault
153                 tst     ip, #4
154                 movne   r3, r7, pull #8
155                 ldrne   r7, [r1], #4
156                 orrne   r3, r3, r7, push #24
157                 strnet  r3, [r0], #4                    @ Shouldnt fault
158                 ands    ip, ip, #3
159                 beq     .Lc2u_1fupi
160 .Lc2u_1nowords: mov     r3, r7, get_byte_1
161                 teq     ip, #0
162                 beq     .Lc2u_finished
163                 cmp     ip, #2
164 USER(           strbt   r3, [r0], #1)                   @ May fault
165                 movge   r3, r7, get_byte_2
166 USER(           strgebt r3, [r0], #1)                   @ May fault
167                 movgt   r3, r7, get_byte_3
168 USER(           strgtbt r3, [r0], #1)                   @ May fault
169                 b       .Lc2u_finished
170
171 .Lc2u_2fupi:    subs    r2, r2, #4
172                 addmi   ip, r2, #4
173                 bmi     .Lc2u_2nowords
174                 mov     r3, r7, pull #16
175                 ldr     r7, [r1], #4
176                 orr     r3, r3, r7, push #16
177 USER(           strt    r3, [r0], #4)                   @ May fault
178                 mov     ip, r0, lsl #32 - PAGE_SHIFT
179                 rsb     ip, ip, #0
180                 movs    ip, ip, lsr #32 - PAGE_SHIFT
181                 beq     .Lc2u_2fupi
182                 cmp     r2, ip
183                 movlt   ip, r2
184                 sub     r2, r2, ip
185                 subs    ip, ip, #16
186                 blt     .Lc2u_2rem8lp
187
188 .Lc2u_2cpy8lp:  mov     r3, r7, pull #16
189                 ldmia   r1!, {r4 - r7}
190                 subs    ip, ip, #16
191                 orr     r3, r3, r4, push #16
192                 mov     r4, r4, pull #16
193                 orr     r4, r4, r5, push #16
194                 mov     r5, r5, pull #16
195                 orr     r5, r5, r6, push #16
196                 mov     r6, r6, pull #16
197                 orr     r6, r6, r7, push #16
198                 stmia   r0!, {r3 - r6}                  @ Shouldnt fault
199                 bpl     .Lc2u_2cpy8lp
200
201 .Lc2u_2rem8lp:  tst     ip, #8
202                 movne   r3, r7, pull #16
203                 ldmneia r1!, {r4, r7}
204                 orrne   r3, r3, r4, push #16
205                 movne   r4, r4, pull #16
206                 orrne   r4, r4, r7, push #16
207                 stmneia r0!, {r3 - r4}                  @ Shouldnt fault
208                 tst     ip, #4
209                 movne   r3, r7, pull #16
210                 ldrne   r7, [r1], #4
211                 orrne   r3, r3, r7, push #16
212                 strnet  r3, [r0], #4                    @ Shouldnt fault
213                 ands    ip, ip, #3
214                 beq     .Lc2u_2fupi
215 .Lc2u_2nowords: mov     r3, r7, get_byte_2
216                 teq     ip, #0
217                 beq     .Lc2u_finished
218                 cmp     ip, #2
219 USER(           strbt   r3, [r0], #1)                   @ May fault
220                 movge   r3, r7, get_byte_3
221 USER(           strgebt r3, [r0], #1)                   @ May fault
222                 ldrgtb  r3, [r1], #0
223 USER(           strgtbt r3, [r0], #1)                   @ May fault
224                 b       .Lc2u_finished
225
226 .Lc2u_3fupi:    subs    r2, r2, #4
227                 addmi   ip, r2, #4
228                 bmi     .Lc2u_3nowords
229                 mov     r3, r7, pull #24
230                 ldr     r7, [r1], #4
231                 orr     r3, r3, r7, push #8
232 USER(           strt    r3, [r0], #4)                   @ May fault
233                 mov     ip, r0, lsl #32 - PAGE_SHIFT
234                 rsb     ip, ip, #0
235                 movs    ip, ip, lsr #32 - PAGE_SHIFT
236                 beq     .Lc2u_3fupi
237                 cmp     r2, ip
238                 movlt   ip, r2
239                 sub     r2, r2, ip
240                 subs    ip, ip, #16
241                 blt     .Lc2u_3rem8lp
242
243 .Lc2u_3cpy8lp:  mov     r3, r7, pull #24
244                 ldmia   r1!, {r4 - r7}
245                 subs    ip, ip, #16
246                 orr     r3, r3, r4, push #8
247                 mov     r4, r4, pull #24
248                 orr     r4, r4, r5, push #8
249                 mov     r5, r5, pull #24
250                 orr     r5, r5, r6, push #8
251                 mov     r6, r6, pull #24
252                 orr     r6, r6, r7, push #8
253                 stmia   r0!, {r3 - r6}                  @ Shouldnt fault
254                 bpl     .Lc2u_3cpy8lp
255
256 .Lc2u_3rem8lp:  tst     ip, #8
257                 movne   r3, r7, pull #24
258                 ldmneia r1!, {r4, r7}
259                 orrne   r3, r3, r4, push #8
260                 movne   r4, r4, pull #24
261                 orrne   r4, r4, r7, push #8
262                 stmneia r0!, {r3 - r4}                  @ Shouldnt fault
263                 tst     ip, #4
264                 movne   r3, r7, pull #24
265                 ldrne   r7, [r1], #4
266                 orrne   r3, r3, r7, push #8
267                 strnet  r3, [r0], #4                    @ Shouldnt fault
268                 ands    ip, ip, #3
269                 beq     .Lc2u_3fupi
270 .Lc2u_3nowords: mov     r3, r7, get_byte_3
271                 teq     ip, #0
272                 beq     .Lc2u_finished
273                 cmp     ip, #2
274 USER(           strbt   r3, [r0], #1)                   @ May fault
275                 ldrgeb  r3, [r1], #1
276 USER(           strgebt r3, [r0], #1)                   @ May fault
277                 ldrgtb  r3, [r1], #0
278 USER(           strgtbt r3, [r0], #1)                   @ May fault
279                 b       .Lc2u_finished
280
281                 .section .fixup,"ax"
282                 .align  0
283 9001:           LOADREGS(fd,sp!, {r0, r4 - r7, pc})
284                 .previous
285
286 /* Prototype: unsigned long __arch_copy_from_user(void *to,const void *from,unsigned long n);
287  * Purpose  : copy a block from user memory to kernel memory
288  * Params   : to   - kernel memory
289  *          : from - user memory
290  *          : n    - number of bytes to copy
291  * Returns  : Number of bytes NOT copied.
292  */
293 .Lcfu_dest_not_aligned:
294                 rsb     ip, ip, #4
295                 cmp     ip, #2
296 USER(           ldrbt   r3, [r1], #1)                   @ May fault
297                 strb    r3, [r0], #1
298 USER(           ldrgebt r3, [r1], #1)                   @ May fault
299                 strgeb  r3, [r0], #1
300 USER(           ldrgtbt r3, [r1], #1)                   @ May fault
301                 strgtb  r3, [r0], #1
302                 sub     r2, r2, ip
303                 b       .Lcfu_dest_aligned
304
305 ENTRY(__arch_copy_from_user)
306                 stmfd   sp!, {r0, r2, r4 - r7, lr}
307                 cmp     r2, #4
308                 blt     .Lcfu_not_enough
309                 ands    ip, r0, #3
310                 bne     .Lcfu_dest_not_aligned
311 .Lcfu_dest_aligned:
312                 ands    ip, r1, #3
313                 bne     .Lcfu_src_not_aligned
314
315 /*
316  * Seeing as there has to be at least 8 bytes to copy, we can
317  * copy one word, and force a user-mode page fault...
318  */
319
320 .Lcfu_0fupi:    subs    r2, r2, #4
321                 addmi   ip, r2, #4
322                 bmi     .Lcfu_0nowords
323 USER(           ldrt    r3, [r1], #4)
324                 str     r3, [r0], #4
325                 mov     ip, r1, lsl #32 - PAGE_SHIFT    @ On each page, use a ld/st??t instruction
326                 rsb     ip, ip, #0
327                 movs    ip, ip, lsr #32 - PAGE_SHIFT
328                 beq     .Lcfu_0fupi
329 /*
330  * ip = max no. of bytes to copy before needing another "strt" insn
331  */
332                 cmp     r2, ip
333                 movlt   ip, r2
334                 sub     r2, r2, ip
335                 subs    ip, ip, #32
336                 blt     .Lcfu_0rem8lp
337
338 .Lcfu_0cpy8lp:  ldmia   r1!, {r3 - r6}                  @ Shouldnt fault
339                 stmia   r0!, {r3 - r6}
340                 ldmia   r1!, {r3 - r6}                  @ Shouldnt fault
341                 subs    ip, ip, #32
342                 stmia   r0!, {r3 - r6}
343                 bpl     .Lcfu_0cpy8lp
344
345 .Lcfu_0rem8lp:  cmn     ip, #16
346                 ldmgeia r1!, {r3 - r6}                  @ Shouldnt fault
347                 stmgeia r0!, {r3 - r6}
348                 tst     ip, #8
349                 ldmneia r1!, {r3 - r4}                  @ Shouldnt fault
350                 stmneia r0!, {r3 - r4}
351                 tst     ip, #4
352                 ldrnet  r3, [r1], #4                    @ Shouldnt fault
353                 strne   r3, [r0], #4
354                 ands    ip, ip, #3
355                 beq     .Lcfu_0fupi
356 .Lcfu_0nowords: teq     ip, #0
357                 beq     .Lcfu_finished
358 .Lcfu_nowords:  cmp     ip, #2
359 USER(           ldrbt   r3, [r1], #1)                   @ May fault
360                 strb    r3, [r0], #1
361 USER(           ldrgebt r3, [r1], #1)                   @ May fault
362                 strgeb  r3, [r0], #1
363 USER(           ldrgtbt r3, [r1], #1)                   @ May fault
364                 strgtb  r3, [r0], #1
365                 b       .Lcfu_finished
366
367 .Lcfu_not_enough:
368                 movs    ip, r2
369                 bne     .Lcfu_nowords
370 .Lcfu_finished: mov     r0, #0
371                 add     sp, sp, #8
372                 LOADREGS(fd,sp!,{r4 - r7, pc})
373
374 .Lcfu_src_not_aligned:
375                 bic     r1, r1, #3
376 USER(           ldrt    r7, [r1], #4)                   @ May fault
377                 cmp     ip, #2
378                 bgt     .Lcfu_3fupi
379                 beq     .Lcfu_2fupi
380 .Lcfu_1fupi:    subs    r2, r2, #4
381                 addmi   ip, r2, #4
382                 bmi     .Lcfu_1nowords
383                 mov     r3, r7, pull #8
384 USER(           ldrt    r7, [r1], #4)                   @ May fault
385                 orr     r3, r3, r7, push #24
386                 str     r3, [r0], #4
387                 mov     ip, r1, lsl #32 - PAGE_SHIFT
388                 rsb     ip, ip, #0
389                 movs    ip, ip, lsr #32 - PAGE_SHIFT
390                 beq     .Lcfu_1fupi
391                 cmp     r2, ip
392                 movlt   ip, r2
393                 sub     r2, r2, ip
394                 subs    ip, ip, #16
395                 blt     .Lcfu_1rem8lp
396
397 .Lcfu_1cpy8lp:  mov     r3, r7, pull #8
398                 ldmia   r1!, {r4 - r7}                  @ Shouldnt fault
399                 subs    ip, ip, #16
400                 orr     r3, r3, r4, push #24
401                 mov     r4, r4, pull #8
402                 orr     r4, r4, r5, push #24
403                 mov     r5, r5, pull #8
404                 orr     r5, r5, r6, push #24
405                 mov     r6, r6, pull #8
406                 orr     r6, r6, r7, push #24
407                 stmia   r0!, {r3 - r6}
408                 bpl     .Lcfu_1cpy8lp
409
410 .Lcfu_1rem8lp:  tst     ip, #8
411                 movne   r3, r7, pull #8
412                 ldmneia r1!, {r4, r7}                   @ Shouldnt fault
413                 orrne   r3, r3, r4, push #24
414                 movne   r4, r4, pull #8
415                 orrne   r4, r4, r7, push #24
416                 stmneia r0!, {r3 - r4}
417                 tst     ip, #4
418                 movne   r3, r7, pull #8
419 USER(           ldrnet  r7, [r1], #4)                   @ May fault
420                 orrne   r3, r3, r7, push #24
421                 strne   r3, [r0], #4
422                 ands    ip, ip, #3
423                 beq     .Lcfu_1fupi
424 .Lcfu_1nowords: mov     r3, r7, get_byte_1
425                 teq     ip, #0
426                 beq     .Lcfu_finished
427                 cmp     ip, #2
428                 strb    r3, [r0], #1
429                 movge   r3, r7, get_byte_2
430                 strgeb  r3, [r0], #1
431                 movgt   r3, r7, get_byte_3
432                 strgtb  r3, [r0], #1
433                 b       .Lcfu_finished
434
435 .Lcfu_2fupi:    subs    r2, r2, #4
436                 addmi   ip, r2, #4
437                 bmi     .Lcfu_2nowords
438                 mov     r3, r7, pull #16
439 USER(           ldrt    r7, [r1], #4)                   @ May fault
440                 orr     r3, r3, r7, push #16
441                 str     r3, [r0], #4
442                 mov     ip, r1, lsl #32 - PAGE_SHIFT
443                 rsb     ip, ip, #0
444                 movs    ip, ip, lsr #32 - PAGE_SHIFT
445                 beq     .Lcfu_2fupi
446                 cmp     r2, ip
447                 movlt   ip, r2
448                 sub     r2, r2, ip
449                 subs    ip, ip, #16
450                 blt     .Lcfu_2rem8lp
451
452
453 .Lcfu_2cpy8lp:  mov     r3, r7, pull #16
454                 ldmia   r1!, {r4 - r7}                  @ Shouldnt fault
455                 subs    ip, ip, #16
456                 orr     r3, r3, r4, push #16
457                 mov     r4, r4, pull #16
458                 orr     r4, r4, r5, push #16
459                 mov     r5, r5, pull #16
460                 orr     r5, r5, r6, push #16
461                 mov     r6, r6, pull #16
462                 orr     r6, r6, r7, push #16
463                 stmia   r0!, {r3 - r6}
464                 bpl     .Lcfu_2cpy8lp
465
466 .Lcfu_2rem8lp:  tst     ip, #8
467                 movne   r3, r7, pull #16
468                 ldmneia r1!, {r4, r7}                   @ Shouldnt fault
469                 orrne   r3, r3, r4, push #16
470                 movne   r4, r4, pull #16
471                 orrne   r4, r4, r7, push #16
472                 stmneia r0!, {r3 - r4}
473                 tst     ip, #4
474                 movne   r3, r7, pull #16
475 USER(           ldrnet  r7, [r1], #4)                   @ May fault
476                 orrne   r3, r3, r7, push #16
477                 strne   r3, [r0], #4
478                 ands    ip, ip, #3
479                 beq     .Lcfu_2fupi
480 .Lcfu_2nowords: mov     r3, r7, get_byte_2
481                 teq     ip, #0
482                 beq     .Lcfu_finished
483                 cmp     ip, #2
484                 strb    r3, [r0], #1
485                 movge   r3, r7, get_byte_3
486                 strgeb  r3, [r0], #1
487 USER(           ldrgtbt r3, [r1], #0)                   @ May fault
488                 strgtb  r3, [r0], #1
489                 b       .Lcfu_finished
490
491 .Lcfu_3fupi:    subs    r2, r2, #4
492                 addmi   ip, r2, #4
493                 bmi     .Lcfu_3nowords
494                 mov     r3, r7, pull #24
495 USER(           ldrt    r7, [r1], #4)                   @ May fault
496                 orr     r3, r3, r7, push #8
497                 str     r3, [r0], #4
498                 mov     ip, r1, lsl #32 - PAGE_SHIFT
499                 rsb     ip, ip, #0
500                 movs    ip, ip, lsr #32 - PAGE_SHIFT
501                 beq     .Lcfu_3fupi
502                 cmp     r2, ip
503                 movlt   ip, r2
504                 sub     r2, r2, ip
505                 subs    ip, ip, #16
506                 blt     .Lcfu_3rem8lp
507
508 .Lcfu_3cpy8lp:  mov     r3, r7, pull #24
509                 ldmia   r1!, {r4 - r7}                  @ Shouldnt fault
510                 orr     r3, r3, r4, push #8
511                 mov     r4, r4, pull #24
512                 orr     r4, r4, r5, push #8
513                 mov     r5, r5, pull #24
514                 orr     r5, r5, r6, push #8
515                 mov     r6, r6, pull #24
516                 orr     r6, r6, r7, push #8
517                 stmia   r0!, {r3 - r6}
518                 subs    ip, ip, #16
519                 bpl     .Lcfu_3cpy8lp
520
521 .Lcfu_3rem8lp:  tst     ip, #8
522                 movne   r3, r7, pull #24
523                 ldmneia r1!, {r4, r7}                   @ Shouldnt fault
524                 orrne   r3, r3, r4, push #8
525                 movne   r4, r4, pull #24
526                 orrne   r4, r4, r7, push #8
527                 stmneia r0!, {r3 - r4}
528                 tst     ip, #4
529                 movne   r3, r7, pull #24
530 USER(           ldrnet  r7, [r1], #4)                   @ May fault
531                 orrne   r3, r3, r7, push #8
532                 strne   r3, [r0], #4
533                 ands    ip, ip, #3
534                 beq     .Lcfu_3fupi
535 .Lcfu_3nowords: mov     r3, r7, get_byte_3
536                 teq     ip, #0
537                 beq     .Lcfu_finished
538                 cmp     ip, #2
539                 strb    r3, [r0], #1
540 USER(           ldrgebt r3, [r1], #1)                   @ May fault
541                 strgeb  r3, [r0], #1
542 USER(           ldrgtbt r3, [r1], #1)                   @ May fault
543                 strgtb  r3, [r0], #1
544                 b       .Lcfu_finished
545
546                 .section .fixup,"ax"
547                 .align  0
548                 /*
549                  * We took an exception.  r0 contains a pointer to
550                  * the byte not copied.
551                  */
552 9001:           ldr     r2, [sp], #4                    @ void *to
553                 sub     r2, r0, r2                      @ bytes copied
554                 ldr     r1, [sp], #4                    @ unsigned long count
555                 subs    r4, r1, r2                      @ bytes left to copy
556                 movne   r1, r4
557                 blne    __memzero
558                 mov     r0, r4
559                 LOADREGS(fd,sp!, {r4 - r7, pc})
560                 .previous
561