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Merge tag 'v3.3.7' into 3.3/master
[zen-stable.git] / arch / cris / arch-v10 / lib / usercopy.c
blobb0a608da7bd13d5eff6f2e925153dbd7c47eadb0
1 /*
2 * User address space access functions.
3 * The non-inlined parts of asm-cris/uaccess.h are here.
4 *
5 * Copyright (C) 2000, Axis Communications AB.
6 *
7 * Written by Hans-Peter Nilsson.
8 * Pieces used from memcpy, originally by Kenny Ranerup long time ago.
9 */
10
11 #include <asm/uaccess.h>
12
13 /* Asm:s have been tweaked (within the domain of correctness) to give
14 satisfactory results for "gcc version 2.96 20000427 (experimental)".
15
16 Check regularly...
17
18 Note that the PC saved at a bus-fault is the address *after* the
19 faulting instruction, which means the branch-target for instructions in
20 delay-slots for taken branches. Note also that the postincrement in
21 the instruction is performed regardless of bus-fault; the register is
22 seen updated in fault handlers.
23
24 Oh, and on the code formatting issue, to whomever feels like "fixing
25 it" to Conformity: I'm too "lazy", but why don't you go ahead and "fix"
26 string.c too. I just don't think too many people will hack this file
27 for the code format to be an issue. */
28
29
30 /* Copy to userspace. This is based on the memcpy used for
31 kernel-to-kernel copying; see "string.c". */
32
33 unsigned long
34 __copy_user (void __user *pdst, const void *psrc, unsigned long pn)
35 {
36 /* We want the parameters put in special registers.
37 Make sure the compiler is able to make something useful of this.
38 As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
39
40 FIXME: Comment for old gcc version. Check.
41 If gcc was alright, it really would need no temporaries, and no
42 stack space to save stuff on. */
43
44 register char *dst __asm__ ("r13") = pdst;
45 register const char *src __asm__ ("r11") = psrc;
46 register int n __asm__ ("r12") = pn;
47 register int retn __asm__ ("r10") = 0;
48
49
50 /* When src is aligned but not dst, this makes a few extra needless
51 cycles. I believe it would take as many to check that the
52 re-alignment was unnecessary. */
53 if (((unsigned long) dst & 3) != 0
54 /* Don't align if we wouldn't copy more than a few bytes; so we
55 don't have to check further for overflows. */
56 && n >= 3)
57 {
58 if ((unsigned long) dst & 1)
59 {
60 __asm_copy_to_user_1 (dst, src, retn);
61 n--;
62 }
63
64 if ((unsigned long) dst & 2)
65 {
66 __asm_copy_to_user_2 (dst, src, retn);
67 n -= 2;
68 }
69 }
70
71 /* Decide which copying method to use. */
72 if (n >= 44*2) /* Break even between movem and
73 move16 is at 38.7*2, but modulo 44. */
74 {
75 /* For large copies we use 'movem'. */
76
77 /* It is not optimal to tell the compiler about clobbering any
78 registers; that will move the saving/restoring of those registers
79 to the function prologue/epilogue, and make non-movem sizes
80 suboptimal.
81
82 This method is not foolproof; it assumes that the "asm reg"
83 declarations at the beginning of the function really are used
84 here (beware: they may be moved to temporary registers).
85 This way, we do not have to save/move the registers around into
86 temporaries; we can safely use them straight away.
87
88 If you want to check that the allocation was right; then
89 check the equalities in the first comment. It should say
90 "r13=r13, r11=r11, r12=r12". */
91 __asm__ volatile ("\
92 .ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
93 .err \n\
94 .endif \n\
95 \n\
96 ;; Save the registers we'll use in the movem process \n\
97 ;; on the stack. \n\
98 subq 11*4,$sp \n\
99 movem $r10,[$sp] \n\
100 \n\
101 ;; Now we've got this: \n\
102 ;; r11 - src \n\
103 ;; r13 - dst \n\
104 ;; r12 - n \n\
105 \n\
106 ;; Update n for the first loop \n\
107 subq 44,$r12 \n\
108 \n\
109 ; Since the noted PC of a faulting instruction in a delay-slot of a taken \n\
110 ; branch, is that of the branch target, we actually point at the from-movem \n\
111 ; for this case. There is no ambiguity here; if there was a fault in that \n\
112 ; instruction (meaning a kernel oops), the faulted PC would be the address \n\
113 ; after *that* movem. \n\
114 \n\
115 0: \n\
116 movem [$r11+],$r10 \n\
117 subq 44,$r12 \n\
118 bge 0b \n\
119 movem $r10,[$r13+] \n\
120 1: \n\
121 addq 44,$r12 ;; compensate for last loop underflowing n \n\
122 \n\
123 ;; Restore registers from stack \n\
124 movem [$sp+],$r10 \n\
125 2: \n\
126 .section .fixup,\"ax\" \n\
127 \n\
128 ; To provide a correct count in r10 of bytes that failed to be copied, \n\
129 ; we jump back into the loop if the loop-branch was taken. There is no \n\
130 ; performance penalty for sany use; the program will segfault soon enough.\n\
131 \n\
132 3: \n\
133 move.d [$sp],$r10 \n\
134 addq 44,$r10 \n\
135 move.d $r10,[$sp] \n\
136 jump 0b \n\
137 4: \n\
138 movem [$sp+],$r10 \n\
139 addq 44,$r10 \n\
140 addq 44,$r12 \n\
141 jump 2b \n\
142 \n\
143 .previous \n\
144 .section __ex_table,\"a\" \n\
145 .dword 0b,3b \n\
146 .dword 1b,4b \n\
147 .previous"
148
149 /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
150 /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
151
152 }
153
154 /* Either we directly start copying, using dword copying in a loop, or
155 we copy as much as possible with 'movem' and then the last block (<44
156 bytes) is copied here. This will work since 'movem' will have
157 updated SRC, DST and N. */
158
159 while (n >= 16)
160 {
161 __asm_copy_to_user_16 (dst, src, retn);
162 n -= 16;
163 }
164
165 /* Having a separate by-four loops cuts down on cache footprint.
166 FIXME: Test with and without; increasing switch to be 0..15. */
167 while (n >= 4)
168 {
169 __asm_copy_to_user_4 (dst, src, retn);
170 n -= 4;
171 }
172
173 switch (n)
174 {
175 case 0:
176 break;
177 case 1:
178 __asm_copy_to_user_1 (dst, src, retn);
179 break;
180 case 2:
181 __asm_copy_to_user_2 (dst, src, retn);
182 break;
183 case 3:
184 __asm_copy_to_user_3 (dst, src, retn);
185 break;
186 }
187
188 return retn;
189 }
190
191 /* Copy from user to kernel, zeroing the bytes that were inaccessible in
192 userland. The return-value is the number of bytes that were
193 inaccessible. */
194
195 unsigned long
196 __copy_user_zeroing(void *pdst, const void __user *psrc, unsigned long pn)
197 {
198 /* We want the parameters put in special registers.
199 Make sure the compiler is able to make something useful of this.
200 As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
201
202 FIXME: Comment for old gcc version. Check.
203 If gcc was alright, it really would need no temporaries, and no
204 stack space to save stuff on. */
205
206 register char *dst __asm__ ("r13") = pdst;
207 register const char *src __asm__ ("r11") = psrc;
208 register int n __asm__ ("r12") = pn;
209 register int retn __asm__ ("r10") = 0;
210
211 /* The best reason to align src is that we then know that a read-fault
212 was for aligned bytes; there's no 1..3 remaining good bytes to
213 pickle. */
214 if (((unsigned long) src & 3) != 0)
215 {
216 if (((unsigned long) src & 1) && n != 0)
217 {
218 __asm_copy_from_user_1 (dst, src, retn);
219 n--;
220 }
221
222 if (((unsigned long) src & 2) && n >= 2)
223 {
224 __asm_copy_from_user_2 (dst, src, retn);
225 n -= 2;
226 }
227
228 /* We only need one check after the unalignment-adjustments, because
229 if both adjustments were done, either both or neither reference
230 had an exception. */
231 if (retn != 0)
232 goto copy_exception_bytes;
233 }
234
235 /* Decide which copying method to use. */
236 if (n >= 44*2) /* Break even between movem and
237 move16 is at 38.7*2, but modulo 44.
238 FIXME: We use move4 now. */
239 {
240 /* For large copies we use 'movem' */
241
242 /* It is not optimal to tell the compiler about clobbering any
243 registers; that will move the saving/restoring of those registers
244 to the function prologue/epilogue, and make non-movem sizes
245 suboptimal.
246
247 This method is not foolproof; it assumes that the "asm reg"
248 declarations at the beginning of the function really are used
249 here (beware: they may be moved to temporary registers).
250 This way, we do not have to save/move the registers around into
251 temporaries; we can safely use them straight away.
252
253 If you want to check that the allocation was right; then
254 check the equalities in the first comment. It should say
255 "r13=r13, r11=r11, r12=r12" */
256 __asm__ volatile ("\n\
257 .ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
258 .err \n\
259 .endif \n\
260 \n\
261 ;; Save the registers we'll use in the movem process \n\
262 ;; on the stack. \n\
263 subq 11*4,$sp \n\
264 movem $r10,[$sp] \n\
265 \n\
266 ;; Now we've got this: \n\
267 ;; r11 - src \n\
268 ;; r13 - dst \n\
269 ;; r12 - n \n\
270 \n\
271 ;; Update n for the first loop \n\
272 subq 44,$r12 \n\
273 0: \n\
274 movem [$r11+],$r10 \n\
275 1: \n\
276 subq 44,$r12 \n\
277 bge 0b \n\
278 movem $r10,[$r13+] \n\
279 \n\
280 addq 44,$r12 ;; compensate for last loop underflowing n \n\
281 \n\
282 ;; Restore registers from stack \n\
283 movem [$sp+],$r10 \n\
284 4: \n\
285 .section .fixup,\"ax\" \n\
286 \n\
287 ;; Do not jump back into the loop if we fail. For some uses, we get a \n\
288 ;; page fault somewhere on the line. Without checking for page limits, \n\
289 ;; we don't know where, but we need to copy accurately and keep an \n\
290 ;; accurate count; not just clear the whole line. To do that, we fall \n\
291 ;; down in the code below, proceeding with smaller amounts. It should \n\
292 ;; be kept in mind that we have to cater to code like what at one time \n\
293 ;; was in fs/super.c: \n\
294 ;; i = size - copy_from_user((void *)page, data, size); \n\
295 ;; which would cause repeated faults while clearing the remainder of \n\
296 ;; the SIZE bytes at PAGE after the first fault. \n\
297 ;; A caveat here is that we must not fall through from a failing page \n\
298 ;; to a valid page. \n\
299 \n\
300 3: \n\
301 movem [$sp+],$r10 \n\
302 addq 44,$r12 ;; Get back count before faulting point. \n\
303 subq 44,$r11 ;; Get back pointer to faulting movem-line. \n\
304 jump 4b ;; Fall through, pretending the fault didn't happen.\n\
305 \n\
306 .previous \n\
307 .section __ex_table,\"a\" \n\
308 .dword 1b,3b \n\
309 .previous"
310
311 /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
312 /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
313
314 }
315
316 /* Either we directly start copying here, using dword copying in a loop,
317 or we copy as much as possible with 'movem' and then the last block
318 (<44 bytes) is copied here. This will work since 'movem' will have
319 updated src, dst and n. (Except with failing src.)
320
321 Since we want to keep src accurate, we can't use
322 __asm_copy_from_user_N with N != (1, 2, 4); it updates dst and
323 retn, but not src (by design; it's value is ignored elsewhere). */
324
325 while (n >= 4)
326 {
327 __asm_copy_from_user_4 (dst, src, retn);
328 n -= 4;
329
330 if (retn)
331 goto copy_exception_bytes;
332 }
333
334 /* If we get here, there were no memory read faults. */
335 switch (n)
336 {
337 /* These copies are at least "naturally aligned" (so we don't have
338 to check each byte), due to the src alignment code before the
339 movem loop. The *_3 case *will* get the correct count for retn. */
340 case 0:
341 /* This case deliberately left in (if you have doubts check the
342 generated assembly code). */
343 break;
344 case 1:
345 __asm_copy_from_user_1 (dst, src, retn);
346 break;
347 case 2:
348 __asm_copy_from_user_2 (dst, src, retn);
349 break;
350 case 3:
351 __asm_copy_from_user_3 (dst, src, retn);
352 break;
353 }
354
355 /* If we get here, retn correctly reflects the number of failing
356 bytes. */
357 return retn;
358
359 copy_exception_bytes:
360 /* We already have "retn" bytes cleared, and need to clear the
361 remaining "n" bytes. A non-optimized simple byte-for-byte in-line
362 memset is preferred here, since this isn't speed-critical code and
363 we'd rather have this a leaf-function than calling memset. */
364 {
365 char *endp;
366 for (endp = dst + n; dst < endp; dst++)
367 *dst = 0;
368 }
369
370 return retn + n;
371 }
372
373 /* Zero userspace. */
374
375 unsigned long
376 __do_clear_user (void __user *pto, unsigned long pn)
377 {
378 /* We want the parameters put in special registers.
379 Make sure the compiler is able to make something useful of this.
380 As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
381
382 FIXME: Comment for old gcc version. Check.
383 If gcc was alright, it really would need no temporaries, and no
384 stack space to save stuff on. */
385
386 register char *dst __asm__ ("r13") = pto;
387 register int n __asm__ ("r12") = pn;
388 register int retn __asm__ ("r10") = 0;
389
390
391 if (((unsigned long) dst & 3) != 0
392 /* Don't align if we wouldn't copy more than a few bytes. */
393 && n >= 3)
394 {
395 if ((unsigned long) dst & 1)
396 {
397 __asm_clear_1 (dst, retn);
398 n--;
399 }
400
401 if ((unsigned long) dst & 2)
402 {
403 __asm_clear_2 (dst, retn);
404 n -= 2;
405 }
406 }
407
408 /* Decide which copying method to use.
409 FIXME: This number is from the "ordinary" kernel memset. */
410 if (n >= (1*48))
411 {
412 /* For large clears we use 'movem' */
413
414 /* It is not optimal to tell the compiler about clobbering any
415 call-saved registers; that will move the saving/restoring of
416 those registers to the function prologue/epilogue, and make
417 non-movem sizes suboptimal.
418
419 This method is not foolproof; it assumes that the "asm reg"
420 declarations at the beginning of the function really are used
421 here (beware: they may be moved to temporary registers).
422 This way, we do not have to save/move the registers around into
423 temporaries; we can safely use them straight away.
424
425 If you want to check that the allocation was right; then
426 check the equalities in the first comment. It should say
427 something like "r13=r13, r11=r11, r12=r12". */
428 __asm__ volatile ("\n\
429 .ifnc %0%1%2,$r13$r12$r10 \n\
430 .err \n\
431 .endif \n\
432 \n\
433 ;; Save the registers we'll clobber in the movem process \n\
434 ;; on the stack. Don't mention them to gcc, it will only be \n\
435 ;; upset. \n\
436 subq 11*4,$sp \n\
437 movem $r10,[$sp] \n\
438 \n\
439 clear.d $r0 \n\
440 clear.d $r1 \n\
441 clear.d $r2 \n\
442 clear.d $r3 \n\
443 clear.d $r4 \n\
444 clear.d $r5 \n\
445 clear.d $r6 \n\
446 clear.d $r7 \n\
447 clear.d $r8 \n\
448 clear.d $r9 \n\
449 clear.d $r10 \n\
450 clear.d $r11 \n\
451 \n\
452 ;; Now we've got this: \n\
453 ;; r13 - dst \n\
454 ;; r12 - n \n\
455 \n\
456 ;; Update n for the first loop \n\
457 subq 12*4,$r12 \n\
458 0: \n\
459 subq 12*4,$r12 \n\
460 bge 0b \n\
461 movem $r11,[$r13+] \n\
462 1: \n\
463 addq 12*4,$r12 ;; compensate for last loop underflowing n\n\
464 \n\
465 ;; Restore registers from stack \n\
466 movem [$sp+],$r10 \n\
467 2: \n\
468 .section .fixup,\"ax\" \n\
469 3: \n\
470 move.d [$sp],$r10 \n\
471 addq 12*4,$r10 \n\
472 move.d $r10,[$sp] \n\
473 clear.d $r10 \n\
474 jump 0b \n\
475 \n\
476 4: \n\
477 movem [$sp+],$r10 \n\
478 addq 12*4,$r10 \n\
479 addq 12*4,$r12 \n\
480 jump 2b \n\
481 \n\
482 .previous \n\
483 .section __ex_table,\"a\" \n\
484 .dword 0b,3b \n\
485 .dword 1b,4b \n\
486 .previous"
487
488 /* Outputs */ : "=r" (dst), "=r" (n), "=r" (retn)
489 /* Inputs */ : "0" (dst), "1" (n), "2" (retn)
490 /* Clobber */ : "r11");
491 }
492
493 while (n >= 16)
494 {
495 __asm_clear_16 (dst, retn);
496 n -= 16;
497 }
498
499 /* Having a separate by-four loops cuts down on cache footprint.
500 FIXME: Test with and without; increasing switch to be 0..15. */
501 while (n >= 4)
502 {
503 __asm_clear_4 (dst, retn);
504 n -= 4;
505 }
506
507 switch (n)
508 {
509 case 0:
510 break;
511 case 1:
512 __asm_clear_1 (dst, retn);
513 break;
514 case 2:
515 __asm_clear_2 (dst, retn);
516 break;
517 case 3:
518 __asm_clear_3 (dst, retn);
519 break;
520 }
521
522 return retn;
523 }