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sysfs: Remove support for tagged directories with untagged members (again)
[linux-btrfs-devel.git] / arch / cris / arch-v32 / lib / usercopy.c
blob0b5b70d5f58a45ca2554daf64ccb4625c1ff725f
1 /*
2 * User address space access functions.
3 * The non-inlined parts of asm-cris/uaccess.h are here.
4 *
5 * Copyright (C) 2000, 2003 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 3.2.1 Axis release R53/1.53-v32".
15
16 Check regularly...
17
18 Note that for CRISv32, the PC saved at a bus-fault is the address
19 *at* the faulting instruction, with a special case for instructions
20 in delay slots: then it's the address of the branch. Note also that
21 in contrast to v10, a postincrement in the instruction is *not*
22 performed at a bus-fault; the register is seen having the original
23 value in fault handlers. */
24
25
26 /* Copy to userspace. This is based on the memcpy used for
27 kernel-to-kernel copying; see "string.c". */
28
29 unsigned long
30 __copy_user (void __user *pdst, const void *psrc, unsigned long pn)
31 {
32 /* We want the parameters put in special registers.
33 Make sure the compiler is able to make something useful of this.
34 As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
35
36 FIXME: Comment for old gcc version. Check.
37 If gcc was alright, it really would need no temporaries, and no
38 stack space to save stuff on. */
39
40 register char *dst __asm__ ("r13") = pdst;
41 register const char *src __asm__ ("r11") = psrc;
42 register int n __asm__ ("r12") = pn;
43 register int retn __asm__ ("r10") = 0;
44
45
46 /* When src is aligned but not dst, this makes a few extra needless
47 cycles. I believe it would take as many to check that the
48 re-alignment was unnecessary. */
49 if (((unsigned long) dst & 3) != 0
50 /* Don't align if we wouldn't copy more than a few bytes; so we
51 don't have to check further for overflows. */
52 && n >= 3)
53 {
54 if ((unsigned long) dst & 1)
55 {
56 __asm_copy_to_user_1 (dst, src, retn);
57 n--;
58 }
59
60 if ((unsigned long) dst & 2)
61 {
62 __asm_copy_to_user_2 (dst, src, retn);
63 n -= 2;
64 }
65 }
66
67 /* Movem is dirt cheap. The overheap is low enough to always use the
68 minimum possible block size as the threshold. */
69 if (n >= 44)
70 {
71 /* For large copies we use 'movem'. */
72
73 /* It is not optimal to tell the compiler about clobbering any
74 registers; that will move the saving/restoring of those registers
75 to the function prologue/epilogue, and make non-movem sizes
76 suboptimal. */
77 __asm__ volatile ("\
78 ;; Check that the register asm declaration got right. \n\
79 ;; The GCC manual explicitly says TRT will happen. \n\
80 .ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
81 .err \n\
82 .endif \n\
83 \n\
84 ;; Save the registers we'll use in the movem process \n\
85 ;; on the stack. \n\
86 subq 11*4,$sp \n\
87 movem $r10,[$sp] \n\
88 \n\
89 ;; Now we've got this: \n\
90 ;; r11 - src \n\
91 ;; r13 - dst \n\
92 ;; r12 - n \n\
93 \n\
94 ;; Update n for the first loop \n\
95 subq 44,$r12 \n\
96 0: \n\
97 movem [$r11+],$r10 \n\
98 subq 44,$r12 \n\
99 1: bge 0b \n\
100 movem $r10,[$r13+] \n\
101 3: \n\
102 addq 44,$r12 ;; compensate for last loop underflowing n \n\
103 \n\
104 ;; Restore registers from stack \n\
105 movem [$sp+],$r10 \n\
106 2: \n\
107 .section .fixup,\"ax\" \n\
108 4: \n\
109 ; When failing on any of the 1..44 bytes in a chunk, we adjust back the \n\
110 ; source pointer and just drop through to the by-16 and by-4 loops to \n\
111 ; get the correct number of failing bytes. This necessarily means a \n\
112 ; few extra exceptions, but invalid user pointers shouldn't happen in \n\
113 ; time-critical code anyway. \n\
114 jump 3b \n\
115 subq 44,$r11 \n\
116 \n\
117 .previous \n\
118 .section __ex_table,\"a\" \n\
119 .dword 1b,4b \n\
120 .previous"
121
122 /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
123 /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
124
125 }
126
127 while (n >= 16)
128 {
129 __asm_copy_to_user_16 (dst, src, retn);
130 n -= 16;
131 }
132
133 /* Having a separate by-four loops cuts down on cache footprint.
134 FIXME: Test with and without; increasing switch to be 0..15. */
135 while (n >= 4)
136 {
137 __asm_copy_to_user_4 (dst, src, retn);
138 n -= 4;
139 }
140
141 switch (n)
142 {
143 case 0:
144 break;
145 case 1:
146 __asm_copy_to_user_1 (dst, src, retn);
147 break;
148 case 2:
149 __asm_copy_to_user_2 (dst, src, retn);
150 break;
151 case 3:
152 __asm_copy_to_user_3 (dst, src, retn);
153 break;
154 }
155
156 return retn;
157 }
158
159 /* Copy from user to kernel, zeroing the bytes that were inaccessible in
160 userland. The return-value is the number of bytes that were
161 inaccessible. */
162
163 unsigned long
164 __copy_user_zeroing(void *pdst, const void __user *psrc, unsigned long pn)
165 {
166 /* We want the parameters put in special registers.
167 Make sure the compiler is able to make something useful of this.
168 As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
169
170 FIXME: Comment for old gcc version. Check.
171 If gcc was alright, it really would need no temporaries, and no
172 stack space to save stuff on. */
173
174 register char *dst __asm__ ("r13") = pdst;
175 register const char *src __asm__ ("r11") = psrc;
176 register int n __asm__ ("r12") = pn;
177 register int retn __asm__ ("r10") = 0;
178
179 /* The best reason to align src is that we then know that a read-fault
180 was for aligned bytes; there's no 1..3 remaining good bytes to
181 pickle. */
182 if (((unsigned long) src & 3) != 0)
183 {
184 if (((unsigned long) src & 1) && n != 0)
185 {
186 __asm_copy_from_user_1 (dst, src, retn);
187 n--;
188 }
189
190 if (((unsigned long) src & 2) && n >= 2)
191 {
192 __asm_copy_from_user_2 (dst, src, retn);
193 n -= 2;
194 }
195
196 /* We only need one check after the unalignment-adjustments, because
197 if both adjustments were done, either both or neither reference
198 had an exception. */
199 if (retn != 0)
200 goto copy_exception_bytes;
201 }
202
203 /* Movem is dirt cheap. The overheap is low enough to always use the
204 minimum possible block size as the threshold. */
205 if (n >= 44)
206 {
207 /* It is not optimal to tell the compiler about clobbering any
208 registers; that will move the saving/restoring of those registers
209 to the function prologue/epilogue, and make non-movem sizes
210 suboptimal. */
211 __asm__ volatile ("\
212 .ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
213 .err \n\
214 .endif \n\
215 \n\
216 ;; Save the registers we'll use in the movem process \n\
217 ;; on the stack. \n\
218 subq 11*4,$sp \n\
219 movem $r10,[$sp] \n\
220 \n\
221 ;; Now we've got this: \n\
222 ;; r11 - src \n\
223 ;; r13 - dst \n\
224 ;; r12 - n \n\
225 \n\
226 ;; Update n for the first loop \n\
227 subq 44,$r12 \n\
228 0: \n\
229 movem [$r11+],$r10 \n\
230 \n\
231 subq 44,$r12 \n\
232 bge 0b \n\
233 movem $r10,[$r13+] \n\
234 \n\
235 4: \n\
236 addq 44,$r12 ;; compensate for last loop underflowing n \n\
237 \n\
238 ;; Restore registers from stack \n\
239 movem [$sp+],$r10 \n\
240 .section .fixup,\"ax\" \n\
241 \n\
242 ;; Do not jump back into the loop if we fail. For some uses, we get a \n\
243 ;; page fault somewhere on the line. Without checking for page limits, \n\
244 ;; we don't know where, but we need to copy accurately and keep an \n\
245 ;; accurate count; not just clear the whole line. To do that, we fall \n\
246 ;; down in the code below, proceeding with smaller amounts. It should \n\
247 ;; be kept in mind that we have to cater to code like what at one time \n\
248 ;; was in fs/super.c: \n\
249 ;; i = size - copy_from_user((void *)page, data, size); \n\
250 ;; which would cause repeated faults while clearing the remainder of \n\
251 ;; the SIZE bytes at PAGE after the first fault. \n\
252 ;; A caveat here is that we must not fall through from a failing page \n\
253 ;; to a valid page. \n\
254 \n\
255 3: \n\
256 jump 4b ;; Fall through, pretending the fault didn't happen. \n\
257 nop \n\
258 \n\
259 .previous \n\
260 .section __ex_table,\"a\" \n\
261 .dword 0b,3b \n\
262 .previous"
263
264 /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
265 /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
266 }
267
268 /* Either we directly start copying here, using dword copying in a loop,
269 or we copy as much as possible with 'movem' and then the last block
270 (<44 bytes) is copied here. This will work since 'movem' will have
271 updated src, dst and n. (Except with failing src.)
272
273 Since we want to keep src accurate, we can't use
274 __asm_copy_from_user_N with N != (1, 2, 4); it updates dst and
275 retn, but not src (by design; it's value is ignored elsewhere). */
276
277 while (n >= 4)
278 {
279 __asm_copy_from_user_4 (dst, src, retn);
280 n -= 4;
281
282 if (retn)
283 goto copy_exception_bytes;
284 }
285
286 /* If we get here, there were no memory read faults. */
287 switch (n)
288 {
289 /* These copies are at least "naturally aligned" (so we don't have
290 to check each byte), due to the src alignment code before the
291 movem loop. The *_3 case *will* get the correct count for retn. */
292 case 0:
293 /* This case deliberately left in (if you have doubts check the
294 generated assembly code). */
295 break;
296 case 1:
297 __asm_copy_from_user_1 (dst, src, retn);
298 break;
299 case 2:
300 __asm_copy_from_user_2 (dst, src, retn);
301 break;
302 case 3:
303 __asm_copy_from_user_3 (dst, src, retn);
304 break;
305 }
306
307 /* If we get here, retn correctly reflects the number of failing
308 bytes. */
309 return retn;
310
311 copy_exception_bytes:
312 /* We already have "retn" bytes cleared, and need to clear the
313 remaining "n" bytes. A non-optimized simple byte-for-byte in-line
314 memset is preferred here, since this isn't speed-critical code and
315 we'd rather have this a leaf-function than calling memset. */
316 {
317 char *endp;
318 for (endp = dst + n; dst < endp; dst++)
319 *dst = 0;
320 }
321
322 return retn + n;
323 }
324
325 /* Zero userspace. */
326
327 unsigned long
328 __do_clear_user (void __user *pto, unsigned long pn)
329 {
330 /* We want the parameters put in special registers.
331 Make sure the compiler is able to make something useful of this.
332 As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
333
334 FIXME: Comment for old gcc version. Check.
335 If gcc was alright, it really would need no temporaries, and no
336 stack space to save stuff on. */
337
338 register char *dst __asm__ ("r13") = pto;
339 register int n __asm__ ("r12") = pn;
340 register int retn __asm__ ("r10") = 0;
341
342
343 if (((unsigned long) dst & 3) != 0
344 /* Don't align if we wouldn't copy more than a few bytes. */
345 && n >= 3)
346 {
347 if ((unsigned long) dst & 1)
348 {
349 __asm_clear_1 (dst, retn);
350 n--;
351 }
352
353 if ((unsigned long) dst & 2)
354 {
355 __asm_clear_2 (dst, retn);
356 n -= 2;
357 }
358 }
359
360 /* Decide which copying method to use.
361 FIXME: This number is from the "ordinary" kernel memset. */
362 if (n >= 48)
363 {
364 /* For large clears we use 'movem' */
365
366 /* It is not optimal to tell the compiler about clobbering any
367 call-saved registers; that will move the saving/restoring of
368 those registers to the function prologue/epilogue, and make
369 non-movem sizes suboptimal.
370
371 This method is not foolproof; it assumes that the "asm reg"
372 declarations at the beginning of the function really are used
373 here (beware: they may be moved to temporary registers).
374 This way, we do not have to save/move the registers around into
375 temporaries; we can safely use them straight away.
376
377 If you want to check that the allocation was right; then
378 check the equalities in the first comment. It should say
379 something like "r13=r13, r11=r11, r12=r12". */
380 __asm__ volatile ("\
381 .ifnc %0%1%2,$r13$r12$r10 \n\
382 .err \n\
383 .endif \n\
384 \n\
385 ;; Save the registers we'll clobber in the movem process \n\
386 ;; on the stack. Don't mention them to gcc, it will only be \n\
387 ;; upset. \n\
388 subq 11*4,$sp \n\
389 movem $r10,[$sp] \n\
390 \n\
391 clear.d $r0 \n\
392 clear.d $r1 \n\
393 clear.d $r2 \n\
394 clear.d $r3 \n\
395 clear.d $r4 \n\
396 clear.d $r5 \n\
397 clear.d $r6 \n\
398 clear.d $r7 \n\
399 clear.d $r8 \n\
400 clear.d $r9 \n\
401 clear.d $r10 \n\
402 clear.d $r11 \n\
403 \n\
404 ;; Now we've got this: \n\
405 ;; r13 - dst \n\
406 ;; r12 - n \n\
407 \n\
408 ;; Update n for the first loop \n\
409 subq 12*4,$r12 \n\
410 0: \n\
411 subq 12*4,$r12 \n\
412 1: \n\
413 bge 0b \n\
414 movem $r11,[$r13+] \n\
415 \n\
416 addq 12*4,$r12 ;; compensate for last loop underflowing n \n\
417 \n\
418 ;; Restore registers from stack \n\
419 movem [$sp+],$r10 \n\
420 2: \n\
421 .section .fixup,\"ax\" \n\
422 3: \n\
423 movem [$sp],$r10 \n\
424 addq 12*4,$r10 \n\
425 addq 12*4,$r13 \n\
426 movem $r10,[$sp] \n\
427 jump 0b \n\
428 clear.d $r10 \n\
429 \n\
430 .previous \n\
431 .section __ex_table,\"a\" \n\
432 .dword 1b,3b \n\
433 .previous"
434
435 /* Outputs */ : "=r" (dst), "=r" (n), "=r" (retn)
436 /* Inputs */ : "0" (dst), "1" (n), "2" (retn)
437 /* Clobber */ : "r11");
438 }
439
440 while (n >= 16)
441 {
442 __asm_clear_16 (dst, retn);
443 n -= 16;
444 }
445
446 /* Having a separate by-four loops cuts down on cache footprint.
447 FIXME: Test with and without; increasing switch to be 0..15. */
448 while (n >= 4)
449 {
450 __asm_clear_4 (dst, retn);
451 n -= 4;
452 }
453
454 switch (n)
455 {
456 case 0:
457 break;
458 case 1:
459 __asm_clear_1 (dst, retn);
460 break;
461 case 2:
462 __asm_clear_2 (dst, retn);
463 break;
464 case 3:
465 __asm_clear_3 (dst, retn);
466 break;
467 }
468
469 return retn;
470 }
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