Merge master.kernel.org:/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6] / arch / mips / kernel / unaligned.c
1 /*
2  * Handle unaligned accesses by emulation.
3  *
4  * This file is subject to the terms and conditions of the GNU General Public
5  * License.  See the file "COPYING" in the main directory of this archive
6  * for more details.
7  *
8  * Copyright (C) 1996, 1998, 1999, 2002 by Ralf Baechle
9  * Copyright (C) 1999 Silicon Graphics, Inc.
10  *
11  * This file contains exception handler for address error exception with the
12  * special capability to execute faulting instructions in software.  The
13  * handler does not try to handle the case when the program counter points
14  * to an address not aligned to a word boundary.
15  *
16  * Putting data to unaligned addresses is a bad practice even on Intel where
17  * only the performance is affected.  Much worse is that such code is non-
18  * portable.  Due to several programs that die on MIPS due to alignment
19  * problems I decided to implement this handler anyway though I originally
20  * didn't intend to do this at all for user code.
21  *
22  * For now I enable fixing of address errors by default to make life easier.
23  * I however intend to disable this somewhen in the future when the alignment
24  * problems with user programs have been fixed.  For programmers this is the
25  * right way to go.
26  *
27  * Fixing address errors is a per process option.  The option is inherited
28  * across fork(2) and execve(2) calls.  If you really want to use the
29  * option in your user programs - I discourage the use of the software
30  * emulation strongly - use the following code in your userland stuff:
31  *
32  * #include <sys/sysmips.h>
33  *
34  * ...
35  * sysmips(MIPS_FIXADE, x);
36  * ...
37  *
38  * The argument x is 0 for disabling software emulation, enabled otherwise.
39  *
40  * Below a little program to play around with this feature.
41  *
42  * #include <stdio.h>
43  * #include <sys/sysmips.h>
44  *
45  * struct foo {
46  *         unsigned char bar[8];
47  * };
48  *
49  * main(int argc, char *argv[])
50  * {
51  *         struct foo x = {0, 1, 2, 3, 4, 5, 6, 7};
52  *         unsigned int *p = (unsigned int *) (x.bar + 3);
53  *         int i;
54  *
55  *         if (argc > 1)
56  *                 sysmips(MIPS_FIXADE, atoi(argv[1]));
57  *
58  *         printf("*p = %08lx\n", *p);
59  *
60  *         *p = 0xdeadface;
61  *
62  *         for(i = 0; i <= 7; i++)
63  *         printf("%02x ", x.bar[i]);
64  *         printf("\n");
65  * }
66  *
67  * Coprocessor loads are not supported; I think this case is unimportant
68  * in the practice.
69  *
70  * TODO: Handle ndc (attempted store to doubleword in uncached memory)
71  *       exception for the R6000.
72  *       A store crossing a page boundary might be executed only partially.
73  *       Undo the partial store in this case.
74  */
75 #include <linux/mm.h>
76 #include <linux/module.h>
77 #include <linux/signal.h>
78 #include <linux/smp.h>
79 #include <linux/smp_lock.h>
80
81 #include <asm/asm.h>
82 #include <asm/branch.h>
83 #include <asm/byteorder.h>
84 #include <asm/inst.h>
85 #include <asm/uaccess.h>
86 #include <asm/system.h>
87
88 #define STR(x)  __STR(x)
89 #define __STR(x)  #x
90
91 #ifdef CONFIG_PROC_FS
92 unsigned long unaligned_instructions;
93 #endif
94
95 static inline int emulate_load_store_insn(struct pt_regs *regs,
96         void __user *addr, unsigned int __user *pc,
97         unsigned long **regptr, unsigned long *newvalue)
98 {
99         union mips_instruction insn;
100         unsigned long value;
101         unsigned int res;
102
103         regs->regs[0] = 0;
104         *regptr=NULL;
105
106         /*
107          * This load never faults.
108          */
109         __get_user(insn.word, pc);
110
111         switch (insn.i_format.opcode) {
112         /*
113          * These are instructions that a compiler doesn't generate.  We
114          * can assume therefore that the code is MIPS-aware and
115          * really buggy.  Emulating these instructions would break the
116          * semantics anyway.
117          */
118         case ll_op:
119         case lld_op:
120         case sc_op:
121         case scd_op:
122
123         /*
124          * For these instructions the only way to create an address
125          * error is an attempted access to kernel/supervisor address
126          * space.
127          */
128         case ldl_op:
129         case ldr_op:
130         case lwl_op:
131         case lwr_op:
132         case sdl_op:
133         case sdr_op:
134         case swl_op:
135         case swr_op:
136         case lb_op:
137         case lbu_op:
138         case sb_op:
139                 goto sigbus;
140
141         /*
142          * The remaining opcodes are the ones that are really of interest.
143          */
144         case lh_op:
145                 if (!access_ok(VERIFY_READ, addr, 2))
146                         goto sigbus;
147
148                 __asm__ __volatile__ (".set\tnoat\n"
149 #ifdef __BIG_ENDIAN
150                         "1:\tlb\t%0, 0(%2)\n"
151                         "2:\tlbu\t$1, 1(%2)\n\t"
152 #endif
153 #ifdef __LITTLE_ENDIAN
154                         "1:\tlb\t%0, 1(%2)\n"
155                         "2:\tlbu\t$1, 0(%2)\n\t"
156 #endif
157                         "sll\t%0, 0x8\n\t"
158                         "or\t%0, $1\n\t"
159                         "li\t%1, 0\n"
160                         "3:\t.set\tat\n\t"
161                         ".section\t.fixup,\"ax\"\n\t"
162                         "4:\tli\t%1, %3\n\t"
163                         "j\t3b\n\t"
164                         ".previous\n\t"
165                         ".section\t__ex_table,\"a\"\n\t"
166                         STR(PTR)"\t1b, 4b\n\t"
167                         STR(PTR)"\t2b, 4b\n\t"
168                         ".previous"
169                         : "=&r" (value), "=r" (res)
170                         : "r" (addr), "i" (-EFAULT));
171                 if (res)
172                         goto fault;
173                 *newvalue = value;
174                 *regptr = &regs->regs[insn.i_format.rt];
175                 break;
176
177         case lw_op:
178                 if (!access_ok(VERIFY_READ, addr, 4))
179                         goto sigbus;
180
181                 __asm__ __volatile__ (
182 #ifdef __BIG_ENDIAN
183                         "1:\tlwl\t%0, (%2)\n"
184                         "2:\tlwr\t%0, 3(%2)\n\t"
185 #endif
186 #ifdef __LITTLE_ENDIAN
187                         "1:\tlwl\t%0, 3(%2)\n"
188                         "2:\tlwr\t%0, (%2)\n\t"
189 #endif
190                         "li\t%1, 0\n"
191                         "3:\t.section\t.fixup,\"ax\"\n\t"
192                         "4:\tli\t%1, %3\n\t"
193                         "j\t3b\n\t"
194                         ".previous\n\t"
195                         ".section\t__ex_table,\"a\"\n\t"
196                         STR(PTR)"\t1b, 4b\n\t"
197                         STR(PTR)"\t2b, 4b\n\t"
198                         ".previous"
199                         : "=&r" (value), "=r" (res)
200                         : "r" (addr), "i" (-EFAULT));
201                 if (res)
202                         goto fault;
203                 *newvalue = value;
204                 *regptr = &regs->regs[insn.i_format.rt];
205                 break;
206
207         case lhu_op:
208                 if (!access_ok(VERIFY_READ, addr, 2))
209                         goto sigbus;
210
211                 __asm__ __volatile__ (
212                         ".set\tnoat\n"
213 #ifdef __BIG_ENDIAN
214                         "1:\tlbu\t%0, 0(%2)\n"
215                         "2:\tlbu\t$1, 1(%2)\n\t"
216 #endif
217 #ifdef __LITTLE_ENDIAN
218                         "1:\tlbu\t%0, 1(%2)\n"
219                         "2:\tlbu\t$1, 0(%2)\n\t"
220 #endif
221                         "sll\t%0, 0x8\n\t"
222                         "or\t%0, $1\n\t"
223                         "li\t%1, 0\n"
224                         "3:\t.set\tat\n\t"
225                         ".section\t.fixup,\"ax\"\n\t"
226                         "4:\tli\t%1, %3\n\t"
227                         "j\t3b\n\t"
228                         ".previous\n\t"
229                         ".section\t__ex_table,\"a\"\n\t"
230                         STR(PTR)"\t1b, 4b\n\t"
231                         STR(PTR)"\t2b, 4b\n\t"
232                         ".previous"
233                         : "=&r" (value), "=r" (res)
234                         : "r" (addr), "i" (-EFAULT));
235                 if (res)
236                         goto fault;
237                 *newvalue = value;
238                 *regptr = &regs->regs[insn.i_format.rt];
239                 break;
240
241         case lwu_op:
242 #ifdef CONFIG_64BIT
243                 /*
244                  * A 32-bit kernel might be running on a 64-bit processor.  But
245                  * if we're on a 32-bit processor and an i-cache incoherency
246                  * or race makes us see a 64-bit instruction here the sdl/sdr
247                  * would blow up, so for now we don't handle unaligned 64-bit
248                  * instructions on 32-bit kernels.
249                  */
250                 if (!access_ok(VERIFY_READ, addr, 4))
251                         goto sigbus;
252
253                 __asm__ __volatile__ (
254 #ifdef __BIG_ENDIAN
255                         "1:\tlwl\t%0, (%2)\n"
256                         "2:\tlwr\t%0, 3(%2)\n\t"
257 #endif
258 #ifdef __LITTLE_ENDIAN
259                         "1:\tlwl\t%0, 3(%2)\n"
260                         "2:\tlwr\t%0, (%2)\n\t"
261 #endif
262                         "dsll\t%0, %0, 32\n\t"
263                         "dsrl\t%0, %0, 32\n\t"
264                         "li\t%1, 0\n"
265                         "3:\t.section\t.fixup,\"ax\"\n\t"
266                         "4:\tli\t%1, %3\n\t"
267                         "j\t3b\n\t"
268                         ".previous\n\t"
269                         ".section\t__ex_table,\"a\"\n\t"
270                         STR(PTR)"\t1b, 4b\n\t"
271                         STR(PTR)"\t2b, 4b\n\t"
272                         ".previous"
273                         : "=&r" (value), "=r" (res)
274                         : "r" (addr), "i" (-EFAULT));
275                 if (res)
276                         goto fault;
277                 *newvalue = value;
278                 *regptr = &regs->regs[insn.i_format.rt];
279                 break;
280 #endif /* CONFIG_64BIT */
281
282                 /* Cannot handle 64-bit instructions in 32-bit kernel */
283                 goto sigill;
284
285         case ld_op:
286 #ifdef CONFIG_64BIT
287                 /*
288                  * A 32-bit kernel might be running on a 64-bit processor.  But
289                  * if we're on a 32-bit processor and an i-cache incoherency
290                  * or race makes us see a 64-bit instruction here the sdl/sdr
291                  * would blow up, so for now we don't handle unaligned 64-bit
292                  * instructions on 32-bit kernels.
293                  */
294                 if (!access_ok(VERIFY_READ, addr, 8))
295                         goto sigbus;
296
297                 __asm__ __volatile__ (
298 #ifdef __BIG_ENDIAN
299                         "1:\tldl\t%0, (%2)\n"
300                         "2:\tldr\t%0, 7(%2)\n\t"
301 #endif
302 #ifdef __LITTLE_ENDIAN
303                         "1:\tldl\t%0, 7(%2)\n"
304                         "2:\tldr\t%0, (%2)\n\t"
305 #endif
306                         "li\t%1, 0\n"
307                         "3:\t.section\t.fixup,\"ax\"\n\t"
308                         "4:\tli\t%1, %3\n\t"
309                         "j\t3b\n\t"
310                         ".previous\n\t"
311                         ".section\t__ex_table,\"a\"\n\t"
312                         STR(PTR)"\t1b, 4b\n\t"
313                         STR(PTR)"\t2b, 4b\n\t"
314                         ".previous"
315                         : "=&r" (value), "=r" (res)
316                         : "r" (addr), "i" (-EFAULT));
317                 if (res)
318                         goto fault;
319                 *newvalue = value;
320                 *regptr = &regs->regs[insn.i_format.rt];
321                 break;
322 #endif /* CONFIG_64BIT */
323
324                 /* Cannot handle 64-bit instructions in 32-bit kernel */
325                 goto sigill;
326
327         case sh_op:
328                 if (!access_ok(VERIFY_WRITE, addr, 2))
329                         goto sigbus;
330
331                 value = regs->regs[insn.i_format.rt];
332                 __asm__ __volatile__ (
333 #ifdef __BIG_ENDIAN
334                         ".set\tnoat\n"
335                         "1:\tsb\t%1, 1(%2)\n\t"
336                         "srl\t$1, %1, 0x8\n"
337                         "2:\tsb\t$1, 0(%2)\n\t"
338                         ".set\tat\n\t"
339 #endif
340 #ifdef __LITTLE_ENDIAN
341                         ".set\tnoat\n"
342                         "1:\tsb\t%1, 0(%2)\n\t"
343                         "srl\t$1,%1, 0x8\n"
344                         "2:\tsb\t$1, 1(%2)\n\t"
345                         ".set\tat\n\t"
346 #endif
347                         "li\t%0, 0\n"
348                         "3:\n\t"
349                         ".section\t.fixup,\"ax\"\n\t"
350                         "4:\tli\t%0, %3\n\t"
351                         "j\t3b\n\t"
352                         ".previous\n\t"
353                         ".section\t__ex_table,\"a\"\n\t"
354                         STR(PTR)"\t1b, 4b\n\t"
355                         STR(PTR)"\t2b, 4b\n\t"
356                         ".previous"
357                         : "=r" (res)
358                         : "r" (value), "r" (addr), "i" (-EFAULT));
359                 if (res)
360                         goto fault;
361                 break;
362
363         case sw_op:
364                 if (!access_ok(VERIFY_WRITE, addr, 4))
365                         goto sigbus;
366
367                 value = regs->regs[insn.i_format.rt];
368                 __asm__ __volatile__ (
369 #ifdef __BIG_ENDIAN
370                         "1:\tswl\t%1,(%2)\n"
371                         "2:\tswr\t%1, 3(%2)\n\t"
372 #endif
373 #ifdef __LITTLE_ENDIAN
374                         "1:\tswl\t%1, 3(%2)\n"
375                         "2:\tswr\t%1, (%2)\n\t"
376 #endif
377                         "li\t%0, 0\n"
378                         "3:\n\t"
379                         ".section\t.fixup,\"ax\"\n\t"
380                         "4:\tli\t%0, %3\n\t"
381                         "j\t3b\n\t"
382                         ".previous\n\t"
383                         ".section\t__ex_table,\"a\"\n\t"
384                         STR(PTR)"\t1b, 4b\n\t"
385                         STR(PTR)"\t2b, 4b\n\t"
386                         ".previous"
387                 : "=r" (res)
388                 : "r" (value), "r" (addr), "i" (-EFAULT));
389                 if (res)
390                         goto fault;
391                 break;
392
393         case sd_op:
394 #ifdef CONFIG_64BIT
395                 /*
396                  * A 32-bit kernel might be running on a 64-bit processor.  But
397                  * if we're on a 32-bit processor and an i-cache incoherency
398                  * or race makes us see a 64-bit instruction here the sdl/sdr
399                  * would blow up, so for now we don't handle unaligned 64-bit
400                  * instructions on 32-bit kernels.
401                  */
402                 if (!access_ok(VERIFY_WRITE, addr, 8))
403                         goto sigbus;
404
405                 value = regs->regs[insn.i_format.rt];
406                 __asm__ __volatile__ (
407 #ifdef __BIG_ENDIAN
408                         "1:\tsdl\t%1,(%2)\n"
409                         "2:\tsdr\t%1, 7(%2)\n\t"
410 #endif
411 #ifdef __LITTLE_ENDIAN
412                         "1:\tsdl\t%1, 7(%2)\n"
413                         "2:\tsdr\t%1, (%2)\n\t"
414 #endif
415                         "li\t%0, 0\n"
416                         "3:\n\t"
417                         ".section\t.fixup,\"ax\"\n\t"
418                         "4:\tli\t%0, %3\n\t"
419                         "j\t3b\n\t"
420                         ".previous\n\t"
421                         ".section\t__ex_table,\"a\"\n\t"
422                         STR(PTR)"\t1b, 4b\n\t"
423                         STR(PTR)"\t2b, 4b\n\t"
424                         ".previous"
425                 : "=r" (res)
426                 : "r" (value), "r" (addr), "i" (-EFAULT));
427                 if (res)
428                         goto fault;
429                 break;
430 #endif /* CONFIG_64BIT */
431
432                 /* Cannot handle 64-bit instructions in 32-bit kernel */
433                 goto sigill;
434
435         case lwc1_op:
436         case ldc1_op:
437         case swc1_op:
438         case sdc1_op:
439                 /*
440                  * I herewith declare: this does not happen.  So send SIGBUS.
441                  */
442                 goto sigbus;
443
444         case lwc2_op:
445         case ldc2_op:
446         case swc2_op:
447         case sdc2_op:
448                 /*
449                  * These are the coprocessor 2 load/stores.  The current
450                  * implementations don't use cp2 and cp2 should always be
451                  * disabled in c0_status.  So send SIGILL.
452                  * (No longer true: The Sony Praystation uses cp2 for
453                  * 3D matrix operations.  Dunno if that thingy has a MMU ...)
454                  */
455         default:
456                 /*
457                  * Pheeee...  We encountered an yet unknown instruction or
458                  * cache coherence problem.  Die sucker, die ...
459                  */
460                 goto sigill;
461         }
462
463 #ifdef CONFIG_PROC_FS
464         unaligned_instructions++;
465 #endif
466
467         return 0;
468
469 fault:
470         /* Did we have an exception handler installed? */
471         if (fixup_exception(regs))
472                 return 1;
473
474         die_if_kernel ("Unhandled kernel unaligned access", regs);
475         send_sig(SIGSEGV, current, 1);
476
477         return 0;
478
479 sigbus:
480         die_if_kernel("Unhandled kernel unaligned access", regs);
481         send_sig(SIGBUS, current, 1);
482
483         return 0;
484
485 sigill:
486         die_if_kernel("Unhandled kernel unaligned access or invalid instruction", regs);
487         send_sig(SIGILL, current, 1);
488
489         return 0;
490 }
491
492 asmlinkage void do_ade(struct pt_regs *regs)
493 {
494         unsigned long *regptr, newval;
495         extern int do_dsemulret(struct pt_regs *);
496         unsigned int __user *pc;
497         mm_segment_t seg;
498
499         /*
500          * Address errors may be deliberately induced by the FPU emulator to
501          * retake control of the CPU after executing the instruction in the
502          * delay slot of an emulated branch.
503          */
504         /* Terminate if exception was recognized as a delay slot return */
505         if (do_dsemulret(regs))
506                 return;
507
508         /* Otherwise handle as normal */
509
510         /*
511          * Did we catch a fault trying to load an instruction?
512          * Or are we running in MIPS16 mode?
513          */
514         if ((regs->cp0_badvaddr == regs->cp0_epc) || (regs->cp0_epc & 0x1))
515                 goto sigbus;
516
517         pc = (unsigned int __user *) exception_epc(regs);
518         if ((current->thread.mflags & MF_FIXADE) == 0)
519                 goto sigbus;
520
521         /*
522          * Do branch emulation only if we didn't forward the exception.
523          * This is all so but ugly ...
524          */
525         seg = get_fs();
526         if (!user_mode(regs))
527                 set_fs(KERNEL_DS);
528         if (!emulate_load_store_insn(regs, (void __user *)regs->cp0_badvaddr, pc,
529                                      &regptr, &newval)) {
530                 compute_return_epc(regs);
531                 /*
532                  * Now that branch is evaluated, update the dest
533                  * register if necessary
534                  */
535                 if (regptr)
536                         *regptr = newval;
537         }
538         set_fs(seg);
539
540         return;
541
542 sigbus:
543         die_if_kernel("Kernel unaligned instruction access", regs);
544         force_sig(SIGBUS, current);
545
546         /*
547          * XXX On return from the signal handler we should advance the epc
548          */
549 }