1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/arch/arm/mm/alignment.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 * Modifications for ARM processor (c) 1995-2001 Russell King
7 * Thumb alignment fault fixups (c) 2004 MontaVista Software, Inc.
8 * - Adapted from gdb/sim/arm/thumbemu.c -- Thumb instruction emulation.
9 * Copyright (C) 1996, Cygnus Software Technologies Ltd.
10 */
11 #include <linux/moduleparam.h>
12 #include <linux/compiler.h>
13 #include <linux/kernel.h>
14 #include <linux/sched/debug.h>
15 #include <linux/errno.h>
16 #include <linux/string.h>
17 #include <linux/proc_fs.h>
18 #include <linux/seq_file.h>
19 #include <linux/init.h>
20 #include <linux/sched/signal.h>
21 #include <linux/uaccess.h>
22
23 #include <asm/cp15.h>
24 #include <asm/system_info.h>
25 #include <asm/unaligned.h>
26 #include <asm/opcodes.h>
27
28 #include "fault.h"
29 #include "mm.h"
30
31 /*
32 * 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
33 * /proc/sys/debug/alignment, modified and integrated into
34 * Linux 2.1 by Russell King
35 *
36 * Speed optimisations and better fault handling by Russell King.
37 *
38 * *** NOTE ***
39 * This code is not portable to processors with late data abort handling.
40 */
41 #define CODING_BITS(i) (i & 0x0e000000)
42 #define COND_BITS(i) (i & 0xf0000000)
43
44 #define LDST_I_BIT(i) (i & (1 << 26)) /* Immediate constant */
45 #define LDST_P_BIT(i) (i & (1 << 24)) /* Preindex */
46 #define LDST_U_BIT(i) (i & (1 << 23)) /* Add offset */
47 #define LDST_W_BIT(i) (i & (1 << 21)) /* Writeback */
48 #define LDST_L_BIT(i) (i & (1 << 20)) /* Load */
49
50 #define LDST_P_EQ_U(i) ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
51
52 #define LDSTHD_I_BIT(i) (i & (1 << 22)) /* double/half-word immed */
53 #define LDM_S_BIT(i) (i & (1 << 22)) /* write CPSR from SPSR */
54
55 #define RN_BITS(i) ((i >> 16) & 15) /* Rn */
56 #define RD_BITS(i) ((i >> 12) & 15) /* Rd */
57 #define RM_BITS(i) (i & 15) /* Rm */
58
59 #define REGMASK_BITS(i) (i & 0xffff)
60 #define OFFSET_BITS(i) (i & 0x0fff)
61
62 #define IS_SHIFT(i) (i & 0x0ff0)
63 #define SHIFT_BITS(i) ((i >> 7) & 0x1f)
64 #define SHIFT_TYPE(i) (i & 0x60)
65 #define SHIFT_LSL 0x00
66 #define SHIFT_LSR 0x20
67 #define SHIFT_ASR 0x40
68 #define SHIFT_RORRRX 0x60
69
70 #define BAD_INSTR 0xdeadc0de
71
72 /* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
73 #define IS_T32(hi16) \
74 (((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
75
76 static unsigned long ai_user;
77 static unsigned long ai_sys;
78 static void *ai_sys_last_pc;
79 static unsigned long ai_skipped;
80 static unsigned long ai_half;
81 static unsigned long ai_word;
82 static unsigned long ai_dword;
83 static unsigned long ai_multi;
84 static int ai_usermode;
85 static unsigned long cr_no_alignment;
86
87 core_param(alignment, ai_usermode, int, 0600);
88
89 #define UM_WARN (1 << 0)
90 #define UM_FIXUP (1 << 1)
91 #define UM_SIGNAL (1 << 2)
92
93 /* Return true if and only if the ARMv6 unaligned access model is in use. */
94 static bool cpu_is_v6_unaligned(void)
95 {
96 return cpu_architecture() >= CPU_ARCH_ARMv6 && get_cr() & CR_U;
97 }
98
99 static int safe_usermode(int new_usermode, bool warn)
100 {
101 /*
102 * ARMv6 and later CPUs can perform unaligned accesses for
103 * most single load and store instructions up to word size.
104 * LDM, STM, LDRD and STRD still need to be handled.
105 *
106 * Ignoring the alignment fault is not an option on these
107 * CPUs since we spin re-faulting the instruction without
108 * making any progress.
109 */
110 if (cpu_is_v6_unaligned() && !(new_usermode & (UM_FIXUP | UM_SIGNAL))) {
111 new_usermode |= UM_FIXUP;
112
113 if (warn)
114 pr_warn("alignment: ignoring faults is unsafe on this CPU. Defaulting to fixup mode.\n");
115 }
116
117 return new_usermode;
118 }
119
120 #ifdef CONFIG_PROC_FS
121 static const char *usermode_action[] = {
122 "ignored",
123 "warn",
124 "fixup",
125 "fixup+warn",
126 "signal",
127 "signal+warn"
128 };
129
130 static int alignment_proc_show(struct seq_file *m, void *v)
131 {
132 seq_printf(m, "User:\t\t%lu\n", ai_user);
133 seq_printf(m, "System:\t\t%lu (%pS)\n", ai_sys, ai_sys_last_pc);
134 seq_printf(m, "Skipped:\t%lu\n", ai_skipped);
135 seq_printf(m, "Half:\t\t%lu\n", ai_half);
136 seq_printf(m, "Word:\t\t%lu\n", ai_word);
137 if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
138 seq_printf(m, "DWord:\t\t%lu\n", ai_dword);
139 seq_printf(m, "Multi:\t\t%lu\n", ai_multi);
140 seq_printf(m, "User faults:\t%i (%s)\n", ai_usermode,
141 usermode_action[ai_usermode]);
142
143 return 0;
144 }
145
146 static int alignment_proc_open(struct inode *inode, struct file *file)
147 {
148 return single_open(file, alignment_proc_show, NULL);
149 }
150
151 static ssize_t alignment_proc_write(struct file *file, const char __user *buffer,
152 size_t count, loff_t *pos)
153 {
154 char mode;
155
156 if (count > 0) {
157 if (get_user(mode, buffer))
158 return -EFAULT;
159 if (mode >= '' && mode <= '5')
160 ai_usermode = safe_usermode(mode - '', true);
161 }
162 return count;
163 }
164
165 static const struct proc_ops alignment_proc_ops = {
166 .proc_open = alignment_proc_open,
167 .proc_read = seq_read,
168 .proc_lseek = seq_lseek,
169 .proc_release = single_release,
170 .proc_write = alignment_proc_write,
171 };
172 #endif /* CONFIG_PROC_FS */
173
174 union offset_union {
175 unsigned long un;
176 signed long sn;
177 };
178
179 #define TYPE_ERROR 0
180 #define TYPE_FAULT 1
181 #define TYPE_LDST 2
182 #define TYPE_DONE 3
183
184 #ifdef __ARMEB__
185 #define BE 1
186 #define FIRST_BYTE_16 "mov %1, %1, ror #8\n"
187 #define FIRST_BYTE_32 "mov %1, %1, ror #24\n"
188 #define NEXT_BYTE "ror #24"
189 #else
190 #define BE 0
191 #define FIRST_BYTE_16
192 #define FIRST_BYTE_32
193 #define NEXT_BYTE "lsr #8"
194 #endif
195
196 #define __get8_unaligned_check(ins,val,addr,err) \
197 __asm__( \
198 ARM( "1: "ins" %1, [%2], #1\n" ) \
199 THUMB( "1: "ins" %1, [%2]\n" ) \
200 THUMB( " add %2, %2, #1\n" ) \
201 "2:\n" \
202 " .pushsection .text.fixup,\"ax\"\n" \
203 " .align 2\n" \
204 "3: mov %0, #1\n" \
205 " b 2b\n" \
206 " .popsection\n" \
207 " .pushsection __ex_table,\"a\"\n" \
208 " .align 3\n" \
209 " .long 1b, 3b\n" \
210 " .popsection\n" \
211 : "=r" (err), "=&r" (val), "=r" (addr) \
212 : "" (err), "2" (addr))
213
214 #define __get16_unaligned_check(ins,val,addr) \
215 do { \
216 unsigned int err = 0, v, a = addr; \
217 __get8_unaligned_check(ins,v,a,err); \
218 val = v << ((BE) ? 8 : 0); \
219 __get8_unaligned_check(ins,v,a,err); \
220 val |= v << ((BE) ? 0 : 8); \
221 if (err) \
222 goto fault; \
223 } while (0)
224
225 #define get16_unaligned_check(val,addr) \
226 __get16_unaligned_check("ldrb",val,addr)
227
228 #define get16t_unaligned_check(val,addr) \
229 __get16_unaligned_check("ldrbt",val,addr)
230
231 #define __get32_unaligned_check(ins,val,addr) \
232 do { \
233 unsigned int err = 0, v, a = addr; \
234 __get8_unaligned_check(ins,v,a,err); \
235 val = v << ((BE) ? 24 : 0); \
236 __get8_unaligned_check(ins,v,a,err); \
237 val |= v << ((BE) ? 16 : 8); \
238 __get8_unaligned_check(ins,v,a,err); \
239 val |= v << ((BE) ? 8 : 16); \
240 __get8_unaligned_check(ins,v,a,err); \
241 val |= v << ((BE) ? 0 : 24); \
242 if (err) \
243 goto fault; \
244 } while (0)
245
246 #define get32_unaligned_check(val,addr) \
247 __get32_unaligned_check("ldrb",val,addr)
248
249 #define get32t_unaligned_check(val,addr) \
250 __get32_unaligned_check("ldrbt",val,addr)
251
252 #define __put16_unaligned_check(ins,val,addr) \
253 do { \
254 unsigned int err = 0, v = val, a = addr; \
255 __asm__( FIRST_BYTE_16 \
256 ARM( "1: "ins" %1, [%2], #1\n" ) \
257 THUMB( "1: "ins" %1, [%2]\n" ) \
258 THUMB( " add %2, %2, #1\n" ) \
259 " mov %1, %1, "NEXT_BYTE"\n" \
260 "2: "ins" %1, [%2]\n" \
261 "3:\n" \
262 " .pushsection .text.fixup,\"ax\"\n" \
263 " .align 2\n" \
264 "4: mov %0, #1\n" \
265 " b 3b\n" \
266 " .popsection\n" \
267 " .pushsection __ex_table,\"a\"\n" \
268 " .align 3\n" \
269 " .long 1b, 4b\n" \
270 " .long 2b, 4b\n" \
271 " .popsection\n" \
272 : "=r" (err), "=&r" (v), "=&r" (a) \
273 : "" (err), "1" (v), "2" (a)); \
274 if (err) \
275 goto fault; \
276 } while (0)
277
278 #define put16_unaligned_check(val,addr) \
279 __put16_unaligned_check("strb",val,addr)
280
281 #define put16t_unaligned_check(val,addr) \
282 __put16_unaligned_check("strbt",val,addr)
283
284 #define __put32_unaligned_check(ins,val,addr) \
285 do { \
286 unsigned int err = 0, v = val, a = addr; \
287 __asm__( FIRST_BYTE_32 \
288 ARM( "1: "ins" %1, [%2], #1\n" ) \
289 THUMB( "1: "ins" %1, [%2]\n" ) \
290 THUMB( " add %2, %2, #1\n" ) \
291 " mov %1, %1, "NEXT_BYTE"\n" \
292 ARM( "2: "ins" %1, [%2], #1\n" ) \
293 THUMB( "2: "ins" %1, [%2]\n" ) \
294 THUMB( " add %2, %2, #1\n" ) \
295 " mov %1, %1, "NEXT_BYTE"\n" \
296 ARM( "3: "ins" %1, [%2], #1\n" ) \
297 THUMB( "3: "ins" %1, [%2]\n" ) \
298 THUMB( " add %2, %2, #1\n" ) \
299 " mov %1, %1, "NEXT_BYTE"\n" \
300 "4: "ins" %1, [%2]\n" \
301 "5:\n" \
302 " .pushsection .text.fixup,\"ax\"\n" \
303 " .align 2\n" \
304 "6: mov %0, #1\n" \
305 " b 5b\n" \
306 " .popsection\n" \
307 " .pushsection __ex_table,\"a\"\n" \
308 " .align 3\n" \
309 " .long 1b, 6b\n" \
310 " .long 2b, 6b\n" \
311 " .long 3b, 6b\n" \
312 " .long 4b, 6b\n" \
313 " .popsection\n" \
314 : "=r" (err), "=&r" (v), "=&r" (a) \
315 : "" (err), "1" (v), "2" (a)); \
316 if (err) \
317 goto fault; \
318 } while (0)
319
320 #define put32_unaligned_check(val,addr) \
321 __put32_unaligned_check("strb", val, addr)
322
323 #define put32t_unaligned_check(val,addr) \
324 __put32_unaligned_check("strbt", val, addr)
325
326 static void
327 do_alignment_finish_ldst(unsigned long addr, u32 instr, struct pt_regs *regs, union offset_union offset)
328 {
329 if (!LDST_U_BIT(instr))
330 offset.un = -offset.un;
331
332 if (!LDST_P_BIT(instr))
333 addr += offset.un;
334
335 if (!LDST_P_BIT(instr) || LDST_W_BIT(instr))
336 regs->uregs[RN_BITS(instr)] = addr;
337 }
338
339 static int
340 do_alignment_ldrhstrh(unsigned long addr, u32 instr, struct pt_regs *regs)
341 {
342 unsigned int rd = RD_BITS(instr);
343
344 ai_half += 1;
345
346 if (user_mode(regs))
347 goto user;
348
349 if (LDST_L_BIT(instr)) {
350 unsigned long val;
351 get16_unaligned_check(val, addr);
352
353 /* signed half-word? */
354 if (instr & 0x40)
355 val = (signed long)((signed short) val);
356
357 regs->uregs[rd] = val;
358 } else
359 put16_unaligned_check(regs->uregs[rd], addr);
360
361 return TYPE_LDST;
362
363 user:
364 if (LDST_L_BIT(instr)) {
365 unsigned long val;
366 unsigned int __ua_flags = uaccess_save_and_enable();
367
368 get16t_unaligned_check(val, addr);
369 uaccess_restore(__ua_flags);
370
371 /* signed half-word? */
372 if (instr & 0x40)
373 val = (signed long)((signed short) val);
374
375 regs->uregs[rd] = val;
376 } else {
377 unsigned int __ua_flags = uaccess_save_and_enable();
378 put16t_unaligned_check(regs->uregs[rd], addr);
379 uaccess_restore(__ua_flags);
380 }
381
382 return TYPE_LDST;
383
384 fault:
385 return TYPE_FAULT;
386 }
387
388 static int
389 do_alignment_ldrdstrd(unsigned long addr, u32 instr, struct pt_regs *regs)
390 {
391 unsigned int rd = RD_BITS(instr);
392 unsigned int rd2;
393 int load;
394
395 if ((instr & 0xfe000000) == 0xe8000000) {
396 /* ARMv7 Thumb-2 32-bit LDRD/STRD */
397 rd2 = (instr >> 8) & 0xf;
398 load = !!(LDST_L_BIT(instr));
399 } else if (((rd & 1) == 1) || (rd == 14))
400 goto bad;
401 else {
402 load = ((instr & 0xf0) == 0xd0);
403 rd2 = rd + 1;
404 }
405
406 ai_dword += 1;
407
408 if (user_mode(regs))
409 goto user;
410
411 if (load) {
412 unsigned long val;
413 get32_unaligned_check(val, addr);
414 regs->uregs[rd] = val;
415 get32_unaligned_check(val, addr + 4);
416 regs->uregs[rd2] = val;
417 } else {
418 put32_unaligned_check(regs->uregs[rd], addr);
419 put32_unaligned_check(regs->uregs[rd2], addr + 4);
420 }
421
422 return TYPE_LDST;
423
424 user:
425 if (load) {
426 unsigned long val, val2;
427 unsigned int __ua_flags = uaccess_save_and_enable();
428
429 get32t_unaligned_check(val, addr);
430 get32t_unaligned_check(val2, addr + 4);
431
432 uaccess_restore(__ua_flags);
433
434 regs->uregs[rd] = val;
435 regs->uregs[rd2] = val2;
436 } else {
437 unsigned int __ua_flags = uaccess_save_and_enable();
438 put32t_unaligned_check(regs->uregs[rd], addr);
439 put32t_unaligned_check(regs->uregs[rd2], addr + 4);
440 uaccess_restore(__ua_flags);
441 }
442
443 return TYPE_LDST;
444 bad:
445 return TYPE_ERROR;
446 fault:
447 return TYPE_FAULT;
448 }
449
450 static int
451 do_alignment_ldrstr(unsigned long addr, u32 instr, struct pt_regs *regs)
452 {
453 unsigned int rd = RD_BITS(instr);
454
455 ai_word += 1;
456
457 if ((!LDST_P_BIT(instr) && LDST_W_BIT(instr)) || user_mode(regs))
458 goto trans;
459
460 if (LDST_L_BIT(instr)) {
461 unsigned int val;
462 get32_unaligned_check(val, addr);
463 regs->uregs[rd] = val;
464 } else
465 put32_unaligned_check(regs->uregs[rd], addr);
466 return TYPE_LDST;
467
468 trans:
469 if (LDST_L_BIT(instr)) {
470 unsigned int val;
471 unsigned int __ua_flags = uaccess_save_and_enable();
472 get32t_unaligned_check(val, addr);
473 uaccess_restore(__ua_flags);
474 regs->uregs[rd] = val;
475 } else {
476 unsigned int __ua_flags = uaccess_save_and_enable();
477 put32t_unaligned_check(regs->uregs[rd], addr);
478 uaccess_restore(__ua_flags);
479 }
480 return TYPE_LDST;
481
482 fault:
483 return TYPE_FAULT;
484 }
485
486 /*
487 * LDM/STM alignment handler.
488 *
489 * There are 4 variants of this instruction:
490 *
491 * B = rn pointer before instruction, A = rn pointer after instruction
492 * ------ increasing address ----->
493 * | | r0 | r1 | ... | rx | |
494 * PU = 01 B A
495 * PU = 11 B A
496 * PU = 00 A B
497 * PU = 10 A B
498 */
499 static int
500 do_alignment_ldmstm(unsigned long addr, u32 instr, struct pt_regs *regs)
501 {
502 unsigned int rd, rn, correction, nr_regs, regbits;
503 unsigned long eaddr, newaddr;
504
505 if (LDM_S_BIT(instr))
506 goto bad;
507
508 correction = 4; /* processor implementation defined */
509 regs->ARM_pc += correction;
510
511 ai_multi += 1;
512
513 /* count the number of registers in the mask to be transferred */
514 nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
515
516 rn = RN_BITS(instr);
517 newaddr = eaddr = regs->uregs[rn];
518
519 if (!LDST_U_BIT(instr))
520 nr_regs = -nr_regs;
521 newaddr += nr_regs;
522 if (!LDST_U_BIT(instr))
523 eaddr = newaddr;
524
525 if (LDST_P_EQ_U(instr)) /* U = P */
526 eaddr += 4;
527
528 /*
529 * For alignment faults on the ARM922T/ARM920T the MMU makes
530 * the FSR (and hence addr) equal to the updated base address
531 * of the multiple access rather than the restored value.
532 * Switch this message off if we've got a ARM92[02], otherwise
533 * [ls]dm alignment faults are noisy!
534 */
535 #if !(defined CONFIG_CPU_ARM922T) && !(defined CONFIG_CPU_ARM920T)
536 /*
537 * This is a "hint" - we already have eaddr worked out by the
538 * processor for us.
539 */
540 if (addr != eaddr) {
541 pr_err("LDMSTM: PC = %08lx, instr = %08x, "
542 "addr = %08lx, eaddr = %08lx\n",
543 instruction_pointer(regs), instr, addr, eaddr);
544 show_regs(regs);
545 }
546 #endif
547
548 if (user_mode(regs)) {
549 unsigned int __ua_flags = uaccess_save_and_enable();
550 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
551 regbits >>= 1, rd += 1)
552 if (regbits & 1) {
553 if (LDST_L_BIT(instr)) {
554 unsigned int val;
555 get32t_unaligned_check(val, eaddr);
556 regs->uregs[rd] = val;
557 } else
558 put32t_unaligned_check(regs->uregs[rd], eaddr);
559 eaddr += 4;
560 }
561 uaccess_restore(__ua_flags);
562 } else {
563 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
564 regbits >>= 1, rd += 1)
565 if (regbits & 1) {
566 if (LDST_L_BIT(instr)) {
567 unsigned int val;
568 get32_unaligned_check(val, eaddr);
569 regs->uregs[rd] = val;
570 } else
571 put32_unaligned_check(regs->uregs[rd], eaddr);
572 eaddr += 4;
573 }
574 }
575
576 if (LDST_W_BIT(instr))
577 regs->uregs[rn] = newaddr;
578 if (!LDST_L_BIT(instr) || !(REGMASK_BITS(instr) & (1 << 15)))
579 regs->ARM_pc -= correction;
580 return TYPE_DONE;
581
582 fault:
583 regs->ARM_pc -= correction;
584 return TYPE_FAULT;
585
586 bad:
587 pr_err("Alignment trap: not handling ldm with s-bit set\n");
588 return TYPE_ERROR;
589 }
590
591 /*
592 * Convert Thumb ld/st instruction forms to equivalent ARM instructions so
593 * we can reuse ARM userland alignment fault fixups for Thumb.
594 *
595 * This implementation was initially based on the algorithm found in
596 * gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
597 * to convert only Thumb ld/st instruction forms to equivalent ARM forms.
598 *
599 * NOTES:
600 * 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
601 * 2. If for some reason we're passed an non-ld/st Thumb instruction to
602 * decode, we return 0xdeadc0de. This should never happen under normal
603 * circumstances but if it does, we've got other problems to deal with
604 * elsewhere and we obviously can't fix those problems here.
605 */
606
607 static unsigned long
608 thumb2arm(u16 tinstr)
609 {
610 u32 L = (tinstr & (1<<11)) >> 11;
611
612 switch ((tinstr & 0xf800) >> 11) {
613 /* 6.5.1 Format 1: */
614 case 0x6000 >> 11: /* 7.1.52 STR(1) */
615 case 0x6800 >> 11: /* 7.1.26 LDR(1) */
616 case 0x7000 >> 11: /* 7.1.55 STRB(1) */
617 case 0x7800 >> 11: /* 7.1.30 LDRB(1) */
618 return 0xe5800000 |
619 ((tinstr & (1<<12)) << (22-12)) | /* fixup */
620 (L<<20) | /* L==1? */
621 ((tinstr & (7<<0)) << (12-0)) | /* Rd */
622 ((tinstr & (7<<3)) << (16-3)) | /* Rn */
623 ((tinstr & (31<<6)) >> /* immed_5 */
624 (6 - ((tinstr & (1<<12)) ? 0 : 2)));
625 case 0x8000 >> 11: /* 7.1.57 STRH(1) */
626 case 0x8800 >> 11: /* 7.1.32 LDRH(1) */
627 return 0xe1c000b0 |
628 (L<<20) | /* L==1? */
629 ((tinstr & (7<<0)) << (12-0)) | /* Rd */
630 ((tinstr & (7<<3)) << (16-3)) | /* Rn */
631 ((tinstr & (7<<6)) >> (6-1)) | /* immed_5[2:0] */
632 ((tinstr & (3<<9)) >> (9-8)); /* immed_5[4:3] */
633
634 /* 6.5.1 Format 2: */
635 case 0x5000 >> 11:
636 case 0x5800 >> 11:
637 {
638 static const u32 subset[8] = {
639 0xe7800000, /* 7.1.53 STR(2) */
640 0xe18000b0, /* 7.1.58 STRH(2) */
641 0xe7c00000, /* 7.1.56 STRB(2) */
642 0xe19000d0, /* 7.1.34 LDRSB */
643 0xe7900000, /* 7.1.27 LDR(2) */
644 0xe19000b0, /* 7.1.33 LDRH(2) */
645 0xe7d00000, /* 7.1.31 LDRB(2) */
646 0xe19000f0 /* 7.1.35 LDRSH */
647 };
648 return subset[(tinstr & (7<<9)) >> 9] |
649 ((tinstr & (7<<0)) << (12-0)) | /* Rd */
650 ((tinstr & (7<<3)) << (16-3)) | /* Rn */
651 ((tinstr & (7<<6)) >> (6-0)); /* Rm */
652 }
653
654 /* 6.5.1 Format 3: */
655 case 0x4800 >> 11: /* 7.1.28 LDR(3) */
656 /* NOTE: This case is not technically possible. We're
657 * loading 32-bit memory data via PC relative
658 * addressing mode. So we can and should eliminate
659 * this case. But I'll leave it here for now.
660 */
661 return 0xe59f0000 |
662 ((tinstr & (7<<8)) << (12-8)) | /* Rd */
663 ((tinstr & 255) << (2-0)); /* immed_8 */
664
665 /* 6.5.1 Format 4: */
666 case 0x9000 >> 11: /* 7.1.54 STR(3) */
667 case 0x9800 >> 11: /* 7.1.29 LDR(4) */
668 return 0xe58d0000 |
669 (L<<20) | /* L==1? */
670 ((tinstr & (7<<8)) << (12-8)) | /* Rd */
671 ((tinstr & 255) << 2); /* immed_8 */
672
673 /* 6.6.1 Format 1: */
674 case 0xc000 >> 11: /* 7.1.51 STMIA */
675 case 0xc800 >> 11: /* 7.1.25 LDMIA */
676 {
677 u32 Rn = (tinstr & (7<<8)) >> 8;
678 u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
679
680 return 0xe8800000 | W | (L<<20) | (Rn<<16) |
681 (tinstr&255);
682 }
683
684 /* 6.6.1 Format 2: */
685 case 0xb000 >> 11: /* 7.1.48 PUSH */
686 case 0xb800 >> 11: /* 7.1.47 POP */
687 if ((tinstr & (3 << 9)) == 0x0400) {
688 static const u32 subset[4] = {
689 0xe92d0000, /* STMDB sp!,{registers} */
690 0xe92d4000, /* STMDB sp!,{registers,lr} */
691 0xe8bd0000, /* LDMIA sp!,{registers} */
692 0xe8bd8000 /* LDMIA sp!,{registers,pc} */
693 };
694 return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
695 (tinstr & 255); /* register_list */
696 }
697 fallthrough; /* for illegal instruction case */
698
699 default:
700 return BAD_INSTR;
701 }
702 }
703
704 /*
705 * Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
706 * handlable by ARM alignment handler, also find the corresponding handler,
707 * so that we can reuse ARM userland alignment fault fixups for Thumb.
708 *
709 * @pinstr: original Thumb-2 instruction; returns new handlable instruction
710 * @regs: register context.
711 * @poffset: return offset from faulted addr for later writeback
712 *
713 * NOTES:
714 * 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
715 * 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
716 */
717 static void *
718 do_alignment_t32_to_handler(u32 *pinstr, struct pt_regs *regs,
719 union offset_union *poffset)
720 {
721 u32 instr = *pinstr;
722 u16 tinst1 = (instr >> 16) & 0xffff;
723 u16 tinst2 = instr & 0xffff;
724
725 switch (tinst1 & 0xffe0) {
726 /* A6.3.5 Load/Store multiple */
727 case 0xe880: /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
728 case 0xe8a0: /* ...above writeback version */
729 case 0xe900: /* STMDB/STMFD, LDMDB/LDMEA */
730 case 0xe920: /* ...above writeback version */
731 /* no need offset decision since handler calculates it */
732 return do_alignment_ldmstm;
733
734 case 0xf840: /* POP/PUSH T3 (single register) */
735 if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
736 u32 L = !!(LDST_L_BIT(instr));
737 const u32 subset[2] = {
738 0xe92d0000, /* STMDB sp!,{registers} */
739 0xe8bd0000, /* LDMIA sp!,{registers} */
740 };
741 *pinstr = subset[L] | (1<<RD_BITS(instr));
742 return do_alignment_ldmstm;
743 }
744 /* Else fall through for illegal instruction case */
745 break;
746
747 /* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
748 case 0xe860:
749 case 0xe960:
750 case 0xe8e0:
751 case 0xe9e0:
752 poffset->un = (tinst2 & 0xff) << 2;
753 fallthrough;
754
755 case 0xe940:
756 case 0xe9c0:
757 return do_alignment_ldrdstrd;
758
759 /*
760 * No need to handle load/store instructions up to word size
761 * since ARMv6 and later CPUs can perform unaligned accesses.
762 */
763 default:
764 break;
765 }
766 return NULL;
767 }
768
769 static int alignment_get_arm(struct pt_regs *regs, u32 *ip, u32 *inst)
770 {
771 u32 instr = 0;
772 int fault;
773
774 if (user_mode(regs))
775 fault = get_user(instr, ip);
776 else
777 fault = get_kernel_nofault(instr, ip);
778
779 *inst = __mem_to_opcode_arm(instr);
780
781 return fault;
782 }
783
784 static int alignment_get_thumb(struct pt_regs *regs, u16 *ip, u16 *inst)
785 {
786 u16 instr = 0;
787 int fault;
788
789 if (user_mode(regs))
790 fault = get_user(instr, ip);
791 else
792 fault = get_kernel_nofault(instr, ip);
793
794 *inst = __mem_to_opcode_thumb16(instr);
795
796 return fault;
797 }
798
799 static int
800 do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
801 {
802 union offset_union offset;
803 unsigned long instrptr;
804 int (*handler)(unsigned long addr, u32 instr, struct pt_regs *regs);
805 unsigned int type;
806 u32 instr = 0;
807 u16 tinstr = 0;
808 int isize = 4;
809 int thumb2_32b = 0;
810 int fault;
811
812 if (interrupts_enabled(regs))
813 local_irq_enable();
814
815 instrptr = instruction_pointer(regs);
816
817 if (thumb_mode(regs)) {
818 u16 *ptr = (u16 *)(instrptr & ~1);
819
820 fault = alignment_get_thumb(regs, ptr, &tinstr);
821 if (!fault) {
822 if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
823 IS_T32(tinstr)) {
824 /* Thumb-2 32-bit */
825 u16 tinst2;
826 fault = alignment_get_thumb(regs, ptr + 1, &tinst2);
827 instr = __opcode_thumb32_compose(tinstr, tinst2);
828 thumb2_32b = 1;
829 } else {
830 isize = 2;
831 instr = thumb2arm(tinstr);
832 }
833 }
834 } else {
835 fault = alignment_get_arm(regs, (void *)instrptr, &instr);
836 }
837
838 if (fault) {
839 type = TYPE_FAULT;
840 goto bad_or_fault;
841 }
842
843 if (user_mode(regs))
844 goto user;
845
846 ai_sys += 1;
847 ai_sys_last_pc = (void *)instruction_pointer(regs);
848
849 fixup:
850
851 regs->ARM_pc += isize;
852
853 switch (CODING_BITS(instr)) {
854 case 0x00000000: /* 3.13.4 load/store instruction extensions */
855 if (LDSTHD_I_BIT(instr))
856 offset.un = (instr & 0xf00) >> 4 | (instr & 15);
857 else
858 offset.un = regs->uregs[RM_BITS(instr)];
859
860 if ((instr & 0x000000f0) == 0x000000b0 || /* LDRH, STRH */
861 (instr & 0x001000f0) == 0x001000f0) /* LDRSH */
862 handler = do_alignment_ldrhstrh;
863 else if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
864 (instr & 0x001000f0) == 0x000000f0) /* STRD */
865 handler = do_alignment_ldrdstrd;
866 else if ((instr & 0x01f00ff0) == 0x01000090) /* SWP */
867 goto swp;
868 else
869 goto bad;
870 break;
871
872 case 0x04000000: /* ldr or str immediate */
873 if (COND_BITS(instr) == 0xf0000000) /* NEON VLDn, VSTn */
874 goto bad;
875 offset.un = OFFSET_BITS(instr);
876 handler = do_alignment_ldrstr;
877 break;
878
879 case 0x06000000: /* ldr or str register */
880 offset.un = regs->uregs[RM_BITS(instr)];
881
882 if (IS_SHIFT(instr)) {
883 unsigned int shiftval = SHIFT_BITS(instr);
884
885 switch(SHIFT_TYPE(instr)) {
886 case SHIFT_LSL:
887 offset.un <<= shiftval;
888 break;
889
890 case SHIFT_LSR:
891 offset.un >>= shiftval;
892 break;
893
894 case SHIFT_ASR:
895 offset.sn >>= shiftval;
896 break;
897
898 case SHIFT_RORRRX:
899 if (shiftval == 0) {
900 offset.un >>= 1;
901 if (regs->ARM_cpsr & PSR_C_BIT)
902 offset.un |= 1 << 31;
903 } else
904 offset.un = offset.un >> shiftval |
905 offset.un << (32 - shiftval);
906 break;
907 }
908 }
909 handler = do_alignment_ldrstr;
910 break;
911
912 case 0x08000000: /* ldm or stm, or thumb-2 32bit instruction */
913 if (thumb2_32b) {
914 offset.un = 0;
915 handler = do_alignment_t32_to_handler(&instr, regs, &offset);
916 } else {
917 offset.un = 0;
918 handler = do_alignment_ldmstm;
919 }
920 break;
921
922 default:
923 goto bad;
924 }
925
926 if (!handler)
927 goto bad;
928 type = handler(addr, instr, regs);
929
930 if (type == TYPE_ERROR || type == TYPE_FAULT) {
931 regs->ARM_pc -= isize;
932 goto bad_or_fault;
933 }
934
935 if (type == TYPE_LDST)
936 do_alignment_finish_ldst(addr, instr, regs, offset);
937
938 if (thumb_mode(regs))
939 regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
940
941 return 0;
942
943 bad_or_fault:
944 if (type == TYPE_ERROR)
945 goto bad;
946 /*
947 * We got a fault - fix it up, or die.
948 */
949 do_bad_area(addr, fsr, regs);
950 return 0;
951
952 swp:
953 pr_err("Alignment trap: not handling swp instruction\n");
954
955 bad:
956 /*
957 * Oops, we didn't handle the instruction.
958 */
959 pr_err("Alignment trap: not handling instruction "
960 "%0*x at [<%08lx>]\n",
961 isize << 1,
962 isize == 2 ? tinstr : instr, instrptr);
963 ai_skipped += 1;
964 return 1;
965
966 user:
967 ai_user += 1;
968
969 if (ai_usermode & UM_WARN)
970 printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*x "
971 "Address=0x%08lx FSR 0x%03x\n", current->comm,
972 task_pid_nr(current), instrptr,
973 isize << 1,
974 isize == 2 ? tinstr : instr,
975 addr, fsr);
976
977 if (ai_usermode & UM_FIXUP)
978 goto fixup;
979
980 if (ai_usermode & UM_SIGNAL) {
981 force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *)addr);
982 } else {
983 /*
984 * We're about to disable the alignment trap and return to
985 * user space. But if an interrupt occurs before actually
986 * reaching user space, then the IRQ vector entry code will
987 * notice that we were still in kernel space and therefore
988 * the alignment trap won't be re-enabled in that case as it
989 * is presumed to be always on from kernel space.
990 * Let's prevent that race by disabling interrupts here (they
991 * are disabled on the way back to user space anyway in
992 * entry-common.S) and disable the alignment trap only if
993 * there is no work pending for this thread.
994 */
995 raw_local_irq_disable();
996 if (!(read_thread_flags() & _TIF_WORK_MASK))
997 set_cr(cr_no_alignment);
998 }
999
1000 return 0;
1001 }
1002
1003 static int __init noalign_setup(char *__unused)
1004 {
1005 set_cr(__clear_cr(CR_A));
1006 return 1;
1007 }
1008 __setup("noalign", noalign_setup);
1009
1010 /*
1011 * This needs to be done after sysctl_init_bases(), otherwise sys/ will be
1012 * overwritten. Actually, this shouldn't be in sys/ at all since
1013 * it isn't a sysctl, and it doesn't contain sysctl information.
1014 * We now locate it in /proc/cpu/alignment instead.
1015 */
1016 static int __init alignment_init(void)
1017 {
1018 #ifdef CONFIG_PROC_FS
1019 struct proc_dir_entry *res;
1020
1021 res = proc_create("cpu/alignment", S_IWUSR | S_IRUGO, NULL,
1022 &alignment_proc_ops);
1023 if (!res)
1024 return -ENOMEM;
1025 #endif
1026
1027 if (cpu_is_v6_unaligned()) {
1028 set_cr(__clear_cr(CR_A));
1029 ai_usermode = safe_usermode(ai_usermode, false);
1030 }
1031
1032 cr_no_alignment = get_cr() & ~CR_A;
1033
1034 hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
1035 "alignment exception");
1036
1037 /*
1038 * ARMv6K and ARMv7 use fault status 3 (0b00011) as Access Flag section
1039 * fault, not as alignment error.
1040 *
1041 * TODO: handle ARMv6K properly. Runtime check for 'K' extension is
1042 * needed.
1043 */
1044 if (cpu_architecture() <= CPU_ARCH_ARMv6) {
1045 hook_fault_code(3, do_alignment, SIGBUS, BUS_ADRALN,
1046 "alignment exception");
1047 }
1048
1049 return 0;
1050 }
1051
1052 fs_initcall(alignment_init);
1053
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.