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Merge branch 'for-5.4/apple' into for-linus
[linux-2.6-block.git] / arch / arm / mm / alignment.c
CommitLineData
d2912cb1 1// SPDX-License-Identifier: GPL-2.0-only
1da177e4
LT		 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
6cbdc8c5 7 * Thumb alignment fault fixups (c) 2004 MontaVista Software, Inc.
1da177e4
LT		 8 * - Adapted from gdb/sim/arm/thumbemu.c -- Thumb instruction emulation.
9 * Copyright (C) 1996, Cygnus Software Technologies Ltd.
1da177e4 10 */
d944d549 11#include <linux/moduleparam.h>
1da177e4
LT		 12#include <linux/compiler.h>
13#include <linux/kernel.h>
b17b0153 14#include <linux/sched/debug.h>
1da177e4
LT		 15#include <linux/errno.h>
16#include <linux/string.h>
1da177e4 17#include <linux/proc_fs.h>
b7072c63 18#include <linux/seq_file.h>
1da177e4 19#include <linux/init.h>
3f07c014 20#include <linux/sched/signal.h>
33fa9b13 21#include <linux/uaccess.h>
1da177e4 22
15d07dc9 23#include <asm/cp15.h>
9f97da78 24#include <asm/system_info.h>
1da177e4 25#include <asm/unaligned.h>
8592edf0 26#include <asm/opcodes.h>
1da177e4
LT		 27
28#include "fault.h"
b4b20ad8 29#include "mm.h"
1da177e4
LT		 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)
5ca918e5 42#define COND_BITS(i) (i & 0xf0000000)
1da177e4
LT		 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
f21ee2d4 52#define LDSTHD_I_BIT(i) (i & (1 << 22)) /* double/half-word immed */
1da177e4
LT		 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
c2860d43
GD		 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
1da177e4
LT		 76static unsigned long ai_user;
77static unsigned long ai_sys;
1e7e3211 78static void *ai_sys_last_pc;
1da177e4
LT		 79static unsigned long ai_skipped;
80static unsigned long ai_half;
81static unsigned long ai_word;
f21ee2d4 82static unsigned long ai_dword;
1da177e4
LT		 83static unsigned long ai_multi;
84static int ai_usermode;
0aeb3408 85static unsigned long cr_no_alignment;
1da177e4 86
d944d549
RK		 87core_param(alignment, ai_usermode, int, 0600);
88
baa745a3
RK		 89#define UM_WARN (1 << 0)
90#define UM_FIXUP (1 << 1)
91#define UM_SIGNAL (1 << 2)
92
088c01f1
DM		 93/* Return true if and only if the ARMv6 unaligned access model is in use. */
94static bool cpu_is_v6_unaligned(void)
95{
4585eaff 96 return cpu_architecture() >= CPU_ARCH_ARMv6 && get_cr() & CR_U;
088c01f1
DM		 97}
98
99static 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)
4ed89f22 114 pr_warn("alignment: ignoring faults is unsafe on this CPU. Defaulting to fixup mode.\n");
088c01f1
DM		 115 }
116
117 return new_usermode;
118}
119
ffc660c5
AB		 120#ifdef CONFIG_PROC_FS
121static const char *usermode_action[] = {
122 "ignored",
123 "warn",
124 "fixup",
125 "fixup+warn",
126 "signal",
127 "signal+warn"
128};
129
b7072c63 130static int alignment_proc_show(struct seq_file *m, void *v)
1da177e4 131{
b7072c63 132 seq_printf(m, "User:\t\t%lu\n", ai_user);
d75f773c 133 seq_printf(m, "System:\t\t%lu (%pS)\n", ai_sys, ai_sys_last_pc);
b7072c63
AD		 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);
f21ee2d4 137 if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
b7072c63
AD		 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,
1da177e4
LT		 141 usermode_action[ai_usermode]);
142
b7072c63
AD		 143 return 0;
144}
1da177e4 145
b7072c63
AD		 146static int alignment_proc_open(struct inode *inode, struct file *file)
147{
148 return single_open(file, alignment_proc_show, NULL);
1da177e4
LT		 149}
150
b7072c63
AD		 151static ssize_t alignment_proc_write(struct file *file, const char __user *buffer,
152 size_t count, loff_t *pos)
1da177e4
LT		 153{
154 char mode;
155
156 if (count > 0) {
157 if (get_user(mode, buffer))
158 return -EFAULT;
159 if (mode >= '0' && mode <= '5')
088c01f1 160 ai_usermode = safe_usermode(mode - '0', true);
1da177e4
LT		 161 }
162 return count;
163}
164
b7072c63
AD		 165static const struct file_operations alignment_proc_fops = {
166 .open = alignment_proc_open,
167 .read = seq_read,
168 .llseek = seq_lseek,
169 .release = single_release,
170 .write = alignment_proc_write,
171};
1da177e4
LT		 172#endif /* CONFIG_PROC_FS */
173
174union 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__( \
347c8b70
CM		 198 ARM( "1: "ins" %1, [%2], #1\n" ) \
199 THUMB( "1: "ins" %1, [%2]\n" ) \
200 THUMB( " add %2, %2, #1\n" ) \
1da177e4 201 "2:\n" \
c4a84ae3 202 " .pushsection .text.fixup,\"ax\"\n" \
1da177e4
LT		 203 " .align 2\n" \
204 "3: mov %0, #1\n" \
205 " b 2b\n" \
4260415f
RK		 206 " .popsection\n" \
207 " .pushsection __ex_table,\"a\"\n" \
1da177e4
LT		 208 " .align 3\n" \
209 " .long 1b, 3b\n" \
4260415f 210 " .popsection\n" \
1da177e4
LT		 211 : "=r" (err), "=&r" (val), "=r" (addr) \
212 : "0" (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 \
347c8b70
CM		 256 ARM( "1: "ins" %1, [%2], #1\n" ) \
257 THUMB( "1: "ins" %1, [%2]\n" ) \
258 THUMB( " add %2, %2, #1\n" ) \
1da177e4
LT		 259 " mov %1, %1, "NEXT_BYTE"\n" \
260 "2: "ins" %1, [%2]\n" \
261 "3:\n" \
c4a84ae3 262 " .pushsection .text.fixup,\"ax\"\n" \
1da177e4
LT		 263 " .align 2\n" \
264 "4: mov %0, #1\n" \
265 " b 3b\n" \
4260415f
RK		 266 " .popsection\n" \
267 " .pushsection __ex_table,\"a\"\n" \
1da177e4
LT		 268 " .align 3\n" \
269 " .long 1b, 4b\n" \
270 " .long 2b, 4b\n" \
4260415f 271 " .popsection\n" \
1da177e4
LT		 272 : "=r" (err), "=&r" (v), "=&r" (a) \
273 : "0" (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 \
347c8b70
CM		 288 ARM( "1: "ins" %1, [%2], #1\n" ) \
289 THUMB( "1: "ins" %1, [%2]\n" ) \
290 THUMB( " add %2, %2, #1\n" ) \
1da177e4 291 " mov %1, %1, "NEXT_BYTE"\n" \
347c8b70
CM		 292 ARM( "2: "ins" %1, [%2], #1\n" ) \
293 THUMB( "2: "ins" %1, [%2]\n" ) \
294 THUMB( " add %2, %2, #1\n" ) \
1da177e4 295 " mov %1, %1, "NEXT_BYTE"\n" \
347c8b70
CM		 296 ARM( "3: "ins" %1, [%2], #1\n" ) \
297 THUMB( "3: "ins" %1, [%2]\n" ) \
298 THUMB( " add %2, %2, #1\n" ) \
1da177e4
LT		 299 " mov %1, %1, "NEXT_BYTE"\n" \
300 "4: "ins" %1, [%2]\n" \
301 "5:\n" \
c4a84ae3 302 " .pushsection .text.fixup,\"ax\"\n" \
1da177e4
LT		 303 " .align 2\n" \
304 "6: mov %0, #1\n" \
305 " b 5b\n" \
4260415f
RK		 306 " .popsection\n" \
307 " .pushsection __ex_table,\"a\"\n" \
1da177e4
LT		 308 " .align 3\n" \
309 " .long 1b, 6b\n" \
310 " .long 2b, 6b\n" \
311 " .long 3b, 6b\n" \
312 " .long 4b, 6b\n" \
4260415f 313 " .popsection\n" \
1da177e4
LT		 314 : "=r" (err), "=&r" (v), "=&r" (a) \
315 : "0" (err), "1" (v), "2" (a)); \
316 if (err) \
317 goto fault; \
318 } while (0)
319
737d0bb7 320#define put32_unaligned_check(val,addr) \
1da177e4
LT		 321 __put32_unaligned_check("strb", val, addr)
322
323#define put32t_unaligned_check(val,addr) \
324 __put32_unaligned_check("strbt", val, addr)
325
326static void
327do_alignment_finish_ldst(unsigned long addr, unsigned long 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
339static int
340do_alignment_ldrhstrh(unsigned long addr, unsigned long instr, struct pt_regs *regs)
341{
342 unsigned int rd = RD_BITS(instr);
343
1da177e4
LT		 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:
737d0bb7
GD		 364 if (LDST_L_BIT(instr)) {
365 unsigned long val;
274e91b8
RK		 366 unsigned int __ua_flags = uaccess_save_and_enable();
367
737d0bb7 368 get16t_unaligned_check(val, addr);
274e91b8 369 uaccess_restore(__ua_flags);
1da177e4 370
737d0bb7
GD		 371 /* signed half-word? */
372 if (instr & 0x40)
373 val = (signed long)((signed short) val);
1da177e4 374
737d0bb7 375 regs->uregs[rd] = val;
274e91b8
RK		 376 } else {
377 unsigned int __ua_flags = uaccess_save_and_enable();
737d0bb7 378 put16t_unaligned_check(regs->uregs[rd], addr);
274e91b8
RK		 379 uaccess_restore(__ua_flags);
380 }
1da177e4 381
737d0bb7 382 return TYPE_LDST;
1da177e4 383
f21ee2d4
SL		 384 fault:
385 return TYPE_FAULT;
386}
387
388static int
389do_alignment_ldrdstrd(unsigned long addr, unsigned long instr,
390 struct pt_regs *regs)
391{
392 unsigned int rd = RD_BITS(instr);
c2860d43
GD		 393 unsigned int rd2;
394 int load;
395
396 if ((instr & 0xfe000000) == 0xe8000000) {
397 /* ARMv7 Thumb-2 32-bit LDRD/STRD */
398 rd2 = (instr >> 8) & 0xf;
399 load = !!(LDST_L_BIT(instr));
400 } else if (((rd & 1) == 1) || (rd == 14))
19da83f6 401 goto bad;
c2860d43
GD		 402 else {
403 load = ((instr & 0xf0) == 0xd0);
404 rd2 = rd + 1;
405 }
19da83f6 406
f21ee2d4
SL		 407 ai_dword += 1;
408
409 if (user_mode(regs))
410 goto user;
411
c2860d43 412 if (load) {
f21ee2d4
SL		 413 unsigned long val;
414 get32_unaligned_check(val, addr);
415 regs->uregs[rd] = val;
737d0bb7 416 get32_unaligned_check(val, addr + 4);
c2860d43 417 regs->uregs[rd2] = val;
f21ee2d4
SL		 418 } else {
419 put32_unaligned_check(regs->uregs[rd], addr);
c2860d43 420 put32_unaligned_check(regs->uregs[rd2], addr + 4);
f21ee2d4
SL		 421 }
422
423 return TYPE_LDST;
424
425 user:
c2860d43 426 if (load) {
274e91b8
RK		 427 unsigned long val, val2;
428 unsigned int __ua_flags = uaccess_save_and_enable();
429
f21ee2d4 430 get32t_unaligned_check(val, addr);
274e91b8
RK		 431 get32t_unaligned_check(val2, addr + 4);
432
433 uaccess_restore(__ua_flags);
434
f21ee2d4 435 regs->uregs[rd] = val;
274e91b8 436 regs->uregs[rd2] = val2;
f21ee2d4 437 } else {
274e91b8 438 unsigned int __ua_flags = uaccess_save_and_enable();
f21ee2d4 439 put32t_unaligned_check(regs->uregs[rd], addr);
c2860d43 440 put32t_unaligned_check(regs->uregs[rd2], addr + 4);
274e91b8 441 uaccess_restore(__ua_flags);
f21ee2d4
SL		 442 }
443
444 return TYPE_LDST;
19da83f6
GD		 445 bad:
446 return TYPE_ERROR;
1da177e4
LT		 447 fault:
448 return TYPE_FAULT;
449}
450
451static int
452do_alignment_ldrstr(unsigned long addr, unsigned long instr, struct pt_regs *regs)
453{
454 unsigned int rd = RD_BITS(instr);
455
456 ai_word += 1;
457
458 if ((!LDST_P_BIT(instr) && LDST_W_BIT(instr)) || user_mode(regs))
459 goto trans;
460
461 if (LDST_L_BIT(instr)) {
462 unsigned int val;
463 get32_unaligned_check(val, addr);
464 regs->uregs[rd] = val;
465 } else
466 put32_unaligned_check(regs->uregs[rd], addr);
467 return TYPE_LDST;
468
469 trans:
470 if (LDST_L_BIT(instr)) {
471 unsigned int val;
274e91b8 472 unsigned int __ua_flags = uaccess_save_and_enable();
1da177e4 473 get32t_unaligned_check(val, addr);
274e91b8 474 uaccess_restore(__ua_flags);
1da177e4 475 regs->uregs[rd] = val;
274e91b8
RK		 476 } else {
477 unsigned int __ua_flags = uaccess_save_and_enable();
1da177e4 478 put32t_unaligned_check(regs->uregs[rd], addr);
274e91b8
RK		 479 uaccess_restore(__ua_flags);
480 }
1da177e4
LT		 481 return TYPE_LDST;
482
483 fault:
484 return TYPE_FAULT;
485}
486
487/*
488 * LDM/STM alignment handler.
489 *
490 * There are 4 variants of this instruction:
491 *
492 * B = rn pointer before instruction, A = rn pointer after instruction
493 * ------ increasing address ----->
494 * | | r0 | r1 | ... | rx | |
495 * PU = 01 B A
496 * PU = 11 B A
497 * PU = 00 A B
498 * PU = 10 A B
499 */
500static int
501do_alignment_ldmstm(unsigned long addr, unsigned long instr, struct pt_regs *regs)
502{
503 unsigned int rd, rn, correction, nr_regs, regbits;
504 unsigned long eaddr, newaddr;
505
506 if (LDM_S_BIT(instr))
507 goto bad;
508
509 correction = 4; /* processor implementation defined */
510 regs->ARM_pc += correction;
511
512 ai_multi += 1;
513
514 /* count the number of registers in the mask to be transferred */
515 nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
516
517 rn = RN_BITS(instr);
518 newaddr = eaddr = regs->uregs[rn];
519
520 if (!LDST_U_BIT(instr))
521 nr_regs = -nr_regs;
522 newaddr += nr_regs;
523 if (!LDST_U_BIT(instr))
524 eaddr = newaddr;
525
526 if (LDST_P_EQ_U(instr)) /* U = P */
527 eaddr += 4;
528
737d0bb7 529 /*
1da177e4
LT		 530 * For alignment faults on the ARM922T/ARM920T the MMU makes
531 * the FSR (and hence addr) equal to the updated base address
532 * of the multiple access rather than the restored value.
533 * Switch this message off if we've got a ARM92[02], otherwise
534 * [ls]dm alignment faults are noisy!
535 */
536#if !(defined CONFIG_CPU_ARM922T) && !(defined CONFIG_CPU_ARM920T)
537 /*
538 * This is a "hint" - we already have eaddr worked out by the
539 * processor for us.
540 */
541 if (addr != eaddr) {
4ed89f22 542 pr_err("LDMSTM: PC = %08lx, instr = %08lx, "
1da177e4
LT		 543 "addr = %08lx, eaddr = %08lx\n",
544 instruction_pointer(regs), instr, addr, eaddr);
545 show_regs(regs);
546 }
547#endif
548
549 if (user_mode(regs)) {
274e91b8 550 unsigned int __ua_flags = uaccess_save_and_enable();
1da177e4
LT		 551 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
552 regbits >>= 1, rd += 1)
553 if (regbits & 1) {
554 if (LDST_L_BIT(instr)) {
555 unsigned int val;
556 get32t_unaligned_check(val, eaddr);
557 regs->uregs[rd] = val;
558 } else
559 put32t_unaligned_check(regs->uregs[rd], eaddr);
560 eaddr += 4;
561 }
274e91b8 562 uaccess_restore(__ua_flags);
1da177e4
LT		 563 } else {
564 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
565 regbits >>= 1, rd += 1)
566 if (regbits & 1) {
567 if (LDST_L_BIT(instr)) {
568 unsigned int val;
569 get32_unaligned_check(val, eaddr);
570 regs->uregs[rd] = val;
571 } else
572 put32_unaligned_check(regs->uregs[rd], eaddr);
573 eaddr += 4;
574 }
575 }
576
577 if (LDST_W_BIT(instr))
578 regs->uregs[rn] = newaddr;
579 if (!LDST_L_BIT(instr) || !(REGMASK_BITS(instr) & (1 << 15)))
580 regs->ARM_pc -= correction;
581 return TYPE_DONE;
582
583fault:
584 regs->ARM_pc -= correction;
585 return TYPE_FAULT;
586
587bad:
4ed89f22 588 pr_err("Alignment trap: not handling ldm with s-bit set\n");
1da177e4
LT		 589 return TYPE_ERROR;
590}
591
592/*
593 * Convert Thumb ld/st instruction forms to equivalent ARM instructions so
594 * we can reuse ARM userland alignment fault fixups for Thumb.
595 *
596 * This implementation was initially based on the algorithm found in
597 * gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
598 * to convert only Thumb ld/st instruction forms to equivalent ARM forms.
599 *
600 * NOTES:
601 * 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
602 * 2. If for some reason we're passed an non-ld/st Thumb instruction to
603 * decode, we return 0xdeadc0de. This should never happen under normal
604 * circumstances but if it does, we've got other problems to deal with
605 * elsewhere and we obviously can't fix those problems here.
606 */
607
608static unsigned long
609thumb2arm(u16 tinstr)
610{
611 u32 L = (tinstr & (1<<11)) >> 11;
612
613 switch ((tinstr & 0xf800) >> 11) {
614 /* 6.5.1 Format 1: */
615 case 0x6000 >> 11: /* 7.1.52 STR(1) */
616 case 0x6800 >> 11: /* 7.1.26 LDR(1) */
617 case 0x7000 >> 11: /* 7.1.55 STRB(1) */
618 case 0x7800 >> 11: /* 7.1.30 LDRB(1) */
619 return 0xe5800000 |
620 ((tinstr & (1<<12)) << (22-12)) | /* fixup */
621 (L<<20) | /* L==1? */
622 ((tinstr & (7<<0)) << (12-0)) | /* Rd */
623 ((tinstr & (7<<3)) << (16-3)) | /* Rn */
624 ((tinstr & (31<<6)) >> /* immed_5 */
625 (6 - ((tinstr & (1<<12)) ? 0 : 2)));
626 case 0x8000 >> 11: /* 7.1.57 STRH(1) */
627 case 0x8800 >> 11: /* 7.1.32 LDRH(1) */
628 return 0xe1c000b0 |
629 (L<<20) | /* L==1? */
630 ((tinstr & (7<<0)) << (12-0)) | /* Rd */
631 ((tinstr & (7<<3)) << (16-3)) | /* Rn */
632 ((tinstr & (7<<6)) >> (6-1)) | /* immed_5[2:0] */
633 ((tinstr & (3<<9)) >> (9-8)); /* immed_5[4:3] */
634
635 /* 6.5.1 Format 2: */
636 case 0x5000 >> 11:
637 case 0x5800 >> 11:
638 {
639 static const u32 subset[8] = {
640 0xe7800000, /* 7.1.53 STR(2) */
641 0xe18000b0, /* 7.1.58 STRH(2) */
642 0xe7c00000, /* 7.1.56 STRB(2) */
643 0xe19000d0, /* 7.1.34 LDRSB */
644 0xe7900000, /* 7.1.27 LDR(2) */
645 0xe19000b0, /* 7.1.33 LDRH(2) */
646 0xe7d00000, /* 7.1.31 LDRB(2) */
647 0xe19000f0 /* 7.1.35 LDRSH */
648 };
649 return subset[(tinstr & (7<<9)) >> 9] |
650 ((tinstr & (7<<0)) << (12-0)) | /* Rd */
651 ((tinstr & (7<<3)) << (16-3)) | /* Rn */
652 ((tinstr & (7<<6)) >> (6-0)); /* Rm */
653 }
654
655 /* 6.5.1 Format 3: */
656 case 0x4800 >> 11: /* 7.1.28 LDR(3) */
657 /* NOTE: This case is not technically possible. We're
737d0bb7 658 * loading 32-bit memory data via PC relative
1da177e4
LT		 659 * addressing mode. So we can and should eliminate
660 * this case. But I'll leave it here for now.
661 */
662 return 0xe59f0000 |
663 ((tinstr & (7<<8)) << (12-8)) | /* Rd */
664 ((tinstr & 255) << (2-0)); /* immed_8 */
665
666 /* 6.5.1 Format 4: */
667 case 0x9000 >> 11: /* 7.1.54 STR(3) */
668 case 0x9800 >> 11: /* 7.1.29 LDR(4) */
669 return 0xe58d0000 |
670 (L<<20) | /* L==1? */
671 ((tinstr & (7<<8)) << (12-8)) | /* Rd */
672 ((tinstr & 255) << 2); /* immed_8 */
673
674 /* 6.6.1 Format 1: */
675 case 0xc000 >> 11: /* 7.1.51 STMIA */
676 case 0xc800 >> 11: /* 7.1.25 LDMIA */
677 {
678 u32 Rn = (tinstr & (7<<8)) >> 8;
679 u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
680
681 return 0xe8800000 | W | (L<<20) | (Rn<<16) |
682 (tinstr&255);
683 }
684
685 /* 6.6.1 Format 2: */
686 case 0xb000 >> 11: /* 7.1.48 PUSH */
687 case 0xb800 >> 11: /* 7.1.47 POP */
688 if ((tinstr & (3 << 9)) == 0x0400) {
689 static const u32 subset[4] = {
690 0xe92d0000, /* STMDB sp!,{registers} */
691 0xe92d4000, /* STMDB sp!,{registers,lr} */
692 0xe8bd0000, /* LDMIA sp!,{registers} */
693 0xe8bd8000 /* LDMIA sp!,{registers,pc} */
694 };
695 return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
696 (tinstr & 255); /* register_list */
697 }
e7c0c9f6 698 /* Else, fall through - for illegal instruction case */
1da177e4
LT		 699
700 default:
c2860d43
GD		 701 return BAD_INSTR;
702 }
703}
704
705/*
706 * Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
707 * handlable by ARM alignment handler, also find the corresponding handler,
708 * so that we can reuse ARM userland alignment fault fixups for Thumb.
709 *
710 * @pinstr: original Thumb-2 instruction; returns new handlable instruction
711 * @regs: register context.
712 * @poffset: return offset from faulted addr for later writeback
713 *
714 * NOTES:
715 * 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
716 * 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
717 */
718static void *
719do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
720 union offset_union *poffset)
721{
722 unsigned long instr = *pinstr;
723 u16 tinst1 = (instr >> 16) & 0xffff;
724 u16 tinst2 = instr & 0xffff;
c2860d43
GD		 725
726 switch (tinst1 & 0xffe0) {
727 /* A6.3.5 Load/Store multiple */
728 case 0xe880: /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
729 case 0xe8a0: /* ...above writeback version */
730 case 0xe900: /* STMDB/STMFD, LDMDB/LDMEA */
731 case 0xe920: /* ...above writeback version */
732 /* no need offset decision since handler calculates it */
733 return do_alignment_ldmstm;
734
735 case 0xf840: /* POP/PUSH T3 (single register) */
736 if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
737 u32 L = !!(LDST_L_BIT(instr));
738 const u32 subset[2] = {
739 0xe92d0000, /* STMDB sp!,{registers} */
740 0xe8bd0000, /* LDMIA sp!,{registers} */
741 };
742 *pinstr = subset[L] | (1<<RD_BITS(instr));
743 return do_alignment_ldmstm;
744 }
745 /* Else fall through for illegal instruction case */
746 break;
747
748 /* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
749 case 0xe860:
750 case 0xe960:
751 case 0xe8e0:
752 case 0xe9e0:
753 poffset->un = (tinst2 & 0xff) << 2;
e7c0c9f6
GS		 754 /* Fall through */
755
c2860d43
GD		 756 case 0xe940:
757 case 0xe9c0:
758 return do_alignment_ldrdstrd;
759
760 /*
761 * No need to handle load/store instructions up to word size
762 * since ARMv6 and later CPUs can perform unaligned accesses.
763 */
764 default:
765 break;
1da177e4 766 }
c2860d43 767 return NULL;
1da177e4
LT		 768}
769
770static int
771do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
772{
6404f0b7 773 union offset_union uninitialized_var(offset);
1da177e4
LT		 774 unsigned long instr = 0, instrptr;
775 int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs);
776 unsigned int type;
1da177e4
LT		 777 unsigned int fault;
778 u16 tinstr = 0;
c2860d43
GD		 779 int isize = 4;
780 int thumb2_32b = 0;
1da177e4 781
02fe2845
RK		 782 if (interrupts_enabled(regs))
783 local_irq_enable();
784
1da177e4
LT		 785 instrptr = instruction_pointer(regs);
786
f8343685 787 if (thumb_mode(regs)) {
b255188f
RK		 788 u16 *ptr = (u16 *)(instrptr & ~1);
789 fault = probe_kernel_address(ptr, tinstr);
8592edf0 790 tinstr = __mem_to_opcode_thumb16(tinstr);
c2860d43
GD		 791 if (!fault) {
792 if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
793 IS_T32(tinstr)) {
794 /* Thumb-2 32-bit */
795 u16 tinst2 = 0;
b255188f 796 fault = probe_kernel_address(ptr + 1, tinst2);
8592edf0
BD		 797 tinst2 = __mem_to_opcode_thumb16(tinst2);
798 instr = __opcode_thumb32_compose(tinstr, tinst2);
c2860d43
GD		 799 thumb2_32b = 1;
800 } else {
801 isize = 2;
802 instr = thumb2arm(tinstr);
803 }
804 }
8592edf0 805 } else {
0ab32b6f 806 fault = probe_kernel_address((void *)instrptr, instr);
8592edf0
BD		 807 instr = __mem_to_opcode_arm(instr);
808 }
1da177e4
LT		 809
810 if (fault) {
811 type = TYPE_FAULT;
737d0bb7 812 goto bad_or_fault;
1da177e4
LT		 813 }
814
815 if (user_mode(regs))
816 goto user;
817
818 ai_sys += 1;
1e7e3211 819 ai_sys_last_pc = (void *)instruction_pointer(regs);
1da177e4
LT		 820
821 fixup:
822
c2860d43 823 regs->ARM_pc += isize;
1da177e4
LT		 824
825 switch (CODING_BITS(instr)) {
f21ee2d4
SL		 826 case 0x00000000: /* 3.13.4 load/store instruction extensions */
827 if (LDSTHD_I_BIT(instr))
1da177e4
LT		 828 offset.un = (instr & 0xf00) >> 4 | (instr & 15);
829 else
830 offset.un = regs->uregs[RM_BITS(instr)];
f21ee2d4
SL		 831
832 if ((instr & 0x000000f0) == 0x000000b0 || /* LDRH, STRH */
833 (instr & 0x001000f0) == 0x001000f0) /* LDRSH */
834 handler = do_alignment_ldrhstrh;
835 else if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
836 (instr & 0x001000f0) == 0x000000f0) /* STRD */
837 handler = do_alignment_ldrdstrd;
19da83f6
GD		 838 else if ((instr & 0x01f00ff0) == 0x01000090) /* SWP */
839 goto swp;
f21ee2d4
SL		 840 else
841 goto bad;
1da177e4
LT		 842 break;
843
844 case 0x04000000: /* ldr or str immediate */
5ca918e5
RM		 845 if (COND_BITS(instr) == 0xf0000000) /* NEON VLDn, VSTn */
846 goto bad;
1da177e4
LT		 847 offset.un = OFFSET_BITS(instr);
848 handler = do_alignment_ldrstr;
849 break;
850
851 case 0x06000000: /* ldr or str register */
852 offset.un = regs->uregs[RM_BITS(instr)];
853
854 if (IS_SHIFT(instr)) {
855 unsigned int shiftval = SHIFT_BITS(instr);
856
857 switch(SHIFT_TYPE(instr)) {
858 case SHIFT_LSL:
859 offset.un <<= shiftval;
860 break;
861
862 case SHIFT_LSR:
863 offset.un >>= shiftval;
864 break;
865
866 case SHIFT_ASR:
867 offset.sn >>= shiftval;
868 break;
869
870 case SHIFT_RORRRX:
871 if (shiftval == 0) {
872 offset.un >>= 1;
873 if (regs->ARM_cpsr & PSR_C_BIT)
874 offset.un |= 1 << 31;
875 } else
876 offset.un = offset.un >> shiftval |
877 offset.un << (32 - shiftval);
878 break;
879 }
880 }
881 handler = do_alignment_ldrstr;
882 break;
883
c2860d43 884 case 0x08000000: /* ldm or stm, or thumb-2 32bit instruction */
a761cebf
RK		 885 if (thumb2_32b) {
886 offset.un = 0;
c2860d43 887 handler = do_alignment_t32_to_handler(&instr, regs, &offset);
31d2a638
AB		 888 } else {
889 offset.un = 0;
c2860d43 890 handler = do_alignment_ldmstm;
31d2a638 891 }
1da177e4
LT		 892 break;
893
894 default:
895 goto bad;
896 }
897
c2860d43
GD		 898 if (!handler)
899 goto bad;
1da177e4
LT		 900 type = handler(addr, instr, regs);
901
c2860d43
GD		 902 if (type == TYPE_ERROR || type == TYPE_FAULT) {
903 regs->ARM_pc -= isize;
1da177e4 904 goto bad_or_fault;
c2860d43 905 }
1da177e4
LT		 906
907 if (type == TYPE_LDST)
908 do_alignment_finish_ldst(addr, instr, regs, offset);
909
910 return 0;
911
912 bad_or_fault:
913 if (type == TYPE_ERROR)
914 goto bad;
1da177e4
LT		 915 /*
916 * We got a fault - fix it up, or die.
917 */
e5beac37 918 do_bad_area(addr, fsr, regs);
1da177e4
LT		 919 return 0;
920
19da83f6 921 swp:
4ed89f22 922 pr_err("Alignment trap: not handling swp instruction\n");
19da83f6 923
1da177e4
LT		 924 bad:
925 /*
926 * Oops, we didn't handle the instruction.
927 */
4ed89f22 928 pr_err("Alignment trap: not handling instruction "
1da177e4 929 "%0*lx at [<%08lx>]\n",
c2860d43
GD		 930 isize << 1,
931 isize == 2 ? tinstr : instr, instrptr);
1da177e4
LT		 932 ai_skipped += 1;
933 return 1;
934
935 user:
936 ai_user += 1;
937
baa745a3 938 if (ai_usermode & UM_WARN)
1da177e4
LT		 939 printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*lx "
940 "Address=0x%08lx FSR 0x%03x\n", current->comm,
19c5870c 941 task_pid_nr(current), instrptr,
c2860d43
GD		 942 isize << 1,
943 isize == 2 ? tinstr : instr,
1da177e4
LT		 944 addr, fsr);
945
baa745a3 946 if (ai_usermode & UM_FIXUP)
1da177e4
LT		 947 goto fixup;
948
2102a65e 949 if (ai_usermode & UM_SIGNAL) {
2e1661d2 950 force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *)addr);
2102a65e 951 } else {
2f27bf83
NP		 952 /*
953 * We're about to disable the alignment trap and return to
954 * user space. But if an interrupt occurs before actually
955 * reaching user space, then the IRQ vector entry code will
956 * notice that we were still in kernel space and therefore
957 * the alignment trap won't be re-enabled in that case as it
958 * is presumed to be always on from kernel space.
959 * Let's prevent that race by disabling interrupts here (they
960 * are disabled on the way back to user space anyway in
961 * entry-common.S) and disable the alignment trap only if
962 * there is no work pending for this thread.
963 */
964 raw_local_irq_disable();
965 if (!(current_thread_info()->flags & _TIF_WORK_MASK))
966 set_cr(cr_no_alignment);
967 }
1da177e4
LT		 968
969 return 0;
970}
971
175352a5
RK		 972static int __init noalign_setup(char *__unused)
973{
974 set_cr(__clear_cr(CR_A));
975 return 1;
976}
977__setup("noalign", noalign_setup);
978
1da177e4
LT		 979/*
980 * This needs to be done after sysctl_init, otherwise sys/ will be
981 * overwritten. Actually, this shouldn't be in sys/ at all since
982 * it isn't a sysctl, and it doesn't contain sysctl information.
983 * We now locate it in /proc/cpu/alignment instead.
984 */
985static int __init alignment_init(void)
986{
987#ifdef CONFIG_PROC_FS
988 struct proc_dir_entry *res;
989
b7072c63
AD		 990 res = proc_create("cpu/alignment", S_IWUSR | S_IRUGO, NULL,
991 &alignment_proc_fops);
1da177e4
LT		 992 if (!res)
993 return -ENOMEM;
1da177e4
LT		 994#endif
995
088c01f1 996 if (cpu_is_v6_unaligned()) {
b4b20ad8 997 set_cr(__clear_cr(CR_A));
088c01f1 998 ai_usermode = safe_usermode(ai_usermode, false);
baa745a3
RK		 999 }
1000
0aeb3408
RK		 1001 cr_no_alignment = get_cr() & ~CR_A;
1002
f7b8156d 1003 hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
6338a6aa 1004 "alignment exception");
b8ab5397
KS		 1005
1006 /*
1007 * ARMv6K and ARMv7 use fault status 3 (0b00011) as Access Flag section
1008 * fault, not as alignment error.
1009 *
1010 * TODO: handle ARMv6K properly. Runtime check for 'K' extension is
1011 * needed.
1012 */
1013 if (cpu_architecture() <= CPU_ARCH_ARMv6) {
1014 hook_fault_code(3, do_alignment, SIGBUS, BUS_ADRALN,
1015 "alignment exception");
1016 }
1da177e4
LT		 1017
1018 return 0;
1019}
1020
1021fs_initcall(alignment_init);
Linux 6.x block layer and io_uring tree(s)