1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2014 ARM Limited
4 */
5
6 #include <linux/cpu.h>
7 #include <linux/init.h>
8 #include <linux/list.h>
9 #include <linux/perf_event.h>
10 #include <linux/sched.h>
11 #include <linux/slab.h>
12 #include <linux/sysctl.h>
13 #include <linux/uaccess.h>
14
15 #include <asm/cpufeature.h>
16 #include <asm/insn.h>
17 #include <asm/sysreg.h>
18 #include <asm/system_misc.h>
19 #include <asm/traps.h>
20 #include <asm/kprobes.h>
21
22 #define CREATE_TRACE_POINTS
23 #include "trace-events-emulation.h"
24
25 /*
26 * The runtime support for deprecated instruction support can be in one of
27 * following three states -
28 *
29 * 0 = undef
30 * 1 = emulate (software emulation)
31 * 2 = hw (supported in hardware)
32 */
33 enum insn_emulation_mode {
34 INSN_UNDEF,
35 INSN_EMULATE,
36 INSN_HW,
37 };
38
39 enum legacy_insn_status {
40 INSN_DEPRECATED,
41 INSN_OBSOLETE,
42 };
43
44 struct insn_emulation_ops {
45 const char *name;
46 enum legacy_insn_status status;
47 struct undef_hook *hooks;
48 int (*set_hw_mode)(bool enable);
49 };
50
51 struct insn_emulation {
52 struct list_head node;
53 struct insn_emulation_ops *ops;
54 int current_mode;
55 int min;
56 int max;
57 };
58
59 static LIST_HEAD(insn_emulation);
60 static int nr_insn_emulated __initdata;
61 static DEFINE_RAW_SPINLOCK(insn_emulation_lock);
62
register_emulation_hooks(struct insn_emulation_ops * ops)63 static void register_emulation_hooks(struct insn_emulation_ops *ops)
64 {
65 struct undef_hook *hook;
66
67 BUG_ON(!ops->hooks);
68
69 for (hook = ops->hooks; hook->instr_mask; hook++)
70 register_undef_hook(hook);
71
72 pr_notice("Registered %s emulation handler\n", ops->name);
73 }
74
remove_emulation_hooks(struct insn_emulation_ops * ops)75 static void remove_emulation_hooks(struct insn_emulation_ops *ops)
76 {
77 struct undef_hook *hook;
78
79 BUG_ON(!ops->hooks);
80
81 for (hook = ops->hooks; hook->instr_mask; hook++)
82 unregister_undef_hook(hook);
83
84 pr_notice("Removed %s emulation handler\n", ops->name);
85 }
86
enable_insn_hw_mode(void * data)87 static void enable_insn_hw_mode(void *data)
88 {
89 struct insn_emulation *insn = (struct insn_emulation *)data;
90 if (insn->ops->set_hw_mode)
91 insn->ops->set_hw_mode(true);
92 }
93
disable_insn_hw_mode(void * data)94 static void disable_insn_hw_mode(void *data)
95 {
96 struct insn_emulation *insn = (struct insn_emulation *)data;
97 if (insn->ops->set_hw_mode)
98 insn->ops->set_hw_mode(false);
99 }
100
101 /* Run set_hw_mode(mode) on all active CPUs */
run_all_cpu_set_hw_mode(struct insn_emulation * insn,bool enable)102 static int run_all_cpu_set_hw_mode(struct insn_emulation *insn, bool enable)
103 {
104 if (!insn->ops->set_hw_mode)
105 return -EINVAL;
106 if (enable)
107 on_each_cpu(enable_insn_hw_mode, (void *)insn, true);
108 else
109 on_each_cpu(disable_insn_hw_mode, (void *)insn, true);
110 return 0;
111 }
112
113 /*
114 * Run set_hw_mode for all insns on a starting CPU.
115 * Returns:
116 * 0 - If all the hooks ran successfully.
117 * -EINVAL - At least one hook is not supported by the CPU.
118 */
run_all_insn_set_hw_mode(unsigned int cpu)119 static int run_all_insn_set_hw_mode(unsigned int cpu)
120 {
121 int rc = 0;
122 unsigned long flags;
123 struct insn_emulation *insn;
124
125 raw_spin_lock_irqsave(&insn_emulation_lock, flags);
126 list_for_each_entry(insn, &insn_emulation, node) {
127 bool enable = (insn->current_mode == INSN_HW);
128 if (insn->ops->set_hw_mode && insn->ops->set_hw_mode(enable)) {
129 pr_warn("CPU[%u] cannot support the emulation of %s",
130 cpu, insn->ops->name);
131 rc = -EINVAL;
132 }
133 }
134 raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
135 return rc;
136 }
137
update_insn_emulation_mode(struct insn_emulation * insn,enum insn_emulation_mode prev)138 static int update_insn_emulation_mode(struct insn_emulation *insn,
139 enum insn_emulation_mode prev)
140 {
141 int ret = 0;
142
143 switch (prev) {
144 case INSN_UNDEF: /* Nothing to be done */
145 break;
146 case INSN_EMULATE:
147 remove_emulation_hooks(insn->ops);
148 break;
149 case INSN_HW:
150 if (!run_all_cpu_set_hw_mode(insn, false))
151 pr_notice("Disabled %s support\n", insn->ops->name);
152 break;
153 }
154
155 switch (insn->current_mode) {
156 case INSN_UNDEF:
157 break;
158 case INSN_EMULATE:
159 register_emulation_hooks(insn->ops);
160 break;
161 case INSN_HW:
162 ret = run_all_cpu_set_hw_mode(insn, true);
163 if (!ret)
164 pr_notice("Enabled %s support\n", insn->ops->name);
165 break;
166 }
167
168 return ret;
169 }
170
register_insn_emulation(struct insn_emulation_ops * ops)171 static void __init register_insn_emulation(struct insn_emulation_ops *ops)
172 {
173 unsigned long flags;
174 struct insn_emulation *insn;
175
176 insn = kzalloc(sizeof(*insn), GFP_KERNEL);
177 if (!insn)
178 return;
179
180 insn->ops = ops;
181 insn->min = INSN_UNDEF;
182
183 switch (ops->status) {
184 case INSN_DEPRECATED:
185 insn->current_mode = INSN_EMULATE;
186 /* Disable the HW mode if it was turned on at early boot time */
187 run_all_cpu_set_hw_mode(insn, false);
188 insn->max = INSN_HW;
189 break;
190 case INSN_OBSOLETE:
191 insn->current_mode = INSN_UNDEF;
192 insn->max = INSN_EMULATE;
193 break;
194 }
195
196 raw_spin_lock_irqsave(&insn_emulation_lock, flags);
197 list_add(&insn->node, &insn_emulation);
198 nr_insn_emulated++;
199 raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
200
201 /* Register any handlers if required */
202 update_insn_emulation_mode(insn, INSN_UNDEF);
203 }
204
emulation_proc_handler(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)205 static int emulation_proc_handler(struct ctl_table *table, int write,
206 void *buffer, size_t *lenp,
207 loff_t *ppos)
208 {
209 int ret = 0;
210 struct insn_emulation *insn = (struct insn_emulation *) table->data;
211 enum insn_emulation_mode prev_mode = insn->current_mode;
212
213 table->data = &insn->current_mode;
214 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
215
216 if (ret || !write || prev_mode == insn->current_mode)
217 goto ret;
218
219 ret = update_insn_emulation_mode(insn, prev_mode);
220 if (ret) {
221 /* Mode change failed, revert to previous mode. */
222 insn->current_mode = prev_mode;
223 update_insn_emulation_mode(insn, INSN_UNDEF);
224 }
225 ret:
226 table->data = insn;
227 return ret;
228 }
229
register_insn_emulation_sysctl(void)230 static void __init register_insn_emulation_sysctl(void)
231 {
232 unsigned long flags;
233 int i = 0;
234 struct insn_emulation *insn;
235 struct ctl_table *insns_sysctl, *sysctl;
236
237 insns_sysctl = kcalloc(nr_insn_emulated + 1, sizeof(*sysctl),
238 GFP_KERNEL);
239 if (!insns_sysctl)
240 return;
241
242 raw_spin_lock_irqsave(&insn_emulation_lock, flags);
243 list_for_each_entry(insn, &insn_emulation, node) {
244 sysctl = &insns_sysctl[i];
245
246 sysctl->mode = 0644;
247 sysctl->maxlen = sizeof(int);
248
249 sysctl->procname = insn->ops->name;
250 sysctl->data = insn;
251 sysctl->extra1 = &insn->min;
252 sysctl->extra2 = &insn->max;
253 sysctl->proc_handler = emulation_proc_handler;
254 i++;
255 }
256 raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
257
258 register_sysctl("abi", insns_sysctl);
259 }
260
261 /*
262 * Implement emulation of the SWP/SWPB instructions using load-exclusive and
263 * store-exclusive.
264 *
265 * Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
266 * Where: Rt = destination
267 * Rt2 = source
268 * Rn = address
269 */
270
271 /*
272 * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
273 */
274
275 /* Arbitrary constant to ensure forward-progress of the LL/SC loop */
276 #define __SWP_LL_SC_LOOPS 4
277
278 #define __user_swpX_asm(data, addr, res, temp, temp2, B) \
279 do { \
280 uaccess_enable(); \
281 __asm__ __volatile__( \
282 " mov %w3, %w7\n" \
283 "0: ldxr"B" %w2, [%4]\n" \
284 "1: stxr"B" %w0, %w1, [%4]\n" \
285 " cbz %w0, 2f\n" \
286 " sub %w3, %w3, #1\n" \
287 " cbnz %w3, 0b\n" \
288 " mov %w0, %w5\n" \
289 " b 3f\n" \
290 "2:\n" \
291 " mov %w1, %w2\n" \
292 "3:\n" \
293 " .pushsection .fixup,\"ax\"\n" \
294 " .align 2\n" \
295 "4: mov %w0, %w6\n" \
296 " b 3b\n" \
297 " .popsection" \
298 _ASM_EXTABLE(0b, 4b) \
299 _ASM_EXTABLE(1b, 4b) \
300 : "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2) \
301 : "r" ((unsigned long)addr), "i" (-EAGAIN), \
302 "i" (-EFAULT), \
303 "i" (__SWP_LL_SC_LOOPS) \
304 : "memory"); \
305 uaccess_disable(); \
306 } while (0)
307
308 #define __user_swp_asm(data, addr, res, temp, temp2) \
309 __user_swpX_asm(data, addr, res, temp, temp2, "")
310 #define __user_swpb_asm(data, addr, res, temp, temp2) \
311 __user_swpX_asm(data, addr, res, temp, temp2, "b")
312
313 /*
314 * Bit 22 of the instruction encoding distinguishes between
315 * the SWP and SWPB variants (bit set means SWPB).
316 */
317 #define TYPE_SWPB (1 << 22)
318
emulate_swpX(unsigned int address,unsigned int * data,unsigned int type)319 static int emulate_swpX(unsigned int address, unsigned int *data,
320 unsigned int type)
321 {
322 unsigned int res = 0;
323
324 if ((type != TYPE_SWPB) && (address & 0x3)) {
325 /* SWP to unaligned address not permitted */
326 pr_debug("SWP instruction on unaligned pointer!\n");
327 return -EFAULT;
328 }
329
330 while (1) {
331 unsigned long temp, temp2;
332
333 if (type == TYPE_SWPB)
334 __user_swpb_asm(*data, address, res, temp, temp2);
335 else
336 __user_swp_asm(*data, address, res, temp, temp2);
337
338 if (likely(res != -EAGAIN) || signal_pending(current))
339 break;
340
341 cond_resched();
342 }
343
344 return res;
345 }
346
347 #define ARM_OPCODE_CONDTEST_FAIL 0
348 #define ARM_OPCODE_CONDTEST_PASS 1
349 #define ARM_OPCODE_CONDTEST_UNCOND 2
350
351 #define ARM_OPCODE_CONDITION_UNCOND 0xf
352
aarch32_check_condition(u32 opcode,u32 psr)353 static unsigned int __kprobes aarch32_check_condition(u32 opcode, u32 psr)
354 {
355 u32 cc_bits = opcode >> 28;
356
357 if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
358 if ((*aarch32_opcode_cond_checks[cc_bits])(psr))
359 return ARM_OPCODE_CONDTEST_PASS;
360 else
361 return ARM_OPCODE_CONDTEST_FAIL;
362 }
363 return ARM_OPCODE_CONDTEST_UNCOND;
364 }
365
366 /*
367 * swp_handler logs the id of calling process, dissects the instruction, sanity
368 * checks the memory location, calls emulate_swpX for the actual operation and
369 * deals with fixup/error handling before returning
370 */
swp_handler(struct pt_regs * regs,u32 instr)371 static int swp_handler(struct pt_regs *regs, u32 instr)
372 {
373 u32 destreg, data, type, address = 0;
374 const void __user *user_ptr;
375 int rn, rt2, res = 0;
376
377 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
378
379 type = instr & TYPE_SWPB;
380
381 switch (aarch32_check_condition(instr, regs->pstate)) {
382 case ARM_OPCODE_CONDTEST_PASS:
383 break;
384 case ARM_OPCODE_CONDTEST_FAIL:
385 /* Condition failed - return to next instruction */
386 goto ret;
387 case ARM_OPCODE_CONDTEST_UNCOND:
388 /* If unconditional encoding - not a SWP, undef */
389 return -EFAULT;
390 default:
391 return -EINVAL;
392 }
393
394 rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET);
395 rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET);
396
397 address = (u32)regs->user_regs.regs[rn];
398 data = (u32)regs->user_regs.regs[rt2];
399 destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET);
400
401 pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
402 rn, address, destreg,
403 aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data);
404
405 /* Check access in reasonable access range for both SWP and SWPB */
406 user_ptr = (const void __user *)(unsigned long)(address & ~3);
407 if (!access_ok(user_ptr, 4)) {
408 pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n",
409 address);
410 goto fault;
411 }
412
413 res = emulate_swpX(address, &data, type);
414 if (res == -EFAULT)
415 goto fault;
416 else if (res == 0)
417 regs->user_regs.regs[destreg] = data;
418
419 ret:
420 if (type == TYPE_SWPB)
421 trace_instruction_emulation("swpb", regs->pc);
422 else
423 trace_instruction_emulation("swp", regs->pc);
424
425 pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
426 current->comm, (unsigned long)current->pid, regs->pc);
427
428 arm64_skip_faulting_instruction(regs, 4);
429 return 0;
430
431 fault:
432 pr_debug("SWP{B} emulation: access caused memory abort!\n");
433 arm64_notify_segfault(address);
434
435 return 0;
436 }
437
438 /*
439 * Only emulate SWP/SWPB executed in ARM state/User mode.
440 * The kernel must be SWP free and SWP{B} does not exist in Thumb.
441 */
442 static struct undef_hook swp_hooks[] = {
443 {
444 .instr_mask = 0x0fb00ff0,
445 .instr_val = 0x01000090,
446 .pstate_mask = PSR_AA32_MODE_MASK,
447 .pstate_val = PSR_AA32_MODE_USR,
448 .fn = swp_handler
449 },
450 { }
451 };
452
453 static struct insn_emulation_ops swp_ops = {
454 .name = "swp",
455 .status = INSN_OBSOLETE,
456 .hooks = swp_hooks,
457 .set_hw_mode = NULL,
458 };
459
cp15barrier_handler(struct pt_regs * regs,u32 instr)460 static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
461 {
462 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
463
464 switch (aarch32_check_condition(instr, regs->pstate)) {
465 case ARM_OPCODE_CONDTEST_PASS:
466 break;
467 case ARM_OPCODE_CONDTEST_FAIL:
468 /* Condition failed - return to next instruction */
469 goto ret;
470 case ARM_OPCODE_CONDTEST_UNCOND:
471 /* If unconditional encoding - not a barrier instruction */
472 return -EFAULT;
473 default:
474 return -EINVAL;
475 }
476
477 switch (aarch32_insn_mcr_extract_crm(instr)) {
478 case 10:
479 /*
480 * dmb - mcr p15, 0, Rt, c7, c10, 5
481 * dsb - mcr p15, 0, Rt, c7, c10, 4
482 */
483 if (aarch32_insn_mcr_extract_opc2(instr) == 5) {
484 dmb(sy);
485 trace_instruction_emulation(
486 "mcr p15, 0, Rt, c7, c10, 5 ; dmb", regs->pc);
487 } else {
488 dsb(sy);
489 trace_instruction_emulation(
490 "mcr p15, 0, Rt, c7, c10, 4 ; dsb", regs->pc);
491 }
492 break;
493 case 5:
494 /*
495 * isb - mcr p15, 0, Rt, c7, c5, 4
496 *
497 * Taking an exception or returning from one acts as an
498 * instruction barrier. So no explicit barrier needed here.
499 */
500 trace_instruction_emulation(
501 "mcr p15, 0, Rt, c7, c5, 4 ; isb", regs->pc);
502 break;
503 }
504
505 ret:
506 pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n",
507 current->comm, (unsigned long)current->pid, regs->pc);
508
509 arm64_skip_faulting_instruction(regs, 4);
510 return 0;
511 }
512
cp15_barrier_set_hw_mode(bool enable)513 static int cp15_barrier_set_hw_mode(bool enable)
514 {
515 if (enable)
516 sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_CP15BEN);
517 else
518 sysreg_clear_set(sctlr_el1, SCTLR_EL1_CP15BEN, 0);
519 return 0;
520 }
521
522 static struct undef_hook cp15_barrier_hooks[] = {
523 {
524 .instr_mask = 0x0fff0fdf,
525 .instr_val = 0x0e070f9a,
526 .pstate_mask = PSR_AA32_MODE_MASK,
527 .pstate_val = PSR_AA32_MODE_USR,
528 .fn = cp15barrier_handler,
529 },
530 {
531 .instr_mask = 0x0fff0fff,
532 .instr_val = 0x0e070f95,
533 .pstate_mask = PSR_AA32_MODE_MASK,
534 .pstate_val = PSR_AA32_MODE_USR,
535 .fn = cp15barrier_handler,
536 },
537 { }
538 };
539
540 static struct insn_emulation_ops cp15_barrier_ops = {
541 .name = "cp15_barrier",
542 .status = INSN_DEPRECATED,
543 .hooks = cp15_barrier_hooks,
544 .set_hw_mode = cp15_barrier_set_hw_mode,
545 };
546
setend_set_hw_mode(bool enable)547 static int setend_set_hw_mode(bool enable)
548 {
549 if (!cpu_supports_mixed_endian_el0())
550 return -EINVAL;
551
552 if (enable)
553 sysreg_clear_set(sctlr_el1, SCTLR_EL1_SED, 0);
554 else
555 sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_SED);
556 return 0;
557 }
558
compat_setend_handler(struct pt_regs * regs,u32 big_endian)559 static int compat_setend_handler(struct pt_regs *regs, u32 big_endian)
560 {
561 char *insn;
562
563 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
564
565 if (big_endian) {
566 insn = "setend be";
567 regs->pstate |= PSR_AA32_E_BIT;
568 } else {
569 insn = "setend le";
570 regs->pstate &= ~PSR_AA32_E_BIT;
571 }
572
573 trace_instruction_emulation(insn, regs->pc);
574 pr_warn_ratelimited("\"%s\" (%ld) uses deprecated setend instruction at 0x%llx\n",
575 current->comm, (unsigned long)current->pid, regs->pc);
576
577 return 0;
578 }
579
a32_setend_handler(struct pt_regs * regs,u32 instr)580 static int a32_setend_handler(struct pt_regs *regs, u32 instr)
581 {
582 int rc = compat_setend_handler(regs, (instr >> 9) & 1);
583 arm64_skip_faulting_instruction(regs, 4);
584 return rc;
585 }
586
t16_setend_handler(struct pt_regs * regs,u32 instr)587 static int t16_setend_handler(struct pt_regs *regs, u32 instr)
588 {
589 int rc = compat_setend_handler(regs, (instr >> 3) & 1);
590 arm64_skip_faulting_instruction(regs, 2);
591 return rc;
592 }
593
594 static struct undef_hook setend_hooks[] = {
595 {
596 .instr_mask = 0xfffffdff,
597 .instr_val = 0xf1010000,
598 .pstate_mask = PSR_AA32_MODE_MASK,
599 .pstate_val = PSR_AA32_MODE_USR,
600 .fn = a32_setend_handler,
601 },
602 {
603 /* Thumb mode */
604 .instr_mask = 0xfffffff7,
605 .instr_val = 0x0000b650,
606 .pstate_mask = (PSR_AA32_T_BIT | PSR_AA32_MODE_MASK),
607 .pstate_val = (PSR_AA32_T_BIT | PSR_AA32_MODE_USR),
608 .fn = t16_setend_handler,
609 },
610 {}
611 };
612
613 static struct insn_emulation_ops setend_ops = {
614 .name = "setend",
615 .status = INSN_DEPRECATED,
616 .hooks = setend_hooks,
617 .set_hw_mode = setend_set_hw_mode,
618 };
619
620 /*
621 * Invoked as core_initcall, which guarantees that the instruction
622 * emulation is ready for userspace.
623 */
armv8_deprecated_init(void)624 static int __init armv8_deprecated_init(void)
625 {
626 if (IS_ENABLED(CONFIG_SWP_EMULATION))
627 register_insn_emulation(&swp_ops);
628
629 if (IS_ENABLED(CONFIG_CP15_BARRIER_EMULATION))
630 register_insn_emulation(&cp15_barrier_ops);
631
632 if (IS_ENABLED(CONFIG_SETEND_EMULATION)) {
633 if (system_supports_mixed_endian_el0())
634 register_insn_emulation(&setend_ops);
635 else
636 pr_info("setend instruction emulation is not supported on this system\n");
637 }
638
639 cpuhp_setup_state_nocalls(CPUHP_AP_ARM64_ISNDEP_STARTING,
640 "arm64/isndep:starting",
641 run_all_insn_set_hw_mode, NULL);
642 register_insn_emulation_sysctl();
643
644 return 0;
645 }
646
647 core_initcall(armv8_deprecated_init);
648
