1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Based on arch/arm/kernel/signal.c
4 *
5 * Copyright (C) 1995-2009 Russell King
6 * Copyright (C) 2012 ARM Ltd.
7 */
8
9 #include <linux/cache.h>
10 #include <linux/compat.h>
11 #include <linux/errno.h>
12 #include <linux/kernel.h>
13 #include <linux/signal.h>
14 #include <linux/personality.h>
15 #include <linux/freezer.h>
16 #include <linux/stddef.h>
17 #include <linux/uaccess.h>
18 #include <linux/sizes.h>
19 #include <linux/string.h>
20 #include <linux/tracehook.h>
21 #include <linux/ratelimit.h>
22 #include <linux/syscalls.h>
23
24 #include <asm/daifflags.h>
25 #include <asm/debug-monitors.h>
26 #include <asm/elf.h>
27 #include <asm/cacheflush.h>
28 #include <asm/ucontext.h>
29 #include <asm/unistd.h>
30 #include <asm/fpsimd.h>
31 #include <asm/ptrace.h>
32 #include <asm/syscall.h>
33 #include <asm/signal32.h>
34 #include <asm/traps.h>
35 #include <asm/vdso.h>
36
37 /*
38 * Do a signal return; undo the signal stack. These are aligned to 128-bit.
39 */
40 struct rt_sigframe {
41 struct siginfo info;
42 struct ucontext uc;
43 };
44
45 struct frame_record {
46 u64 fp;
47 u64 lr;
48 };
49
50 struct rt_sigframe_user_layout {
51 struct rt_sigframe __user *sigframe;
52 struct frame_record __user *next_frame;
53
54 unsigned long size; /* size of allocated sigframe data */
55 unsigned long limit; /* largest allowed size */
56
57 unsigned long fpsimd_offset;
58 unsigned long esr_offset;
59 unsigned long sve_offset;
60 unsigned long extra_offset;
61 unsigned long end_offset;
62 };
63
64 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
65 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
66 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
67
init_user_layout(struct rt_sigframe_user_layout * user)68 static void init_user_layout(struct rt_sigframe_user_layout *user)
69 {
70 const size_t reserved_size =
71 sizeof(user->sigframe->uc.uc_mcontext.__reserved);
72
73 memset(user, 0, sizeof(*user));
74 user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
75
76 user->limit = user->size + reserved_size;
77
78 user->limit -= TERMINATOR_SIZE;
79 user->limit -= EXTRA_CONTEXT_SIZE;
80 /* Reserve space for extension and terminator ^ */
81 }
82
sigframe_size(struct rt_sigframe_user_layout const * user)83 static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
84 {
85 return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
86 }
87
88 /*
89 * Sanity limit on the approximate maximum size of signal frame we'll
90 * try to generate. Stack alignment padding and the frame record are
91 * not taken into account. This limit is not a guarantee and is
92 * NOT ABI.
93 */
94 #define SIGFRAME_MAXSZ SZ_64K
95
__sigframe_alloc(struct rt_sigframe_user_layout * user,unsigned long * offset,size_t size,bool extend)96 static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
97 unsigned long *offset, size_t size, bool extend)
98 {
99 size_t padded_size = round_up(size, 16);
100
101 if (padded_size > user->limit - user->size &&
102 !user->extra_offset &&
103 extend) {
104 int ret;
105
106 user->limit += EXTRA_CONTEXT_SIZE;
107 ret = __sigframe_alloc(user, &user->extra_offset,
108 sizeof(struct extra_context), false);
109 if (ret) {
110 user->limit -= EXTRA_CONTEXT_SIZE;
111 return ret;
112 }
113
114 /* Reserve space for the __reserved[] terminator */
115 user->size += TERMINATOR_SIZE;
116
117 /*
118 * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
119 * the terminator:
120 */
121 user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
122 }
123
124 /* Still not enough space? Bad luck! */
125 if (padded_size > user->limit - user->size)
126 return -ENOMEM;
127
128 *offset = user->size;
129 user->size += padded_size;
130
131 return 0;
132 }
133
134 /*
135 * Allocate space for an optional record of <size> bytes in the user
136 * signal frame. The offset from the signal frame base address to the
137 * allocated block is assigned to *offset.
138 */
sigframe_alloc(struct rt_sigframe_user_layout * user,unsigned long * offset,size_t size)139 static int sigframe_alloc(struct rt_sigframe_user_layout *user,
140 unsigned long *offset, size_t size)
141 {
142 return __sigframe_alloc(user, offset, size, true);
143 }
144
145 /* Allocate the null terminator record and prevent further allocations */
sigframe_alloc_end(struct rt_sigframe_user_layout * user)146 static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
147 {
148 int ret;
149
150 /* Un-reserve the space reserved for the terminator: */
151 user->limit += TERMINATOR_SIZE;
152
153 ret = sigframe_alloc(user, &user->end_offset,
154 sizeof(struct _aarch64_ctx));
155 if (ret)
156 return ret;
157
158 /* Prevent further allocation: */
159 user->limit = user->size;
160 return 0;
161 }
162
apply_user_offset(struct rt_sigframe_user_layout const * user,unsigned long offset)163 static void __user *apply_user_offset(
164 struct rt_sigframe_user_layout const *user, unsigned long offset)
165 {
166 char __user *base = (char __user *)user->sigframe;
167
168 return base + offset;
169 }
170
preserve_fpsimd_context(struct fpsimd_context __user * ctx)171 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
172 {
173 struct user_fpsimd_state const *fpsimd =
174 ¤t->thread.uw.fpsimd_state;
175 int err;
176
177 /* copy the FP and status/control registers */
178 err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
179 __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
180 __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
181
182 /* copy the magic/size information */
183 __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
184 __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
185
186 return err ? -EFAULT : 0;
187 }
188
restore_fpsimd_context(struct fpsimd_context __user * ctx)189 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
190 {
191 struct user_fpsimd_state fpsimd;
192 __u32 magic, size;
193 int err = 0;
194
195 /* check the magic/size information */
196 __get_user_error(magic, &ctx->head.magic, err);
197 __get_user_error(size, &ctx->head.size, err);
198 if (err)
199 return -EFAULT;
200 if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
201 return -EINVAL;
202
203 /* copy the FP and status/control registers */
204 err = __copy_from_user(fpsimd.vregs, ctx->vregs,
205 sizeof(fpsimd.vregs));
206 __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
207 __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
208
209 clear_thread_flag(TIF_SVE);
210
211 /* load the hardware registers from the fpsimd_state structure */
212 if (!err)
213 fpsimd_update_current_state(&fpsimd);
214
215 return err ? -EFAULT : 0;
216 }
217
218
219 struct user_ctxs {
220 struct fpsimd_context __user *fpsimd;
221 struct sve_context __user *sve;
222 };
223
224 #ifdef CONFIG_ARM64_SVE
225
preserve_sve_context(struct sve_context __user * ctx)226 static int preserve_sve_context(struct sve_context __user *ctx)
227 {
228 int err = 0;
229 u16 reserved[ARRAY_SIZE(ctx->__reserved)];
230 unsigned int vl = current->thread.sve_vl;
231 unsigned int vq = 0;
232
233 if (test_thread_flag(TIF_SVE))
234 vq = sve_vq_from_vl(vl);
235
236 memset(reserved, 0, sizeof(reserved));
237
238 __put_user_error(SVE_MAGIC, &ctx->head.magic, err);
239 __put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16),
240 &ctx->head.size, err);
241 __put_user_error(vl, &ctx->vl, err);
242 BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
243 err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
244
245 if (vq) {
246 /*
247 * This assumes that the SVE state has already been saved to
248 * the task struct by calling the function
249 * fpsimd_signal_preserve_current_state().
250 */
251 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
252 current->thread.sve_state,
253 SVE_SIG_REGS_SIZE(vq));
254 }
255
256 return err ? -EFAULT : 0;
257 }
258
restore_sve_fpsimd_context(struct user_ctxs * user)259 static int restore_sve_fpsimd_context(struct user_ctxs *user)
260 {
261 int err;
262 unsigned int vq;
263 struct user_fpsimd_state fpsimd;
264 struct sve_context sve;
265
266 if (__copy_from_user(&sve, user->sve, sizeof(sve)))
267 return -EFAULT;
268
269 if (sve.vl != current->thread.sve_vl)
270 return -EINVAL;
271
272 if (sve.head.size <= sizeof(*user->sve)) {
273 clear_thread_flag(TIF_SVE);
274 goto fpsimd_only;
275 }
276
277 vq = sve_vq_from_vl(sve.vl);
278
279 if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq))
280 return -EINVAL;
281
282 /*
283 * Careful: we are about __copy_from_user() directly into
284 * thread.sve_state with preemption enabled, so protection is
285 * needed to prevent a racing context switch from writing stale
286 * registers back over the new data.
287 */
288
289 fpsimd_flush_task_state(current);
290 /* From now, fpsimd_thread_switch() won't touch thread.sve_state */
291
292 sve_alloc(current);
293 err = __copy_from_user(current->thread.sve_state,
294 (char __user const *)user->sve +
295 SVE_SIG_REGS_OFFSET,
296 SVE_SIG_REGS_SIZE(vq));
297 if (err)
298 return -EFAULT;
299
300 set_thread_flag(TIF_SVE);
301
302 fpsimd_only:
303 /* copy the FP and status/control registers */
304 /* restore_sigframe() already checked that user->fpsimd != NULL. */
305 err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
306 sizeof(fpsimd.vregs));
307 __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
308 __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
309
310 /* load the hardware registers from the fpsimd_state structure */
311 if (!err)
312 fpsimd_update_current_state(&fpsimd);
313
314 return err ? -EFAULT : 0;
315 }
316
317 #else /* ! CONFIG_ARM64_SVE */
318
319 /* Turn any non-optimised out attempts to use these into a link error: */
320 extern int preserve_sve_context(void __user *ctx);
321 extern int restore_sve_fpsimd_context(struct user_ctxs *user);
322
323 #endif /* ! CONFIG_ARM64_SVE */
324
325
parse_user_sigframe(struct user_ctxs * user,struct rt_sigframe __user * sf)326 static int parse_user_sigframe(struct user_ctxs *user,
327 struct rt_sigframe __user *sf)
328 {
329 struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
330 struct _aarch64_ctx __user *head;
331 char __user *base = (char __user *)&sc->__reserved;
332 size_t offset = 0;
333 size_t limit = sizeof(sc->__reserved);
334 bool have_extra_context = false;
335 char const __user *const sfp = (char const __user *)sf;
336
337 user->fpsimd = NULL;
338 user->sve = NULL;
339
340 if (!IS_ALIGNED((unsigned long)base, 16))
341 goto invalid;
342
343 while (1) {
344 int err = 0;
345 u32 magic, size;
346 char const __user *userp;
347 struct extra_context const __user *extra;
348 u64 extra_datap;
349 u32 extra_size;
350 struct _aarch64_ctx const __user *end;
351 u32 end_magic, end_size;
352
353 if (limit - offset < sizeof(*head))
354 goto invalid;
355
356 if (!IS_ALIGNED(offset, 16))
357 goto invalid;
358
359 head = (struct _aarch64_ctx __user *)(base + offset);
360 __get_user_error(magic, &head->magic, err);
361 __get_user_error(size, &head->size, err);
362 if (err)
363 return err;
364
365 if (limit - offset < size)
366 goto invalid;
367
368 switch (magic) {
369 case 0:
370 if (size)
371 goto invalid;
372
373 goto done;
374
375 case FPSIMD_MAGIC:
376 if (!system_supports_fpsimd())
377 goto invalid;
378 if (user->fpsimd)
379 goto invalid;
380
381 if (size < sizeof(*user->fpsimd))
382 goto invalid;
383
384 user->fpsimd = (struct fpsimd_context __user *)head;
385 break;
386
387 case ESR_MAGIC:
388 /* ignore */
389 break;
390
391 case SVE_MAGIC:
392 if (!system_supports_sve())
393 goto invalid;
394
395 if (user->sve)
396 goto invalid;
397
398 if (size < sizeof(*user->sve))
399 goto invalid;
400
401 user->sve = (struct sve_context __user *)head;
402 break;
403
404 case EXTRA_MAGIC:
405 if (have_extra_context)
406 goto invalid;
407
408 if (size < sizeof(*extra))
409 goto invalid;
410
411 userp = (char const __user *)head;
412
413 extra = (struct extra_context const __user *)userp;
414 userp += size;
415
416 __get_user_error(extra_datap, &extra->datap, err);
417 __get_user_error(extra_size, &extra->size, err);
418 if (err)
419 return err;
420
421 /* Check for the dummy terminator in __reserved[]: */
422
423 if (limit - offset - size < TERMINATOR_SIZE)
424 goto invalid;
425
426 end = (struct _aarch64_ctx const __user *)userp;
427 userp += TERMINATOR_SIZE;
428
429 __get_user_error(end_magic, &end->magic, err);
430 __get_user_error(end_size, &end->size, err);
431 if (err)
432 return err;
433
434 if (end_magic || end_size)
435 goto invalid;
436
437 /* Prevent looping/repeated parsing of extra_context */
438 have_extra_context = true;
439
440 base = (__force void __user *)extra_datap;
441 if (!IS_ALIGNED((unsigned long)base, 16))
442 goto invalid;
443
444 if (!IS_ALIGNED(extra_size, 16))
445 goto invalid;
446
447 if (base != userp)
448 goto invalid;
449
450 /* Reject "unreasonably large" frames: */
451 if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
452 goto invalid;
453
454 /*
455 * Ignore trailing terminator in __reserved[]
456 * and start parsing extra data:
457 */
458 offset = 0;
459 limit = extra_size;
460
461 if (!access_ok(base, limit))
462 goto invalid;
463
464 continue;
465
466 default:
467 goto invalid;
468 }
469
470 if (size < sizeof(*head))
471 goto invalid;
472
473 if (limit - offset < size)
474 goto invalid;
475
476 offset += size;
477 }
478
479 done:
480 return 0;
481
482 invalid:
483 return -EINVAL;
484 }
485
restore_sigframe(struct pt_regs * regs,struct rt_sigframe __user * sf)486 static int restore_sigframe(struct pt_regs *regs,
487 struct rt_sigframe __user *sf)
488 {
489 sigset_t set;
490 int i, err;
491 struct user_ctxs user;
492
493 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
494 if (err == 0)
495 set_current_blocked(&set);
496
497 for (i = 0; i < 31; i++)
498 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
499 err);
500 __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
501 __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
502 __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
503
504 /*
505 * Avoid sys_rt_sigreturn() restarting.
506 */
507 forget_syscall(regs);
508
509 err |= !valid_user_regs(®s->user_regs, current);
510 if (err == 0)
511 err = parse_user_sigframe(&user, sf);
512
513 if (err == 0 && system_supports_fpsimd()) {
514 if (!user.fpsimd)
515 return -EINVAL;
516
517 if (user.sve) {
518 if (!system_supports_sve())
519 return -EINVAL;
520
521 err = restore_sve_fpsimd_context(&user);
522 } else {
523 err = restore_fpsimd_context(user.fpsimd);
524 }
525 }
526
527 return err;
528 }
529
SYSCALL_DEFINE0(rt_sigreturn)530 SYSCALL_DEFINE0(rt_sigreturn)
531 {
532 struct pt_regs *regs = current_pt_regs();
533 struct rt_sigframe __user *frame;
534
535 /* Always make any pending restarted system calls return -EINTR */
536 current->restart_block.fn = do_no_restart_syscall;
537
538 /*
539 * Since we stacked the signal on a 128-bit boundary, then 'sp' should
540 * be word aligned here.
541 */
542 if (regs->sp & 15)
543 goto badframe;
544
545 frame = (struct rt_sigframe __user *)regs->sp;
546
547 if (!access_ok(frame, sizeof (*frame)))
548 goto badframe;
549
550 if (restore_sigframe(regs, frame))
551 goto badframe;
552
553 if (restore_altstack(&frame->uc.uc_stack))
554 goto badframe;
555
556 return regs->regs[0];
557
558 badframe:
559 arm64_notify_segfault(regs->sp);
560 return 0;
561 }
562
563 /*
564 * Determine the layout of optional records in the signal frame
565 *
566 * add_all: if true, lays out the biggest possible signal frame for
567 * this task; otherwise, generates a layout for the current state
568 * of the task.
569 */
setup_sigframe_layout(struct rt_sigframe_user_layout * user,bool add_all)570 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
571 bool add_all)
572 {
573 int err;
574
575 if (system_supports_fpsimd()) {
576 err = sigframe_alloc(user, &user->fpsimd_offset,
577 sizeof(struct fpsimd_context));
578 if (err)
579 return err;
580 }
581
582 /* fault information, if valid */
583 if (add_all || current->thread.fault_code) {
584 err = sigframe_alloc(user, &user->esr_offset,
585 sizeof(struct esr_context));
586 if (err)
587 return err;
588 }
589
590 if (system_supports_sve()) {
591 unsigned int vq = 0;
592
593 if (add_all || test_thread_flag(TIF_SVE)) {
594 int vl = sve_max_vl;
595
596 if (!add_all)
597 vl = current->thread.sve_vl;
598
599 vq = sve_vq_from_vl(vl);
600 }
601
602 err = sigframe_alloc(user, &user->sve_offset,
603 SVE_SIG_CONTEXT_SIZE(vq));
604 if (err)
605 return err;
606 }
607
608 return sigframe_alloc_end(user);
609 }
610
setup_sigframe(struct rt_sigframe_user_layout * user,struct pt_regs * regs,sigset_t * set)611 static int setup_sigframe(struct rt_sigframe_user_layout *user,
612 struct pt_regs *regs, sigset_t *set)
613 {
614 int i, err = 0;
615 struct rt_sigframe __user *sf = user->sigframe;
616
617 /* set up the stack frame for unwinding */
618 __put_user_error(regs->regs[29], &user->next_frame->fp, err);
619 __put_user_error(regs->regs[30], &user->next_frame->lr, err);
620
621 for (i = 0; i < 31; i++)
622 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
623 err);
624 __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
625 __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
626 __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
627
628 __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
629
630 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
631
632 if (err == 0 && system_supports_fpsimd()) {
633 struct fpsimd_context __user *fpsimd_ctx =
634 apply_user_offset(user, user->fpsimd_offset);
635 err |= preserve_fpsimd_context(fpsimd_ctx);
636 }
637
638 /* fault information, if valid */
639 if (err == 0 && user->esr_offset) {
640 struct esr_context __user *esr_ctx =
641 apply_user_offset(user, user->esr_offset);
642
643 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
644 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
645 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
646 }
647
648 /* Scalable Vector Extension state, if present */
649 if (system_supports_sve() && err == 0 && user->sve_offset) {
650 struct sve_context __user *sve_ctx =
651 apply_user_offset(user, user->sve_offset);
652 err |= preserve_sve_context(sve_ctx);
653 }
654
655 if (err == 0 && user->extra_offset) {
656 char __user *sfp = (char __user *)user->sigframe;
657 char __user *userp =
658 apply_user_offset(user, user->extra_offset);
659
660 struct extra_context __user *extra;
661 struct _aarch64_ctx __user *end;
662 u64 extra_datap;
663 u32 extra_size;
664
665 extra = (struct extra_context __user *)userp;
666 userp += EXTRA_CONTEXT_SIZE;
667
668 end = (struct _aarch64_ctx __user *)userp;
669 userp += TERMINATOR_SIZE;
670
671 /*
672 * extra_datap is just written to the signal frame.
673 * The value gets cast back to a void __user *
674 * during sigreturn.
675 */
676 extra_datap = (__force u64)userp;
677 extra_size = sfp + round_up(user->size, 16) - userp;
678
679 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
680 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
681 __put_user_error(extra_datap, &extra->datap, err);
682 __put_user_error(extra_size, &extra->size, err);
683
684 /* Add the terminator */
685 __put_user_error(0, &end->magic, err);
686 __put_user_error(0, &end->size, err);
687 }
688
689 /* set the "end" magic */
690 if (err == 0) {
691 struct _aarch64_ctx __user *end =
692 apply_user_offset(user, user->end_offset);
693
694 __put_user_error(0, &end->magic, err);
695 __put_user_error(0, &end->size, err);
696 }
697
698 return err;
699 }
700
get_sigframe(struct rt_sigframe_user_layout * user,struct ksignal * ksig,struct pt_regs * regs)701 static int get_sigframe(struct rt_sigframe_user_layout *user,
702 struct ksignal *ksig, struct pt_regs *regs)
703 {
704 unsigned long sp, sp_top;
705 int err;
706
707 init_user_layout(user);
708 err = setup_sigframe_layout(user, false);
709 if (err)
710 return err;
711
712 sp = sp_top = sigsp(regs->sp, ksig);
713
714 sp = round_down(sp - sizeof(struct frame_record), 16);
715 user->next_frame = (struct frame_record __user *)sp;
716
717 sp = round_down(sp, 16) - sigframe_size(user);
718 user->sigframe = (struct rt_sigframe __user *)sp;
719
720 /*
721 * Check that we can actually write to the signal frame.
722 */
723 if (!access_ok(user->sigframe, sp_top - sp))
724 return -EFAULT;
725
726 return 0;
727 }
728
setup_return(struct pt_regs * regs,struct k_sigaction * ka,struct rt_sigframe_user_layout * user,int usig)729 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
730 struct rt_sigframe_user_layout *user, int usig)
731 {
732 __sigrestore_t sigtramp;
733
734 regs->regs[0] = usig;
735 regs->sp = (unsigned long)user->sigframe;
736 regs->regs[29] = (unsigned long)&user->next_frame->fp;
737 regs->pc = (unsigned long)ka->sa.sa_handler;
738
739 /*
740 * Signal delivery is a (wacky) indirect function call in
741 * userspace, so simulate the same setting of BTYPE as a BLR
742 * <register containing the signal handler entry point>.
743 * Signal delivery to a location in a PROT_BTI guarded page
744 * that is not a function entry point will now trigger a
745 * SIGILL in userspace.
746 *
747 * If the signal handler entry point is not in a PROT_BTI
748 * guarded page, this is harmless.
749 */
750 if (system_supports_bti()) {
751 regs->pstate &= ~PSR_BTYPE_MASK;
752 regs->pstate |= PSR_BTYPE_C;
753 }
754
755 /* TCO (Tag Check Override) always cleared for signal handlers */
756 regs->pstate &= ~PSR_TCO_BIT;
757
758 if (ka->sa.sa_flags & SA_RESTORER)
759 sigtramp = ka->sa.sa_restorer;
760 else
761 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
762
763 regs->regs[30] = (unsigned long)sigtramp;
764 }
765
setup_rt_frame(int usig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)766 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
767 struct pt_regs *regs)
768 {
769 struct rt_sigframe_user_layout user;
770 struct rt_sigframe __user *frame;
771 int err = 0;
772
773 fpsimd_signal_preserve_current_state();
774
775 if (get_sigframe(&user, ksig, regs))
776 return 1;
777
778 frame = user.sigframe;
779
780 __put_user_error(0, &frame->uc.uc_flags, err);
781 __put_user_error(NULL, &frame->uc.uc_link, err);
782
783 err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
784 err |= setup_sigframe(&user, regs, set);
785 if (err == 0) {
786 setup_return(regs, &ksig->ka, &user, usig);
787 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
788 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
789 regs->regs[1] = (unsigned long)&frame->info;
790 regs->regs[2] = (unsigned long)&frame->uc;
791 }
792 }
793
794 return err;
795 }
796
setup_restart_syscall(struct pt_regs * regs)797 static void setup_restart_syscall(struct pt_regs *regs)
798 {
799 if (is_compat_task())
800 compat_setup_restart_syscall(regs);
801 else
802 regs->regs[8] = __NR_restart_syscall;
803 }
804
805 /*
806 * OK, we're invoking a handler
807 */
handle_signal(struct ksignal * ksig,struct pt_regs * regs)808 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
809 {
810 sigset_t *oldset = sigmask_to_save();
811 int usig = ksig->sig;
812 int ret;
813
814 rseq_signal_deliver(ksig, regs);
815
816 /*
817 * Set up the stack frame
818 */
819 if (is_compat_task()) {
820 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
821 ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
822 else
823 ret = compat_setup_frame(usig, ksig, oldset, regs);
824 } else {
825 ret = setup_rt_frame(usig, ksig, oldset, regs);
826 }
827
828 /*
829 * Check that the resulting registers are actually sane.
830 */
831 ret |= !valid_user_regs(®s->user_regs, current);
832
833 /* Step into the signal handler if we are stepping */
834 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
835 }
836
837 /*
838 * Note that 'init' is a special process: it doesn't get signals it doesn't
839 * want to handle. Thus you cannot kill init even with a SIGKILL even by
840 * mistake.
841 *
842 * Note that we go through the signals twice: once to check the signals that
843 * the kernel can handle, and then we build all the user-level signal handling
844 * stack-frames in one go after that.
845 */
do_signal(struct pt_regs * regs)846 static void do_signal(struct pt_regs *regs)
847 {
848 unsigned long continue_addr = 0, restart_addr = 0;
849 int retval = 0;
850 struct ksignal ksig;
851 bool syscall = in_syscall(regs);
852
853 /*
854 * If we were from a system call, check for system call restarting...
855 */
856 if (syscall) {
857 continue_addr = regs->pc;
858 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
859 retval = regs->regs[0];
860
861 /*
862 * Avoid additional syscall restarting via ret_to_user.
863 */
864 forget_syscall(regs);
865
866 /*
867 * Prepare for system call restart. We do this here so that a
868 * debugger will see the already changed PC.
869 */
870 switch (retval) {
871 case -ERESTARTNOHAND:
872 case -ERESTARTSYS:
873 case -ERESTARTNOINTR:
874 case -ERESTART_RESTARTBLOCK:
875 regs->regs[0] = regs->orig_x0;
876 regs->pc = restart_addr;
877 break;
878 }
879 }
880
881 /*
882 * Get the signal to deliver. When running under ptrace, at this point
883 * the debugger may change all of our registers.
884 */
885 if (get_signal(&ksig)) {
886 /*
887 * Depending on the signal settings, we may need to revert the
888 * decision to restart the system call, but skip this if a
889 * debugger has chosen to restart at a different PC.
890 */
891 if (regs->pc == restart_addr &&
892 (retval == -ERESTARTNOHAND ||
893 retval == -ERESTART_RESTARTBLOCK ||
894 (retval == -ERESTARTSYS &&
895 !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
896 syscall_set_return_value(current, regs, -EINTR, 0);
897 regs->pc = continue_addr;
898 }
899
900 handle_signal(&ksig, regs);
901 return;
902 }
903
904 /*
905 * Handle restarting a different system call. As above, if a debugger
906 * has chosen to restart at a different PC, ignore the restart.
907 */
908 if (syscall && regs->pc == restart_addr) {
909 if (retval == -ERESTART_RESTARTBLOCK)
910 setup_restart_syscall(regs);
911 user_rewind_single_step(current);
912 }
913
914 restore_saved_sigmask();
915 }
916
do_notify_resume(struct pt_regs * regs,unsigned long thread_flags)917 asmlinkage void do_notify_resume(struct pt_regs *regs,
918 unsigned long thread_flags)
919 {
920 do {
921 /* Check valid user FS if needed */
922 addr_limit_user_check();
923
924 if (thread_flags & _TIF_NEED_RESCHED) {
925 /* Unmask Debug and SError for the next task */
926 local_daif_restore(DAIF_PROCCTX_NOIRQ);
927
928 schedule();
929 } else {
930 local_daif_restore(DAIF_PROCCTX);
931
932 if (thread_flags & _TIF_UPROBE)
933 uprobe_notify_resume(regs);
934
935 if (thread_flags & _TIF_MTE_ASYNC_FAULT) {
936 clear_thread_flag(TIF_MTE_ASYNC_FAULT);
937 send_sig_fault(SIGSEGV, SEGV_MTEAERR,
938 (void __user *)NULL, current);
939 }
940
941 if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
942 do_signal(regs);
943
944 if (thread_flags & _TIF_NOTIFY_RESUME) {
945 tracehook_notify_resume(regs);
946 rseq_handle_notify_resume(NULL, regs);
947 }
948
949 if (thread_flags & _TIF_FOREIGN_FPSTATE)
950 fpsimd_restore_current_state();
951 }
952
953 local_daif_mask();
954 thread_flags = READ_ONCE(current_thread_info()->flags);
955 } while (thread_flags & _TIF_WORK_MASK);
956 }
957
958 unsigned long __ro_after_init signal_minsigstksz;
959
960 /*
961 * Determine the stack space required for guaranteed signal devliery.
962 * This function is used to populate AT_MINSIGSTKSZ at process startup.
963 * cpufeatures setup is assumed to be complete.
964 */
minsigstksz_setup(void)965 void __init minsigstksz_setup(void)
966 {
967 struct rt_sigframe_user_layout user;
968
969 init_user_layout(&user);
970
971 /*
972 * If this fails, SIGFRAME_MAXSZ needs to be enlarged. It won't
973 * be big enough, but it's our best guess:
974 */
975 if (WARN_ON(setup_sigframe_layout(&user, true)))
976 return;
977
978 signal_minsigstksz = sigframe_size(&user) +
979 round_up(sizeof(struct frame_record), 16) +
980 16; /* max alignment padding */
981 }
982