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Linux/arch/arm64/kernel/signal.c

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

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