arch/arm64/kernel/signal.c

   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
  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
  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
  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  */
 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 */
 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
 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
 171 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 172 {
 173         struct user_fpsimd_state const *fpsimd =
 174                 &current->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
 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
 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
 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         if (!current->thread.sve_state) {
 294                 clear_thread_flag(TIF_SVE);
 295                 return -ENOMEM;
 296         }
 297
 298         err = __copy_from_user(current->thread.sve_state,
 299                                (char __user const *)user->sve +
 300                                         SVE_SIG_REGS_OFFSET,
 301                                SVE_SIG_REGS_SIZE(vq));
 302         if (err)
 303                 return -EFAULT;
 304
 305         set_thread_flag(TIF_SVE);
 306
 307 fpsimd_only:
 308         /* copy the FP and status/control registers */
 309         /* restore_sigframe() already checked that user->fpsimd != NULL. */
 310         err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
 311                                sizeof(fpsimd.vregs));
 312         __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
 313         __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
 314
 315         /* load the hardware registers from the fpsimd_state structure */
 316         if (!err)
 317                 fpsimd_update_current_state(&fpsimd);
 318
 319         return err ? -EFAULT : 0;
 320 }
 321
 322 #else /* ! CONFIG_ARM64_SVE */
 323
 324 /* Turn any non-optimised out attempts to use these into a link error: */
 325 extern int preserve_sve_context(void __user *ctx);
 326 extern int restore_sve_fpsimd_context(struct user_ctxs *user);
 327
 328 #endif /* ! CONFIG_ARM64_SVE */
 329
 330
 331 static int parse_user_sigframe(struct user_ctxs *user,
 332                                struct rt_sigframe __user *sf)
 333 {
 334         struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
 335         struct _aarch64_ctx __user *head;
 336         char __user *base = (char __user *)&sc->__reserved;
 337         size_t offset = 0;
 338         size_t limit = sizeof(sc->__reserved);
 339         bool have_extra_context = false;
 340         char const __user *const sfp = (char const __user *)sf;
 341
 342         user->fpsimd = NULL;
 343         user->sve = NULL;
 344
 345         if (!IS_ALIGNED((unsigned long)base, 16))
 346                 goto invalid;
 347
 348         while (1) {
 349                 int err = 0;
 350                 u32 magic, size;
 351                 char const __user *userp;
 352                 struct extra_context const __user *extra;
 353                 u64 extra_datap;
 354                 u32 extra_size;
 355                 struct _aarch64_ctx const __user *end;
 356                 u32 end_magic, end_size;
 357
 358                 if (limit - offset < sizeof(*head))
 359                         goto invalid;
 360
 361                 if (!IS_ALIGNED(offset, 16))
 362                         goto invalid;
 363
 364                 head = (struct _aarch64_ctx __user *)(base + offset);
 365                 __get_user_error(magic, &head->magic, err);
 366                 __get_user_error(size, &head->size, err);
 367                 if (err)
 368                         return err;
 369
 370                 if (limit - offset < size)
 371                         goto invalid;
 372
 373                 switch (magic) {
 374                 case 0:
 375                         if (size)
 376                                 goto invalid;
 377
 378                         goto done;
 379
 380                 case FPSIMD_MAGIC:
 381                         if (!system_supports_fpsimd())
 382                                 goto invalid;
 383                         if (user->fpsimd)
 384                                 goto invalid;
 385
 386                         if (size < sizeof(*user->fpsimd))
 387                                 goto invalid;
 388
 389                         user->fpsimd = (struct fpsimd_context __user *)head;
 390                         break;
 391
 392                 case ESR_MAGIC:
 393                         /* ignore */
 394                         break;
 395
 396                 case SVE_MAGIC:
 397                         if (!system_supports_sve())
 398                                 goto invalid;
 399
 400                         if (user->sve)
 401                                 goto invalid;
 402
 403                         if (size < sizeof(*user->sve))
 404                                 goto invalid;
 405
 406                         user->sve = (struct sve_context __user *)head;
 407                         break;
 408
 409                 case EXTRA_MAGIC:
 410                         if (have_extra_context)
 411                                 goto invalid;
 412
 413                         if (size < sizeof(*extra))
 414                                 goto invalid;
 415
 416                         userp = (char const __user *)head;
 417
 418                         extra = (struct extra_context const __user *)userp;
 419                         userp += size;
 420
 421                         __get_user_error(extra_datap, &extra->datap, err);
 422                         __get_user_error(extra_size, &extra->size, err);
 423                         if (err)
 424                                 return err;
 425
 426                         /* Check for the dummy terminator in __reserved[]: */
 427
 428                         if (limit - offset - size < TERMINATOR_SIZE)
 429                                 goto invalid;
 430
 431                         end = (struct _aarch64_ctx const __user *)userp;
 432                         userp += TERMINATOR_SIZE;
 433
 434                         __get_user_error(end_magic, &end->magic, err);
 435                         __get_user_error(end_size, &end->size, err);
 436                         if (err)
 437                                 return err;
 438
 439                         if (end_magic || end_size)
 440                                 goto invalid;
 441
 442                         /* Prevent looping/repeated parsing of extra_context */
 443                         have_extra_context = true;
 444
 445                         base = (__force void __user *)extra_datap;
 446                         if (!IS_ALIGNED((unsigned long)base, 16))
 447                                 goto invalid;
 448
 449                         if (!IS_ALIGNED(extra_size, 16))
 450                                 goto invalid;
 451
 452                         if (base != userp)
 453                                 goto invalid;
 454
 455                         /* Reject "unreasonably large" frames: */
 456                         if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
 457                                 goto invalid;
 458
 459                         /*
 460                          * Ignore trailing terminator in __reserved[]
 461                          * and start parsing extra data:
 462                          */
 463                         offset = 0;
 464                         limit = extra_size;
 465
 466                         if (!access_ok(base, limit))
 467                                 goto invalid;
 468
 469                         continue;
 470
 471                 default:
 472                         goto invalid;
 473                 }
 474
 475                 if (size < sizeof(*head))
 476                         goto invalid;
 477
 478                 if (limit - offset < size)
 479                         goto invalid;
 480
 481                 offset += size;
 482         }
 483
 484 done:
 485         return 0;
 486
 487 invalid:
 488         return -EINVAL;
 489 }
 490
 491 static int restore_sigframe(struct pt_regs *regs,
 492                             struct rt_sigframe __user *sf)
 493 {
 494         sigset_t set;
 495         int i, err;
 496         struct user_ctxs user;
 497
 498         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 499         if (err == 0)
 500                 set_current_blocked(&set);
 501
 502         for (i = 0; i < 31; i++)
 503                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 504                                  err);
 505         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 506         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 507         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 508
 509         /*
 510          * Avoid sys_rt_sigreturn() restarting.
 511          */
 512         forget_syscall(regs);
 513
 514         err |= !valid_user_regs(&regs->user_regs, current);
 515         if (err == 0)
 516                 err = parse_user_sigframe(&user, sf);
 517
 518         if (err == 0 && system_supports_fpsimd()) {
 519                 if (!user.fpsimd)
 520                         return -EINVAL;
 521
 522                 if (user.sve) {
 523                         if (!system_supports_sve())
 524                                 return -EINVAL;
 525
 526                         err = restore_sve_fpsimd_context(&user);
 527                 } else {
 528                         err = restore_fpsimd_context(user.fpsimd);
 529                 }
 530         }
 531
 532         return err;
 533 }
 534
 535 SYSCALL_DEFINE0(rt_sigreturn)
 536 {
 537         struct pt_regs *regs = current_pt_regs();
 538         struct rt_sigframe __user *frame;
 539
 540         /* Always make any pending restarted system calls return -EINTR */
 541         current->restart_block.fn = do_no_restart_syscall;
 542
 543         /*
 544          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 545          * be word aligned here.
 546          */
 547         if (regs->sp & 15)
 548                 goto badframe;
 549
 550         frame = (struct rt_sigframe __user *)regs->sp;
 551
 552         if (!access_ok(frame, sizeof (*frame)))
 553                 goto badframe;
 554
 555         if (restore_sigframe(regs, frame))
 556                 goto badframe;
 557
 558         if (restore_altstack(&frame->uc.uc_stack))
 559                 goto badframe;
 560
 561         return regs->regs[0];
 562
 563 badframe:
 564         arm64_notify_segfault(regs->sp);
 565         return 0;
 566 }
 567
 568 /*
 569  * Determine the layout of optional records in the signal frame
 570  *
 571  * add_all: if true, lays out the biggest possible signal frame for
 572  *      this task; otherwise, generates a layout for the current state
 573  *      of the task.
 574  */
 575 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 576                                  bool add_all)
 577 {
 578         int err;
 579
 580         err = sigframe_alloc(user, &user->fpsimd_offset,
 581                              sizeof(struct fpsimd_context));
 582         if (err)
 583                 return err;
 584
 585         /* fault information, if valid */
 586         if (add_all || current->thread.fault_code) {
 587                 err = sigframe_alloc(user, &user->esr_offset,
 588                                      sizeof(struct esr_context));
 589                 if (err)
 590                         return err;
 591         }
 592
 593         if (system_supports_sve()) {
 594                 unsigned int vq = 0;
 595
 596                 if (add_all || test_thread_flag(TIF_SVE)) {
 597                         int vl = sve_max_vl;
 598
 599                         if (!add_all)
 600                                 vl = current->thread.sve_vl;
 601
 602                         vq = sve_vq_from_vl(vl);
 603                 }
 604
 605                 err = sigframe_alloc(user, &user->sve_offset,
 606                                      SVE_SIG_CONTEXT_SIZE(vq));
 607                 if (err)
 608                         return err;
 609         }
 610
 611         return sigframe_alloc_end(user);
 612 }
 613
 614 static int setup_sigframe(struct rt_sigframe_user_layout *user,
 615                           struct pt_regs *regs, sigset_t *set)
 616 {
 617         int i, err = 0;
 618         struct rt_sigframe __user *sf = user->sigframe;
 619
 620         /* set up the stack frame for unwinding */
 621         __put_user_error(regs->regs[29], &user->next_frame->fp, err);
 622         __put_user_error(regs->regs[30], &user->next_frame->lr, err);
 623
 624         for (i = 0; i < 31; i++)
 625                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 626                                  err);
 627         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 628         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 629         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 630
 631         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 632
 633         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 634
 635         if (err == 0 && system_supports_fpsimd()) {
 636                 struct fpsimd_context __user *fpsimd_ctx =
 637                         apply_user_offset(user, user->fpsimd_offset);
 638                 err |= preserve_fpsimd_context(fpsimd_ctx);
 639         }
 640
 641         /* fault information, if valid */
 642         if (err == 0 && user->esr_offset) {
 643                 struct esr_context __user *esr_ctx =
 644                         apply_user_offset(user, user->esr_offset);
 645
 646                 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
 647                 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
 648                 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
 649         }
 650
 651         /* Scalable Vector Extension state, if present */
 652         if (system_supports_sve() && err == 0 && user->sve_offset) {
 653                 struct sve_context __user *sve_ctx =
 654                         apply_user_offset(user, user->sve_offset);
 655                 err |= preserve_sve_context(sve_ctx);
 656         }
 657
 658         if (err == 0 && user->extra_offset) {
 659                 char __user *sfp = (char __user *)user->sigframe;
 660                 char __user *userp =
 661                         apply_user_offset(user, user->extra_offset);
 662
 663                 struct extra_context __user *extra;
 664                 struct _aarch64_ctx __user *end;
 665                 u64 extra_datap;
 666                 u32 extra_size;
 667
 668                 extra = (struct extra_context __user *)userp;
 669                 userp += EXTRA_CONTEXT_SIZE;
 670
 671                 end = (struct _aarch64_ctx __user *)userp;
 672                 userp += TERMINATOR_SIZE;
 673
 674                 /*
 675                  * extra_datap is just written to the signal frame.
 676                  * The value gets cast back to a void __user *
 677                  * during sigreturn.
 678                  */
 679                 extra_datap = (__force u64)userp;
 680                 extra_size = sfp + round_up(user->size, 16) - userp;
 681
 682                 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
 683                 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
 684                 __put_user_error(extra_datap, &extra->datap, err);
 685                 __put_user_error(extra_size, &extra->size, err);
 686
 687                 /* Add the terminator */
 688                 __put_user_error(0, &end->magic, err);
 689                 __put_user_error(0, &end->size, err);
 690         }
 691
 692         /* set the "end" magic */
 693         if (err == 0) {
 694                 struct _aarch64_ctx __user *end =
 695                         apply_user_offset(user, user->end_offset);
 696
 697                 __put_user_error(0, &end->magic, err);
 698                 __put_user_error(0, &end->size, err);
 699         }
 700
 701         return err;
 702 }
 703
 704 static int get_sigframe(struct rt_sigframe_user_layout *user,
 705                          struct ksignal *ksig, struct pt_regs *regs)
 706 {
 707         unsigned long sp, sp_top;
 708         int err;
 709
 710         init_user_layout(user);
 711         err = setup_sigframe_layout(user, false);
 712         if (err)
 713                 return err;
 714
 715         sp = sp_top = sigsp(regs->sp, ksig);
 716
 717         sp = round_down(sp - sizeof(struct frame_record), 16);
 718         user->next_frame = (struct frame_record __user *)sp;
 719
 720         sp = round_down(sp, 16) - sigframe_size(user);
 721         user->sigframe = (struct rt_sigframe __user *)sp;
 722
 723         /*
 724          * Check that we can actually write to the signal frame.
 725          */
 726         if (!access_ok(user->sigframe, sp_top - sp))
 727                 return -EFAULT;
 728
 729         return 0;
 730 }
 731
 732 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 733                          struct rt_sigframe_user_layout *user, int usig)
 734 {
 735         __sigrestore_t sigtramp;
 736
 737         regs->regs[0] = usig;
 738         regs->sp = (unsigned long)user->sigframe;
 739         regs->regs[29] = (unsigned long)&user->next_frame->fp;
 740         regs->pc = (unsigned long)ka->sa.sa_handler;
 741
 742         /*
 743          * Signal delivery is a (wacky) indirect function call in
 744          * userspace, so simulate the same setting of BTYPE as a BLR
 745          * <register containing the signal handler entry point>.
 746          * Signal delivery to a location in a PROT_BTI guarded page
 747          * that is not a function entry point will now trigger a
 748          * SIGILL in userspace.
 749          *
 750          * If the signal handler entry point is not in a PROT_BTI
 751          * guarded page, this is harmless.
 752          */
 753         if (system_supports_bti()) {
 754                 regs->pstate &= ~PSR_BTYPE_MASK;
 755                 regs->pstate |= PSR_BTYPE_C;
 756         }
 757
 758         /* TCO (Tag Check Override) always cleared for signal handlers */
 759         regs->pstate &= ~PSR_TCO_BIT;
 760
 761         if (ka->sa.sa_flags & SA_RESTORER)
 762                 sigtramp = ka->sa.sa_restorer;
 763         else
 764                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 765
 766         regs->regs[30] = (unsigned long)sigtramp;
 767 }
 768
 769 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 770                           struct pt_regs *regs)
 771 {
 772         struct rt_sigframe_user_layout user;
 773         struct rt_sigframe __user *frame;
 774         int err = 0;
 775
 776         fpsimd_signal_preserve_current_state();
 777
 778         if (get_sigframe(&user, ksig, regs))
 779                 return 1;
 780
 781         frame = user.sigframe;
 782
 783         __put_user_error(0, &frame->uc.uc_flags, err);
 784         __put_user_error(NULL, &frame->uc.uc_link, err);
 785
 786         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 787         err |= setup_sigframe(&user, regs, set);
 788         if (err == 0) {
 789                 setup_return(regs, &ksig->ka, &user, usig);
 790                 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 791                         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 792                         regs->regs[1] = (unsigned long)&frame->info;
 793                         regs->regs[2] = (unsigned long)&frame->uc;
 794                 }
 795         }
 796
 797         return err;
 798 }
 799
 800 static void setup_restart_syscall(struct pt_regs *regs)
 801 {
 802         if (is_compat_task())
 803                 compat_setup_restart_syscall(regs);
 804         else
 805                 regs->regs[8] = __NR_restart_syscall;
 806 }
 807
 808 /*
 809  * OK, we're invoking a handler
 810  */
 811 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 812 {
 813         sigset_t *oldset = sigmask_to_save();
 814         int usig = ksig->sig;
 815         int ret;
 816
 817         rseq_signal_deliver(ksig, regs);
 818
 819         /*
 820          * Set up the stack frame
 821          */
 822         if (is_compat_task()) {
 823                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 824                         ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
 825                 else
 826                         ret = compat_setup_frame(usig, ksig, oldset, regs);
 827         } else {
 828                 ret = setup_rt_frame(usig, ksig, oldset, regs);
 829         }
 830
 831         /*
 832          * Check that the resulting registers are actually sane.
 833          */
 834         ret |= !valid_user_regs(&regs->user_regs, current);
 835
 836         /* Step into the signal handler if we are stepping */
 837         signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
 838 }
 839
 840 /*
 841  * Note that 'init' is a special process: it doesn't get signals it doesn't
 842  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 843  * mistake.
 844  *
 845  * Note that we go through the signals twice: once to check the signals that
 846  * the kernel can handle, and then we build all the user-level signal handling
 847  * stack-frames in one go after that.
 848  */
 849 static void do_signal(struct pt_regs *regs)
 850 {
 851         unsigned long continue_addr = 0, restart_addr = 0;
 852         int retval = 0;
 853         struct ksignal ksig;
 854         bool syscall = in_syscall(regs);
 855
 856         /*
 857          * If we were from a system call, check for system call restarting...
 858          */
 859         if (syscall) {
 860                 continue_addr = regs->pc;
 861                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 862                 retval = regs->regs[0];
 863
 864                 /*
 865                  * Avoid additional syscall restarting via ret_to_user.
 866                  */
 867                 forget_syscall(regs);
 868
 869                 /*
 870                  * Prepare for system call restart. We do this here so that a
 871                  * debugger will see the already changed PC.
 872                  */
 873                 switch (retval) {
 874                 case -ERESTARTNOHAND:
 875                 case -ERESTARTSYS:
 876                 case -ERESTARTNOINTR:
 877                 case -ERESTART_RESTARTBLOCK:
 878                         regs->regs[0] = regs->orig_x0;
 879                         regs->pc = restart_addr;
 880                         break;
 881                 }
 882         }
 883
 884         /*
 885          * Get the signal to deliver. When running under ptrace, at this point
 886          * the debugger may change all of our registers.
 887          */
 888         if (get_signal(&ksig)) {
 889                 /*
 890                  * Depending on the signal settings, we may need to revert the
 891                  * decision to restart the system call, but skip this if a
 892                  * debugger has chosen to restart at a different PC.
 893                  */
 894                 if (regs->pc == restart_addr &&
 895                     (retval == -ERESTARTNOHAND ||
 896                      retval == -ERESTART_RESTARTBLOCK ||
 897                      (retval == -ERESTARTSYS &&
 898                       !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
 899                         syscall_set_return_value(current, regs, -EINTR, 0);
 900                         regs->pc = continue_addr;
 901                 }
 902
 903                 handle_signal(&ksig, regs);
 904                 return;
 905         }
 906
 907         /*
 908          * Handle restarting a different system call. As above, if a debugger
 909          * has chosen to restart at a different PC, ignore the restart.
 910          */
 911         if (syscall && regs->pc == restart_addr) {
 912                 if (retval == -ERESTART_RESTARTBLOCK)
 913                         setup_restart_syscall(regs);
 914                 user_rewind_single_step(current);
 915         }
 916
 917         restore_saved_sigmask();
 918 }
 919
 920 void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
 921 {
 922         do {
 923                 if (thread_flags & _TIF_NEED_RESCHED) {
 924                         /* Unmask Debug and SError for the next task */
 925                         local_daif_restore(DAIF_PROCCTX_NOIRQ);
 926
 927                         schedule();
 928                 } else {
 929                         local_daif_restore(DAIF_PROCCTX);
 930
 931                         if (thread_flags & _TIF_UPROBE)
 932                                 uprobe_notify_resume(regs);
 933
 934                         if (thread_flags & _TIF_MTE_ASYNC_FAULT) {
 935                                 clear_thread_flag(TIF_MTE_ASYNC_FAULT);
 936                                 send_sig_fault(SIGSEGV, SEGV_MTEAERR,
 937                                                (void __user *)NULL, current);
 938                         }
 939
 940                         if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 941                                 do_signal(regs);
 942
 943                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 944                                 tracehook_notify_resume(regs);
 945                                 rseq_handle_notify_resume(NULL, regs);
 946                         }
 947
 948                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 949                                 fpsimd_restore_current_state();
 950                 }
 951
 952                 local_daif_mask();
 953                 thread_flags = READ_ONCE(current_thread_info()->flags);
 954         } while (thread_flags & _TIF_WORK_MASK);
 955 }
 956
 957 unsigned long __ro_after_init signal_minsigstksz;
 958
 959 /*
 960  * Determine the stack space required for guaranteed signal devliery.
 961  * This function is used to populate AT_MINSIGSTKSZ at process startup.
 962  * cpufeatures setup is assumed to be complete.
 963  */
 964 void __init minsigstksz_setup(void)
 965 {
 966         struct rt_sigframe_user_layout user;
 967
 968         init_user_layout(&user);
 969
 970         /*
 971          * If this fails, SIGFRAME_MAXSZ needs to be enlarged.  It won't
 972          * be big enough, but it's our best guess:
 973          */
 974         if (WARN_ON(setup_sigframe_layout(&user, true)))
 975                 return;
 976
 977         signal_minsigstksz = sigframe_size(&user) +
 978                 round_up(sizeof(struct frame_record), 16) +
 979                 16; /* max alignment padding */
 980 }