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/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         /*
 918          * The assembly code enters us with IRQs off, but it hasn't
 919          * informed the tracing code of that for efficiency reasons.
 920          * Update the trace code with the current status.
 921          */
 922         trace_hardirqs_off();
 923
 924         do {
 925                 if (thread_flags & _TIF_NEED_RESCHED) {
 926                         /* Unmask Debug and SError for the next task */
 927                         local_daif_restore(DAIF_PROCCTX_NOIRQ);
 928
 929                         schedule();
 930                 } else {
 931                         local_daif_restore(DAIF_PROCCTX);
 932
 933                         if (thread_flags & _TIF_UPROBE)
 934                                 uprobe_notify_resume(regs);
 935
 936                         if (thread_flags & _TIF_MTE_ASYNC_FAULT) {
 937                                 clear_thread_flag(TIF_MTE_ASYNC_FAULT);
 938                                 send_sig_fault(SIGSEGV, SEGV_MTEAERR,
 939                                                (void __user *)NULL, current);
 940                         }
 941
 942                         if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 943                                 do_signal(regs);
 944
 945                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 946                                 tracehook_notify_resume(regs);
 947                                 rseq_handle_notify_resume(NULL, regs);
 948                         }
 949
 950                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 951                                 fpsimd_restore_current_state();
 952                 }
 953
 954                 local_daif_mask();
 955                 thread_flags = READ_ONCE(current_thread_info()->flags);
 956         } while (thread_flags & _TIF_WORK_MASK);
 957 }
 958
 959 unsigned long __ro_after_init signal_minsigstksz;
 960
 961 /*
 962  * Determine the stack space required for guaranteed signal devliery.
 963  * This function is used to populate AT_MINSIGSTKSZ at process startup.
 964  * cpufeatures setup is assumed to be complete.
 965  */
 966 void __init minsigstksz_setup(void)
 967 {
 968         struct rt_sigframe_user_layout user;
 969
 970         init_user_layout(&user);
 971
 972         /*
 973          * If this fails, SIGFRAME_MAXSZ needs to be enlarged.  It won't
 974          * be big enough, but it's our best guess:
 975          */
 976         if (WARN_ON(setup_sigframe_layout(&user, true)))
 977                 return;
 978
 979         signal_minsigstksz = sigframe_size(&user) +
 980                 round_up(sizeof(struct frame_record), 16) +
 981                 16; /* max alignment padding */
 982 }