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 preserve_fpsimd_context().
 248                  */
 249                 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
 250                                       current->thread.sve_state,
 251                                       SVE_SIG_REGS_SIZE(vq));
 252         }
 253
 254         return err ? -EFAULT : 0;
 255 }
 256
 257 static int restore_sve_fpsimd_context(struct user_ctxs *user)
 258 {
 259         int err;
 260         unsigned int vq;
 261         struct user_fpsimd_state fpsimd;
 262         struct sve_context sve;
 263
 264         if (__copy_from_user(&sve, user->sve, sizeof(sve)))
 265                 return -EFAULT;
 266
 267         if (sve.vl != current->thread.sve_vl)
 268                 return -EINVAL;
 269
 270         if (sve.head.size <= sizeof(*user->sve)) {
 271                 clear_thread_flag(TIF_SVE);
 272                 goto fpsimd_only;
 273         }
 274
 275         vq = sve_vq_from_vl(sve.vl);
 276
 277         if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq))
 278                 return -EINVAL;
 279
 280         /*
 281          * Careful: we are about __copy_from_user() directly into
 282          * thread.sve_state with preemption enabled, so protection is
 283          * needed to prevent a racing context switch from writing stale
 284          * registers back over the new data.
 285          */
 286
 287         fpsimd_flush_task_state(current);
 288         /* From now, fpsimd_thread_switch() won't touch thread.sve_state */
 289
 290         sve_alloc(current);
 291         err = __copy_from_user(current->thread.sve_state,
 292                                (char __user const *)user->sve +
 293                                         SVE_SIG_REGS_OFFSET,
 294                                SVE_SIG_REGS_SIZE(vq));
 295         if (err)
 296                 return -EFAULT;
 297
 298         set_thread_flag(TIF_SVE);
 299
 300 fpsimd_only:
 301         /* copy the FP and status/control registers */
 302         /* restore_sigframe() already checked that user->fpsimd != NULL. */
 303         err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
 304                                sizeof(fpsimd.vregs));
 305         __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
 306         __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
 307
 308         /* load the hardware registers from the fpsimd_state structure */
 309         if (!err)
 310                 fpsimd_update_current_state(&fpsimd);
 311
 312         return err ? -EFAULT : 0;
 313 }
 314
 315 #else /* ! CONFIG_ARM64_SVE */
 316
 317 /* Turn any non-optimised out attempts to use these into a link error: */
 318 extern int preserve_sve_context(void __user *ctx);
 319 extern int restore_sve_fpsimd_context(struct user_ctxs *user);
 320
 321 #endif /* ! CONFIG_ARM64_SVE */
 322
 323
 324 static int parse_user_sigframe(struct user_ctxs *user,
 325                                struct rt_sigframe __user *sf)
 326 {
 327         struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
 328         struct _aarch64_ctx __user *head;
 329         char __user *base = (char __user *)&sc->__reserved;
 330         size_t offset = 0;
 331         size_t limit = sizeof(sc->__reserved);
 332         bool have_extra_context = false;
 333         char const __user *const sfp = (char const __user *)sf;
 334
 335         user->fpsimd = NULL;
 336         user->sve = NULL;
 337
 338         if (!IS_ALIGNED((unsigned long)base, 16))
 339                 goto invalid;
 340
 341         while (1) {
 342                 int err = 0;
 343                 u32 magic, size;
 344                 char const __user *userp;
 345                 struct extra_context const __user *extra;
 346                 u64 extra_datap;
 347                 u32 extra_size;
 348                 struct _aarch64_ctx const __user *end;
 349                 u32 end_magic, end_size;
 350
 351                 if (limit - offset < sizeof(*head))
 352                         goto invalid;
 353
 354                 if (!IS_ALIGNED(offset, 16))
 355                         goto invalid;
 356
 357                 head = (struct _aarch64_ctx __user *)(base + offset);
 358                 __get_user_error(magic, &head->magic, err);
 359                 __get_user_error(size, &head->size, err);
 360                 if (err)
 361                         return err;
 362
 363                 if (limit - offset < size)
 364                         goto invalid;
 365
 366                 switch (magic) {
 367                 case 0:
 368                         if (size)
 369                                 goto invalid;
 370
 371                         goto done;
 372
 373                 case FPSIMD_MAGIC:
 374                         if (!system_supports_fpsimd())
 375                                 goto invalid;
 376                         if (user->fpsimd)
 377                                 goto invalid;
 378
 379                         if (size < sizeof(*user->fpsimd))
 380                                 goto invalid;
 381
 382                         user->fpsimd = (struct fpsimd_context __user *)head;
 383                         break;
 384
 385                 case ESR_MAGIC:
 386                         /* ignore */
 387                         break;
 388
 389                 case SVE_MAGIC:
 390                         if (!system_supports_sve())
 391                                 goto invalid;
 392
 393                         if (user->sve)
 394                                 goto invalid;
 395
 396                         if (size < sizeof(*user->sve))
 397                                 goto invalid;
 398
 399                         user->sve = (struct sve_context __user *)head;
 400                         break;
 401
 402                 case EXTRA_MAGIC:
 403                         if (have_extra_context)
 404                                 goto invalid;
 405
 406                         if (size < sizeof(*extra))
 407                                 goto invalid;
 408
 409                         userp = (char const __user *)head;
 410
 411                         extra = (struct extra_context const __user *)userp;
 412                         userp += size;
 413
 414                         __get_user_error(extra_datap, &extra->datap, err);
 415                         __get_user_error(extra_size, &extra->size, err);
 416                         if (err)
 417                                 return err;
 418
 419                         /* Check for the dummy terminator in __reserved[]: */
 420
 421                         if (limit - offset - size < TERMINATOR_SIZE)
 422                                 goto invalid;
 423
 424                         end = (struct _aarch64_ctx const __user *)userp;
 425                         userp += TERMINATOR_SIZE;
 426
 427                         __get_user_error(end_magic, &end->magic, err);
 428                         __get_user_error(end_size, &end->size, err);
 429                         if (err)
 430                                 return err;
 431
 432                         if (end_magic || end_size)
 433                                 goto invalid;
 434
 435                         /* Prevent looping/repeated parsing of extra_context */
 436                         have_extra_context = true;
 437
 438                         base = (__force void __user *)extra_datap;
 439                         if (!IS_ALIGNED((unsigned long)base, 16))
 440                                 goto invalid;
 441
 442                         if (!IS_ALIGNED(extra_size, 16))
 443                                 goto invalid;
 444
 445                         if (base != userp)
 446                                 goto invalid;
 447
 448                         /* Reject "unreasonably large" frames: */
 449                         if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
 450                                 goto invalid;
 451
 452                         /*
 453                          * Ignore trailing terminator in __reserved[]
 454                          * and start parsing extra data:
 455                          */
 456                         offset = 0;
 457                         limit = extra_size;
 458
 459                         if (!access_ok(base, limit))
 460                                 goto invalid;
 461
 462                         continue;
 463
 464                 default:
 465                         goto invalid;
 466                 }
 467
 468                 if (size < sizeof(*head))
 469                         goto invalid;
 470
 471                 if (limit - offset < size)
 472                         goto invalid;
 473
 474                 offset += size;
 475         }
 476
 477 done:
 478         return 0;
 479
 480 invalid:
 481         return -EINVAL;
 482 }
 483
 484 static int restore_sigframe(struct pt_regs *regs,
 485                             struct rt_sigframe __user *sf)
 486 {
 487         sigset_t set;
 488         int i, err;
 489         struct user_ctxs user;
 490
 491         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 492         if (err == 0)
 493                 set_current_blocked(&set);
 494
 495         for (i = 0; i < 31; i++)
 496                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 497                                  err);
 498         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 499         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 500         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 501
 502         /*
 503          * Avoid sys_rt_sigreturn() restarting.
 504          */
 505         forget_syscall(regs);
 506
 507         err |= !valid_user_regs(&regs->user_regs, current);
 508         if (err == 0)
 509                 err = parse_user_sigframe(&user, sf);
 510
 511         if (err == 0 && system_supports_fpsimd()) {
 512                 if (!user.fpsimd)
 513                         return -EINVAL;
 514
 515                 if (user.sve) {
 516                         if (!system_supports_sve())
 517                                 return -EINVAL;
 518
 519                         err = restore_sve_fpsimd_context(&user);
 520                 } else {
 521                         err = restore_fpsimd_context(user.fpsimd);
 522                 }
 523         }
 524
 525         return err;
 526 }
 527
 528 SYSCALL_DEFINE0(rt_sigreturn)
 529 {
 530         struct pt_regs *regs = current_pt_regs();
 531         struct rt_sigframe __user *frame;
 532
 533         /* Always make any pending restarted system calls return -EINTR */
 534         current->restart_block.fn = do_no_restart_syscall;
 535
 536         /*
 537          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 538          * be word aligned here.
 539          */
 540         if (regs->sp & 15)
 541                 goto badframe;
 542
 543         frame = (struct rt_sigframe __user *)regs->sp;
 544
 545         if (!access_ok(frame, sizeof (*frame)))
 546                 goto badframe;
 547
 548         if (restore_sigframe(regs, frame))
 549                 goto badframe;
 550
 551         if (restore_altstack(&frame->uc.uc_stack))
 552                 goto badframe;
 553
 554         return regs->regs[0];
 555
 556 badframe:
 557         arm64_notify_segfault(regs->sp);
 558         return 0;
 559 }
 560
 561 /*
 562  * Determine the layout of optional records in the signal frame
 563  *
 564  * add_all: if true, lays out the biggest possible signal frame for
 565  *      this task; otherwise, generates a layout for the current state
 566  *      of the task.
 567  */
 568 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 569                                  bool add_all)
 570 {
 571         int err;
 572
 573         err = sigframe_alloc(user, &user->fpsimd_offset,
 574                              sizeof(struct fpsimd_context));
 575         if (err)
 576                 return err;
 577
 578         /* fault information, if valid */
 579         if (add_all || current->thread.fault_code) {
 580                 err = sigframe_alloc(user, &user->esr_offset,
 581                                      sizeof(struct esr_context));
 582                 if (err)
 583                         return err;
 584         }
 585
 586         if (system_supports_sve()) {
 587                 unsigned int vq = 0;
 588
 589                 if (add_all || test_thread_flag(TIF_SVE)) {
 590                         int vl = sve_max_vl;
 591
 592                         if (!add_all)
 593                                 vl = current->thread.sve_vl;
 594
 595                         vq = sve_vq_from_vl(vl);
 596                 }
 597
 598                 err = sigframe_alloc(user, &user->sve_offset,
 599                                      SVE_SIG_CONTEXT_SIZE(vq));
 600                 if (err)
 601                         return err;
 602         }
 603
 604         return sigframe_alloc_end(user);
 605 }
 606
 607 static int setup_sigframe(struct rt_sigframe_user_layout *user,
 608                           struct pt_regs *regs, sigset_t *set)
 609 {
 610         int i, err = 0;
 611         struct rt_sigframe __user *sf = user->sigframe;
 612
 613         /* set up the stack frame for unwinding */
 614         __put_user_error(regs->regs[29], &user->next_frame->fp, err);
 615         __put_user_error(regs->regs[30], &user->next_frame->lr, err);
 616
 617         for (i = 0; i < 31; i++)
 618                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 619                                  err);
 620         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 621         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 622         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 623
 624         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 625
 626         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 627
 628         if (err == 0 && system_supports_fpsimd()) {
 629                 struct fpsimd_context __user *fpsimd_ctx =
 630                         apply_user_offset(user, user->fpsimd_offset);
 631                 err |= preserve_fpsimd_context(fpsimd_ctx);
 632         }
 633
 634         /* fault information, if valid */
 635         if (err == 0 && user->esr_offset) {
 636                 struct esr_context __user *esr_ctx =
 637                         apply_user_offset(user, user->esr_offset);
 638
 639                 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
 640                 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
 641                 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
 642         }
 643
 644         /* Scalable Vector Extension state, if present */
 645         if (system_supports_sve() && err == 0 && user->sve_offset) {
 646                 struct sve_context __user *sve_ctx =
 647                         apply_user_offset(user, user->sve_offset);
 648                 err |= preserve_sve_context(sve_ctx);
 649         }
 650
 651         if (err == 0 && user->extra_offset) {
 652                 char __user *sfp = (char __user *)user->sigframe;
 653                 char __user *userp =
 654                         apply_user_offset(user, user->extra_offset);
 655
 656                 struct extra_context __user *extra;
 657                 struct _aarch64_ctx __user *end;
 658                 u64 extra_datap;
 659                 u32 extra_size;
 660
 661                 extra = (struct extra_context __user *)userp;
 662                 userp += EXTRA_CONTEXT_SIZE;
 663
 664                 end = (struct _aarch64_ctx __user *)userp;
 665                 userp += TERMINATOR_SIZE;
 666
 667                 /*
 668                  * extra_datap is just written to the signal frame.
 669                  * The value gets cast back to a void __user *
 670                  * during sigreturn.
 671                  */
 672                 extra_datap = (__force u64)userp;
 673                 extra_size = sfp + round_up(user->size, 16) - userp;
 674
 675                 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
 676                 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
 677                 __put_user_error(extra_datap, &extra->datap, err);
 678                 __put_user_error(extra_size, &extra->size, err);
 679
 680                 /* Add the terminator */
 681                 __put_user_error(0, &end->magic, err);
 682                 __put_user_error(0, &end->size, err);
 683         }
 684
 685         /* set the "end" magic */
 686         if (err == 0) {
 687                 struct _aarch64_ctx __user *end =
 688                         apply_user_offset(user, user->end_offset);
 689
 690                 __put_user_error(0, &end->magic, err);
 691                 __put_user_error(0, &end->size, err);
 692         }
 693
 694         return err;
 695 }
 696
 697 static int get_sigframe(struct rt_sigframe_user_layout *user,
 698                          struct ksignal *ksig, struct pt_regs *regs)
 699 {
 700         unsigned long sp, sp_top;
 701         int err;
 702
 703         init_user_layout(user);
 704         err = setup_sigframe_layout(user, false);
 705         if (err)
 706                 return err;
 707
 708         sp = sp_top = sigsp(regs->sp, ksig);
 709
 710         sp = round_down(sp - sizeof(struct frame_record), 16);
 711         user->next_frame = (struct frame_record __user *)sp;
 712
 713         sp = round_down(sp, 16) - sigframe_size(user);
 714         user->sigframe = (struct rt_sigframe __user *)sp;
 715
 716         /*
 717          * Check that we can actually write to the signal frame.
 718          */
 719         if (!access_ok(user->sigframe, sp_top - sp))
 720                 return -EFAULT;
 721
 722         return 0;
 723 }
 724
 725 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 726                          struct rt_sigframe_user_layout *user, int usig)
 727 {
 728         __sigrestore_t sigtramp;
 729
 730         regs->regs[0] = usig;
 731         regs->sp = (unsigned long)user->sigframe;
 732         regs->regs[29] = (unsigned long)&user->next_frame->fp;
 733         regs->pc = (unsigned long)ka->sa.sa_handler;
 734
 735         /*
 736          * Signal delivery is a (wacky) indirect function call in
 737          * userspace, so simulate the same setting of BTYPE as a BLR
 738          * <register containing the signal handler entry point>.
 739          * Signal delivery to a location in a PROT_BTI guarded page
 740          * that is not a function entry point will now trigger a
 741          * SIGILL in userspace.
 742          *
 743          * If the signal handler entry point is not in a PROT_BTI
 744          * guarded page, this is harmless.
 745          */
 746         if (system_supports_bti()) {
 747                 regs->pstate &= ~PSR_BTYPE_MASK;
 748                 regs->pstate |= PSR_BTYPE_C;
 749         }
 750
 751         if (ka->sa.sa_flags & SA_RESTORER)
 752                 sigtramp = ka->sa.sa_restorer;
 753         else
 754                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 755
 756         regs->regs[30] = (unsigned long)sigtramp;
 757 }
 758
 759 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 760                           struct pt_regs *regs)
 761 {
 762         struct rt_sigframe_user_layout user;
 763         struct rt_sigframe __user *frame;
 764         int err = 0;
 765
 766         fpsimd_signal_preserve_current_state();
 767
 768         if (get_sigframe(&user, ksig, regs))
 769                 return 1;
 770
 771         frame = user.sigframe;
 772
 773         __put_user_error(0, &frame->uc.uc_flags, err);
 774         __put_user_error(NULL, &frame->uc.uc_link, err);
 775
 776         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 777         err |= setup_sigframe(&user, regs, set);
 778         if (err == 0) {
 779                 setup_return(regs, &ksig->ka, &user, usig);
 780                 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 781                         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 782                         regs->regs[1] = (unsigned long)&frame->info;
 783                         regs->regs[2] = (unsigned long)&frame->uc;
 784                 }
 785         }
 786
 787         return err;
 788 }
 789
 790 static void setup_restart_syscall(struct pt_regs *regs)
 791 {
 792         if (is_compat_task())
 793                 compat_setup_restart_syscall(regs);
 794         else
 795                 regs->regs[8] = __NR_restart_syscall;
 796 }
 797
 798 /*
 799  * OK, we're invoking a handler
 800  */
 801 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 802 {
 803         struct task_struct *tsk = current;
 804         sigset_t *oldset = sigmask_to_save();
 805         int usig = ksig->sig;
 806         int ret;
 807
 808         rseq_signal_deliver(ksig, regs);
 809
 810         /*
 811          * Set up the stack frame
 812          */
 813         if (is_compat_task()) {
 814                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 815                         ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
 816                 else
 817                         ret = compat_setup_frame(usig, ksig, oldset, regs);
 818         } else {
 819                 ret = setup_rt_frame(usig, ksig, oldset, regs);
 820         }
 821
 822         /*
 823          * Check that the resulting registers are actually sane.
 824          */
 825         ret |= !valid_user_regs(&regs->user_regs, current);
 826
 827         /*
 828          * Fast forward the stepping logic so we step into the signal
 829          * handler.
 830          */
 831         if (!ret)
 832                 user_fastforward_single_step(tsk);
 833
 834         signal_setup_done(ret, ksig, 0);
 835 }
 836
 837 /*
 838  * Note that 'init' is a special process: it doesn't get signals it doesn't
 839  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 840  * mistake.
 841  *
 842  * Note that we go through the signals twice: once to check the signals that
 843  * the kernel can handle, and then we build all the user-level signal handling
 844  * stack-frames in one go after that.
 845  */
 846 static void do_signal(struct pt_regs *regs)
 847 {
 848         unsigned long continue_addr = 0, restart_addr = 0;
 849         int retval = 0;
 850         struct ksignal ksig;
 851         bool syscall = in_syscall(regs);
 852
 853         /*
 854          * If we were from a system call, check for system call restarting...
 855          */
 856         if (syscall) {
 857                 continue_addr = regs->pc;
 858                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 859                 retval = regs->regs[0];
 860
 861                 /*
 862                  * Avoid additional syscall restarting via ret_to_user.
 863                  */
 864                 forget_syscall(regs);
 865
 866                 /*
 867                  * Prepare for system call restart. We do this here so that a
 868                  * debugger will see the already changed PC.
 869                  */
 870                 switch (retval) {
 871                 case -ERESTARTNOHAND:
 872                 case -ERESTARTSYS:
 873                 case -ERESTARTNOINTR:
 874                 case -ERESTART_RESTARTBLOCK:
 875                         regs->regs[0] = regs->orig_x0;
 876                         regs->pc = restart_addr;
 877                         break;
 878                 }
 879         }
 880
 881         /*
 882          * Get the signal to deliver. When running under ptrace, at this point
 883          * the debugger may change all of our registers.
 884          */
 885         if (get_signal(&ksig)) {
 886                 /*
 887                  * Depending on the signal settings, we may need to revert the
 888                  * decision to restart the system call, but skip this if a
 889                  * debugger has chosen to restart at a different PC.
 890                  */
 891                 if (regs->pc == restart_addr &&
 892                     (retval == -ERESTARTNOHAND ||
 893                      retval == -ERESTART_RESTARTBLOCK ||
 894                      (retval == -ERESTARTSYS &&
 895                       !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
 896                         regs->regs[0] = -EINTR;
 897                         regs->pc = continue_addr;
 898                 }
 899
 900                 handle_signal(&ksig, regs);
 901                 return;
 902         }
 903
 904         /*
 905          * Handle restarting a different system call. As above, if a debugger
 906          * has chosen to restart at a different PC, ignore the restart.
 907          */
 908         if (syscall && regs->pc == restart_addr) {
 909                 if (retval == -ERESTART_RESTARTBLOCK)
 910                         setup_restart_syscall(regs);
 911                 user_rewind_single_step(current);
 912         }
 913
 914         restore_saved_sigmask();
 915 }
 916
 917 asmlinkage void do_notify_resume(struct pt_regs *regs,
 918                                  unsigned long thread_flags)
 919 {
 920         /*
 921          * The assembly code enters us with IRQs off, but it hasn't
 922          * informed the tracing code of that for efficiency reasons.
 923          * Update the trace code with the current status.
 924          */
 925         trace_hardirqs_off();
 926
 927         do {
 928                 /* Check valid user FS if needed */
 929                 addr_limit_user_check();
 930
 931                 if (thread_flags & _TIF_NEED_RESCHED) {
 932                         /* Unmask Debug and SError for the next task */
 933                         local_daif_restore(DAIF_PROCCTX_NOIRQ);
 934
 935                         schedule();
 936                 } else {
 937                         local_daif_restore(DAIF_PROCCTX);
 938
 939                         if (thread_flags & _TIF_UPROBE)
 940                                 uprobe_notify_resume(regs);
 941
 942                         if (thread_flags & _TIF_SIGPENDING)
 943                                 do_signal(regs);
 944
 945                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 946                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 947                                 tracehook_notify_resume(regs);
 948                                 rseq_handle_notify_resume(NULL, regs);
 949                         }
 950
 951                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 952                                 fpsimd_restore_current_state();
 953                 }
 954
 955                 local_daif_mask();
 956                 thread_flags = READ_ONCE(current_thread_info()->flags);
 957         } while (thread_flags & _TIF_WORK_MASK);
 958 }
 959
 960 unsigned long __ro_after_init signal_minsigstksz;
 961
 962 /*
 963  * Determine the stack space required for guaranteed signal devliery.
 964  * This function is used to populate AT_MINSIGSTKSZ at process startup.
 965  * cpufeatures setup is assumed to be complete.
 966  */
 967 void __init minsigstksz_setup(void)
 968 {
 969         struct rt_sigframe_user_layout user;
 970
 971         init_user_layout(&user);
 972
 973         /*
 974          * If this fails, SIGFRAME_MAXSZ needs to be enlarged.  It won't
 975          * be big enough, but it's our best guess:
 976          */
 977         if (WARN_ON(setup_sigframe_layout(&user, true)))
 978                 return;
 979
 980         signal_minsigstksz = sigframe_size(&user) +
 981                 round_up(sizeof(struct frame_record), 16) +
 982                 16; /* max alignment padding */
 983 }