arch/arm64/kernel/signal.c

   1 /*
   2  * Based on arch/arm/kernel/signal.c
   3  *
   4  * Copyright (C) 1995-2009 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/compat.h>
  21 #include <linux/errno.h>
  22 #include <linux/kernel.h>
  23 #include <linux/signal.h>
  24 #include <linux/personality.h>
  25 #include <linux/freezer.h>
  26 #include <linux/stddef.h>
  27 #include <linux/uaccess.h>
  28 #include <linux/sizes.h>
  29 #include <linux/string.h>
  30 #include <linux/tracehook.h>
  31 #include <linux/ratelimit.h>
  32 #include <linux/syscalls.h>
  33
  34 #include <asm/daifflags.h>
  35 #include <asm/debug-monitors.h>
  36 #include <asm/elf.h>
  37 #include <asm/cacheflush.h>
  38 #include <asm/ucontext.h>
  39 #include <asm/unistd.h>
  40 #include <asm/fpsimd.h>
  41 #include <asm/ptrace.h>
  42 #include <asm/signal32.h>
  43 #include <asm/traps.h>
  44 #include <asm/vdso.h>
  45
  46 /*
  47  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  48  */
  49 struct rt_sigframe {
  50         struct siginfo info;
  51         struct ucontext uc;
  52 };
  53
  54 struct frame_record {
  55         u64 fp;
  56         u64 lr;
  57 };
  58
  59 struct rt_sigframe_user_layout {
  60         struct rt_sigframe __user *sigframe;
  61         struct frame_record __user *next_frame;
  62
  63         unsigned long size;     /* size of allocated sigframe data */
  64         unsigned long limit;    /* largest allowed size */
  65
  66         unsigned long fpsimd_offset;
  67         unsigned long esr_offset;
  68         unsigned long sve_offset;
  69         unsigned long extra_offset;
  70         unsigned long end_offset;
  71 };
  72
  73 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
  74 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
  75 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
  76
  77 static void init_user_layout(struct rt_sigframe_user_layout *user)
  78 {
  79         const size_t reserved_size =
  80                 sizeof(user->sigframe->uc.uc_mcontext.__reserved);
  81
  82         memset(user, 0, sizeof(*user));
  83         user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
  84
  85         user->limit = user->size + reserved_size;
  86
  87         user->limit -= TERMINATOR_SIZE;
  88         user->limit -= EXTRA_CONTEXT_SIZE;
  89         /* Reserve space for extension and terminator ^ */
  90 }
  91
  92 static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
  93 {
  94         return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
  95 }
  96
  97 /*
  98  * Sanity limit on the approximate maximum size of signal frame we'll
  99  * try to generate.  Stack alignment padding and the frame record are
 100  * not taken into account.  This limit is not a guarantee and is
 101  * NOT ABI.
 102  */
 103 #define SIGFRAME_MAXSZ SZ_64K
 104
 105 static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
 106                             unsigned long *offset, size_t size, bool extend)
 107 {
 108         size_t padded_size = round_up(size, 16);
 109
 110         if (padded_size > user->limit - user->size &&
 111             !user->extra_offset &&
 112             extend) {
 113                 int ret;
 114
 115                 user->limit += EXTRA_CONTEXT_SIZE;
 116                 ret = __sigframe_alloc(user, &user->extra_offset,
 117                                        sizeof(struct extra_context), false);
 118                 if (ret) {
 119                         user->limit -= EXTRA_CONTEXT_SIZE;
 120                         return ret;
 121                 }
 122
 123                 /* Reserve space for the __reserved[] terminator */
 124                 user->size += TERMINATOR_SIZE;
 125
 126                 /*
 127                  * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
 128                  * the terminator:
 129                  */
 130                 user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
 131         }
 132
 133         /* Still not enough space?  Bad luck! */
 134         if (padded_size > user->limit - user->size)
 135                 return -ENOMEM;
 136
 137         *offset = user->size;
 138         user->size += padded_size;
 139
 140         return 0;
 141 }
 142
 143 /*
 144  * Allocate space for an optional record of <size> bytes in the user
 145  * signal frame.  The offset from the signal frame base address to the
 146  * allocated block is assigned to *offset.
 147  */
 148 static int sigframe_alloc(struct rt_sigframe_user_layout *user,
 149                           unsigned long *offset, size_t size)
 150 {
 151         return __sigframe_alloc(user, offset, size, true);
 152 }
 153
 154 /* Allocate the null terminator record and prevent further allocations */
 155 static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
 156 {
 157         int ret;
 158
 159         /* Un-reserve the space reserved for the terminator: */
 160         user->limit += TERMINATOR_SIZE;
 161
 162         ret = sigframe_alloc(user, &user->end_offset,
 163                              sizeof(struct _aarch64_ctx));
 164         if (ret)
 165                 return ret;
 166
 167         /* Prevent further allocation: */
 168         user->limit = user->size;
 169         return 0;
 170 }
 171
 172 static void __user *apply_user_offset(
 173         struct rt_sigframe_user_layout const *user, unsigned long offset)
 174 {
 175         char __user *base = (char __user *)user->sigframe;
 176
 177         return base + offset;
 178 }
 179
 180 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 181 {
 182         struct user_fpsimd_state const *fpsimd =
 183                 &current->thread.uw.fpsimd_state;
 184         int err;
 185
 186         /* copy the FP and status/control registers */
 187         err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
 188         __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
 189         __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
 190
 191         /* copy the magic/size information */
 192         __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
 193         __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
 194
 195         return err ? -EFAULT : 0;
 196 }
 197
 198 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
 199 {
 200         struct user_fpsimd_state fpsimd;
 201         __u32 magic, size;
 202         int err = 0;
 203
 204         /* check the magic/size information */
 205         __get_user_error(magic, &ctx->head.magic, err);
 206         __get_user_error(size, &ctx->head.size, err);
 207         if (err)
 208                 return -EFAULT;
 209         if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
 210                 return -EINVAL;
 211
 212         /* copy the FP and status/control registers */
 213         err = __copy_from_user(fpsimd.vregs, ctx->vregs,
 214                                sizeof(fpsimd.vregs));
 215         __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
 216         __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
 217
 218         clear_thread_flag(TIF_SVE);
 219
 220         /* load the hardware registers from the fpsimd_state structure */
 221         if (!err)
 222                 fpsimd_update_current_state(&fpsimd);
 223
 224         return err ? -EFAULT : 0;
 225 }
 226
 227
 228 struct user_ctxs {
 229         struct fpsimd_context __user *fpsimd;
 230         struct sve_context __user *sve;
 231 };
 232
 233 #ifdef CONFIG_ARM64_SVE
 234
 235 static int preserve_sve_context(struct sve_context __user *ctx)
 236 {
 237         int err = 0;
 238         u16 reserved[ARRAY_SIZE(ctx->__reserved)];
 239         unsigned int vl = current->thread.sve_vl;
 240         unsigned int vq = 0;
 241
 242         if (test_thread_flag(TIF_SVE))
 243                 vq = sve_vq_from_vl(vl);
 244
 245         memset(reserved, 0, sizeof(reserved));
 246
 247         __put_user_error(SVE_MAGIC, &ctx->head.magic, err);
 248         __put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16),
 249                          &ctx->head.size, err);
 250         __put_user_error(vl, &ctx->vl, err);
 251         BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
 252         err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 253
 254         if (vq) {
 255                 /*
 256                  * This assumes that the SVE state has already been saved to
 257                  * the task struct by calling preserve_fpsimd_context().
 258                  */
 259                 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
 260                                       current->thread.sve_state,
 261                                       SVE_SIG_REGS_SIZE(vq));
 262         }
 263
 264         return err ? -EFAULT : 0;
 265 }
 266
 267 static int restore_sve_fpsimd_context(struct user_ctxs *user)
 268 {
 269         int err;
 270         unsigned int vq;
 271         struct user_fpsimd_state fpsimd;
 272         struct sve_context sve;
 273
 274         if (__copy_from_user(&sve, user->sve, sizeof(sve)))
 275                 return -EFAULT;
 276
 277         if (sve.vl != current->thread.sve_vl)
 278                 return -EINVAL;
 279
 280         if (sve.head.size <= sizeof(*user->sve)) {
 281                 clear_thread_flag(TIF_SVE);
 282                 goto fpsimd_only;
 283         }
 284
 285         vq = sve_vq_from_vl(sve.vl);
 286
 287         if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq))
 288                 return -EINVAL;
 289
 290         /*
 291          * Careful: we are about __copy_from_user() directly into
 292          * thread.sve_state with preemption enabled, so protection is
 293          * needed to prevent a racing context switch from writing stale
 294          * registers back over the new data.
 295          */
 296
 297         fpsimd_flush_task_state(current);
 298         barrier();
 299         /* From now, fpsimd_thread_switch() won't clear TIF_FOREIGN_FPSTATE */
 300
 301         set_thread_flag(TIF_FOREIGN_FPSTATE);
 302         barrier();
 303         /* From now, fpsimd_thread_switch() won't touch thread.sve_state */
 304
 305         sve_alloc(current);
 306         err = __copy_from_user(current->thread.sve_state,
 307                                (char __user const *)user->sve +
 308                                         SVE_SIG_REGS_OFFSET,
 309                                SVE_SIG_REGS_SIZE(vq));
 310         if (err)
 311                 return -EFAULT;
 312
 313         set_thread_flag(TIF_SVE);
 314
 315 fpsimd_only:
 316         /* copy the FP and status/control registers */
 317         /* restore_sigframe() already checked that user->fpsimd != NULL. */
 318         err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
 319                                sizeof(fpsimd.vregs));
 320         __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
 321         __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
 322
 323         /* load the hardware registers from the fpsimd_state structure */
 324         if (!err)
 325                 fpsimd_update_current_state(&fpsimd);
 326
 327         return err ? -EFAULT : 0;
 328 }
 329
 330 #else /* ! CONFIG_ARM64_SVE */
 331
 332 /* Turn any non-optimised out attempts to use these into a link error: */
 333 extern int preserve_sve_context(void __user *ctx);
 334 extern int restore_sve_fpsimd_context(struct user_ctxs *user);
 335
 336 #endif /* ! CONFIG_ARM64_SVE */
 337
 338
 339 static int parse_user_sigframe(struct user_ctxs *user,
 340                                struct rt_sigframe __user *sf)
 341 {
 342         struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
 343         struct _aarch64_ctx __user *head;
 344         char __user *base = (char __user *)&sc->__reserved;
 345         size_t offset = 0;
 346         size_t limit = sizeof(sc->__reserved);
 347         bool have_extra_context = false;
 348         char const __user *const sfp = (char const __user *)sf;
 349
 350         user->fpsimd = NULL;
 351         user->sve = NULL;
 352
 353         if (!IS_ALIGNED((unsigned long)base, 16))
 354                 goto invalid;
 355
 356         while (1) {
 357                 int err = 0;
 358                 u32 magic, size;
 359                 char const __user *userp;
 360                 struct extra_context const __user *extra;
 361                 u64 extra_datap;
 362                 u32 extra_size;
 363                 struct _aarch64_ctx const __user *end;
 364                 u32 end_magic, end_size;
 365
 366                 if (limit - offset < sizeof(*head))
 367                         goto invalid;
 368
 369                 if (!IS_ALIGNED(offset, 16))
 370                         goto invalid;
 371
 372                 head = (struct _aarch64_ctx __user *)(base + offset);
 373                 __get_user_error(magic, &head->magic, err);
 374                 __get_user_error(size, &head->size, err);
 375                 if (err)
 376                         return err;
 377
 378                 if (limit - offset < size)
 379                         goto invalid;
 380
 381                 switch (magic) {
 382                 case 0:
 383                         if (size)
 384                                 goto invalid;
 385
 386                         goto done;
 387
 388                 case FPSIMD_MAGIC:
 389                         if (user->fpsimd)
 390                                 goto invalid;
 391
 392                         if (size < sizeof(*user->fpsimd))
 393                                 goto invalid;
 394
 395                         user->fpsimd = (struct fpsimd_context __user *)head;
 396                         break;
 397
 398                 case ESR_MAGIC:
 399                         /* ignore */
 400                         break;
 401
 402                 case SVE_MAGIC:
 403                         if (!system_supports_sve())
 404                                 goto invalid;
 405
 406                         if (user->sve)
 407                                 goto invalid;
 408
 409                         if (size < sizeof(*user->sve))
 410                                 goto invalid;
 411
 412                         user->sve = (struct sve_context __user *)head;
 413                         break;
 414
 415                 case EXTRA_MAGIC:
 416                         if (have_extra_context)
 417                                 goto invalid;
 418
 419                         if (size < sizeof(*extra))
 420                                 goto invalid;
 421
 422                         userp = (char const __user *)head;
 423
 424                         extra = (struct extra_context const __user *)userp;
 425                         userp += size;
 426
 427                         __get_user_error(extra_datap, &extra->datap, err);
 428                         __get_user_error(extra_size, &extra->size, err);
 429                         if (err)
 430                                 return err;
 431
 432                         /* Check for the dummy terminator in __reserved[]: */
 433
 434                         if (limit - offset - size < TERMINATOR_SIZE)
 435                                 goto invalid;
 436
 437                         end = (struct _aarch64_ctx const __user *)userp;
 438                         userp += TERMINATOR_SIZE;
 439
 440                         __get_user_error(end_magic, &end->magic, err);
 441                         __get_user_error(end_size, &end->size, err);
 442                         if (err)
 443                                 return err;
 444
 445                         if (end_magic || end_size)
 446                                 goto invalid;
 447
 448                         /* Prevent looping/repeated parsing of extra_context */
 449                         have_extra_context = true;
 450
 451                         base = (__force void __user *)extra_datap;
 452                         if (!IS_ALIGNED((unsigned long)base, 16))
 453                                 goto invalid;
 454
 455                         if (!IS_ALIGNED(extra_size, 16))
 456                                 goto invalid;
 457
 458                         if (base != userp)
 459                                 goto invalid;
 460
 461                         /* Reject "unreasonably large" frames: */
 462                         if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
 463                                 goto invalid;
 464
 465                         /*
 466                          * Ignore trailing terminator in __reserved[]
 467                          * and start parsing extra data:
 468                          */
 469                         offset = 0;
 470                         limit = extra_size;
 471
 472                         if (!access_ok(VERIFY_READ, base, limit))
 473                                 goto invalid;
 474
 475                         continue;
 476
 477                 default:
 478                         goto invalid;
 479                 }
 480
 481                 if (size < sizeof(*head))
 482                         goto invalid;
 483
 484                 if (limit - offset < size)
 485                         goto invalid;
 486
 487                 offset += size;
 488         }
 489
 490 done:
 491         return 0;
 492
 493 invalid:
 494         return -EINVAL;
 495 }
 496
 497 static int restore_sigframe(struct pt_regs *regs,
 498                             struct rt_sigframe __user *sf)
 499 {
 500         sigset_t set;
 501         int i, err;
 502         struct user_ctxs user;
 503
 504         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 505         if (err == 0)
 506                 set_current_blocked(&set);
 507
 508         for (i = 0; i < 31; i++)
 509                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 510                                  err);
 511         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 512         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 513         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 514
 515         /*
 516          * Avoid sys_rt_sigreturn() restarting.
 517          */
 518         forget_syscall(regs);
 519
 520         err |= !valid_user_regs(&regs->user_regs, current);
 521         if (err == 0)
 522                 err = parse_user_sigframe(&user, sf);
 523
 524         if (err == 0) {
 525                 if (!user.fpsimd)
 526                         return -EINVAL;
 527
 528                 if (user.sve) {
 529                         if (!system_supports_sve())
 530                                 return -EINVAL;
 531
 532                         err = restore_sve_fpsimd_context(&user);
 533                 } else {
 534                         err = restore_fpsimd_context(user.fpsimd);
 535                 }
 536         }
 537
 538         return err;
 539 }
 540
 541 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 542 {
 543         struct rt_sigframe __user *frame;
 544
 545         /* Always make any pending restarted system calls return -EINTR */
 546         current->restart_block.fn = do_no_restart_syscall;
 547
 548         /*
 549          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 550          * be word aligned here.
 551          */
 552         if (regs->sp & 15)
 553                 goto badframe;
 554
 555         frame = (struct rt_sigframe __user *)regs->sp;
 556
 557         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 558                 goto badframe;
 559
 560         if (restore_sigframe(regs, frame))
 561                 goto badframe;
 562
 563         if (restore_altstack(&frame->uc.uc_stack))
 564                 goto badframe;
 565
 566         return regs->regs[0];
 567
 568 badframe:
 569         arm64_notify_segfault(regs->sp);
 570         return 0;
 571 }
 572
 573 /* Determine the layout of optional records in the signal frame */
 574 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user)
 575 {
 576         int err;
 577
 578         err = sigframe_alloc(user, &user->fpsimd_offset,
 579                              sizeof(struct fpsimd_context));
 580         if (err)
 581                 return err;
 582
 583         /* fault information, if valid */
 584         if (current->thread.fault_code) {
 585                 err = sigframe_alloc(user, &user->esr_offset,
 586                                      sizeof(struct esr_context));
 587                 if (err)
 588                         return err;
 589         }
 590
 591         if (system_supports_sve()) {
 592                 unsigned int vq = 0;
 593
 594                 if (test_thread_flag(TIF_SVE))
 595                         vq = sve_vq_from_vl(current->thread.sve_vl);
 596
 597                 err = sigframe_alloc(user, &user->sve_offset,
 598                                      SVE_SIG_CONTEXT_SIZE(vq));
 599                 if (err)
 600                         return err;
 601         }
 602
 603         return sigframe_alloc_end(user);
 604 }
 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) {
 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);
 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(VERIFY_WRITE, 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         if (ka->sa.sa_flags & SA_RESTORER)
 736                 sigtramp = ka->sa.sa_restorer;
 737         else
 738                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 739
 740         regs->regs[30] = (unsigned long)sigtramp;
 741 }
 742
 743 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 744                           struct pt_regs *regs)
 745 {
 746         struct rt_sigframe_user_layout user;
 747         struct rt_sigframe __user *frame;
 748         int err = 0;
 749
 750         fpsimd_signal_preserve_current_state();
 751
 752         if (get_sigframe(&user, ksig, regs))
 753                 return 1;
 754
 755         frame = user.sigframe;
 756
 757         __put_user_error(0, &frame->uc.uc_flags, err);
 758         __put_user_error(NULL, &frame->uc.uc_link, err);
 759
 760         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 761         err |= setup_sigframe(&user, regs, set);
 762         if (err == 0) {
 763                 setup_return(regs, &ksig->ka, &user, usig);
 764                 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 765                         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 766                         regs->regs[1] = (unsigned long)&frame->info;
 767                         regs->regs[2] = (unsigned long)&frame->uc;
 768                 }
 769         }
 770
 771         return err;
 772 }
 773
 774 static void setup_restart_syscall(struct pt_regs *regs)
 775 {
 776         if (is_compat_task())
 777                 compat_setup_restart_syscall(regs);
 778         else
 779                 regs->regs[8] = __NR_restart_syscall;
 780 }
 781
 782 /*
 783  * OK, we're invoking a handler
 784  */
 785 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 786 {
 787         struct task_struct *tsk = current;
 788         sigset_t *oldset = sigmask_to_save();
 789         int usig = ksig->sig;
 790         int ret;
 791
 792         /*
 793          * Set up the stack frame
 794          */
 795         if (is_compat_task()) {
 796                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 797                         ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
 798                 else
 799                         ret = compat_setup_frame(usig, ksig, oldset, regs);
 800         } else {
 801                 ret = setup_rt_frame(usig, ksig, oldset, regs);
 802         }
 803
 804         /*
 805          * Check that the resulting registers are actually sane.
 806          */
 807         ret |= !valid_user_regs(&regs->user_regs, current);
 808
 809         /*
 810          * Fast forward the stepping logic so we step into the signal
 811          * handler.
 812          */
 813         if (!ret)
 814                 user_fastforward_single_step(tsk);
 815
 816         signal_setup_done(ret, ksig, 0);
 817 }
 818
 819 /*
 820  * Note that 'init' is a special process: it doesn't get signals it doesn't
 821  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 822  * mistake.
 823  *
 824  * Note that we go through the signals twice: once to check the signals that
 825  * the kernel can handle, and then we build all the user-level signal handling
 826  * stack-frames in one go after that.
 827  */
 828 static void do_signal(struct pt_regs *regs)
 829 {
 830         unsigned long continue_addr = 0, restart_addr = 0;
 831         int retval = 0;
 832         struct ksignal ksig;
 833
 834         /*
 835          * If we were from a system call, check for system call restarting...
 836          */
 837         if (in_syscall(regs)) {
 838                 continue_addr = regs->pc;
 839                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 840                 retval = regs->regs[0];
 841
 842                 /*
 843                  * Avoid additional syscall restarting via ret_to_user.
 844                  */
 845                 forget_syscall(regs);
 846
 847                 /*
 848                  * Prepare for system call restart. We do this here so that a
 849                  * debugger will see the already changed PC.
 850                  */
 851                 switch (retval) {
 852                 case -ERESTARTNOHAND:
 853                 case -ERESTARTSYS:
 854                 case -ERESTARTNOINTR:
 855                 case -ERESTART_RESTARTBLOCK:
 856                         regs->regs[0] = regs->orig_x0;
 857                         regs->pc = restart_addr;
 858                         break;
 859                 }
 860         }
 861
 862         /*
 863          * Get the signal to deliver. When running under ptrace, at this point
 864          * the debugger may change all of our registers.
 865          */
 866         if (get_signal(&ksig)) {
 867                 /*
 868                  * Depending on the signal settings, we may need to revert the
 869                  * decision to restart the system call, but skip this if a
 870                  * debugger has chosen to restart at a different PC.
 871                  */
 872                 if (regs->pc == restart_addr &&
 873                     (retval == -ERESTARTNOHAND ||
 874                      retval == -ERESTART_RESTARTBLOCK ||
 875                      (retval == -ERESTARTSYS &&
 876                       !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
 877                         regs->regs[0] = -EINTR;
 878                         regs->pc = continue_addr;
 879                 }
 880
 881                 handle_signal(&ksig, regs);
 882                 return;
 883         }
 884
 885         /*
 886          * Handle restarting a different system call. As above, if a debugger
 887          * has chosen to restart at a different PC, ignore the restart.
 888          */
 889         if (in_syscall(regs) && regs->pc == restart_addr) {
 890                 if (retval == -ERESTART_RESTARTBLOCK)
 891                         setup_restart_syscall(regs);
 892                 user_rewind_single_step(current);
 893         }
 894
 895         restore_saved_sigmask();
 896 }
 897
 898 asmlinkage void do_notify_resume(struct pt_regs *regs,
 899                                  unsigned int thread_flags)
 900 {
 901         /*
 902          * The assembly code enters us with IRQs off, but it hasn't
 903          * informed the tracing code of that for efficiency reasons.
 904          * Update the trace code with the current status.
 905          */
 906         trace_hardirqs_off();
 907
 908         do {
 909                 /* Check valid user FS if needed */
 910                 addr_limit_user_check();
 911
 912                 if (thread_flags & _TIF_NEED_RESCHED) {
 913                         /* Unmask Debug and SError for the next task */
 914                         local_daif_restore(DAIF_PROCCTX_NOIRQ);
 915
 916                         schedule();
 917                 } else {
 918                         local_daif_restore(DAIF_PROCCTX);
 919
 920                         if (thread_flags & _TIF_UPROBE)
 921                                 uprobe_notify_resume(regs);
 922
 923                         if (thread_flags & _TIF_SIGPENDING)
 924                                 do_signal(regs);
 925
 926                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 927                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 928                                 tracehook_notify_resume(regs);
 929                         }
 930
 931                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 932                                 fpsimd_restore_current_state();
 933                 }
 934
 935                 local_daif_mask();
 936                 thread_flags = READ_ONCE(current_thread_info()->flags);
 937         } while (thread_flags & _TIF_WORK_MASK);
 938 }