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/debug-monitors.h>
  35 #include <asm/elf.h>
  36 #include <asm/cacheflush.h>
  37 #include <asm/ucontext.h>
  38 #include <asm/unistd.h>
  39 #include <asm/fpsimd.h>
  40 #include <asm/signal32.h>
  41 #include <asm/vdso.h>
  42
  43 /*
  44  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  45  */
  46 struct rt_sigframe {
  47         struct siginfo info;
  48         struct ucontext uc;
  49 };
  50
  51 struct frame_record {
  52         u64 fp;
  53         u64 lr;
  54 };
  55
  56 struct rt_sigframe_user_layout {
  57         struct rt_sigframe __user *sigframe;
  58         struct frame_record __user *next_frame;
  59
  60         unsigned long size;     /* size of allocated sigframe data */
  61         unsigned long limit;    /* largest allowed size */
  62
  63         unsigned long fpsimd_offset;
  64         unsigned long esr_offset;
  65         unsigned long extra_offset;
  66         unsigned long end_offset;
  67 };
  68
  69 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
  70 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
  71 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
  72
  73 static void init_user_layout(struct rt_sigframe_user_layout *user)
  74 {
  75         const size_t reserved_size =
  76                 sizeof(user->sigframe->uc.uc_mcontext.__reserved);
  77
  78         memset(user, 0, sizeof(*user));
  79         user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
  80
  81         user->limit = user->size + reserved_size;
  82
  83         user->limit -= TERMINATOR_SIZE;
  84         user->limit -= EXTRA_CONTEXT_SIZE;
  85         /* Reserve space for extension and terminator ^ */
  86 }
  87
  88 static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
  89 {
  90         return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
  91 }
  92
  93 /*
  94  * Sanity limit on the approximate maximum size of signal frame we'll
  95  * try to generate.  Stack alignment padding and the frame record are
  96  * not taken into account.  This limit is not a guarantee and is
  97  * NOT ABI.
  98  */
  99 #define SIGFRAME_MAXSZ SZ_64K
 100
 101 static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
 102                             unsigned long *offset, size_t size, bool extend)
 103 {
 104         size_t padded_size = round_up(size, 16);
 105
 106         if (padded_size > user->limit - user->size &&
 107             !user->extra_offset &&
 108             extend) {
 109                 int ret;
 110
 111                 user->limit += EXTRA_CONTEXT_SIZE;
 112                 ret = __sigframe_alloc(user, &user->extra_offset,
 113                                        sizeof(struct extra_context), false);
 114                 if (ret) {
 115                         user->limit -= EXTRA_CONTEXT_SIZE;
 116                         return ret;
 117                 }
 118
 119                 /* Reserve space for the __reserved[] terminator */
 120                 user->size += TERMINATOR_SIZE;
 121
 122                 /*
 123                  * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
 124                  * the terminator:
 125                  */
 126                 user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
 127         }
 128
 129         /* Still not enough space?  Bad luck! */
 130         if (padded_size > user->limit - user->size)
 131                 return -ENOMEM;
 132
 133         *offset = user->size;
 134         user->size += padded_size;
 135
 136         return 0;
 137 }
 138
 139 /*
 140  * Allocate space for an optional record of <size> bytes in the user
 141  * signal frame.  The offset from the signal frame base address to the
 142  * allocated block is assigned to *offset.
 143  */
 144 static int sigframe_alloc(struct rt_sigframe_user_layout *user,
 145                           unsigned long *offset, size_t size)
 146 {
 147         return __sigframe_alloc(user, offset, size, true);
 148 }
 149
 150 /* Allocate the null terminator record and prevent further allocations */
 151 static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
 152 {
 153         int ret;
 154
 155         /* Un-reserve the space reserved for the terminator: */
 156         user->limit += TERMINATOR_SIZE;
 157
 158         ret = sigframe_alloc(user, &user->end_offset,
 159                              sizeof(struct _aarch64_ctx));
 160         if (ret)
 161                 return ret;
 162
 163         /* Prevent further allocation: */
 164         user->limit = user->size;
 165         return 0;
 166 }
 167
 168 static void __user *apply_user_offset(
 169         struct rt_sigframe_user_layout const *user, unsigned long offset)
 170 {
 171         char __user *base = (char __user *)user->sigframe;
 172
 173         return base + offset;
 174 }
 175
 176 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 177 {
 178         struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
 179         int err;
 180
 181         /* dump the hardware registers to the fpsimd_state structure */
 182         fpsimd_preserve_current_state();
 183
 184         /* copy the FP and status/control registers */
 185         err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
 186         __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
 187         __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
 188
 189         /* copy the magic/size information */
 190         __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
 191         __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
 192
 193         return err ? -EFAULT : 0;
 194 }
 195
 196 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
 197 {
 198         struct fpsimd_state fpsimd;
 199         __u32 magic, size;
 200         int err = 0;
 201
 202         /* check the magic/size information */
 203         __get_user_error(magic, &ctx->head.magic, err);
 204         __get_user_error(size, &ctx->head.size, err);
 205         if (err)
 206                 return -EFAULT;
 207         if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
 208                 return -EINVAL;
 209
 210         /* copy the FP and status/control registers */
 211         err = __copy_from_user(fpsimd.vregs, ctx->vregs,
 212                                sizeof(fpsimd.vregs));
 213         __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
 214         __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
 215
 216         /* load the hardware registers from the fpsimd_state structure */
 217         if (!err)
 218                 fpsimd_update_current_state(&fpsimd);
 219
 220         return err ? -EFAULT : 0;
 221 }
 222
 223 struct user_ctxs {
 224         struct fpsimd_context __user *fpsimd;
 225 };
 226
 227 static int parse_user_sigframe(struct user_ctxs *user,
 228                                struct rt_sigframe __user *sf)
 229 {
 230         struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
 231         struct _aarch64_ctx __user *head;
 232         char __user *base = (char __user *)&sc->__reserved;
 233         size_t offset = 0;
 234         size_t limit = sizeof(sc->__reserved);
 235         bool have_extra_context = false;
 236         char const __user *const sfp = (char const __user *)sf;
 237
 238         user->fpsimd = NULL;
 239
 240         if (!IS_ALIGNED((unsigned long)base, 16))
 241                 goto invalid;
 242
 243         while (1) {
 244                 int err = 0;
 245                 u32 magic, size;
 246                 char const __user *userp;
 247                 struct extra_context const __user *extra;
 248                 u64 extra_datap;
 249                 u32 extra_size;
 250                 struct _aarch64_ctx const __user *end;
 251                 u32 end_magic, end_size;
 252
 253                 if (limit - offset < sizeof(*head))
 254                         goto invalid;
 255
 256                 if (!IS_ALIGNED(offset, 16))
 257                         goto invalid;
 258
 259                 head = (struct _aarch64_ctx __user *)(base + offset);
 260                 __get_user_error(magic, &head->magic, err);
 261                 __get_user_error(size, &head->size, err);
 262                 if (err)
 263                         return err;
 264
 265                 if (limit - offset < size)
 266                         goto invalid;
 267
 268                 switch (magic) {
 269                 case 0:
 270                         if (size)
 271                                 goto invalid;
 272
 273                         goto done;
 274
 275                 case FPSIMD_MAGIC:
 276                         if (user->fpsimd)
 277                                 goto invalid;
 278
 279                         if (size < sizeof(*user->fpsimd))
 280                                 goto invalid;
 281
 282                         user->fpsimd = (struct fpsimd_context __user *)head;
 283                         break;
 284
 285                 case ESR_MAGIC:
 286                         /* ignore */
 287                         break;
 288
 289                 case EXTRA_MAGIC:
 290                         if (have_extra_context)
 291                                 goto invalid;
 292
 293                         if (size < sizeof(*extra))
 294                                 goto invalid;
 295
 296                         userp = (char const __user *)head;
 297
 298                         extra = (struct extra_context const __user *)userp;
 299                         userp += size;
 300
 301                         __get_user_error(extra_datap, &extra->datap, err);
 302                         __get_user_error(extra_size, &extra->size, err);
 303                         if (err)
 304                                 return err;
 305
 306                         /* Check for the dummy terminator in __reserved[]: */
 307
 308                         if (limit - offset - size < TERMINATOR_SIZE)
 309                                 goto invalid;
 310
 311                         end = (struct _aarch64_ctx const __user *)userp;
 312                         userp += TERMINATOR_SIZE;
 313
 314                         __get_user_error(end_magic, &end->magic, err);
 315                         __get_user_error(end_size, &end->size, err);
 316                         if (err)
 317                                 return err;
 318
 319                         if (end_magic || end_size)
 320                                 goto invalid;
 321
 322                         /* Prevent looping/repeated parsing of extra_context */
 323                         have_extra_context = true;
 324
 325                         base = (__force void __user *)extra_datap;
 326                         if (!IS_ALIGNED((unsigned long)base, 16))
 327                                 goto invalid;
 328
 329                         if (!IS_ALIGNED(extra_size, 16))
 330                                 goto invalid;
 331
 332                         if (base != userp)
 333                                 goto invalid;
 334
 335                         /* Reject "unreasonably large" frames: */
 336                         if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
 337                                 goto invalid;
 338
 339                         /*
 340                          * Ignore trailing terminator in __reserved[]
 341                          * and start parsing extra data:
 342                          */
 343                         offset = 0;
 344                         limit = extra_size;
 345                         continue;
 346
 347                 default:
 348                         goto invalid;
 349                 }
 350
 351                 if (size < sizeof(*head))
 352                         goto invalid;
 353
 354                 if (limit - offset < size)
 355                         goto invalid;
 356
 357                 offset += size;
 358         }
 359
 360 done:
 361         if (!user->fpsimd)
 362                 goto invalid;
 363
 364         return 0;
 365
 366 invalid:
 367         return -EINVAL;
 368 }
 369
 370 static int restore_sigframe(struct pt_regs *regs,
 371                             struct rt_sigframe __user *sf)
 372 {
 373         sigset_t set;
 374         int i, err;
 375         struct user_ctxs user;
 376
 377         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 378         if (err == 0)
 379                 set_current_blocked(&set);
 380
 381         for (i = 0; i < 31; i++)
 382                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 383                                  err);
 384         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 385         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 386         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 387
 388         /*
 389          * Avoid sys_rt_sigreturn() restarting.
 390          */
 391         regs->syscallno = ~0;
 392
 393         err |= !valid_user_regs(&regs->user_regs, current);
 394         if (err == 0)
 395                 err = parse_user_sigframe(&user, sf);
 396
 397         if (err == 0)
 398                 err = restore_fpsimd_context(user.fpsimd);
 399
 400         return err;
 401 }
 402
 403 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 404 {
 405         struct rt_sigframe __user *frame;
 406
 407         /* Always make any pending restarted system calls return -EINTR */
 408         current->restart_block.fn = do_no_restart_syscall;
 409
 410         /*
 411          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 412          * be word aligned here.
 413          */
 414         if (regs->sp & 15)
 415                 goto badframe;
 416
 417         frame = (struct rt_sigframe __user *)regs->sp;
 418
 419         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 420                 goto badframe;
 421
 422         if (restore_sigframe(regs, frame))
 423                 goto badframe;
 424
 425         if (restore_altstack(&frame->uc.uc_stack))
 426                 goto badframe;
 427
 428         return regs->regs[0];
 429
 430 badframe:
 431         if (show_unhandled_signals)
 432                 pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 433                                     current->comm, task_pid_nr(current), __func__,
 434                                     regs->pc, regs->sp);
 435         force_sig(SIGSEGV, current);
 436         return 0;
 437 }
 438
 439 /* Determine the layout of optional records in the signal frame */
 440 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user)
 441 {
 442         int err;
 443
 444         err = sigframe_alloc(user, &user->fpsimd_offset,
 445                              sizeof(struct fpsimd_context));
 446         if (err)
 447                 return err;
 448
 449         /* fault information, if valid */
 450         if (current->thread.fault_code) {
 451                 err = sigframe_alloc(user, &user->esr_offset,
 452                                      sizeof(struct esr_context));
 453                 if (err)
 454                         return err;
 455         }
 456
 457         return sigframe_alloc_end(user);
 458 }
 459
 460
 461 static int setup_sigframe(struct rt_sigframe_user_layout *user,
 462                           struct pt_regs *regs, sigset_t *set)
 463 {
 464         int i, err = 0;
 465         struct rt_sigframe __user *sf = user->sigframe;
 466
 467         /* set up the stack frame for unwinding */
 468         __put_user_error(regs->regs[29], &user->next_frame->fp, err);
 469         __put_user_error(regs->regs[30], &user->next_frame->lr, err);
 470
 471         for (i = 0; i < 31; i++)
 472                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 473                                  err);
 474         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 475         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 476         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 477
 478         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 479
 480         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 481
 482         if (err == 0) {
 483                 struct fpsimd_context __user *fpsimd_ctx =
 484                         apply_user_offset(user, user->fpsimd_offset);
 485                 err |= preserve_fpsimd_context(fpsimd_ctx);
 486         }
 487
 488         /* fault information, if valid */
 489         if (err == 0 && user->esr_offset) {
 490                 struct esr_context __user *esr_ctx =
 491                         apply_user_offset(user, user->esr_offset);
 492
 493                 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
 494                 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
 495                 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
 496         }
 497
 498         if (err == 0 && user->extra_offset) {
 499                 char __user *sfp = (char __user *)user->sigframe;
 500                 char __user *userp =
 501                         apply_user_offset(user, user->extra_offset);
 502
 503                 struct extra_context __user *extra;
 504                 struct _aarch64_ctx __user *end;
 505                 u64 extra_datap;
 506                 u32 extra_size;
 507
 508                 extra = (struct extra_context __user *)userp;
 509                 userp += EXTRA_CONTEXT_SIZE;
 510
 511                 end = (struct _aarch64_ctx __user *)userp;
 512                 userp += TERMINATOR_SIZE;
 513
 514                 /*
 515                  * extra_datap is just written to the signal frame.
 516                  * The value gets cast back to a void __user *
 517                  * during sigreturn.
 518                  */
 519                 extra_datap = (__force u64)userp;
 520                 extra_size = sfp + round_up(user->size, 16) - userp;
 521
 522                 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
 523                 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
 524                 __put_user_error(extra_datap, &extra->datap, err);
 525                 __put_user_error(extra_size, &extra->size, err);
 526
 527                 /* Add the terminator */
 528                 __put_user_error(0, &end->magic, err);
 529                 __put_user_error(0, &end->size, err);
 530         }
 531
 532         /* set the "end" magic */
 533         if (err == 0) {
 534                 struct _aarch64_ctx __user *end =
 535                         apply_user_offset(user, user->end_offset);
 536
 537                 __put_user_error(0, &end->magic, err);
 538                 __put_user_error(0, &end->size, err);
 539         }
 540
 541         return err;
 542 }
 543
 544 static int get_sigframe(struct rt_sigframe_user_layout *user,
 545                          struct ksignal *ksig, struct pt_regs *regs)
 546 {
 547         unsigned long sp, sp_top;
 548         int err;
 549
 550         init_user_layout(user);
 551         err = setup_sigframe_layout(user);
 552         if (err)
 553                 return err;
 554
 555         sp = sp_top = sigsp(regs->sp, ksig);
 556
 557         sp = round_down(sp - sizeof(struct frame_record), 16);
 558         user->next_frame = (struct frame_record __user *)sp;
 559
 560         sp = round_down(sp, 16) - sigframe_size(user);
 561         user->sigframe = (struct rt_sigframe __user *)sp;
 562
 563         /*
 564          * Check that we can actually write to the signal frame.
 565          */
 566         if (!access_ok(VERIFY_WRITE, user->sigframe, sp_top - sp))
 567                 return -EFAULT;
 568
 569         return 0;
 570 }
 571
 572 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 573                          struct rt_sigframe_user_layout *user, int usig)
 574 {
 575         __sigrestore_t sigtramp;
 576
 577         regs->regs[0] = usig;
 578         regs->sp = (unsigned long)user->sigframe;
 579         regs->regs[29] = (unsigned long)&user->next_frame->fp;
 580         regs->pc = (unsigned long)ka->sa.sa_handler;
 581
 582         if (ka->sa.sa_flags & SA_RESTORER)
 583                 sigtramp = ka->sa.sa_restorer;
 584         else
 585                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 586
 587         regs->regs[30] = (unsigned long)sigtramp;
 588 }
 589
 590 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 591                           struct pt_regs *regs)
 592 {
 593         struct rt_sigframe_user_layout user;
 594         struct rt_sigframe __user *frame;
 595         int err = 0;
 596
 597         if (get_sigframe(&user, ksig, regs))
 598                 return 1;
 599
 600         frame = user.sigframe;
 601
 602         __put_user_error(0, &frame->uc.uc_flags, err);
 603         __put_user_error(NULL, &frame->uc.uc_link, err);
 604
 605         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 606         err |= setup_sigframe(&user, regs, set);
 607         if (err == 0) {
 608                 setup_return(regs, &ksig->ka, &user, usig);
 609                 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 610                         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 611                         regs->regs[1] = (unsigned long)&frame->info;
 612                         regs->regs[2] = (unsigned long)&frame->uc;
 613                 }
 614         }
 615
 616         return err;
 617 }
 618
 619 static void setup_restart_syscall(struct pt_regs *regs)
 620 {
 621         if (is_compat_task())
 622                 compat_setup_restart_syscall(regs);
 623         else
 624                 regs->regs[8] = __NR_restart_syscall;
 625 }
 626
 627 /*
 628  * OK, we're invoking a handler
 629  */
 630 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 631 {
 632         struct task_struct *tsk = current;
 633         sigset_t *oldset = sigmask_to_save();
 634         int usig = ksig->sig;
 635         int ret;
 636
 637         /*
 638          * Set up the stack frame
 639          */
 640         if (is_compat_task()) {
 641                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 642                         ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
 643                 else
 644                         ret = compat_setup_frame(usig, ksig, oldset, regs);
 645         } else {
 646                 ret = setup_rt_frame(usig, ksig, oldset, regs);
 647         }
 648
 649         /*
 650          * Check that the resulting registers are actually sane.
 651          */
 652         ret |= !valid_user_regs(&regs->user_regs, current);
 653
 654         /*
 655          * Fast forward the stepping logic so we step into the signal
 656          * handler.
 657          */
 658         if (!ret)
 659                 user_fastforward_single_step(tsk);
 660
 661         signal_setup_done(ret, ksig, 0);
 662 }
 663
 664 /*
 665  * Note that 'init' is a special process: it doesn't get signals it doesn't
 666  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 667  * mistake.
 668  *
 669  * Note that we go through the signals twice: once to check the signals that
 670  * the kernel can handle, and then we build all the user-level signal handling
 671  * stack-frames in one go after that.
 672  */
 673 static void do_signal(struct pt_regs *regs)
 674 {
 675         unsigned long continue_addr = 0, restart_addr = 0;
 676         int retval = 0;
 677         int syscall = regs->syscallno;
 678         struct ksignal ksig;
 679
 680         /*
 681          * If we were from a system call, check for system call restarting...
 682          */
 683         if (syscall >= 0) {
 684                 continue_addr = regs->pc;
 685                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 686                 retval = regs->regs[0];
 687
 688                 /*
 689                  * Avoid additional syscall restarting via ret_to_user.
 690                  */
 691                 regs->syscallno = ~0;
 692
 693                 /*
 694                  * Prepare for system call restart. We do this here so that a
 695                  * debugger will see the already changed PC.
 696                  */
 697                 switch (retval) {
 698                 case -ERESTARTNOHAND:
 699                 case -ERESTARTSYS:
 700                 case -ERESTARTNOINTR:
 701                 case -ERESTART_RESTARTBLOCK:
 702                         regs->regs[0] = regs->orig_x0;
 703                         regs->pc = restart_addr;
 704                         break;
 705                 }
 706         }
 707
 708         /*
 709          * Get the signal to deliver. When running under ptrace, at this point
 710          * the debugger may change all of our registers.
 711          */
 712         if (get_signal(&ksig)) {
 713                 /*
 714                  * Depending on the signal settings, we may need to revert the
 715                  * decision to restart the system call, but skip this if a
 716                  * debugger has chosen to restart at a different PC.
 717                  */
 718                 if (regs->pc == restart_addr &&
 719                     (retval == -ERESTARTNOHAND ||
 720                      retval == -ERESTART_RESTARTBLOCK ||
 721                      (retval == -ERESTARTSYS &&
 722                       !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
 723                         regs->regs[0] = -EINTR;
 724                         regs->pc = continue_addr;
 725                 }
 726
 727                 handle_signal(&ksig, regs);
 728                 return;
 729         }
 730
 731         /*
 732          * Handle restarting a different system call. As above, if a debugger
 733          * has chosen to restart at a different PC, ignore the restart.
 734          */
 735         if (syscall >= 0 && regs->pc == restart_addr) {
 736                 if (retval == -ERESTART_RESTARTBLOCK)
 737                         setup_restart_syscall(regs);
 738                 user_rewind_single_step(current);
 739         }
 740
 741         restore_saved_sigmask();
 742 }
 743
 744 asmlinkage void do_notify_resume(struct pt_regs *regs,
 745                                  unsigned int thread_flags)
 746 {
 747         /*
 748          * The assembly code enters us with IRQs off, but it hasn't
 749          * informed the tracing code of that for efficiency reasons.
 750          * Update the trace code with the current status.
 751          */
 752         trace_hardirqs_off();
 753
 754         do {
 755                 /* Check valid user FS if needed */
 756                 addr_limit_user_check();
 757
 758                 if (thread_flags & _TIF_NEED_RESCHED) {
 759                         schedule();
 760                 } else {
 761                         local_irq_enable();
 762
 763                         if (thread_flags & _TIF_UPROBE)
 764                                 uprobe_notify_resume(regs);
 765
 766                         if (thread_flags & _TIF_SIGPENDING)
 767                                 do_signal(regs);
 768
 769                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 770                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 771                                 tracehook_notify_resume(regs);
 772                         }
 773
 774                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 775                                 fpsimd_restore_current_state();
 776                 }
 777
 778                 local_irq_disable();
 779                 thread_flags = READ_ONCE(current_thread_info()->flags);
 780         } while (thread_flags & _TIF_WORK_MASK);
 781 }