arch/arm/kernel/signal.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/arch/arm/kernel/signal.c
   4  *
   5  *  Copyright (C) 1995-2009 Russell King
   6  */
   7 #include <linux/errno.h>
   8 #include <linux/random.h>
   9 #include <linux/signal.h>
  10 #include <linux/personality.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/tracehook.h>
  13 #include <linux/uprobes.h>
  14 #include <linux/syscalls.h>
  15
  16 #include <asm/elf.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/traps.h>
  19 #include <asm/unistd.h>
  20 #include <asm/vfp.h>
  21
  22 #include "signal.h"
  23
  24 extern const unsigned long sigreturn_codes[17];
  25
  26 static unsigned long signal_return_offset;
  27
  28 #ifdef CONFIG_CRUNCH
  29 static int preserve_crunch_context(struct crunch_sigframe __user *frame)
  30 {
  31         char kbuf[sizeof(*frame) + 8];
  32         struct crunch_sigframe *kframe;
  33
  34         /* the crunch context must be 64 bit aligned */
  35         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  36         kframe->magic = CRUNCH_MAGIC;
  37         kframe->size = CRUNCH_STORAGE_SIZE;
  38         crunch_task_copy(current_thread_info(), &kframe->storage);
  39         return __copy_to_user(frame, kframe, sizeof(*frame));
  40 }
  41
  42 static int restore_crunch_context(char __user **auxp)
  43 {
  44         struct crunch_sigframe __user *frame =
  45                 (struct crunch_sigframe __user *)*auxp;
  46         char kbuf[sizeof(*frame) + 8];
  47         struct crunch_sigframe *kframe;
  48
  49         /* the crunch context must be 64 bit aligned */
  50         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  51         if (__copy_from_user(kframe, frame, sizeof(*frame)))
  52                 return -1;
  53         if (kframe->magic != CRUNCH_MAGIC ||
  54             kframe->size != CRUNCH_STORAGE_SIZE)
  55                 return -1;
  56         *auxp += CRUNCH_STORAGE_SIZE;
  57         crunch_task_restore(current_thread_info(), &kframe->storage);
  58         return 0;
  59 }
  60 #endif
  61
  62 #ifdef CONFIG_IWMMXT
  63
  64 static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
  65 {
  66         char kbuf[sizeof(*frame) + 8];
  67         struct iwmmxt_sigframe *kframe;
  68         int err = 0;
  69
  70         /* the iWMMXt context must be 64 bit aligned */
  71         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  72
  73         if (test_thread_flag(TIF_USING_IWMMXT)) {
  74                 kframe->magic = IWMMXT_MAGIC;
  75                 kframe->size = IWMMXT_STORAGE_SIZE;
  76                 iwmmxt_task_copy(current_thread_info(), &kframe->storage);
  77         } else {
  78                 /*
  79                  * For bug-compatibility with older kernels, some space
  80                  * has to be reserved for iWMMXt even if it's not used.
  81                  * Set the magic and size appropriately so that properly
  82                  * written userspace can skip it reliably:
  83                  */
  84                 *kframe = (struct iwmmxt_sigframe) {
  85                         .magic = DUMMY_MAGIC,
  86                         .size  = IWMMXT_STORAGE_SIZE,
  87                 };
  88         }
  89
  90         err = __copy_to_user(frame, kframe, sizeof(*kframe));
  91
  92         return err;
  93 }
  94
  95 static int restore_iwmmxt_context(char __user **auxp)
  96 {
  97         struct iwmmxt_sigframe __user *frame =
  98                 (struct iwmmxt_sigframe __user *)*auxp;
  99         char kbuf[sizeof(*frame) + 8];
 100         struct iwmmxt_sigframe *kframe;
 101
 102         /* the iWMMXt context must be 64 bit aligned */
 103         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
 104         if (__copy_from_user(kframe, frame, sizeof(*frame)))
 105                 return -1;
 106
 107         /*
 108          * For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy
 109          * block is discarded for compatibility with setup_sigframe() if
 110          * present, but we don't mandate its presence.  If some other
 111          * magic is here, it's not for us:
 112          */
 113         if (!test_thread_flag(TIF_USING_IWMMXT) &&
 114             kframe->magic != DUMMY_MAGIC)
 115                 return 0;
 116
 117         if (kframe->size != IWMMXT_STORAGE_SIZE)
 118                 return -1;
 119
 120         if (test_thread_flag(TIF_USING_IWMMXT)) {
 121                 if (kframe->magic != IWMMXT_MAGIC)
 122                         return -1;
 123
 124                 iwmmxt_task_restore(current_thread_info(), &kframe->storage);
 125         }
 126
 127         *auxp += IWMMXT_STORAGE_SIZE;
 128         return 0;
 129 }
 130
 131 #endif
 132
 133 #ifdef CONFIG_VFP
 134
 135 static int preserve_vfp_context(struct vfp_sigframe __user *frame)
 136 {
 137         struct vfp_sigframe kframe;
 138         int err = 0;
 139
 140         memset(&kframe, 0, sizeof(kframe));
 141         kframe.magic = VFP_MAGIC;
 142         kframe.size = VFP_STORAGE_SIZE;
 143
 144         err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
 145         if (err)
 146                 return err;
 147
 148         return __copy_to_user(frame, &kframe, sizeof(kframe));
 149 }
 150
 151 static int restore_vfp_context(char __user **auxp)
 152 {
 153         struct vfp_sigframe frame;
 154         int err;
 155
 156         err = __copy_from_user(&frame, *auxp, sizeof(frame));
 157         if (err)
 158                 return err;
 159
 160         if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
 161                 return -EINVAL;
 162
 163         *auxp += sizeof(frame);
 164         return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
 165 }
 166
 167 #endif
 168
 169 /*
 170  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
 171  */
 172
 173 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
 174 {
 175         struct sigcontext context;
 176         char __user *aux;
 177         sigset_t set;
 178         int err;
 179
 180         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 181         if (err == 0)
 182                 set_current_blocked(&set);
 183
 184         err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
 185         if (err == 0) {
 186                 regs->ARM_r0 = context.arm_r0;
 187                 regs->ARM_r1 = context.arm_r1;
 188                 regs->ARM_r2 = context.arm_r2;
 189                 regs->ARM_r3 = context.arm_r3;
 190                 regs->ARM_r4 = context.arm_r4;
 191                 regs->ARM_r5 = context.arm_r5;
 192                 regs->ARM_r6 = context.arm_r6;
 193                 regs->ARM_r7 = context.arm_r7;
 194                 regs->ARM_r8 = context.arm_r8;
 195                 regs->ARM_r9 = context.arm_r9;
 196                 regs->ARM_r10 = context.arm_r10;
 197                 regs->ARM_fp = context.arm_fp;
 198                 regs->ARM_ip = context.arm_ip;
 199                 regs->ARM_sp = context.arm_sp;
 200                 regs->ARM_lr = context.arm_lr;
 201                 regs->ARM_pc = context.arm_pc;
 202                 regs->ARM_cpsr = context.arm_cpsr;
 203         }
 204
 205         err |= !valid_user_regs(regs);
 206
 207         aux = (char __user *) sf->uc.uc_regspace;
 208 #ifdef CONFIG_CRUNCH
 209         if (err == 0)
 210                 err |= restore_crunch_context(&aux);
 211 #endif
 212 #ifdef CONFIG_IWMMXT
 213         if (err == 0)
 214                 err |= restore_iwmmxt_context(&aux);
 215 #endif
 216 #ifdef CONFIG_VFP
 217         if (err == 0)
 218                 err |= restore_vfp_context(&aux);
 219 #endif
 220
 221         return err;
 222 }
 223
 224 asmlinkage int sys_sigreturn(struct pt_regs *regs)
 225 {
 226         struct sigframe __user *frame;
 227
 228         /* Always make any pending restarted system calls return -EINTR */
 229         current->restart_block.fn = do_no_restart_syscall;
 230
 231         /*
 232          * Since we stacked the signal on a 64-bit boundary,
 233          * then 'sp' should be word aligned here.  If it's
 234          * not, then the user is trying to mess with us.
 235          */
 236         if (regs->ARM_sp & 7)
 237                 goto badframe;
 238
 239         frame = (struct sigframe __user *)regs->ARM_sp;
 240
 241         if (!access_ok(frame, sizeof (*frame)))
 242                 goto badframe;
 243
 244         if (restore_sigframe(regs, frame))
 245                 goto badframe;
 246
 247         return regs->ARM_r0;
 248
 249 badframe:
 250         force_sig(SIGSEGV);
 251         return 0;
 252 }
 253
 254 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 255 {
 256         struct rt_sigframe __user *frame;
 257
 258         /* Always make any pending restarted system calls return -EINTR */
 259         current->restart_block.fn = do_no_restart_syscall;
 260
 261         /*
 262          * Since we stacked the signal on a 64-bit boundary,
 263          * then 'sp' should be word aligned here.  If it's
 264          * not, then the user is trying to mess with us.
 265          */
 266         if (regs->ARM_sp & 7)
 267                 goto badframe;
 268
 269         frame = (struct rt_sigframe __user *)regs->ARM_sp;
 270
 271         if (!access_ok(frame, sizeof (*frame)))
 272                 goto badframe;
 273
 274         if (restore_sigframe(regs, &frame->sig))
 275                 goto badframe;
 276
 277         if (restore_altstack(&frame->sig.uc.uc_stack))
 278                 goto badframe;
 279
 280         return regs->ARM_r0;
 281
 282 badframe:
 283         force_sig(SIGSEGV);
 284         return 0;
 285 }
 286
 287 static int
 288 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
 289 {
 290         struct aux_sigframe __user *aux;
 291         struct sigcontext context;
 292         int err = 0;
 293
 294         context = (struct sigcontext) {
 295                 .arm_r0        = regs->ARM_r0,
 296                 .arm_r1        = regs->ARM_r1,
 297                 .arm_r2        = regs->ARM_r2,
 298                 .arm_r3        = regs->ARM_r3,
 299                 .arm_r4        = regs->ARM_r4,
 300                 .arm_r5        = regs->ARM_r5,
 301                 .arm_r6        = regs->ARM_r6,
 302                 .arm_r7        = regs->ARM_r7,
 303                 .arm_r8        = regs->ARM_r8,
 304                 .arm_r9        = regs->ARM_r9,
 305                 .arm_r10       = regs->ARM_r10,
 306                 .arm_fp        = regs->ARM_fp,
 307                 .arm_ip        = regs->ARM_ip,
 308                 .arm_sp        = regs->ARM_sp,
 309                 .arm_lr        = regs->ARM_lr,
 310                 .arm_pc        = regs->ARM_pc,
 311                 .arm_cpsr      = regs->ARM_cpsr,
 312
 313                 .trap_no       = current->thread.trap_no,
 314                 .error_code    = current->thread.error_code,
 315                 .fault_address = current->thread.address,
 316                 .oldmask       = set->sig[0],
 317         };
 318
 319         err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
 320
 321         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 322
 323         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 324 #ifdef CONFIG_CRUNCH
 325         if (err == 0)
 326                 err |= preserve_crunch_context(&aux->crunch);
 327 #endif
 328 #ifdef CONFIG_IWMMXT
 329         if (err == 0)
 330                 err |= preserve_iwmmxt_context(&aux->iwmmxt);
 331 #endif
 332 #ifdef CONFIG_VFP
 333         if (err == 0)
 334                 err |= preserve_vfp_context(&aux->vfp);
 335 #endif
 336         err |= __put_user(0, &aux->end_magic);
 337
 338         return err;
 339 }
 340
 341 static inline void __user *
 342 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
 343 {
 344         unsigned long sp = sigsp(regs->ARM_sp, ksig);
 345         void __user *frame;
 346
 347         /*
 348          * ATPCS B01 mandates 8-byte alignment
 349          */
 350         frame = (void __user *)((sp - framesize) & ~7);
 351
 352         /*
 353          * Check that we can actually write to the signal frame.
 354          */
 355         if (!access_ok(frame, framesize))
 356                 frame = NULL;
 357
 358         return frame;
 359 }
 360
 361 static int
 362 setup_return(struct pt_regs *regs, struct ksignal *ksig,
 363              unsigned long __user *rc, void __user *frame)
 364 {
 365         unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
 366         unsigned long handler_fdpic_GOT = 0;
 367         unsigned long retcode;
 368         unsigned int idx, thumb = 0;
 369         unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
 370         bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
 371                      (current->personality & FDPIC_FUNCPTRS);
 372
 373         if (fdpic) {
 374                 unsigned long __user *fdpic_func_desc =
 375                                         (unsigned long __user *)handler;
 376                 if (__get_user(handler, &fdpic_func_desc[0]) ||
 377                     __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
 378                         return 1;
 379         }
 380
 381         cpsr |= PSR_ENDSTATE;
 382
 383         /*
 384          * Maybe we need to deliver a 32-bit signal to a 26-bit task.
 385          */
 386         if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
 387                 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
 388
 389 #ifdef CONFIG_ARM_THUMB
 390         if (elf_hwcap & HWCAP_THUMB) {
 391                 /*
 392                  * The LSB of the handler determines if we're going to
 393                  * be using THUMB or ARM mode for this signal handler.
 394                  */
 395                 thumb = handler & 1;
 396
 397                 /*
 398                  * Clear the If-Then Thumb-2 execution state.  ARM spec
 399                  * requires this to be all 000s in ARM mode.  Snapdragon
 400                  * S4/Krait misbehaves on a Thumb=>ARM signal transition
 401                  * without this.
 402                  *
 403                  * We must do this whenever we are running on a Thumb-2
 404                  * capable CPU, which includes ARMv6T2.  However, we elect
 405                  * to always do this to simplify the code; this field is
 406                  * marked UNK/SBZP for older architectures.
 407                  */
 408                 cpsr &= ~PSR_IT_MASK;
 409
 410                 if (thumb) {
 411                         cpsr |= PSR_T_BIT;
 412                 } else
 413                         cpsr &= ~PSR_T_BIT;
 414         }
 415 #endif
 416
 417         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 418                 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
 419                 if (fdpic) {
 420                         /*
 421                          * We need code to load the function descriptor.
 422                          * That code follows the standard sigreturn code
 423                          * (6 words), and is made of 3 + 2 words for each
 424                          * variant. The 4th copied word is the actual FD
 425                          * address that the assembly code expects.
 426                          */
 427                         idx = 6 + thumb * 3;
 428                         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 429                                 idx += 5;
 430                         if (__put_user(sigreturn_codes[idx],   rc  ) ||
 431                             __put_user(sigreturn_codes[idx+1], rc+1) ||
 432                             __put_user(sigreturn_codes[idx+2], rc+2) ||
 433                             __put_user(retcode,                rc+3))
 434                                 return 1;
 435                         goto rc_finish;
 436                 }
 437         } else {
 438                 idx = thumb << 1;
 439                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 440                         idx += 3;
 441
 442                 /*
 443                  * Put the sigreturn code on the stack no matter which return
 444                  * mechanism we use in order to remain ABI compliant
 445                  */
 446                 if (__put_user(sigreturn_codes[idx],   rc) ||
 447                     __put_user(sigreturn_codes[idx+1], rc+1))
 448                         return 1;
 449
 450 rc_finish:
 451 #ifdef CONFIG_MMU
 452                 if (cpsr & MODE32_BIT) {
 453                         struct mm_struct *mm = current->mm;
 454
 455                         /*
 456                          * 32-bit code can use the signal return page
 457                          * except when the MPU has protected the vectors
 458                          * page from PL0
 459                          */
 460                         retcode = mm->context.sigpage + signal_return_offset +
 461                                   (idx << 2) + thumb;
 462                 } else
 463 #endif
 464                 {
 465                         /*
 466                          * Ensure that the instruction cache sees
 467                          * the return code written onto the stack.
 468                          */
 469                         flush_icache_range((unsigned long)rc,
 470                                            (unsigned long)(rc + 3));
 471
 472                         retcode = ((unsigned long)rc) + thumb;
 473                 }
 474         }
 475
 476         regs->ARM_r0 = ksig->sig;
 477         regs->ARM_sp = (unsigned long)frame;
 478         regs->ARM_lr = retcode;
 479         regs->ARM_pc = handler;
 480         if (fdpic)
 481                 regs->ARM_r9 = handler_fdpic_GOT;
 482         regs->ARM_cpsr = cpsr;
 483
 484         return 0;
 485 }
 486
 487 static int
 488 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 489 {
 490         struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 491         int err = 0;
 492
 493         if (!frame)
 494                 return 1;
 495
 496         /*
 497          * Set uc.uc_flags to a value which sc.trap_no would never have.
 498          */
 499         err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
 500
 501         err |= setup_sigframe(frame, regs, set);
 502         if (err == 0)
 503                 err = setup_return(regs, ksig, frame->retcode, frame);
 504
 505         return err;
 506 }
 507
 508 static int
 509 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 510 {
 511         struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 512         int err = 0;
 513
 514         if (!frame)
 515                 return 1;
 516
 517         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 518
 519         err |= __put_user(0, &frame->sig.uc.uc_flags);
 520         err |= __put_user(NULL, &frame->sig.uc.uc_link);
 521
 522         err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
 523         err |= setup_sigframe(&frame->sig, regs, set);
 524         if (err == 0)
 525                 err = setup_return(regs, ksig, frame->sig.retcode, frame);
 526
 527         if (err == 0) {
 528                 /*
 529                  * For realtime signals we must also set the second and third
 530                  * arguments for the signal handler.
 531                  *   -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
 532                  */
 533                 regs->ARM_r1 = (unsigned long)&frame->info;
 534                 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
 535         }
 536
 537         return err;
 538 }
 539
 540 /*
 541  * OK, we're invoking a handler
 542  */
 543 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 544 {
 545         sigset_t *oldset = sigmask_to_save();
 546         int ret;
 547
 548         /*
 549          * Perform fixup for the pre-signal frame.
 550          */
 551         rseq_signal_deliver(ksig, regs);
 552
 553         /*
 554          * Set up the stack frame
 555          */
 556         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 557                 ret = setup_rt_frame(ksig, oldset, regs);
 558         else
 559                 ret = setup_frame(ksig, oldset, regs);
 560
 561         /*
 562          * Check that the resulting registers are actually sane.
 563          */
 564         ret |= !valid_user_regs(regs);
 565
 566         signal_setup_done(ret, ksig, 0);
 567 }
 568
 569 /*
 570  * Note that 'init' is a special process: it doesn't get signals it doesn't
 571  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 572  * mistake.
 573  *
 574  * Note that we go through the signals twice: once to check the signals that
 575  * the kernel can handle, and then we build all the user-level signal handling
 576  * stack-frames in one go after that.
 577  */
 578 static int do_signal(struct pt_regs *regs, int syscall)
 579 {
 580         unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
 581         struct ksignal ksig;
 582         int restart = 0;
 583
 584         /*
 585          * If we were from a system call, check for system call restarting...
 586          */
 587         if (syscall) {
 588                 continue_addr = regs->ARM_pc;
 589                 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
 590                 retval = regs->ARM_r0;
 591
 592                 /*
 593                  * Prepare for system call restart.  We do this here so that a
 594                  * debugger will see the already changed PSW.
 595                  */
 596                 switch (retval) {
 597                 case -ERESTART_RESTARTBLOCK:
 598                         restart -= 2;
 599                         fallthrough;
 600                 case -ERESTARTNOHAND:
 601                 case -ERESTARTSYS:
 602                 case -ERESTARTNOINTR:
 603                         restart++;
 604                         regs->ARM_r0 = regs->ARM_ORIG_r0;
 605                         regs->ARM_pc = restart_addr;
 606                         break;
 607                 }
 608         }
 609
 610         /*
 611          * Get the signal to deliver.  When running under ptrace, at this
 612          * point the debugger may change all our registers ...
 613          */
 614         /*
 615          * Depending on the signal settings we may need to revert the
 616          * decision to restart the system call.  But skip this if a
 617          * debugger has chosen to restart at a different PC.
 618          */
 619         if (get_signal(&ksig)) {
 620                 /* handler */
 621                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 622                         if (retval == -ERESTARTNOHAND ||
 623                             retval == -ERESTART_RESTARTBLOCK
 624                             || (retval == -ERESTARTSYS
 625                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 626                                 regs->ARM_r0 = -EINTR;
 627                                 regs->ARM_pc = continue_addr;
 628                         }
 629                 }
 630                 handle_signal(&ksig, regs);
 631         } else {
 632                 /* no handler */
 633                 restore_saved_sigmask();
 634                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 635                         regs->ARM_pc = continue_addr;
 636                         return restart;
 637                 }
 638         }
 639         return 0;
 640 }
 641
 642 asmlinkage int
 643 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 644 {
 645         /*
 646          * The assembly code enters us with IRQs off, but it hasn't
 647          * informed the tracing code of that for efficiency reasons.
 648          * Update the trace code with the current status.
 649          */
 650         trace_hardirqs_off();
 651         do {
 652                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 653                         schedule();
 654                 } else {
 655                         if (unlikely(!user_mode(regs)))
 656                                 return 0;
 657                         local_irq_enable();
 658                         if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
 659                                 int restart = do_signal(regs, syscall);
 660                                 if (unlikely(restart)) {
 661                                         /*
 662                                          * Restart without handlers.
 663                                          * Deal with it without leaving
 664                                          * the kernel space.
 665                                          */
 666                                         return restart;
 667                                 }
 668                                 syscall = 0;
 669                         } else if (thread_flags & _TIF_UPROBE) {
 670                                 uprobe_notify_resume(regs);
 671                         } else {
 672                                 tracehook_notify_resume(regs);
 673                                 rseq_handle_notify_resume(NULL, regs);
 674                         }
 675                 }
 676                 local_irq_disable();
 677                 thread_flags = current_thread_info()->flags;
 678         } while (thread_flags & _TIF_WORK_MASK);
 679         return 0;
 680 }
 681
 682 struct page *get_signal_page(void)
 683 {
 684         unsigned long ptr;
 685         unsigned offset;
 686         struct page *page;
 687         void *addr;
 688
 689         page = alloc_pages(GFP_KERNEL, 0);
 690
 691         if (!page)
 692                 return NULL;
 693
 694         addr = page_address(page);
 695
 696         /* Give the signal return code some randomness */
 697         offset = 0x200 + (get_random_int() & 0x7fc);
 698         signal_return_offset = offset;
 699
 700         /*
 701          * Copy signal return handlers into the vector page, and
 702          * set sigreturn to be a pointer to these.
 703          */
 704         memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
 705
 706         ptr = (unsigned long)addr + offset;
 707         flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
 708
 709         return page;
 710 }
 711
 712 /* Defer to generic check */
 713 asmlinkage void addr_limit_check_failed(void)
 714 {
 715 #ifdef CONFIG_MMU
 716         addr_limit_user_check();
 717 #endif
 718 }
 719
 720 #ifdef CONFIG_DEBUG_RSEQ
 721 asmlinkage void do_rseq_syscall(struct pt_regs *regs)
 722 {
 723         rseq_syscall(regs);
 724 }
 725 #endif