arch/arm/kernel/signal.c

   1 /*
   2  *  linux/arch/arm/kernel/signal.c
   3  *
   4  *  Copyright (C) 1995-2009 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/errno.h>
  11 #include <linux/random.h>
  12 #include <linux/signal.h>
  13 #include <linux/personality.h>
  14 #include <linux/uaccess.h>
  15 #include <linux/tracehook.h>
  16 #include <linux/uprobes.h>
  17 #include <linux/syscalls.h>
  18
  19 #include <asm/elf.h>
  20 #include <asm/cacheflush.h>
  21 #include <asm/traps.h>
  22 #include <asm/unistd.h>
  23 #include <asm/vfp.h>
  24
  25 #include "signal.h"
  26
  27 extern const unsigned long sigreturn_codes[17];
  28
  29 static unsigned long signal_return_offset;
  30
  31 #ifdef CONFIG_CRUNCH
  32 static int preserve_crunch_context(struct crunch_sigframe __user *frame)
  33 {
  34         char kbuf[sizeof(*frame) + 8];
  35         struct crunch_sigframe *kframe;
  36
  37         /* the crunch context must be 64 bit aligned */
  38         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  39         kframe->magic = CRUNCH_MAGIC;
  40         kframe->size = CRUNCH_STORAGE_SIZE;
  41         crunch_task_copy(current_thread_info(), &kframe->storage);
  42         return __copy_to_user(frame, kframe, sizeof(*frame));
  43 }
  44
  45 static int restore_crunch_context(char __user **auxp)
  46 {
  47         struct crunch_sigframe __user *frame =
  48                 (struct crunch_sigframe __user *)*auxp;
  49         char kbuf[sizeof(*frame) + 8];
  50         struct crunch_sigframe *kframe;
  51
  52         /* the crunch context must be 64 bit aligned */
  53         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  54         if (__copy_from_user(kframe, frame, sizeof(*frame)))
  55                 return -1;
  56         if (kframe->magic != CRUNCH_MAGIC ||
  57             kframe->size != CRUNCH_STORAGE_SIZE)
  58                 return -1;
  59         *auxp += CRUNCH_STORAGE_SIZE;
  60         crunch_task_restore(current_thread_info(), &kframe->storage);
  61         return 0;
  62 }
  63 #endif
  64
  65 #ifdef CONFIG_IWMMXT
  66
  67 static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
  68 {
  69         char kbuf[sizeof(*frame) + 8];
  70         struct iwmmxt_sigframe *kframe;
  71         int err = 0;
  72
  73         /* the iWMMXt context must be 64 bit aligned */
  74         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  75
  76         if (test_thread_flag(TIF_USING_IWMMXT)) {
  77                 kframe->magic = IWMMXT_MAGIC;
  78                 kframe->size = IWMMXT_STORAGE_SIZE;
  79                 iwmmxt_task_copy(current_thread_info(), &kframe->storage);
  80         } else {
  81                 /*
  82                  * For bug-compatibility with older kernels, some space
  83                  * has to be reserved for iWMMXt even if it's not used.
  84                  * Set the magic and size appropriately so that properly
  85                  * written userspace can skip it reliably:
  86                  */
  87                 *kframe = (struct iwmmxt_sigframe) {
  88                         .magic = DUMMY_MAGIC,
  89                         .size  = IWMMXT_STORAGE_SIZE,
  90                 };
  91         }
  92
  93         err = __copy_to_user(frame, kframe, sizeof(*kframe));
  94
  95         return err;
  96 }
  97
  98 static int restore_iwmmxt_context(char __user **auxp)
  99 {
 100         struct iwmmxt_sigframe __user *frame =
 101                 (struct iwmmxt_sigframe __user *)*auxp;
 102         char kbuf[sizeof(*frame) + 8];
 103         struct iwmmxt_sigframe *kframe;
 104
 105         /* the iWMMXt context must be 64 bit aligned */
 106         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
 107         if (__copy_from_user(kframe, frame, sizeof(*frame)))
 108                 return -1;
 109
 110         /*
 111          * For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy
 112          * block is discarded for compatibility with setup_sigframe() if
 113          * present, but we don't mandate its presence.  If some other
 114          * magic is here, it's not for us:
 115          */
 116         if (!test_thread_flag(TIF_USING_IWMMXT) &&
 117             kframe->magic != DUMMY_MAGIC)
 118                 return 0;
 119
 120         if (kframe->size != IWMMXT_STORAGE_SIZE)
 121                 return -1;
 122
 123         if (test_thread_flag(TIF_USING_IWMMXT)) {
 124                 if (kframe->magic != IWMMXT_MAGIC)
 125                         return -1;
 126
 127                 iwmmxt_task_restore(current_thread_info(), &kframe->storage);
 128         }
 129
 130         *auxp += IWMMXT_STORAGE_SIZE;
 131         return 0;
 132 }
 133
 134 #endif
 135
 136 #ifdef CONFIG_VFP
 137
 138 static int preserve_vfp_context(struct vfp_sigframe __user *frame)
 139 {
 140         struct vfp_sigframe kframe;
 141         int err = 0;
 142
 143         memset(&kframe, 0, sizeof(kframe));
 144         kframe.magic = VFP_MAGIC;
 145         kframe.size = VFP_STORAGE_SIZE;
 146
 147         err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
 148         if (err)
 149                 return err;
 150
 151         return __copy_to_user(frame, &kframe, sizeof(kframe));
 152 }
 153
 154 static int restore_vfp_context(char __user **auxp)
 155 {
 156         struct vfp_sigframe frame;
 157         int err;
 158
 159         err = __copy_from_user(&frame, *auxp, sizeof(frame));
 160         if (err)
 161                 return err;
 162
 163         if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
 164                 return -EINVAL;
 165
 166         *auxp += sizeof(frame);
 167         return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
 168 }
 169
 170 #endif
 171
 172 /*
 173  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
 174  */
 175
 176 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
 177 {
 178         struct sigcontext context;
 179         char __user *aux;
 180         sigset_t set;
 181         int err;
 182
 183         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 184         if (err == 0)
 185                 set_current_blocked(&set);
 186
 187         err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
 188         if (err == 0) {
 189                 regs->ARM_r0 = context.arm_r0;
 190                 regs->ARM_r1 = context.arm_r1;
 191                 regs->ARM_r2 = context.arm_r2;
 192                 regs->ARM_r3 = context.arm_r3;
 193                 regs->ARM_r4 = context.arm_r4;
 194                 regs->ARM_r5 = context.arm_r5;
 195                 regs->ARM_r6 = context.arm_r6;
 196                 regs->ARM_r7 = context.arm_r7;
 197                 regs->ARM_r8 = context.arm_r8;
 198                 regs->ARM_r9 = context.arm_r9;
 199                 regs->ARM_r10 = context.arm_r10;
 200                 regs->ARM_fp = context.arm_fp;
 201                 regs->ARM_ip = context.arm_ip;
 202                 regs->ARM_sp = context.arm_sp;
 203                 regs->ARM_lr = context.arm_lr;
 204                 regs->ARM_pc = context.arm_pc;
 205                 regs->ARM_cpsr = context.arm_cpsr;
 206         }
 207
 208         err |= !valid_user_regs(regs);
 209
 210         aux = (char __user *) sf->uc.uc_regspace;
 211 #ifdef CONFIG_CRUNCH
 212         if (err == 0)
 213                 err |= restore_crunch_context(&aux);
 214 #endif
 215 #ifdef CONFIG_IWMMXT
 216         if (err == 0)
 217                 err |= restore_iwmmxt_context(&aux);
 218 #endif
 219 #ifdef CONFIG_VFP
 220         if (err == 0)
 221                 err |= restore_vfp_context(&aux);
 222 #endif
 223
 224         return err;
 225 }
 226
 227 asmlinkage int sys_sigreturn(struct pt_regs *regs)
 228 {
 229         struct sigframe __user *frame;
 230
 231         /* Always make any pending restarted system calls return -EINTR */
 232         current->restart_block.fn = do_no_restart_syscall;
 233
 234         /*
 235          * Since we stacked the signal on a 64-bit boundary,
 236          * then 'sp' should be word aligned here.  If it's
 237          * not, then the user is trying to mess with us.
 238          */
 239         if (regs->ARM_sp & 7)
 240                 goto badframe;
 241
 242         frame = (struct sigframe __user *)regs->ARM_sp;
 243
 244         if (!access_ok(frame, sizeof (*frame)))
 245                 goto badframe;
 246
 247         if (restore_sigframe(regs, frame))
 248                 goto badframe;
 249
 250         return regs->ARM_r0;
 251
 252 badframe:
 253         force_sig(SIGSEGV, current);
 254         return 0;
 255 }
 256
 257 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 258 {
 259         struct rt_sigframe __user *frame;
 260
 261         /* Always make any pending restarted system calls return -EINTR */
 262         current->restart_block.fn = do_no_restart_syscall;
 263
 264         /*
 265          * Since we stacked the signal on a 64-bit boundary,
 266          * then 'sp' should be word aligned here.  If it's
 267          * not, then the user is trying to mess with us.
 268          */
 269         if (regs->ARM_sp & 7)
 270                 goto badframe;
 271
 272         frame = (struct rt_sigframe __user *)regs->ARM_sp;
 273
 274         if (!access_ok(frame, sizeof (*frame)))
 275                 goto badframe;
 276
 277         if (restore_sigframe(regs, &frame->sig))
 278                 goto badframe;
 279
 280         if (restore_altstack(&frame->sig.uc.uc_stack))
 281                 goto badframe;
 282
 283         return regs->ARM_r0;
 284
 285 badframe:
 286         force_sig(SIGSEGV, current);
 287         return 0;
 288 }
 289
 290 static int
 291 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
 292 {
 293         struct aux_sigframe __user *aux;
 294         struct sigcontext context;
 295         int err = 0;
 296
 297         context = (struct sigcontext) {
 298                 .arm_r0        = regs->ARM_r0,
 299                 .arm_r1        = regs->ARM_r1,
 300                 .arm_r2        = regs->ARM_r2,
 301                 .arm_r3        = regs->ARM_r3,
 302                 .arm_r4        = regs->ARM_r4,
 303                 .arm_r5        = regs->ARM_r5,
 304                 .arm_r6        = regs->ARM_r6,
 305                 .arm_r7        = regs->ARM_r7,
 306                 .arm_r8        = regs->ARM_r8,
 307                 .arm_r9        = regs->ARM_r9,
 308                 .arm_r10       = regs->ARM_r10,
 309                 .arm_fp        = regs->ARM_fp,
 310                 .arm_ip        = regs->ARM_ip,
 311                 .arm_sp        = regs->ARM_sp,
 312                 .arm_lr        = regs->ARM_lr,
 313                 .arm_pc        = regs->ARM_pc,
 314                 .arm_cpsr      = regs->ARM_cpsr,
 315
 316                 .trap_no       = current->thread.trap_no,
 317                 .error_code    = current->thread.error_code,
 318                 .fault_address = current->thread.address,
 319                 .oldmask       = set->sig[0],
 320         };
 321
 322         err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
 323
 324         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 325
 326         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 327 #ifdef CONFIG_CRUNCH
 328         if (err == 0)
 329                 err |= preserve_crunch_context(&aux->crunch);
 330 #endif
 331 #ifdef CONFIG_IWMMXT
 332         if (err == 0)
 333                 err |= preserve_iwmmxt_context(&aux->iwmmxt);
 334 #endif
 335 #ifdef CONFIG_VFP
 336         if (err == 0)
 337                 err |= preserve_vfp_context(&aux->vfp);
 338 #endif
 339         err |= __put_user(0, &aux->end_magic);
 340
 341         return err;
 342 }
 343
 344 static inline void __user *
 345 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
 346 {
 347         unsigned long sp = sigsp(regs->ARM_sp, ksig);
 348         void __user *frame;
 349
 350         /*
 351          * ATPCS B01 mandates 8-byte alignment
 352          */
 353         frame = (void __user *)((sp - framesize) & ~7);
 354
 355         /*
 356          * Check that we can actually write to the signal frame.
 357          */
 358         if (!access_ok(frame, framesize))
 359                 frame = NULL;
 360
 361         return frame;
 362 }
 363
 364 static int
 365 setup_return(struct pt_regs *regs, struct ksignal *ksig,
 366              unsigned long __user *rc, void __user *frame)
 367 {
 368         unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
 369         unsigned long handler_fdpic_GOT = 0;
 370         unsigned long retcode;
 371         unsigned int idx, thumb = 0;
 372         unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
 373         bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
 374                      (current->personality & FDPIC_FUNCPTRS);
 375
 376         if (fdpic) {
 377                 unsigned long __user *fdpic_func_desc =
 378                                         (unsigned long __user *)handler;
 379                 if (__get_user(handler, &fdpic_func_desc[0]) ||
 380                     __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
 381                         return 1;
 382         }
 383
 384         cpsr |= PSR_ENDSTATE;
 385
 386         /*
 387          * Maybe we need to deliver a 32-bit signal to a 26-bit task.
 388          */
 389         if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
 390                 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
 391
 392 #ifdef CONFIG_ARM_THUMB
 393         if (elf_hwcap & HWCAP_THUMB) {
 394                 /*
 395                  * The LSB of the handler determines if we're going to
 396                  * be using THUMB or ARM mode for this signal handler.
 397                  */
 398                 thumb = handler & 1;
 399
 400                 /*
 401                  * Clear the If-Then Thumb-2 execution state.  ARM spec
 402                  * requires this to be all 000s in ARM mode.  Snapdragon
 403                  * S4/Krait misbehaves on a Thumb=>ARM signal transition
 404                  * without this.
 405                  *
 406                  * We must do this whenever we are running on a Thumb-2
 407                  * capable CPU, which includes ARMv6T2.  However, we elect
 408                  * to always do this to simplify the code; this field is
 409                  * marked UNK/SBZP for older architectures.
 410                  */
 411                 cpsr &= ~PSR_IT_MASK;
 412
 413                 if (thumb) {
 414                         cpsr |= PSR_T_BIT;
 415                 } else
 416                         cpsr &= ~PSR_T_BIT;
 417         }
 418 #endif
 419
 420         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 421                 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
 422                 if (fdpic) {
 423                         /*
 424                          * We need code to load the function descriptor.
 425                          * That code follows the standard sigreturn code
 426                          * (6 words), and is made of 3 + 2 words for each
 427                          * variant. The 4th copied word is the actual FD
 428                          * address that the assembly code expects.
 429                          */
 430                         idx = 6 + thumb * 3;
 431                         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 432                                 idx += 5;
 433                         if (__put_user(sigreturn_codes[idx],   rc  ) ||
 434                             __put_user(sigreturn_codes[idx+1], rc+1) ||
 435                             __put_user(sigreturn_codes[idx+2], rc+2) ||
 436                             __put_user(retcode,                rc+3))
 437                                 return 1;
 438                         goto rc_finish;
 439                 }
 440         } else {
 441                 idx = thumb << 1;
 442                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 443                         idx += 3;
 444
 445                 /*
 446                  * Put the sigreturn code on the stack no matter which return
 447                  * mechanism we use in order to remain ABI compliant
 448                  */
 449                 if (__put_user(sigreturn_codes[idx],   rc) ||
 450                     __put_user(sigreturn_codes[idx+1], rc+1))
 451                         return 1;
 452
 453 rc_finish:
 454 #ifdef CONFIG_MMU
 455                 if (cpsr & MODE32_BIT) {
 456                         struct mm_struct *mm = current->mm;
 457
 458                         /*
 459                          * 32-bit code can use the signal return page
 460                          * except when the MPU has protected the vectors
 461                          * page from PL0
 462                          */
 463                         retcode = mm->context.sigpage + signal_return_offset +
 464                                   (idx << 2) + thumb;
 465                 } else
 466 #endif
 467                 {
 468                         /*
 469                          * Ensure that the instruction cache sees
 470                          * the return code written onto the stack.
 471                          */
 472                         flush_icache_range((unsigned long)rc,
 473                                            (unsigned long)(rc + 3));
 474
 475                         retcode = ((unsigned long)rc) + thumb;
 476                 }
 477         }
 478
 479         regs->ARM_r0 = ksig->sig;
 480         regs->ARM_sp = (unsigned long)frame;
 481         regs->ARM_lr = retcode;
 482         regs->ARM_pc = handler;
 483         if (fdpic)
 484                 regs->ARM_r9 = handler_fdpic_GOT;
 485         regs->ARM_cpsr = cpsr;
 486
 487         return 0;
 488 }
 489
 490 static int
 491 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 492 {
 493         struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 494         int err = 0;
 495
 496         if (!frame)
 497                 return 1;
 498
 499         /*
 500          * Set uc.uc_flags to a value which sc.trap_no would never have.
 501          */
 502         err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
 503
 504         err |= setup_sigframe(frame, regs, set);
 505         if (err == 0)
 506                 err = setup_return(regs, ksig, frame->retcode, frame);
 507
 508         return err;
 509 }
 510
 511 static int
 512 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 513 {
 514         struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 515         int err = 0;
 516
 517         if (!frame)
 518                 return 1;
 519
 520         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 521
 522         err |= __put_user(0, &frame->sig.uc.uc_flags);
 523         err |= __put_user(NULL, &frame->sig.uc.uc_link);
 524
 525         err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
 526         err |= setup_sigframe(&frame->sig, regs, set);
 527         if (err == 0)
 528                 err = setup_return(regs, ksig, frame->sig.retcode, frame);
 529
 530         if (err == 0) {
 531                 /*
 532                  * For realtime signals we must also set the second and third
 533                  * arguments for the signal handler.
 534                  *   -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
 535                  */
 536                 regs->ARM_r1 = (unsigned long)&frame->info;
 537                 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
 538         }
 539
 540         return err;
 541 }
 542
 543 /*
 544  * OK, we're invoking a handler
 545  */
 546 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 547 {
 548         sigset_t *oldset = sigmask_to_save();
 549         int ret;
 550
 551         /*
 552          * Increment event counter and perform fixup for the pre-signal
 553          * frame.
 554          */
 555         rseq_signal_deliver(ksig, regs);
 556
 557         /*
 558          * Set up the stack frame
 559          */
 560         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 561                 ret = setup_rt_frame(ksig, oldset, regs);
 562         else
 563                 ret = setup_frame(ksig, oldset, regs);
 564
 565         /*
 566          * Check that the resulting registers are actually sane.
 567          */
 568         ret |= !valid_user_regs(regs);
 569
 570         signal_setup_done(ret, ksig, 0);
 571 }
 572
 573 /*
 574  * Note that 'init' is a special process: it doesn't get signals it doesn't
 575  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 576  * mistake.
 577  *
 578  * Note that we go through the signals twice: once to check the signals that
 579  * the kernel can handle, and then we build all the user-level signal handling
 580  * stack-frames in one go after that.
 581  */
 582 static int do_signal(struct pt_regs *regs, int syscall)
 583 {
 584         unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
 585         struct ksignal ksig;
 586         int restart = 0;
 587
 588         /*
 589          * If we were from a system call, check for system call restarting...
 590          */
 591         if (syscall) {
 592                 continue_addr = regs->ARM_pc;
 593                 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
 594                 retval = regs->ARM_r0;
 595
 596                 /*
 597                  * Prepare for system call restart.  We do this here so that a
 598                  * debugger will see the already changed PSW.
 599                  */
 600                 switch (retval) {
 601                 case -ERESTART_RESTARTBLOCK:
 602                         restart -= 2;
 603                 case -ERESTARTNOHAND:
 604                 case -ERESTARTSYS:
 605                 case -ERESTARTNOINTR:
 606                         restart++;
 607                         regs->ARM_r0 = regs->ARM_ORIG_r0;
 608                         regs->ARM_pc = restart_addr;
 609                         break;
 610                 }
 611         }
 612
 613         /*
 614          * Get the signal to deliver.  When running under ptrace, at this
 615          * point the debugger may change all our registers ...
 616          */
 617         /*
 618          * Depending on the signal settings we may need to revert the
 619          * decision to restart the system call.  But skip this if a
 620          * debugger has chosen to restart at a different PC.
 621          */
 622         if (get_signal(&ksig)) {
 623                 /* handler */
 624                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 625                         if (retval == -ERESTARTNOHAND ||
 626                             retval == -ERESTART_RESTARTBLOCK
 627                             || (retval == -ERESTARTSYS
 628                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 629                                 regs->ARM_r0 = -EINTR;
 630                                 regs->ARM_pc = continue_addr;
 631                         }
 632                 }
 633                 handle_signal(&ksig, regs);
 634         } else {
 635                 /* no handler */
 636                 restore_saved_sigmask();
 637                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 638                         regs->ARM_pc = continue_addr;
 639                         return restart;
 640                 }
 641         }
 642         return 0;
 643 }
 644
 645 asmlinkage int
 646 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 647 {
 648         /*
 649          * The assembly code enters us with IRQs off, but it hasn't
 650          * informed the tracing code of that for efficiency reasons.
 651          * Update the trace code with the current status.
 652          */
 653         trace_hardirqs_off();
 654         do {
 655                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 656                         schedule();
 657                 } else {
 658                         if (unlikely(!user_mode(regs)))
 659                                 return 0;
 660                         local_irq_enable();
 661                         if (thread_flags & _TIF_SIGPENDING) {
 662                                 int restart = do_signal(regs, syscall);
 663                                 if (unlikely(restart)) {
 664                                         /*
 665                                          * Restart without handlers.
 666                                          * Deal with it without leaving
 667                                          * the kernel space.
 668                                          */
 669                                         return restart;
 670                                 }
 671                                 syscall = 0;
 672                         } else if (thread_flags & _TIF_UPROBE) {
 673                                 uprobe_notify_resume(regs);
 674                         } else {
 675                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 676                                 tracehook_notify_resume(regs);
 677                                 rseq_handle_notify_resume(NULL, regs);
 678                         }
 679                 }
 680                 local_irq_disable();
 681                 thread_flags = current_thread_info()->flags;
 682         } while (thread_flags & _TIF_WORK_MASK);
 683         return 0;
 684 }
 685
 686 struct page *get_signal_page(void)
 687 {
 688         unsigned long ptr;
 689         unsigned offset;
 690         struct page *page;
 691         void *addr;
 692
 693         page = alloc_pages(GFP_KERNEL, 0);
 694
 695         if (!page)
 696                 return NULL;
 697
 698         addr = page_address(page);
 699
 700         /* Give the signal return code some randomness */
 701         offset = 0x200 + (get_random_int() & 0x7fc);
 702         signal_return_offset = offset;
 703
 704         /*
 705          * Copy signal return handlers into the vector page, and
 706          * set sigreturn to be a pointer to these.
 707          */
 708         memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
 709
 710         ptr = (unsigned long)addr + offset;
 711         flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
 712
 713         return page;
 714 }
 715
 716 /* Defer to generic check */
 717 asmlinkage void addr_limit_check_failed(void)
 718 {
 719         addr_limit_user_check();
 720 }
 721
 722 #ifdef CONFIG_DEBUG_RSEQ
 723 asmlinkage void do_rseq_syscall(struct pt_regs *regs)
 724 {
 725         rseq_syscall(regs);
 726 }
 727 #endif