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