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