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
  17 #include <asm/elf.h>
  18 #include <asm/cacheflush.h>
  19 #include <asm/traps.h>
  20 #include <asm/ucontext.h>
  21 #include <asm/unistd.h>
  22 #include <asm/vfp.h>
  23
  24 /*
  25  * For ARM syscalls, we encode the syscall number into the instruction.
  26  */
  27 #define SWI_SYS_SIGRETURN       (0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE))
  28 #define SWI_SYS_RT_SIGRETURN    (0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE))
  29
  30 /*
  31  * With EABI, the syscall number has to be loaded into r7.
  32  */
  33 #define MOV_R7_NR_SIGRETURN     (0xe3a07000 | (__NR_sigreturn - __NR_SYSCALL_BASE))
  34 #define MOV_R7_NR_RT_SIGRETURN  (0xe3a07000 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
  35
  36 /*
  37  * For Thumb syscalls, we pass the syscall number via r7.  We therefore
  38  * need two 16-bit instructions.
  39  */
  40 #define SWI_THUMB_SIGRETURN     (0xdf00 << 16 | 0x2700 | (__NR_sigreturn - __NR_SYSCALL_BASE))
  41 #define SWI_THUMB_RT_SIGRETURN  (0xdf00 << 16 | 0x2700 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
  42
  43 static const unsigned long sigreturn_codes[7] = {
  44         MOV_R7_NR_SIGRETURN,    SWI_SYS_SIGRETURN,    SWI_THUMB_SIGRETURN,
  45         MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
  46 };
  47
  48 static unsigned long signal_return_offset;
  49
  50 #ifdef CONFIG_CRUNCH
  51 static int preserve_crunch_context(struct crunch_sigframe __user *frame)
  52 {
  53         char kbuf[sizeof(*frame) + 8];
  54         struct crunch_sigframe *kframe;
  55
  56         /* the crunch context must be 64 bit aligned */
  57         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  58         kframe->magic = CRUNCH_MAGIC;
  59         kframe->size = CRUNCH_STORAGE_SIZE;
  60         crunch_task_copy(current_thread_info(), &kframe->storage);
  61         return __copy_to_user(frame, kframe, sizeof(*frame));
  62 }
  63
  64 static int restore_crunch_context(struct crunch_sigframe __user *frame)
  65 {
  66         char kbuf[sizeof(*frame) + 8];
  67         struct crunch_sigframe *kframe;
  68
  69         /* the crunch context must be 64 bit aligned */
  70         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  71         if (__copy_from_user(kframe, frame, sizeof(*frame)))
  72                 return -1;
  73         if (kframe->magic != CRUNCH_MAGIC ||
  74             kframe->size != CRUNCH_STORAGE_SIZE)
  75                 return -1;
  76         crunch_task_restore(current_thread_info(), &kframe->storage);
  77         return 0;
  78 }
  79 #endif
  80
  81 #ifdef CONFIG_IWMMXT
  82
  83 static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
  84 {
  85         char kbuf[sizeof(*frame) + 8];
  86         struct iwmmxt_sigframe *kframe;
  87
  88         /* the iWMMXt context must be 64 bit aligned */
  89         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  90         kframe->magic = IWMMXT_MAGIC;
  91         kframe->size = IWMMXT_STORAGE_SIZE;
  92         iwmmxt_task_copy(current_thread_info(), &kframe->storage);
  93         return __copy_to_user(frame, kframe, sizeof(*frame));
  94 }
  95
  96 static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
  97 {
  98         char kbuf[sizeof(*frame) + 8];
  99         struct iwmmxt_sigframe *kframe;
 100
 101         /* the iWMMXt context must be 64 bit aligned */
 102         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
 103         if (__copy_from_user(kframe, frame, sizeof(*frame)))
 104                 return -1;
 105         if (kframe->magic != IWMMXT_MAGIC ||
 106             kframe->size != IWMMXT_STORAGE_SIZE)
 107                 return -1;
 108         iwmmxt_task_restore(current_thread_info(), &kframe->storage);
 109         return 0;
 110 }
 111
 112 #endif
 113
 114 #ifdef CONFIG_VFP
 115
 116 static int preserve_vfp_context(struct vfp_sigframe __user *frame)
 117 {
 118         const unsigned long magic = VFP_MAGIC;
 119         const unsigned long size = VFP_STORAGE_SIZE;
 120         int err = 0;
 121
 122         __put_user_error(magic, &frame->magic, err);
 123         __put_user_error(size, &frame->size, err);
 124
 125         if (err)
 126                 return -EFAULT;
 127
 128         return vfp_preserve_user_clear_hwstate(&frame->ufp, &frame->ufp_exc);
 129 }
 130
 131 static int restore_vfp_context(struct vfp_sigframe __user *frame)
 132 {
 133         unsigned long magic;
 134         unsigned long size;
 135         int err = 0;
 136
 137         __get_user_error(magic, &frame->magic, err);
 138         __get_user_error(size, &frame->size, err);
 139
 140         if (err)
 141                 return -EFAULT;
 142         if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
 143                 return -EINVAL;
 144
 145         return vfp_restore_user_hwstate(&frame->ufp, &frame->ufp_exc);
 146 }
 147
 148 #endif
 149
 150 /*
 151  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
 152  */
 153 struct sigframe {
 154         struct ucontext uc;
 155         unsigned long retcode[2];
 156 };
 157
 158 struct rt_sigframe {
 159         struct siginfo info;
 160         struct sigframe sig;
 161 };
 162
 163 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
 164 {
 165         struct aux_sigframe __user *aux;
 166         sigset_t set;
 167         int err;
 168
 169         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 170         if (err == 0)
 171                 set_current_blocked(&set);
 172
 173         __get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
 174         __get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
 175         __get_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
 176         __get_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
 177         __get_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
 178         __get_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
 179         __get_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
 180         __get_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
 181         __get_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
 182         __get_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
 183         __get_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
 184         __get_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
 185         __get_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
 186         __get_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
 187         __get_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
 188         __get_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
 189         __get_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
 190
 191         err |= !valid_user_regs(regs);
 192
 193         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 194 #ifdef CONFIG_CRUNCH
 195         if (err == 0)
 196                 err |= restore_crunch_context(&aux->crunch);
 197 #endif
 198 #ifdef CONFIG_IWMMXT
 199         if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
 200                 err |= restore_iwmmxt_context(&aux->iwmmxt);
 201 #endif
 202 #ifdef CONFIG_VFP
 203         if (err == 0)
 204                 err |= restore_vfp_context(&aux->vfp);
 205 #endif
 206
 207         return err;
 208 }
 209
 210 asmlinkage int sys_sigreturn(struct pt_regs *regs)
 211 {
 212         struct sigframe __user *frame;
 213
 214         /* Always make any pending restarted system calls return -EINTR */
 215         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 216
 217         /*
 218          * Since we stacked the signal on a 64-bit boundary,
 219          * then 'sp' should be word aligned here.  If it's
 220          * not, then the user is trying to mess with us.
 221          */
 222         if (regs->ARM_sp & 7)
 223                 goto badframe;
 224
 225         frame = (struct sigframe __user *)regs->ARM_sp;
 226
 227         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 228                 goto badframe;
 229
 230         if (restore_sigframe(regs, frame))
 231                 goto badframe;
 232
 233         return regs->ARM_r0;
 234
 235 badframe:
 236         force_sig(SIGSEGV, current);
 237         return 0;
 238 }
 239
 240 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 241 {
 242         struct rt_sigframe __user *frame;
 243
 244         /* Always make any pending restarted system calls return -EINTR */
 245         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 246
 247         /*
 248          * Since we stacked the signal on a 64-bit boundary,
 249          * then 'sp' should be word aligned here.  If it's
 250          * not, then the user is trying to mess with us.
 251          */
 252         if (regs->ARM_sp & 7)
 253                 goto badframe;
 254
 255         frame = (struct rt_sigframe __user *)regs->ARM_sp;
 256
 257         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 258                 goto badframe;
 259
 260         if (restore_sigframe(regs, &frame->sig))
 261                 goto badframe;
 262
 263         if (restore_altstack(&frame->sig.uc.uc_stack))
 264                 goto badframe;
 265
 266         return regs->ARM_r0;
 267
 268 badframe:
 269         force_sig(SIGSEGV, current);
 270         return 0;
 271 }
 272
 273 static int
 274 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
 275 {
 276         struct aux_sigframe __user *aux;
 277         int err = 0;
 278
 279         __put_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
 280         __put_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
 281         __put_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
 282         __put_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
 283         __put_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
 284         __put_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
 285         __put_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
 286         __put_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
 287         __put_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
 288         __put_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
 289         __put_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
 290         __put_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
 291         __put_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
 292         __put_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
 293         __put_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
 294         __put_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
 295         __put_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
 296
 297         __put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no, err);
 298         __put_user_error(current->thread.error_code, &sf->uc.uc_mcontext.error_code, err);
 299         __put_user_error(current->thread.address, &sf->uc.uc_mcontext.fault_address, err);
 300         __put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);
 301
 302         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 303
 304         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 305 #ifdef CONFIG_CRUNCH
 306         if (err == 0)
 307                 err |= preserve_crunch_context(&aux->crunch);
 308 #endif
 309 #ifdef CONFIG_IWMMXT
 310         if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
 311                 err |= preserve_iwmmxt_context(&aux->iwmmxt);
 312 #endif
 313 #ifdef CONFIG_VFP
 314         if (err == 0)
 315                 err |= preserve_vfp_context(&aux->vfp);
 316 #endif
 317         __put_user_error(0, &aux->end_magic, err);
 318
 319         return err;
 320 }
 321
 322 static inline void __user *
 323 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
 324 {
 325         unsigned long sp = sigsp(regs->ARM_sp, ksig);
 326         void __user *frame;
 327
 328         /*
 329          * ATPCS B01 mandates 8-byte alignment
 330          */
 331         frame = (void __user *)((sp - framesize) & ~7);
 332
 333         /*
 334          * Check that we can actually write to the signal frame.
 335          */
 336         if (!access_ok(VERIFY_WRITE, frame, framesize))
 337                 frame = NULL;
 338
 339         return frame;
 340 }
 341
 342 /*
 343  * translate the signal
 344  */
 345 static inline int map_sig(int sig)
 346 {
 347         struct thread_info *thread = current_thread_info();
 348         if (sig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
 349                 sig = thread->exec_domain->signal_invmap[sig];
 350         return sig;
 351 }
 352
 353 static int
 354 setup_return(struct pt_regs *regs, struct ksignal *ksig,
 355              unsigned long __user *rc, void __user *frame)
 356 {
 357         unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
 358         unsigned long retcode;
 359         int thumb = 0;
 360         unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
 361
 362         cpsr |= PSR_ENDSTATE;
 363
 364         /*
 365          * Maybe we need to deliver a 32-bit signal to a 26-bit task.
 366          */
 367         if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
 368                 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
 369
 370 #ifdef CONFIG_ARM_THUMB
 371         if (elf_hwcap & HWCAP_THUMB) {
 372                 /*
 373                  * The LSB of the handler determines if we're going to
 374                  * be using THUMB or ARM mode for this signal handler.
 375                  */
 376                 thumb = handler & 1;
 377
 378                 if (thumb) {
 379                         cpsr |= PSR_T_BIT;
 380 #if __LINUX_ARM_ARCH__ >= 7
 381                         /* clear the If-Then Thumb-2 execution state */
 382                         cpsr &= ~PSR_IT_MASK;
 383 #endif
 384                 } else
 385                         cpsr &= ~PSR_T_BIT;
 386         }
 387 #endif
 388
 389         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 390                 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
 391         } else {
 392                 unsigned int idx = thumb << 1;
 393
 394                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 395                         idx += 3;
 396
 397                 /*
 398                  * Put the sigreturn code on the stack no matter which return
 399                  * mechanism we use in order to remain ABI compliant
 400                  */
 401                 if (__put_user(sigreturn_codes[idx],   rc) ||
 402                     __put_user(sigreturn_codes[idx+1], rc+1))
 403                         return 1;
 404
 405 #ifdef CONFIG_MMU
 406                 if (cpsr & MODE32_BIT) {
 407                         struct mm_struct *mm = current->mm;
 408
 409                         /*
 410                          * 32-bit code can use the signal return page
 411                          * except when the MPU has protected the vectors
 412                          * page from PL0
 413                          */
 414                         retcode = mm->context.sigpage + signal_return_offset +
 415                                   (idx << 2) + thumb;
 416                 } else
 417 #endif
 418                 {
 419                         /*
 420                          * Ensure that the instruction cache sees
 421                          * the return code written onto the stack.
 422                          */
 423                         flush_icache_range((unsigned long)rc,
 424                                            (unsigned long)(rc + 2));
 425
 426                         retcode = ((unsigned long)rc) + thumb;
 427                 }
 428         }
 429
 430         regs->ARM_r0 = map_sig(ksig->sig);
 431         regs->ARM_sp = (unsigned long)frame;
 432         regs->ARM_lr = retcode;
 433         regs->ARM_pc = handler;
 434         regs->ARM_cpsr = cpsr;
 435
 436         return 0;
 437 }
 438
 439 static int
 440 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 441 {
 442         struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 443         int err = 0;
 444
 445         if (!frame)
 446                 return 1;
 447
 448         /*
 449          * Set uc.uc_flags to a value which sc.trap_no would never have.
 450          */
 451         __put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);
 452
 453         err |= setup_sigframe(frame, regs, set);
 454         if (err == 0)
 455                 err = setup_return(regs, ksig, frame->retcode, frame);
 456
 457         return err;
 458 }
 459
 460 static int
 461 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 462 {
 463         struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 464         int err = 0;
 465
 466         if (!frame)
 467                 return 1;
 468
 469         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 470
 471         __put_user_error(0, &frame->sig.uc.uc_flags, err);
 472         __put_user_error(NULL, &frame->sig.uc.uc_link, err);
 473
 474         err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
 475         err |= setup_sigframe(&frame->sig, regs, set);
 476         if (err == 0)
 477                 err = setup_return(regs, ksig, frame->sig.retcode, frame);
 478
 479         if (err == 0) {
 480                 /*
 481                  * For realtime signals we must also set the second and third
 482                  * arguments for the signal handler.
 483                  *   -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
 484                  */
 485                 regs->ARM_r1 = (unsigned long)&frame->info;
 486                 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
 487         }
 488
 489         return err;
 490 }
 491
 492 /*
 493  * OK, we're invoking a handler
 494  */
 495 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 496 {
 497         sigset_t *oldset = sigmask_to_save();
 498         int ret;
 499
 500         /*
 501          * Set up the stack frame
 502          */
 503         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 504                 ret = setup_rt_frame(ksig, oldset, regs);
 505         else
 506                 ret = setup_frame(ksig, oldset, regs);
 507
 508         /*
 509          * Check that the resulting registers are actually sane.
 510          */
 511         ret |= !valid_user_regs(regs);
 512
 513         signal_setup_done(ret, ksig, 0);
 514 }
 515
 516 /*
 517  * Note that 'init' is a special process: it doesn't get signals it doesn't
 518  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 519  * mistake.
 520  *
 521  * Note that we go through the signals twice: once to check the signals that
 522  * the kernel can handle, and then we build all the user-level signal handling
 523  * stack-frames in one go after that.
 524  */
 525 static int do_signal(struct pt_regs *regs, int syscall)
 526 {
 527         unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
 528         struct ksignal ksig;
 529         int restart = 0;
 530
 531         /*
 532          * If we were from a system call, check for system call restarting...
 533          */
 534         if (syscall) {
 535                 continue_addr = regs->ARM_pc;
 536                 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
 537                 retval = regs->ARM_r0;
 538
 539                 /*
 540                  * Prepare for system call restart.  We do this here so that a
 541                  * debugger will see the already changed PSW.
 542                  */
 543                 switch (retval) {
 544                 case -ERESTART_RESTARTBLOCK:
 545                         restart -= 2;
 546                 case -ERESTARTNOHAND:
 547                 case -ERESTARTSYS:
 548                 case -ERESTARTNOINTR:
 549                         restart++;
 550                         regs->ARM_r0 = regs->ARM_ORIG_r0;
 551                         regs->ARM_pc = restart_addr;
 552                         break;
 553                 }
 554         }
 555
 556         /*
 557          * Get the signal to deliver.  When running under ptrace, at this
 558          * point the debugger may change all our registers ...
 559          */
 560         /*
 561          * Depending on the signal settings we may need to revert the
 562          * decision to restart the system call.  But skip this if a
 563          * debugger has chosen to restart at a different PC.
 564          */
 565         if (get_signal(&ksig)) {
 566                 /* handler */
 567                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 568                         if (retval == -ERESTARTNOHAND ||
 569                             retval == -ERESTART_RESTARTBLOCK
 570                             || (retval == -ERESTARTSYS
 571                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 572                                 regs->ARM_r0 = -EINTR;
 573                                 regs->ARM_pc = continue_addr;
 574                         }
 575                 }
 576                 handle_signal(&ksig, regs);
 577         } else {
 578                 /* no handler */
 579                 restore_saved_sigmask();
 580                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 581                         regs->ARM_pc = continue_addr;
 582                         return restart;
 583                 }
 584         }
 585         return 0;
 586 }
 587
 588 asmlinkage int
 589 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 590 {
 591         do {
 592                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 593                         schedule();
 594                 } else {
 595                         if (unlikely(!user_mode(regs)))
 596                                 return 0;
 597                         local_irq_enable();
 598                         if (thread_flags & _TIF_SIGPENDING) {
 599                                 int restart = do_signal(regs, syscall);
 600                                 if (unlikely(restart)) {
 601                                         /*
 602                                          * Restart without handlers.
 603                                          * Deal with it without leaving
 604                                          * the kernel space.
 605                                          */
 606                                         return restart;
 607                                 }
 608                                 syscall = 0;
 609                         } else {
 610                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 611                                 tracehook_notify_resume(regs);
 612                         }
 613                 }
 614                 local_irq_disable();
 615                 thread_flags = current_thread_info()->flags;
 616         } while (thread_flags & _TIF_WORK_MASK);
 617         return 0;
 618 }
 619
 620 struct page *get_signal_page(void)
 621 {
 622         unsigned long ptr;
 623         unsigned offset;
 624         struct page *page;
 625         void *addr;
 626
 627         page = alloc_pages(GFP_KERNEL, 0);
 628
 629         if (!page)
 630                 return NULL;
 631
 632         addr = page_address(page);
 633
 634         /* Give the signal return code some randomness */
 635         offset = 0x200 + (get_random_int() & 0x7fc);
 636         signal_return_offset = offset;
 637
 638         /*
 639          * Copy signal return handlers into the vector page, and
 640          * set sigreturn to be a pointer to these.
 641          */
 642         memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
 643
 644         ptr = (unsigned long)addr + offset;
 645         flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
 646
 647         return page;
 648 }