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/signal.h>
  12 #include <linux/personality.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/tracehook.h>
  15
  16 #include <asm/elf.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/ucontext.h>
  19 #include <asm/unistd.h>
  20 #include <asm/vfp.h>
  21
  22 #include "signal.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 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 #ifdef CONFIG_CRUNCH
  49 static int preserve_crunch_context(struct crunch_sigframe __user *frame)
  50 {
  51         char kbuf[sizeof(*frame) + 8];
  52         struct crunch_sigframe *kframe;
  53
  54         /* the crunch context must be 64 bit aligned */
  55         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  56         kframe->magic = CRUNCH_MAGIC;
  57         kframe->size = CRUNCH_STORAGE_SIZE;
  58         crunch_task_copy(current_thread_info(), &kframe->storage);
  59         return __copy_to_user(frame, kframe, sizeof(*frame));
  60 }
  61
  62 static int restore_crunch_context(struct crunch_sigframe __user *frame)
  63 {
  64         char kbuf[sizeof(*frame) + 8];
  65         struct crunch_sigframe *kframe;
  66
  67         /* the crunch context must be 64 bit aligned */
  68         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  69         if (__copy_from_user(kframe, frame, sizeof(*frame)))
  70                 return -1;
  71         if (kframe->magic != CRUNCH_MAGIC ||
  72             kframe->size != CRUNCH_STORAGE_SIZE)
  73                 return -1;
  74         crunch_task_restore(current_thread_info(), &kframe->storage);
  75         return 0;
  76 }
  77 #endif
  78
  79 #ifdef CONFIG_IWMMXT
  80
  81 static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
  82 {
  83         char kbuf[sizeof(*frame) + 8];
  84         struct iwmmxt_sigframe *kframe;
  85
  86         /* the iWMMXt context must be 64 bit aligned */
  87         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  88         kframe->magic = IWMMXT_MAGIC;
  89         kframe->size = IWMMXT_STORAGE_SIZE;
  90         iwmmxt_task_copy(current_thread_info(), &kframe->storage);
  91         return __copy_to_user(frame, kframe, sizeof(*frame));
  92 }
  93
  94 static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
  95 {
  96         char kbuf[sizeof(*frame) + 8];
  97         struct iwmmxt_sigframe *kframe;
  98
  99         /* the iWMMXt context must be 64 bit aligned */
 100         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
 101         if (__copy_from_user(kframe, frame, sizeof(*frame)))
 102                 return -1;
 103         if (kframe->magic != IWMMXT_MAGIC ||
 104             kframe->size != IWMMXT_STORAGE_SIZE)
 105                 return -1;
 106         iwmmxt_task_restore(current_thread_info(), &kframe->storage);
 107         return 0;
 108 }
 109
 110 #endif
 111
 112 #ifdef CONFIG_VFP
 113
 114 static int preserve_vfp_context(struct vfp_sigframe __user *frame)
 115 {
 116         const unsigned long magic = VFP_MAGIC;
 117         const unsigned long size = VFP_STORAGE_SIZE;
 118         int err = 0;
 119
 120         __put_user_error(magic, &frame->magic, err);
 121         __put_user_error(size, &frame->size, err);
 122
 123         if (err)
 124                 return -EFAULT;
 125
 126         return vfp_preserve_user_clear_hwstate(&frame->ufp, &frame->ufp_exc);
 127 }
 128
 129 static int restore_vfp_context(struct vfp_sigframe __user *frame)
 130 {
 131         unsigned long magic;
 132         unsigned long size;
 133         int err = 0;
 134
 135         __get_user_error(magic, &frame->magic, err);
 136         __get_user_error(size, &frame->size, err);
 137
 138         if (err)
 139                 return -EFAULT;
 140         if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
 141                 return -EINVAL;
 142
 143         return vfp_restore_user_hwstate(&frame->ufp, &frame->ufp_exc);
 144 }
 145
 146 #endif
 147
 148 /*
 149  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
 150  */
 151 struct sigframe {
 152         struct ucontext uc;
 153         unsigned long retcode[2];
 154 };
 155
 156 struct rt_sigframe {
 157         struct siginfo info;
 158         struct sigframe sig;
 159 };
 160
 161 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
 162 {
 163         struct aux_sigframe __user *aux;
 164         sigset_t set;
 165         int err;
 166
 167         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 168         if (err == 0)
 169                 set_current_blocked(&set);
 170
 171         __get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
 172         __get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
 173         __get_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
 174         __get_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
 175         __get_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
 176         __get_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
 177         __get_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
 178         __get_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
 179         __get_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
 180         __get_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
 181         __get_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
 182         __get_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
 183         __get_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
 184         __get_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
 185         __get_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
 186         __get_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
 187         __get_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
 188
 189         err |= !valid_user_regs(regs);
 190
 191         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 192 #ifdef CONFIG_CRUNCH
 193         if (err == 0)
 194                 err |= restore_crunch_context(&aux->crunch);
 195 #endif
 196 #ifdef CONFIG_IWMMXT
 197         if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
 198                 err |= restore_iwmmxt_context(&aux->iwmmxt);
 199 #endif
 200 #ifdef CONFIG_VFP
 201         if (err == 0)
 202                 err |= restore_vfp_context(&aux->vfp);
 203 #endif
 204
 205         return err;
 206 }
 207
 208 asmlinkage int sys_sigreturn(struct pt_regs *regs)
 209 {
 210         struct sigframe __user *frame;
 211
 212         /* Always make any pending restarted system calls return -EINTR */
 213         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 214
 215         /*
 216          * Since we stacked the signal on a 64-bit boundary,
 217          * then 'sp' should be word aligned here.  If it's
 218          * not, then the user is trying to mess with us.
 219          */
 220         if (regs->ARM_sp & 7)
 221                 goto badframe;
 222
 223         frame = (struct sigframe __user *)regs->ARM_sp;
 224
 225         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 226                 goto badframe;
 227
 228         if (restore_sigframe(regs, frame))
 229                 goto badframe;
 230
 231         return regs->ARM_r0;
 232
 233 badframe:
 234         force_sig(SIGSEGV, current);
 235         return 0;
 236 }
 237
 238 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 239 {
 240         struct rt_sigframe __user *frame;
 241
 242         /* Always make any pending restarted system calls return -EINTR */
 243         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 244
 245         /*
 246          * Since we stacked the signal on a 64-bit boundary,
 247          * then 'sp' should be word aligned here.  If it's
 248          * not, then the user is trying to mess with us.
 249          */
 250         if (regs->ARM_sp & 7)
 251                 goto badframe;
 252
 253         frame = (struct rt_sigframe __user *)regs->ARM_sp;
 254
 255         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 256                 goto badframe;
 257
 258         if (restore_sigframe(regs, &frame->sig))
 259                 goto badframe;
 260
 261         if (restore_altstack(&frame->sig.uc.uc_stack))
 262                 goto badframe;
 263
 264         return regs->ARM_r0;
 265
 266 badframe:
 267         force_sig(SIGSEGV, current);
 268         return 0;
 269 }
 270
 271 static int
 272 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
 273 {
 274         struct aux_sigframe __user *aux;
 275         int err = 0;
 276
 277         __put_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
 278         __put_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
 279         __put_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
 280         __put_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
 281         __put_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
 282         __put_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
 283         __put_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
 284         __put_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
 285         __put_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
 286         __put_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
 287         __put_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
 288         __put_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
 289         __put_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
 290         __put_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
 291         __put_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
 292         __put_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
 293         __put_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
 294
 295         __put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no, err);
 296         __put_user_error(current->thread.error_code, &sf->uc.uc_mcontext.error_code, err);
 297         __put_user_error(current->thread.address, &sf->uc.uc_mcontext.fault_address, err);
 298         __put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);
 299
 300         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 301
 302         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 303 #ifdef CONFIG_CRUNCH
 304         if (err == 0)
 305                 err |= preserve_crunch_context(&aux->crunch);
 306 #endif
 307 #ifdef CONFIG_IWMMXT
 308         if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
 309                 err |= preserve_iwmmxt_context(&aux->iwmmxt);
 310 #endif
 311 #ifdef CONFIG_VFP
 312         if (err == 0)
 313                 err |= preserve_vfp_context(&aux->vfp);
 314 #endif
 315         __put_user_error(0, &aux->end_magic, err);
 316
 317         return err;
 318 }
 319
 320 static inline void __user *
 321 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
 322 {
 323         unsigned long sp = sigsp(regs->ARM_sp, ksig);
 324         void __user *frame;
 325
 326         /*
 327          * ATPCS B01 mandates 8-byte alignment
 328          */
 329         frame = (void __user *)((sp - framesize) & ~7);
 330
 331         /*
 332          * Check that we can actually write to the signal frame.
 333          */
 334         if (!access_ok(VERIFY_WRITE, frame, framesize))
 335                 frame = NULL;
 336
 337         return frame;
 338 }
 339
 340 /*
 341  * translate the signal
 342  */
 343 static inline int map_sig(int sig)
 344 {
 345         struct thread_info *thread = current_thread_info();
 346         if (sig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
 347                 sig = thread->exec_domain->signal_invmap[sig];
 348         return sig;
 349 }
 350
 351 static int
 352 setup_return(struct pt_regs *regs, struct ksignal *ksig,
 353              unsigned long __user *rc, void __user *frame)
 354 {
 355         unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
 356         unsigned long retcode;
 357         int thumb = 0;
 358         unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
 359
 360         cpsr |= PSR_ENDSTATE;
 361
 362         /*
 363          * Maybe we need to deliver a 32-bit signal to a 26-bit task.
 364          */
 365         if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
 366                 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
 367
 368 #ifdef CONFIG_ARM_THUMB
 369         if (elf_hwcap & HWCAP_THUMB) {
 370                 /*
 371                  * The LSB of the handler determines if we're going to
 372                  * be using THUMB or ARM mode for this signal handler.
 373                  */
 374                 thumb = handler & 1;
 375
 376                 if (thumb) {
 377                         cpsr |= PSR_T_BIT;
 378 #if __LINUX_ARM_ARCH__ >= 7
 379                         /* clear the If-Then Thumb-2 execution state */
 380                         cpsr &= ~PSR_IT_MASK;
 381 #endif
 382                 } else
 383                         cpsr &= ~PSR_T_BIT;
 384         }
 385 #endif
 386
 387         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 388                 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
 389         } else {
 390                 unsigned int idx = thumb << 1;
 391
 392                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 393                         idx += 3;
 394
 395                 /*
 396                  * Put the sigreturn code on the stack no matter which return
 397                  * mechanism we use in order to remain ABI compliant
 398                  */
 399                 if (__put_user(sigreturn_codes[idx],   rc) ||
 400                     __put_user(sigreturn_codes[idx+1], rc+1))
 401                         return 1;
 402
 403                 if ((cpsr & MODE32_BIT) && !IS_ENABLED(CONFIG_ARM_MPU)) {
 404                         /*
 405                          * 32-bit code can use the new high-page
 406                          * signal return code support except when the MPU has
 407                          * protected the vectors page from PL0
 408                          */
 409                         retcode = KERN_SIGRETURN_CODE + (idx << 2) + thumb;
 410                 } else {
 411                         /*
 412                          * Ensure that the instruction cache sees
 413                          * the return code written onto the stack.
 414                          */
 415                         flush_icache_range((unsigned long)rc,
 416                                            (unsigned long)(rc + 2));
 417
 418                         retcode = ((unsigned long)rc) + thumb;
 419                 }
 420         }
 421
 422         regs->ARM_r0 = map_sig(ksig->sig);
 423         regs->ARM_sp = (unsigned long)frame;
 424         regs->ARM_lr = retcode;
 425         regs->ARM_pc = handler;
 426         regs->ARM_cpsr = cpsr;
 427
 428         return 0;
 429 }
 430
 431 static int
 432 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 433 {
 434         struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 435         int err = 0;
 436
 437         if (!frame)
 438                 return 1;
 439
 440         /*
 441          * Set uc.uc_flags to a value which sc.trap_no would never have.
 442          */
 443         __put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);
 444
 445         err |= setup_sigframe(frame, regs, set);
 446         if (err == 0)
 447                 err = setup_return(regs, ksig, frame->retcode, frame);
 448
 449         return err;
 450 }
 451
 452 static int
 453 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 454 {
 455         struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 456         int err = 0;
 457
 458         if (!frame)
 459                 return 1;
 460
 461         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 462
 463         __put_user_error(0, &frame->sig.uc.uc_flags, err);
 464         __put_user_error(NULL, &frame->sig.uc.uc_link, err);
 465
 466         err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
 467         err |= setup_sigframe(&frame->sig, regs, set);
 468         if (err == 0)
 469                 err = setup_return(regs, ksig, frame->sig.retcode, frame);
 470
 471         if (err == 0) {
 472                 /*
 473                  * For realtime signals we must also set the second and third
 474                  * arguments for the signal handler.
 475                  *   -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
 476                  */
 477                 regs->ARM_r1 = (unsigned long)&frame->info;
 478                 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
 479         }
 480
 481         return err;
 482 }
 483
 484 /*
 485  * OK, we're invoking a handler
 486  */
 487 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 488 {
 489         sigset_t *oldset = sigmask_to_save();
 490         int ret;
 491
 492         /*
 493          * Set up the stack frame
 494          */
 495         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 496                 ret = setup_rt_frame(ksig, oldset, regs);
 497         else
 498                 ret = setup_frame(ksig, oldset, regs);
 499
 500         /*
 501          * Check that the resulting registers are actually sane.
 502          */
 503         ret |= !valid_user_regs(regs);
 504
 505         signal_setup_done(ret, ksig, 0);
 506 }
 507
 508 /*
 509  * Note that 'init' is a special process: it doesn't get signals it doesn't
 510  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 511  * mistake.
 512  *
 513  * Note that we go through the signals twice: once to check the signals that
 514  * the kernel can handle, and then we build all the user-level signal handling
 515  * stack-frames in one go after that.
 516  */
 517 static int do_signal(struct pt_regs *regs, int syscall)
 518 {
 519         unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
 520         struct ksignal ksig;
 521         int restart = 0;
 522
 523         /*
 524          * If we were from a system call, check for system call restarting...
 525          */
 526         if (syscall) {
 527                 continue_addr = regs->ARM_pc;
 528                 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
 529                 retval = regs->ARM_r0;
 530
 531                 /*
 532                  * Prepare for system call restart.  We do this here so that a
 533                  * debugger will see the already changed PSW.
 534                  */
 535                 switch (retval) {
 536                 case -ERESTART_RESTARTBLOCK:
 537                         restart -= 2;
 538                 case -ERESTARTNOHAND:
 539                 case -ERESTARTSYS:
 540                 case -ERESTARTNOINTR:
 541                         restart++;
 542                         regs->ARM_r0 = regs->ARM_ORIG_r0;
 543                         regs->ARM_pc = restart_addr;
 544                         break;
 545                 }
 546         }
 547
 548         /*
 549          * Get the signal to deliver.  When running under ptrace, at this
 550          * point the debugger may change all our registers ...
 551          */
 552         /*
 553          * Depending on the signal settings we may need to revert the
 554          * decision to restart the system call.  But skip this if a
 555          * debugger has chosen to restart at a different PC.
 556          */
 557         if (get_signal(&ksig)) {
 558                 /* handler */
 559                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 560                         if (retval == -ERESTARTNOHAND ||
 561                             retval == -ERESTART_RESTARTBLOCK
 562                             || (retval == -ERESTARTSYS
 563                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 564                                 regs->ARM_r0 = -EINTR;
 565                                 regs->ARM_pc = continue_addr;
 566                         }
 567                 }
 568                 handle_signal(&ksig, regs);
 569         } else {
 570                 /* no handler */
 571                 restore_saved_sigmask();
 572                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 573                         regs->ARM_pc = continue_addr;
 574                         return restart;
 575                 }
 576         }
 577         return 0;
 578 }
 579
 580 asmlinkage int
 581 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 582 {
 583         do {
 584                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 585                         schedule();
 586                 } else {
 587                         if (unlikely(!user_mode(regs)))
 588                                 return 0;
 589                         local_irq_enable();
 590                         if (thread_flags & _TIF_SIGPENDING) {
 591                                 int restart = do_signal(regs, syscall);
 592                                 if (unlikely(restart)) {
 593                                         /*
 594                                          * Restart without handlers.
 595                                          * Deal with it without leaving
 596                                          * the kernel space.
 597                                          */
 598                                         return restart;
 599                                 }
 600                                 syscall = 0;
 601                         } else {
 602                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 603                                 tracehook_notify_resume(regs);
 604                         }
 605                 }
 606                 local_irq_disable();
 607                 thread_flags = current_thread_info()->flags;
 608         } while (thread_flags & _TIF_WORK_MASK);
 609         return 0;
 610 }