1 /* 2 * linux/arch/arm/kernel/signal.c 3 * 4 * Copyright (C) 1995-2002 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/freezer.h> 14 #include <linux/uaccess.h> 15 16 #include <asm/elf.h> 17 #include <asm/cacheflush.h> 18 #include <asm/ucontext.h> 19 #include <asm/unistd.h> 20 21 #include "ptrace.h" 22 #include "signal.h" 23 24 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP))) 25 26 /* 27 * For ARM syscalls, we encode the syscall number into the instruction. 28 */ 29 #define SWI_SYS_SIGRETURN (0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)) 30 #define SWI_SYS_RT_SIGRETURN (0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)) 31 32 /* 33 * With EABI, the syscall number has to be loaded into r7. 34 */ 35 #define MOV_R7_NR_SIGRETURN (0xe3a07000 | (__NR_sigreturn - __NR_SYSCALL_BASE)) 36 #define MOV_R7_NR_RT_SIGRETURN (0xe3a07000 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE)) 37 38 /* 39 * For Thumb syscalls, we pass the syscall number via r7. We therefore 40 * need two 16-bit instructions. 41 */ 42 #define SWI_THUMB_SIGRETURN (0xdf00 << 16 | 0x2700 | (__NR_sigreturn - __NR_SYSCALL_BASE)) 43 #define SWI_THUMB_RT_SIGRETURN (0xdf00 << 16 | 0x2700 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE)) 44 45 const unsigned long sigreturn_codes[7] = { 46 MOV_R7_NR_SIGRETURN, SWI_SYS_SIGRETURN, SWI_THUMB_SIGRETURN, 47 MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN, 48 }; 49 50 static int do_signal(sigset_t *oldset, struct pt_regs * regs, int syscall); 51 52 /* 53 * atomically swap in the new signal mask, and wait for a signal. 54 */ 55 asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, old_sigset_t mask, struct pt_regs *regs) 56 { 57 sigset_t saveset; 58 59 mask &= _BLOCKABLE; 60 spin_lock_irq(¤t->sighand->siglock); 61 saveset = current->blocked; 62 siginitset(¤t->blocked, mask); 63 recalc_sigpending(); 64 spin_unlock_irq(¤t->sighand->siglock); 65 regs->ARM_r0 = -EINTR; 66 67 while (1) { 68 current->state = TASK_INTERRUPTIBLE; 69 schedule(); 70 if (do_signal(&saveset, regs, 0)) 71 return regs->ARM_r0; 72 } 73 } 74 75 asmlinkage int 76 sys_rt_sigsuspend(sigset_t __user *unewset, size_t sigsetsize, struct pt_regs *regs) 77 { 78 sigset_t saveset, newset; 79 80 /* XXX: Don't preclude handling different sized sigset_t's. */ 81 if (sigsetsize != sizeof(sigset_t)) 82 return -EINVAL; 83 84 if (copy_from_user(&newset, unewset, sizeof(newset))) 85 return -EFAULT; 86 sigdelsetmask(&newset, ~_BLOCKABLE); 87 88 spin_lock_irq(¤t->sighand->siglock); 89 saveset = current->blocked; 90 current->blocked = newset; 91 recalc_sigpending(); 92 spin_unlock_irq(¤t->sighand->siglock); 93 regs->ARM_r0 = -EINTR; 94 95 while (1) { 96 current->state = TASK_INTERRUPTIBLE; 97 schedule(); 98 if (do_signal(&saveset, regs, 0)) 99 return regs->ARM_r0; 100 } 101 } 102 103 asmlinkage int 104 sys_sigaction(int sig, const struct old_sigaction __user *act, 105 struct old_sigaction __user *oact) 106 { 107 struct k_sigaction new_ka, old_ka; 108 int ret; 109 110 if (act) { 111 old_sigset_t mask; 112 if (!access_ok(VERIFY_READ, act, sizeof(*act)) || 113 __get_user(new_ka.sa.sa_handler, &act->sa_handler) || 114 __get_user(new_ka.sa.sa_restorer, &act->sa_restorer)) 115 return -EFAULT; 116 __get_user(new_ka.sa.sa_flags, &act->sa_flags); 117 __get_user(mask, &act->sa_mask); 118 siginitset(&new_ka.sa.sa_mask, mask); 119 } 120 121 ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL); 122 123 if (!ret && oact) { 124 if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) || 125 __put_user(old_ka.sa.sa_handler, &oact->sa_handler) || 126 __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer)) 127 return -EFAULT; 128 __put_user(old_ka.sa.sa_flags, &oact->sa_flags); 129 __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask); 130 } 131 132 return ret; 133 } 134 135 #ifdef CONFIG_CRUNCH 136 static int preserve_crunch_context(struct crunch_sigframe *frame) 137 { 138 char kbuf[sizeof(*frame) + 8]; 139 struct crunch_sigframe *kframe; 140 141 /* the crunch context must be 64 bit aligned */ 142 kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7); 143 kframe->magic = CRUNCH_MAGIC; 144 kframe->size = CRUNCH_STORAGE_SIZE; 145 crunch_task_copy(current_thread_info(), &kframe->storage); 146 return __copy_to_user(frame, kframe, sizeof(*frame)); 147 } 148 149 static int restore_crunch_context(struct crunch_sigframe *frame) 150 { 151 char kbuf[sizeof(*frame) + 8]; 152 struct crunch_sigframe *kframe; 153 154 /* the crunch context must be 64 bit aligned */ 155 kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7); 156 if (__copy_from_user(kframe, frame, sizeof(*frame))) 157 return -1; 158 if (kframe->magic != CRUNCH_MAGIC || 159 kframe->size != CRUNCH_STORAGE_SIZE) 160 return -1; 161 crunch_task_restore(current_thread_info(), &kframe->storage); 162 return 0; 163 } 164 #endif 165 166 #ifdef CONFIG_IWMMXT 167 168 static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame) 169 { 170 char kbuf[sizeof(*frame) + 8]; 171 struct iwmmxt_sigframe *kframe; 172 173 /* the iWMMXt context must be 64 bit aligned */ 174 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7); 175 kframe->magic = IWMMXT_MAGIC; 176 kframe->size = IWMMXT_STORAGE_SIZE; 177 iwmmxt_task_copy(current_thread_info(), &kframe->storage); 178 return __copy_to_user(frame, kframe, sizeof(*frame)); 179 } 180 181 static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame) 182 { 183 char kbuf[sizeof(*frame) + 8]; 184 struct iwmmxt_sigframe *kframe; 185 186 /* the iWMMXt context must be 64 bit aligned */ 187 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7); 188 if (__copy_from_user(kframe, frame, sizeof(*frame))) 189 return -1; 190 if (kframe->magic != IWMMXT_MAGIC || 191 kframe->size != IWMMXT_STORAGE_SIZE) 192 return -1; 193 iwmmxt_task_restore(current_thread_info(), &kframe->storage); 194 return 0; 195 } 196 197 #endif 198 199 /* 200 * Do a signal return; undo the signal stack. These are aligned to 64-bit. 201 */ 202 struct sigframe { 203 struct ucontext uc; 204 unsigned long retcode[2]; 205 }; 206 207 struct rt_sigframe { 208 struct siginfo info; 209 struct sigframe sig; 210 }; 211 212 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf) 213 { 214 struct aux_sigframe __user *aux; 215 sigset_t set; 216 int err; 217 218 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); 219 if (err == 0) { 220 sigdelsetmask(&set, ~_BLOCKABLE); 221 spin_lock_irq(¤t->sighand->siglock); 222 current->blocked = set; 223 recalc_sigpending(); 224 spin_unlock_irq(¤t->sighand->siglock); 225 } 226 227 __get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err); 228 __get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err); 229 __get_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err); 230 __get_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err); 231 __get_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err); 232 __get_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err); 233 __get_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err); 234 __get_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err); 235 __get_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err); 236 __get_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err); 237 __get_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err); 238 __get_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err); 239 __get_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err); 240 __get_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err); 241 __get_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err); 242 __get_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err); 243 __get_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err); 244 245 err |= !valid_user_regs(regs); 246 247 aux = (struct aux_sigframe __user *) sf->uc.uc_regspace; 248 #ifdef CONFIG_CRUNCH 249 if (err == 0) 250 err |= restore_crunch_context(&aux->crunch); 251 #endif 252 #ifdef CONFIG_IWMMXT 253 if (err == 0 && test_thread_flag(TIF_USING_IWMMXT)) 254 err |= restore_iwmmxt_context(&aux->iwmmxt); 255 #endif 256 #ifdef CONFIG_VFP 257 // if (err == 0) 258 // err |= vfp_restore_state(&sf->aux.vfp); 259 #endif 260 261 return err; 262 } 263 264 asmlinkage int sys_sigreturn(struct pt_regs *regs) 265 { 266 struct sigframe __user *frame; 267 268 /* Always make any pending restarted system calls return -EINTR */ 269 current_thread_info()->restart_block.fn = do_no_restart_syscall; 270 271 /* 272 * Since we stacked the signal on a 64-bit boundary, 273 * then 'sp' should be word aligned here. If it's 274 * not, then the user is trying to mess with us. 275 */ 276 if (regs->ARM_sp & 7) 277 goto badframe; 278 279 frame = (struct sigframe __user *)regs->ARM_sp; 280 281 if (!access_ok(VERIFY_READ, frame, sizeof (*frame))) 282 goto badframe; 283 284 if (restore_sigframe(regs, frame)) 285 goto badframe; 286 287 single_step_trap(current); 288 289 return regs->ARM_r0; 290 291 badframe: 292 force_sig(SIGSEGV, current); 293 return 0; 294 } 295 296 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs) 297 { 298 struct rt_sigframe __user *frame; 299 300 /* Always make any pending restarted system calls return -EINTR */ 301 current_thread_info()->restart_block.fn = do_no_restart_syscall; 302 303 /* 304 * Since we stacked the signal on a 64-bit boundary, 305 * then 'sp' should be word aligned here. If it's 306 * not, then the user is trying to mess with us. 307 */ 308 if (regs->ARM_sp & 7) 309 goto badframe; 310 311 frame = (struct rt_sigframe __user *)regs->ARM_sp; 312 313 if (!access_ok(VERIFY_READ, frame, sizeof (*frame))) 314 goto badframe; 315 316 if (restore_sigframe(regs, &frame->sig)) 317 goto badframe; 318 319 if (do_sigaltstack(&frame->sig.uc.uc_stack, NULL, regs->ARM_sp) == -EFAULT) 320 goto badframe; 321 322 single_step_trap(current); 323 324 return regs->ARM_r0; 325 326 badframe: 327 force_sig(SIGSEGV, current); 328 return 0; 329 } 330 331 static int 332 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set) 333 { 334 struct aux_sigframe __user *aux; 335 int err = 0; 336 337 __put_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err); 338 __put_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err); 339 __put_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err); 340 __put_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err); 341 __put_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err); 342 __put_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err); 343 __put_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err); 344 __put_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err); 345 __put_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err); 346 __put_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err); 347 __put_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err); 348 __put_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err); 349 __put_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err); 350 __put_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err); 351 __put_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err); 352 __put_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err); 353 __put_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err); 354 355 __put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no, err); 356 __put_user_error(current->thread.error_code, &sf->uc.uc_mcontext.error_code, err); 357 __put_user_error(current->thread.address, &sf->uc.uc_mcontext.fault_address, err); 358 __put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err); 359 360 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set)); 361 362 aux = (struct aux_sigframe __user *) sf->uc.uc_regspace; 363 #ifdef CONFIG_CRUNCH 364 if (err == 0) 365 err |= preserve_crunch_context(&aux->crunch); 366 #endif 367 #ifdef CONFIG_IWMMXT 368 if (err == 0 && test_thread_flag(TIF_USING_IWMMXT)) 369 err |= preserve_iwmmxt_context(&aux->iwmmxt); 370 #endif 371 #ifdef CONFIG_VFP 372 // if (err == 0) 373 // err |= vfp_save_state(&sf->aux.vfp); 374 #endif 375 __put_user_error(0, &aux->end_magic, err); 376 377 return err; 378 } 379 380 static inline void __user * 381 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize) 382 { 383 unsigned long sp = regs->ARM_sp; 384 void __user *frame; 385 386 /* 387 * This is the X/Open sanctioned signal stack switching. 388 */ 389 if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp)) 390 sp = current->sas_ss_sp + current->sas_ss_size; 391 392 /* 393 * ATPCS B01 mandates 8-byte alignment 394 */ 395 frame = (void __user *)((sp - framesize) & ~7); 396 397 /* 398 * Check that we can actually write to the signal frame. 399 */ 400 if (!access_ok(VERIFY_WRITE, frame, framesize)) 401 frame = NULL; 402 403 return frame; 404 } 405 406 static int 407 setup_return(struct pt_regs *regs, struct k_sigaction *ka, 408 unsigned long __user *rc, void __user *frame, int usig) 409 { 410 unsigned long handler = (unsigned long)ka->sa.sa_handler; 411 unsigned long retcode; 412 int thumb = 0; 413 unsigned long cpsr = regs->ARM_cpsr & ~PSR_f; 414 415 /* 416 * Maybe we need to deliver a 32-bit signal to a 26-bit task. 417 */ 418 if (ka->sa.sa_flags & SA_THIRTYTWO) 419 cpsr = (cpsr & ~MODE_MASK) | USR_MODE; 420 421 #ifdef CONFIG_ARM_THUMB 422 if (elf_hwcap & HWCAP_THUMB) { 423 /* 424 * The LSB of the handler determines if we're going to 425 * be using THUMB or ARM mode for this signal handler. 426 */ 427 thumb = handler & 1; 428 429 if (thumb) { 430 cpsr |= PSR_T_BIT; 431 #if __LINUX_ARM_ARCH__ >= 7 432 /* clear the If-Then Thumb-2 execution state */ 433 cpsr &= ~PSR_IT_MASK; 434 #endif 435 } else 436 cpsr &= ~PSR_T_BIT; 437 } 438 #endif 439 440 if (ka->sa.sa_flags & SA_RESTORER) { 441 retcode = (unsigned long)ka->sa.sa_restorer; 442 } else { 443 unsigned int idx = thumb << 1; 444 445 if (ka->sa.sa_flags & SA_SIGINFO) 446 idx += 3; 447 448 if (__put_user(sigreturn_codes[idx], rc) || 449 __put_user(sigreturn_codes[idx+1], rc+1)) 450 return 1; 451 452 if (cpsr & MODE32_BIT) { 453 /* 454 * 32-bit code can use the new high-page 455 * signal return code support. 456 */ 457 retcode = KERN_SIGRETURN_CODE + (idx << 2) + thumb; 458 } else { 459 /* 460 * Ensure that the instruction cache sees 461 * the return code written onto the stack. 462 */ 463 flush_icache_range((unsigned long)rc, 464 (unsigned long)(rc + 2)); 465 466 retcode = ((unsigned long)rc) + thumb; 467 } 468 } 469 470 regs->ARM_r0 = usig; 471 regs->ARM_sp = (unsigned long)frame; 472 regs->ARM_lr = retcode; 473 regs->ARM_pc = handler; 474 regs->ARM_cpsr = cpsr; 475 476 return 0; 477 } 478 479 static int 480 setup_frame(int usig, struct k_sigaction *ka, sigset_t *set, struct pt_regs *regs) 481 { 482 struct sigframe __user *frame = get_sigframe(ka, regs, sizeof(*frame)); 483 int err = 0; 484 485 if (!frame) 486 return 1; 487 488 /* 489 * Set uc.uc_flags to a value which sc.trap_no would never have. 490 */ 491 __put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err); 492 493 err |= setup_sigframe(frame, regs, set); 494 if (err == 0) 495 err = setup_return(regs, ka, frame->retcode, frame, usig); 496 497 return err; 498 } 499 500 static int 501 setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info, 502 sigset_t *set, struct pt_regs *regs) 503 { 504 struct rt_sigframe __user *frame = get_sigframe(ka, regs, sizeof(*frame)); 505 stack_t stack; 506 int err = 0; 507 508 if (!frame) 509 return 1; 510 511 err |= copy_siginfo_to_user(&frame->info, info); 512 513 __put_user_error(0, &frame->sig.uc.uc_flags, err); 514 __put_user_error(NULL, &frame->sig.uc.uc_link, err); 515 516 memset(&stack, 0, sizeof(stack)); 517 stack.ss_sp = (void __user *)current->sas_ss_sp; 518 stack.ss_flags = sas_ss_flags(regs->ARM_sp); 519 stack.ss_size = current->sas_ss_size; 520 err |= __copy_to_user(&frame->sig.uc.uc_stack, &stack, sizeof(stack)); 521 522 err |= setup_sigframe(&frame->sig, regs, set); 523 if (err == 0) 524 err = setup_return(regs, ka, frame->sig.retcode, frame, usig); 525 526 if (err == 0) { 527 /* 528 * For realtime signals we must also set the second and third 529 * arguments for the signal handler. 530 * -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06 531 */ 532 regs->ARM_r1 = (unsigned long)&frame->info; 533 regs->ARM_r2 = (unsigned long)&frame->sig.uc; 534 } 535 536 return err; 537 } 538 539 static inline void setup_syscall_restart(struct pt_regs *regs) 540 { 541 regs->ARM_r0 = regs->ARM_ORIG_r0; 542 regs->ARM_pc -= thumb_mode(regs) ? 2 : 4; 543 } 544 545 /* 546 * OK, we're invoking a handler 547 */ 548 static void 549 handle_signal(unsigned long sig, struct k_sigaction *ka, 550 siginfo_t *info, sigset_t *oldset, 551 struct pt_regs * regs, int syscall) 552 { 553 struct thread_info *thread = current_thread_info(); 554 struct task_struct *tsk = current; 555 int usig = sig; 556 int ret; 557 558 /* 559 * If we were from a system call, check for system call restarting... 560 */ 561 if (syscall) { 562 switch (regs->ARM_r0) { 563 case -ERESTART_RESTARTBLOCK: 564 case -ERESTARTNOHAND: 565 regs->ARM_r0 = -EINTR; 566 break; 567 case -ERESTARTSYS: 568 if (!(ka->sa.sa_flags & SA_RESTART)) { 569 regs->ARM_r0 = -EINTR; 570 break; 571 } 572 /* fallthrough */ 573 case -ERESTARTNOINTR: 574 setup_syscall_restart(regs); 575 } 576 } 577 578 /* 579 * translate the signal 580 */ 581 if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap) 582 usig = thread->exec_domain->signal_invmap[usig]; 583 584 /* 585 * Set up the stack frame 586 */ 587 if (ka->sa.sa_flags & SA_SIGINFO) 588 ret = setup_rt_frame(usig, ka, info, oldset, regs); 589 else 590 ret = setup_frame(usig, ka, oldset, regs); 591 592 /* 593 * Check that the resulting registers are actually sane. 594 */ 595 ret |= !valid_user_regs(regs); 596 597 if (ret != 0) { 598 force_sigsegv(sig, tsk); 599 return; 600 } 601 602 /* 603 * Block the signal if we were successful. 604 */ 605 spin_lock_irq(&tsk->sighand->siglock); 606 sigorsets(&tsk->blocked, &tsk->blocked, 607 &ka->sa.sa_mask); 608 if (!(ka->sa.sa_flags & SA_NODEFER)) 609 sigaddset(&tsk->blocked, sig); 610 recalc_sigpending(); 611 spin_unlock_irq(&tsk->sighand->siglock); 612 613 } 614 615 /* 616 * Note that 'init' is a special process: it doesn't get signals it doesn't 617 * want to handle. Thus you cannot kill init even with a SIGKILL even by 618 * mistake. 619 * 620 * Note that we go through the signals twice: once to check the signals that 621 * the kernel can handle, and then we build all the user-level signal handling 622 * stack-frames in one go after that. 623 */ 624 static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall) 625 { 626 struct k_sigaction ka; 627 siginfo_t info; 628 int signr; 629 630 /* 631 * We want the common case to go fast, which 632 * is why we may in certain cases get here from 633 * kernel mode. Just return without doing anything 634 * if so. 635 */ 636 if (!user_mode(regs)) 637 return 0; 638 639 if (try_to_freeze()) 640 goto no_signal; 641 642 single_step_clear(current); 643 644 signr = get_signal_to_deliver(&info, &ka, regs, NULL); 645 if (signr > 0) { 646 handle_signal(signr, &ka, &info, oldset, regs, syscall); 647 single_step_set(current); 648 return 1; 649 } 650 651 no_signal: 652 /* 653 * No signal to deliver to the process - restart the syscall. 654 */ 655 if (syscall) { 656 if (regs->ARM_r0 == -ERESTART_RESTARTBLOCK) { 657 if (thumb_mode(regs)) { 658 regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE; 659 regs->ARM_pc -= 2; 660 } else { 661 #if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT) 662 regs->ARM_r7 = __NR_restart_syscall; 663 regs->ARM_pc -= 4; 664 #else 665 u32 __user *usp; 666 u32 swival = __NR_restart_syscall; 667 668 regs->ARM_sp -= 12; 669 usp = (u32 __user *)regs->ARM_sp; 670 671 /* 672 * Either we supports OABI only, or we have 673 * EABI with the OABI compat layer enabled. 674 * In the later case we don't know if user 675 * space is EABI or not, and if not we must 676 * not clobber r7. Always using the OABI 677 * syscall solves that issue and works for 678 * all those cases. 679 */ 680 swival = swival - __NR_SYSCALL_BASE + __NR_OABI_SYSCALL_BASE; 681 682 put_user(regs->ARM_pc, &usp[0]); 683 /* swi __NR_restart_syscall */ 684 put_user(0xef000000 | swival, &usp[1]); 685 /* ldr pc, [sp], #12 */ 686 put_user(0xe49df00c, &usp[2]); 687 688 flush_icache_range((unsigned long)usp, 689 (unsigned long)(usp + 3)); 690 691 regs->ARM_pc = regs->ARM_sp + 4; 692 #endif 693 } 694 } 695 if (regs->ARM_r0 == -ERESTARTNOHAND || 696 regs->ARM_r0 == -ERESTARTSYS || 697 regs->ARM_r0 == -ERESTARTNOINTR) { 698 setup_syscall_restart(regs); 699 } 700 } 701 single_step_set(current); 702 return 0; 703 } 704 705 asmlinkage void 706 do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall) 707 { 708 if (thread_flags & _TIF_SIGPENDING) 709 do_signal(¤t->blocked, regs, syscall); 710 } 711