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
  18 #include <asm/elf.h>
  19 #include <asm/cacheflush.h>
  20 #include <asm/traps.h>
  21 #include <asm/ucontext.h>
  22 #include <asm/unistd.h>
  23 #include <asm/vfp.h>
  24
  25 extern const unsigned long sigreturn_codes[7];
  26
  27 static unsigned long signal_return_offset;
  28
  29 #ifdef CONFIG_CRUNCH
  30 static int preserve_crunch_context(struct crunch_sigframe __user *frame)
  31 {
  32         char kbuf[sizeof(*frame) + 8];
  33         struct crunch_sigframe *kframe;
  34
  35         /* the crunch context must be 64 bit aligned */
  36         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  37         kframe->magic = CRUNCH_MAGIC;
  38         kframe->size = CRUNCH_STORAGE_SIZE;
  39         crunch_task_copy(current_thread_info(), &kframe->storage);
  40         return __copy_to_user(frame, kframe, sizeof(*frame));
  41 }
  42
  43 static int restore_crunch_context(struct crunch_sigframe __user *frame)
  44 {
  45         char kbuf[sizeof(*frame) + 8];
  46         struct crunch_sigframe *kframe;
  47
  48         /* the crunch context must be 64 bit aligned */
  49         kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  50         if (__copy_from_user(kframe, frame, sizeof(*frame)))
  51                 return -1;
  52         if (kframe->magic != CRUNCH_MAGIC ||
  53             kframe->size != CRUNCH_STORAGE_SIZE)
  54                 return -1;
  55         crunch_task_restore(current_thread_info(), &kframe->storage);
  56         return 0;
  57 }
  58 #endif
  59
  60 #ifdef CONFIG_IWMMXT
  61
  62 static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
  63 {
  64         char kbuf[sizeof(*frame) + 8];
  65         struct iwmmxt_sigframe *kframe;
  66
  67         /* the iWMMXt context must be 64 bit aligned */
  68         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  69         kframe->magic = IWMMXT_MAGIC;
  70         kframe->size = IWMMXT_STORAGE_SIZE;
  71         iwmmxt_task_copy(current_thread_info(), &kframe->storage);
  72         return __copy_to_user(frame, kframe, sizeof(*frame));
  73 }
  74
  75 static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
  76 {
  77         char kbuf[sizeof(*frame) + 8];
  78         struct iwmmxt_sigframe *kframe;
  79
  80         /* the iWMMXt context must be 64 bit aligned */
  81         kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  82         if (__copy_from_user(kframe, frame, sizeof(*frame)))
  83                 return -1;
  84         if (kframe->magic != IWMMXT_MAGIC ||
  85             kframe->size != IWMMXT_STORAGE_SIZE)
  86                 return -1;
  87         iwmmxt_task_restore(current_thread_info(), &kframe->storage);
  88         return 0;
  89 }
  90
  91 #endif
  92
  93 #ifdef CONFIG_VFP
  94
  95 static int preserve_vfp_context(struct vfp_sigframe __user *frame)
  96 {
  97         struct vfp_sigframe kframe;
  98         int err = 0;
  99
 100         memset(&kframe, 0, sizeof(kframe));
 101         kframe.magic = VFP_MAGIC;
 102         kframe.size = VFP_STORAGE_SIZE;
 103
 104         err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
 105         if (err)
 106                 return err;
 107
 108         return __copy_to_user(frame, &kframe, sizeof(kframe));
 109 }
 110
 111 static int restore_vfp_context(struct vfp_sigframe __user *auxp)
 112 {
 113         struct vfp_sigframe frame;
 114         int err;
 115
 116         err = __copy_from_user(&frame, (char __user *) auxp, sizeof(frame));
 117
 118         if (err)
 119                 return err;
 120
 121         if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
 122                 return -EINVAL;
 123
 124         return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
 125 }
 126
 127 #endif
 128
 129 /*
 130  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
 131  */
 132 struct sigframe {
 133         struct ucontext uc;
 134         unsigned long retcode[2];
 135 };
 136
 137 struct rt_sigframe {
 138         struct siginfo info;
 139         struct sigframe sig;
 140 };
 141
 142 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
 143 {
 144         struct sigcontext context;
 145         struct aux_sigframe __user *aux;
 146         sigset_t set;
 147         int err;
 148
 149         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 150         if (err == 0)
 151                 set_current_blocked(&set);
 152
 153         err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
 154         if (err == 0) {
 155                 regs->ARM_r0 = context.arm_r0;
 156                 regs->ARM_r1 = context.arm_r1;
 157                 regs->ARM_r2 = context.arm_r2;
 158                 regs->ARM_r3 = context.arm_r3;
 159                 regs->ARM_r4 = context.arm_r4;
 160                 regs->ARM_r5 = context.arm_r5;
 161                 regs->ARM_r6 = context.arm_r6;
 162                 regs->ARM_r7 = context.arm_r7;
 163                 regs->ARM_r8 = context.arm_r8;
 164                 regs->ARM_r9 = context.arm_r9;
 165                 regs->ARM_r10 = context.arm_r10;
 166                 regs->ARM_fp = context.arm_fp;
 167                 regs->ARM_ip = context.arm_ip;
 168                 regs->ARM_sp = context.arm_sp;
 169                 regs->ARM_lr = context.arm_lr;
 170                 regs->ARM_pc = context.arm_pc;
 171                 regs->ARM_cpsr = context.arm_cpsr;
 172         }
 173
 174         err |= !valid_user_regs(regs);
 175
 176         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 177 #ifdef CONFIG_CRUNCH
 178         if (err == 0)
 179                 err |= restore_crunch_context(&aux->crunch);
 180 #endif
 181 #ifdef CONFIG_IWMMXT
 182         if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
 183                 err |= restore_iwmmxt_context(&aux->iwmmxt);
 184 #endif
 185 #ifdef CONFIG_VFP
 186         if (err == 0)
 187                 err |= restore_vfp_context(&aux->vfp);
 188 #endif
 189
 190         return err;
 191 }
 192
 193 asmlinkage int sys_sigreturn(struct pt_regs *regs)
 194 {
 195         struct sigframe __user *frame;
 196
 197         /* Always make any pending restarted system calls return -EINTR */
 198         current->restart_block.fn = do_no_restart_syscall;
 199
 200         /*
 201          * Since we stacked the signal on a 64-bit boundary,
 202          * then 'sp' should be word aligned here.  If it's
 203          * not, then the user is trying to mess with us.
 204          */
 205         if (regs->ARM_sp & 7)
 206                 goto badframe;
 207
 208         frame = (struct sigframe __user *)regs->ARM_sp;
 209
 210         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 211                 goto badframe;
 212
 213         if (restore_sigframe(regs, frame))
 214                 goto badframe;
 215
 216         return regs->ARM_r0;
 217
 218 badframe:
 219         force_sig(SIGSEGV, current);
 220         return 0;
 221 }
 222
 223 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 224 {
 225         struct rt_sigframe __user *frame;
 226
 227         /* Always make any pending restarted system calls return -EINTR */
 228         current->restart_block.fn = do_no_restart_syscall;
 229
 230         /*
 231          * Since we stacked the signal on a 64-bit boundary,
 232          * then 'sp' should be word aligned here.  If it's
 233          * not, then the user is trying to mess with us.
 234          */
 235         if (regs->ARM_sp & 7)
 236                 goto badframe;
 237
 238         frame = (struct rt_sigframe __user *)regs->ARM_sp;
 239
 240         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 241                 goto badframe;
 242
 243         if (restore_sigframe(regs, &frame->sig))
 244                 goto badframe;
 245
 246         if (restore_altstack(&frame->sig.uc.uc_stack))
 247                 goto badframe;
 248
 249         return regs->ARM_r0;
 250
 251 badframe:
 252         force_sig(SIGSEGV, current);
 253         return 0;
 254 }
 255
 256 static int
 257 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
 258 {
 259         struct aux_sigframe __user *aux;
 260         struct sigcontext context;
 261         int err = 0;
 262
 263         context = (struct sigcontext) {
 264                 .arm_r0        = regs->ARM_r0,
 265                 .arm_r1        = regs->ARM_r1,
 266                 .arm_r2        = regs->ARM_r2,
 267                 .arm_r3        = regs->ARM_r3,
 268                 .arm_r4        = regs->ARM_r4,
 269                 .arm_r5        = regs->ARM_r5,
 270                 .arm_r6        = regs->ARM_r6,
 271                 .arm_r7        = regs->ARM_r7,
 272                 .arm_r8        = regs->ARM_r8,
 273                 .arm_r9        = regs->ARM_r9,
 274                 .arm_r10       = regs->ARM_r10,
 275                 .arm_fp        = regs->ARM_fp,
 276                 .arm_ip        = regs->ARM_ip,
 277                 .arm_sp        = regs->ARM_sp,
 278                 .arm_lr        = regs->ARM_lr,
 279                 .arm_pc        = regs->ARM_pc,
 280                 .arm_cpsr      = regs->ARM_cpsr,
 281
 282                 .trap_no       = current->thread.trap_no,
 283                 .error_code    = current->thread.error_code,
 284                 .fault_address = current->thread.address,
 285                 .oldmask       = set->sig[0],
 286         };
 287
 288         err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
 289
 290         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 291
 292         aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
 293 #ifdef CONFIG_CRUNCH
 294         if (err == 0)
 295                 err |= preserve_crunch_context(&aux->crunch);
 296 #endif
 297 #ifdef CONFIG_IWMMXT
 298         if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
 299                 err |= preserve_iwmmxt_context(&aux->iwmmxt);
 300 #endif
 301 #ifdef CONFIG_VFP
 302         if (err == 0)
 303                 err |= preserve_vfp_context(&aux->vfp);
 304 #endif
 305         err |= __put_user(0, &aux->end_magic);
 306
 307         return err;
 308 }
 309
 310 static inline void __user *
 311 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
 312 {
 313         unsigned long sp = sigsp(regs->ARM_sp, ksig);
 314         void __user *frame;
 315
 316         /*
 317          * ATPCS B01 mandates 8-byte alignment
 318          */
 319         frame = (void __user *)((sp - framesize) & ~7);
 320
 321         /*
 322          * Check that we can actually write to the signal frame.
 323          */
 324         if (!access_ok(VERIFY_WRITE, frame, framesize))
 325                 frame = NULL;
 326
 327         return frame;
 328 }
 329
 330 static int
 331 setup_return(struct pt_regs *regs, struct ksignal *ksig,
 332              unsigned long __user *rc, void __user *frame)
 333 {
 334         unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
 335         unsigned long retcode;
 336         int thumb = 0;
 337         unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
 338
 339         cpsr |= PSR_ENDSTATE;
 340
 341         /*
 342          * Maybe we need to deliver a 32-bit signal to a 26-bit task.
 343          */
 344         if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
 345                 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
 346
 347 #ifdef CONFIG_ARM_THUMB
 348         if (elf_hwcap & HWCAP_THUMB) {
 349                 /*
 350                  * The LSB of the handler determines if we're going to
 351                  * be using THUMB or ARM mode for this signal handler.
 352                  */
 353                 thumb = handler & 1;
 354
 355                 /*
 356                  * Clear the If-Then Thumb-2 execution state.  ARM spec
 357                  * requires this to be all 000s in ARM mode.  Snapdragon
 358                  * S4/Krait misbehaves on a Thumb=>ARM signal transition
 359                  * without this.
 360                  *
 361                  * We must do this whenever we are running on a Thumb-2
 362                  * capable CPU, which includes ARMv6T2.  However, we elect
 363                  * to always do this to simplify the code; this field is
 364                  * marked UNK/SBZP for older architectures.
 365                  */
 366                 cpsr &= ~PSR_IT_MASK;
 367
 368                 if (thumb) {
 369                         cpsr |= PSR_T_BIT;
 370                 } else
 371                         cpsr &= ~PSR_T_BIT;
 372         }
 373 #endif
 374
 375         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 376                 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
 377         } else {
 378                 unsigned int idx = thumb << 1;
 379
 380                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 381                         idx += 3;
 382
 383                 /*
 384                  * Put the sigreturn code on the stack no matter which return
 385                  * mechanism we use in order to remain ABI compliant
 386                  */
 387                 if (__put_user(sigreturn_codes[idx],   rc) ||
 388                     __put_user(sigreturn_codes[idx+1], rc+1))
 389                         return 1;
 390
 391 #ifdef CONFIG_MMU
 392                 if (cpsr & MODE32_BIT) {
 393                         struct mm_struct *mm = current->mm;
 394
 395                         /*
 396                          * 32-bit code can use the signal return page
 397                          * except when the MPU has protected the vectors
 398                          * page from PL0
 399                          */
 400                         retcode = mm->context.sigpage + signal_return_offset +
 401                                   (idx << 2) + thumb;
 402                 } else
 403 #endif
 404                 {
 405                         /*
 406                          * Ensure that the instruction cache sees
 407                          * the return code written onto the stack.
 408                          */
 409                         flush_icache_range((unsigned long)rc,
 410                                            (unsigned long)(rc + 2));
 411
 412                         retcode = ((unsigned long)rc) + thumb;
 413                 }
 414         }
 415
 416         regs->ARM_r0 = ksig->sig;
 417         regs->ARM_sp = (unsigned long)frame;
 418         regs->ARM_lr = retcode;
 419         regs->ARM_pc = handler;
 420         regs->ARM_cpsr = cpsr;
 421
 422         return 0;
 423 }
 424
 425 static int
 426 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 427 {
 428         struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 429         int err = 0;
 430
 431         if (!frame)
 432                 return 1;
 433
 434         /*
 435          * Set uc.uc_flags to a value which sc.trap_no would never have.
 436          */
 437         err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
 438
 439         err |= setup_sigframe(frame, regs, set);
 440         if (err == 0)
 441                 err = setup_return(regs, ksig, frame->retcode, frame);
 442
 443         return err;
 444 }
 445
 446 static int
 447 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 448 {
 449         struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
 450         int err = 0;
 451
 452         if (!frame)
 453                 return 1;
 454
 455         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 456
 457         err |= __put_user(0, &frame->sig.uc.uc_flags);
 458         err |= __put_user(NULL, &frame->sig.uc.uc_link);
 459
 460         err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
 461         err |= setup_sigframe(&frame->sig, regs, set);
 462         if (err == 0)
 463                 err = setup_return(regs, ksig, frame->sig.retcode, frame);
 464
 465         if (err == 0) {
 466                 /*
 467                  * For realtime signals we must also set the second and third
 468                  * arguments for the signal handler.
 469                  *   -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
 470                  */
 471                 regs->ARM_r1 = (unsigned long)&frame->info;
 472                 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
 473         }
 474
 475         return err;
 476 }
 477
 478 /*
 479  * OK, we're invoking a handler
 480  */
 481 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 482 {
 483         sigset_t *oldset = sigmask_to_save();
 484         int ret;
 485
 486         /*
 487          * Set up the stack frame
 488          */
 489         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 490                 ret = setup_rt_frame(ksig, oldset, regs);
 491         else
 492                 ret = setup_frame(ksig, oldset, regs);
 493
 494         /*
 495          * Check that the resulting registers are actually sane.
 496          */
 497         ret |= !valid_user_regs(regs);
 498
 499         signal_setup_done(ret, ksig, 0);
 500 }
 501
 502 /*
 503  * Note that 'init' is a special process: it doesn't get signals it doesn't
 504  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 505  * mistake.
 506  *
 507  * Note that we go through the signals twice: once to check the signals that
 508  * the kernel can handle, and then we build all the user-level signal handling
 509  * stack-frames in one go after that.
 510  */
 511 static int do_signal(struct pt_regs *regs, int syscall)
 512 {
 513         unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
 514         struct ksignal ksig;
 515         int restart = 0;
 516
 517         /*
 518          * If we were from a system call, check for system call restarting...
 519          */
 520         if (syscall) {
 521                 continue_addr = regs->ARM_pc;
 522                 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
 523                 retval = regs->ARM_r0;
 524
 525                 /*
 526                  * Prepare for system call restart.  We do this here so that a
 527                  * debugger will see the already changed PSW.
 528                  */
 529                 switch (retval) {
 530                 case -ERESTART_RESTARTBLOCK:
 531                         restart -= 2;
 532                 case -ERESTARTNOHAND:
 533                 case -ERESTARTSYS:
 534                 case -ERESTARTNOINTR:
 535                         restart++;
 536                         regs->ARM_r0 = regs->ARM_ORIG_r0;
 537                         regs->ARM_pc = restart_addr;
 538                         break;
 539                 }
 540         }
 541
 542         /*
 543          * Get the signal to deliver.  When running under ptrace, at this
 544          * point the debugger may change all our registers ...
 545          */
 546         /*
 547          * Depending on the signal settings we may need to revert the
 548          * decision to restart the system call.  But skip this if a
 549          * debugger has chosen to restart at a different PC.
 550          */
 551         if (get_signal(&ksig)) {
 552                 /* handler */
 553                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 554                         if (retval == -ERESTARTNOHAND ||
 555                             retval == -ERESTART_RESTARTBLOCK
 556                             || (retval == -ERESTARTSYS
 557                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 558                                 regs->ARM_r0 = -EINTR;
 559                                 regs->ARM_pc = continue_addr;
 560                         }
 561                 }
 562                 handle_signal(&ksig, regs);
 563         } else {
 564                 /* no handler */
 565                 restore_saved_sigmask();
 566                 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
 567                         regs->ARM_pc = continue_addr;
 568                         return restart;
 569                 }
 570         }
 571         return 0;
 572 }
 573
 574 asmlinkage int
 575 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 576 {
 577         /*
 578          * The assembly code enters us with IRQs off, but it hasn't
 579          * informed the tracing code of that for efficiency reasons.
 580          * Update the trace code with the current status.
 581          */
 582         trace_hardirqs_off();
 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 if (thread_flags & _TIF_UPROBE) {
 602                                 uprobe_notify_resume(regs);
 603                         } else {
 604                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 605                                 tracehook_notify_resume(regs);
 606                         }
 607                 }
 608                 local_irq_disable();
 609                 thread_flags = current_thread_info()->flags;
 610         } while (thread_flags & _TIF_WORK_MASK);
 611         return 0;
 612 }
 613
 614 struct page *get_signal_page(void)
 615 {
 616         unsigned long ptr;
 617         unsigned offset;
 618         struct page *page;
 619         void *addr;
 620
 621         page = alloc_pages(GFP_KERNEL, 0);
 622
 623         if (!page)
 624                 return NULL;
 625
 626         addr = page_address(page);
 627
 628         /* Give the signal return code some randomness */
 629         offset = 0x200 + (get_random_int() & 0x7fc);
 630         signal_return_offset = offset;
 631
 632         /*
 633          * Copy signal return handlers into the vector page, and
 634          * set sigreturn to be a pointer to these.
 635          */
 636         memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
 637
 638         ptr = (unsigned long)addr + offset;
 639         flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
 640
 641         return page;
 642 }