arch/x86/kernel/signal_64.c

   1 /*
   2  *  Copyright (C) 1991, 1992  Linus Torvalds
   3  *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
   4  *
   5  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   6  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   7  *  2000-2002   x86-64 support by Andi Kleen
   8  */
   9
  10 #include <linux/sched.h>
  11 #include <linux/mm.h>
  12 #include <linux/smp.h>
  13 #include <linux/kernel.h>
  14 #include <linux/signal.h>
  15 #include <linux/errno.h>
  16 #include <linux/wait.h>
  17 #include <linux/ptrace.h>
  18 #include <linux/unistd.h>
  19 #include <linux/stddef.h>
  20 #include <linux/personality.h>
  21 #include <linux/compiler.h>
  22 #include <asm/ucontext.h>
  23 #include <asm/uaccess.h>
  24 #include <asm/i387.h>
  25 #include <asm/proto.h>
  26 #include <asm/ia32_unistd.h>
  27 #include <asm/mce.h>
  28
  29 /* #define DEBUG_SIG 1 */
  30
  31 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  32
  33 int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
  34                sigset_t *set, struct pt_regs * regs);
  35 int ia32_setup_frame(int sig, struct k_sigaction *ka,
  36             sigset_t *set, struct pt_regs * regs);
  37
  38 asmlinkage long
  39 sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
  40                 struct pt_regs *regs)
  41 {
  42         return do_sigaltstack(uss, uoss, regs->sp);
  43 }
  44
  45
  46 /*
  47  * Do a signal return; undo the signal stack.
  48  */
  49
  50 struct rt_sigframe
  51 {
  52         char __user *pretcode;
  53         struct ucontext uc;
  54         struct siginfo info;
  55 };
  56
  57 static int
  58 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned long *prax)
  59 {
  60         unsigned int err = 0;
  61
  62         /* Always make any pending restarted system calls return -EINTR */
  63         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  64
  65 #define COPY(x)         err |= __get_user(regs->x, &sc->x)
  66
  67         COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
  68         COPY(dx); COPY(cx); COPY(ip);
  69         COPY(r8);
  70         COPY(r9);
  71         COPY(r10);
  72         COPY(r11);
  73         COPY(r12);
  74         COPY(r13);
  75         COPY(r14);
  76         COPY(r15);
  77
  78         /* Kernel saves and restores only the CS segment register on signals,
  79          * which is the bare minimum needed to allow mixed 32/64-bit code.
  80          * App's signal handler can save/restore other segments if needed. */
  81         {
  82                 unsigned cs;
  83                 err |= __get_user(cs, &sc->cs);
  84                 regs->cs = cs | 3;      /* Force into user mode */
  85         }
  86
  87         {
  88                 unsigned int tmpflags;
  89                 err |= __get_user(tmpflags, &sc->flags);
  90                 regs->flags = (regs->flags & ~0x40DD5) | (tmpflags & 0x40DD5);
  91                 regs->orig_ax = -1;             /* disable syscall checks */
  92         }
  93
  94         {
  95                 struct _fpstate __user * buf;
  96                 err |= __get_user(buf, &sc->fpstate);
  97
  98                 if (buf) {
  99                         if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
 100                                 goto badframe;
 101                         err |= restore_i387(buf);
 102                 } else {
 103                         struct task_struct *me = current;
 104                         if (used_math()) {
 105                                 clear_fpu(me);
 106                                 clear_used_math();
 107                         }
 108                 }
 109         }
 110
 111         err |= __get_user(*prax, &sc->ax);
 112         return err;
 113
 114 badframe:
 115         return 1;
 116 }
 117
 118 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 119 {
 120         struct rt_sigframe __user *frame;
 121         sigset_t set;
 122         unsigned long ax;
 123
 124         frame = (struct rt_sigframe __user *)(regs->sp - 8);
 125         if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) {
 126                 goto badframe;
 127         }
 128         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) {
 129                 goto badframe;
 130         }
 131
 132         sigdelsetmask(&set, ~_BLOCKABLE);
 133         spin_lock_irq(&current->sighand->siglock);
 134         current->blocked = set;
 135         recalc_sigpending();
 136         spin_unlock_irq(&current->sighand->siglock);
 137
 138         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 139                 goto badframe;
 140
 141 #ifdef DEBUG_SIG
 142         printk("%d sigreturn ip:%lx sp:%lx frame:%p ax:%lx\n",current->pid,regs->ip,regs->sp,frame,ax);
 143 #endif
 144
 145         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
 146                 goto badframe;
 147
 148         return ax;
 149
 150 badframe:
 151         signal_fault(regs,frame,"sigreturn");
 152         return 0;
 153 }
 154
 155 /*
 156  * Set up a signal frame.
 157  */
 158
 159 static inline int
 160 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
 161 {
 162         int err = 0;
 163
 164         err |= __put_user(regs->cs, &sc->cs);
 165         err |= __put_user(0, &sc->gs);
 166         err |= __put_user(0, &sc->fs);
 167
 168         err |= __put_user(regs->di, &sc->di);
 169         err |= __put_user(regs->si, &sc->si);
 170         err |= __put_user(regs->bp, &sc->bp);
 171         err |= __put_user(regs->sp, &sc->sp);
 172         err |= __put_user(regs->bx, &sc->bx);
 173         err |= __put_user(regs->dx, &sc->dx);
 174         err |= __put_user(regs->cx, &sc->cx);
 175         err |= __put_user(regs->ax, &sc->ax);
 176         err |= __put_user(regs->r8, &sc->r8);
 177         err |= __put_user(regs->r9, &sc->r9);
 178         err |= __put_user(regs->r10, &sc->r10);
 179         err |= __put_user(regs->r11, &sc->r11);
 180         err |= __put_user(regs->r12, &sc->r12);
 181         err |= __put_user(regs->r13, &sc->r13);
 182         err |= __put_user(regs->r14, &sc->r14);
 183         err |= __put_user(regs->r15, &sc->r15);
 184         err |= __put_user(me->thread.trap_no, &sc->trapno);
 185         err |= __put_user(me->thread.error_code, &sc->err);
 186         err |= __put_user(regs->ip, &sc->ip);
 187         err |= __put_user(regs->flags, &sc->flags);
 188         err |= __put_user(mask, &sc->oldmask);
 189         err |= __put_user(me->thread.cr2, &sc->cr2);
 190
 191         return err;
 192 }
 193
 194 /*
 195  * Determine which stack to use..
 196  */
 197
 198 static void __user *
 199 get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
 200 {
 201         unsigned long sp;
 202
 203         /* Default to using normal stack - redzone*/
 204         sp = regs->sp - 128;
 205
 206         /* This is the X/Open sanctioned signal stack switching.  */
 207         if (ka->sa.sa_flags & SA_ONSTACK) {
 208                 if (sas_ss_flags(sp) == 0)
 209                         sp = current->sas_ss_sp + current->sas_ss_size;
 210         }
 211
 212         return (void __user *)round_down(sp - size, 16);
 213 }
 214
 215 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 216                            sigset_t *set, struct pt_regs * regs)
 217 {
 218         struct rt_sigframe __user *frame;
 219         struct _fpstate __user *fp = NULL;
 220         int err = 0;
 221         struct task_struct *me = current;
 222
 223         if (used_math()) {
 224                 fp = get_stack(ka, regs, sizeof(struct _fpstate));
 225                 frame = (void __user *)round_down(
 226                         (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
 227
 228                 if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
 229                         goto give_sigsegv;
 230
 231                 if (save_i387(fp) < 0)
 232                         err |= -1;
 233         } else
 234                 frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
 235
 236         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 237                 goto give_sigsegv;
 238
 239         if (ka->sa.sa_flags & SA_SIGINFO) {
 240                 err |= copy_siginfo_to_user(&frame->info, info);
 241                 if (err)
 242                         goto give_sigsegv;
 243         }
 244
 245         /* Create the ucontext.  */
 246         err |= __put_user(0, &frame->uc.uc_flags);
 247         err |= __put_user(0, &frame->uc.uc_link);
 248         err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 249         err |= __put_user(sas_ss_flags(regs->sp),
 250                           &frame->uc.uc_stack.ss_flags);
 251         err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
 252         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
 253         err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
 254         if (sizeof(*set) == 16) {
 255                 __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 256                 __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
 257         } else
 258                 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 259
 260         /* Set up to return from userspace.  If provided, use a stub
 261            already in userspace.  */
 262         /* x86-64 should always use SA_RESTORER. */
 263         if (ka->sa.sa_flags & SA_RESTORER) {
 264                 err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
 265         } else {
 266                 /* could use a vstub here */
 267                 goto give_sigsegv;
 268         }
 269
 270         if (err)
 271                 goto give_sigsegv;
 272
 273 #ifdef DEBUG_SIG
 274         printk("%d old ip %lx old sp %lx old ax %lx\n", current->pid,regs->ip,regs->sp,regs->ax);
 275 #endif
 276
 277         /* Set up registers for signal handler */
 278         regs->di = sig;
 279         /* In case the signal handler was declared without prototypes */
 280         regs->ax = 0;
 281
 282         /* This also works for non SA_SIGINFO handlers because they expect the
 283            next argument after the signal number on the stack. */
 284         regs->si = (unsigned long)&frame->info;
 285         regs->dx = (unsigned long)&frame->uc;
 286         regs->ip = (unsigned long) ka->sa.sa_handler;
 287
 288         regs->sp = (unsigned long)frame;
 289
 290         /* Set up the CS register to run signal handlers in 64-bit mode,
 291            even if the handler happens to be interrupting 32-bit code. */
 292         regs->cs = __USER_CS;
 293
 294         /* This, by contrast, has nothing to do with segment registers -
 295            see include/asm-x86_64/uaccess.h for details. */
 296         set_fs(USER_DS);
 297
 298         regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
 299         if (test_thread_flag(TIF_SINGLESTEP))
 300                 ptrace_notify(SIGTRAP);
 301 #ifdef DEBUG_SIG
 302         printk("SIG deliver (%s:%d): sp=%p pc=%lx ra=%p\n",
 303                 current->comm, current->pid, frame, regs->ip, frame->pretcode);
 304 #endif
 305
 306         return 0;
 307
 308 give_sigsegv:
 309         force_sigsegv(sig, current);
 310         return -EFAULT;
 311 }
 312
 313 /*
 314  * Return -1L or the syscall number that @regs is executing.
 315  */
 316 static long current_syscall(struct pt_regs *regs)
 317 {
 318         /*
 319          * We always sign-extend a -1 value being set here,
 320          * so this is always either -1L or a syscall number.
 321          */
 322         return regs->orig_ax;
 323 }
 324
 325 /*
 326  * Return a value that is -EFOO if the system call in @regs->orig_ax
 327  * returned an error.  This only works for @regs from @current.
 328  */
 329 static long current_syscall_ret(struct pt_regs *regs)
 330 {
 331 #ifdef CONFIG_IA32_EMULATION
 332         if (test_thread_flag(TIF_IA32))
 333                 /*
 334                  * Sign-extend the value so (int)-EFOO becomes (long)-EFOO
 335                  * and will match correctly in comparisons.
 336                  */
 337                 return (int) regs->ax;
 338 #endif
 339         return regs->ax;
 340 }
 341
 342 /*
 343  * OK, we're invoking a handler
 344  */
 345
 346 static int
 347 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 348                 sigset_t *oldset, struct pt_regs *regs)
 349 {
 350         int ret;
 351
 352 #ifdef DEBUG_SIG
 353         printk("handle_signal pid:%d sig:%lu ip:%lx sp:%lx regs=%p\n",
 354                 current->pid, sig,
 355                 regs->ip, regs->sp, regs);
 356 #endif
 357
 358         /* Are we from a system call? */
 359         if (current_syscall(regs) >= 0) {
 360                 /* If so, check system call restarting.. */
 361                 switch (current_syscall_ret(regs)) {
 362                         case -ERESTART_RESTARTBLOCK:
 363                         case -ERESTARTNOHAND:
 364                                 regs->ax = -EINTR;
 365                                 break;
 366
 367                         case -ERESTARTSYS:
 368                                 if (!(ka->sa.sa_flags & SA_RESTART)) {
 369                                         regs->ax = -EINTR;
 370                                         break;
 371                                 }
 372                                 /* fallthrough */
 373                         case -ERESTARTNOINTR:
 374                                 regs->ax = regs->orig_ax;
 375                                 regs->ip -= 2;
 376                                 break;
 377                 }
 378         }
 379
 380         /*
 381          * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
 382          * flag so that register information in the sigcontext is correct.
 383          */
 384         if (unlikely(regs->flags & X86_EFLAGS_TF) &&
 385             likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 386                 regs->flags &= ~X86_EFLAGS_TF;
 387
 388 #ifdef CONFIG_IA32_EMULATION
 389         if (test_thread_flag(TIF_IA32)) {
 390                 if (ka->sa.sa_flags & SA_SIGINFO)
 391                         ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
 392                 else
 393                         ret = ia32_setup_frame(sig, ka, oldset, regs);
 394         } else
 395 #endif
 396         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 397
 398         if (ret == 0) {
 399                 spin_lock_irq(&current->sighand->siglock);
 400                 sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 401                 if (!(ka->sa.sa_flags & SA_NODEFER))
 402                         sigaddset(&current->blocked,sig);
 403                 recalc_sigpending();
 404                 spin_unlock_irq(&current->sighand->siglock);
 405         }
 406
 407         return ret;
 408 }
 409
 410 /*
 411  * Note that 'init' is a special process: it doesn't get signals it doesn't
 412  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 413  * mistake.
 414  */
 415 static void do_signal(struct pt_regs *regs)
 416 {
 417         struct k_sigaction ka;
 418         siginfo_t info;
 419         int signr;
 420         sigset_t *oldset;
 421
 422         /*
 423          * We want the common case to go fast, which
 424          * is why we may in certain cases get here from
 425          * kernel mode. Just return without doing anything
 426          * if so.
 427          */
 428         if (!user_mode(regs))
 429                 return;
 430
 431         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 432                 oldset = &current->saved_sigmask;
 433         else
 434                 oldset = &current->blocked;
 435
 436         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 437         if (signr > 0) {
 438                 /* Re-enable any watchpoints before delivering the
 439                  * signal to user space. The processor register will
 440                  * have been cleared if the watchpoint triggered
 441                  * inside the kernel.
 442                  */
 443                 if (current->thread.debugreg7)
 444                         set_debugreg(current->thread.debugreg7, 7);
 445
 446                 /* Whee!  Actually deliver the signal.  */
 447                 if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 448                         /* a signal was successfully delivered; the saved
 449                          * sigmask will have been stored in the signal frame,
 450                          * and will be restored by sigreturn, so we can simply
 451                          * clear the TIF_RESTORE_SIGMASK flag */
 452                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 453                 }
 454                 return;
 455         }
 456
 457         /* Did we come from a system call? */
 458         if (current_syscall(regs) >= 0) {
 459                 /* Restart the system call - no handlers present */
 460                 switch (current_syscall_ret(regs)) {
 461                 case -ERESTARTNOHAND:
 462                 case -ERESTARTSYS:
 463                 case -ERESTARTNOINTR:
 464                         regs->ax = regs->orig_ax;
 465                         regs->ip -= 2;
 466                         break;
 467                 case -ERESTART_RESTARTBLOCK:
 468                         regs->ax = test_thread_flag(TIF_IA32) ?
 469                                         __NR_ia32_restart_syscall :
 470                                         __NR_restart_syscall;
 471                         regs->ip -= 2;
 472                         break;
 473                 }
 474         }
 475
 476         /* if there's no signal to deliver, we just put the saved sigmask
 477            back. */
 478         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 479                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 480                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 481         }
 482 }
 483
 484 void
 485 do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
 486 {
 487 #ifdef DEBUG_SIG
 488         printk("do_notify_resume flags:%x ip:%lx sp:%lx caller:%p pending:%x\n",
 489                thread_info_flags, regs->ip, regs->sp, __builtin_return_address(0),signal_pending(current));
 490 #endif
 491
 492         /* Pending single-step? */
 493         if (thread_info_flags & _TIF_SINGLESTEP) {
 494                 regs->flags |= X86_EFLAGS_TF;
 495                 clear_thread_flag(TIF_SINGLESTEP);
 496         }
 497
 498 #ifdef CONFIG_X86_MCE
 499         /* notify userspace of pending MCEs */
 500         if (thread_info_flags & _TIF_MCE_NOTIFY)
 501                 mce_notify_user();
 502 #endif /* CONFIG_X86_MCE */
 503
 504         /* deal with pending signal delivery */
 505         if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))
 506                 do_signal(regs);
 507
 508         if (thread_info_flags & _TIF_HRTICK_RESCHED)
 509                 hrtick_resched();
 510 }
 511
 512 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 513 {
 514         struct task_struct *me = current;
 515         if (show_unhandled_signals && printk_ratelimit()) {
 516                 printk("%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 517                me->comm,me->pid,where,frame,regs->ip,regs->sp,regs->orig_ax);
 518                 print_vma_addr(" in ", regs->ip);
 519                 printk("\n");
 520         }
 521
 522         force_sig(SIGSEGV, me);
 523 }