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/tracehook.h>
  19 #include <linux/unistd.h>
  20 #include <linux/stddef.h>
  21 #include <linux/personality.h>
  22 #include <linux/compiler.h>
  23 #include <linux/uaccess.h>
  24
  25 #include <asm/processor.h>
  26 #include <asm/ucontext.h>
  27 #include <asm/i387.h>
  28 #include <asm/proto.h>
  29 #include <asm/ia32_unistd.h>
  30 #include <asm/mce.h>
  31 #include <asm/syscall.h>
  32 #include <asm/syscalls.h>
  33 #include "sigframe.h"
  34
  35 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  36
  37 #define __FIX_EFLAGS    (X86_EFLAGS_AC | X86_EFLAGS_OF | \
  38                          X86_EFLAGS_DF | X86_EFLAGS_TF | X86_EFLAGS_SF | \
  39                          X86_EFLAGS_ZF | X86_EFLAGS_AF | X86_EFLAGS_PF | \
  40                          X86_EFLAGS_CF)
  41
  42 #ifdef CONFIG_X86_32
  43 # define FIX_EFLAGS     (__FIX_EFLAGS | X86_EFLAGS_RF)
  44 #else
  45 # define FIX_EFLAGS     __FIX_EFLAGS
  46 #endif
  47
  48 asmlinkage long
  49 sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
  50                 struct pt_regs *regs)
  51 {
  52         return do_sigaltstack(uss, uoss, regs->sp);
  53 }
  54
  55 #define COPY(x)                 {               \
  56         err |= __get_user(regs->x, &sc->x);     \
  57 }
  58
  59 #define COPY_SEG_STRICT(seg)    {                       \
  60                 unsigned short tmp;                     \
  61                 err |= __get_user(tmp, &sc->seg);       \
  62                 regs->seg = tmp | 3;                    \
  63 }
  64
  65 /*
  66  * Do a signal return; undo the signal stack.
  67  */
  68 static int
  69 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
  70                    unsigned long *pax)
  71 {
  72         void __user *buf;
  73         unsigned int tmpflags;
  74         unsigned int err = 0;
  75
  76         /* Always make any pending restarted system calls return -EINTR */
  77         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  78
  79         COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
  80         COPY(dx); COPY(cx); COPY(ip);
  81         COPY(r8);
  82         COPY(r9);
  83         COPY(r10);
  84         COPY(r11);
  85         COPY(r12);
  86         COPY(r13);
  87         COPY(r14);
  88         COPY(r15);
  89
  90         /* Kernel saves and restores only the CS segment register on signals,
  91          * which is the bare minimum needed to allow mixed 32/64-bit code.
  92          * App's signal handler can save/restore other segments if needed. */
  93         COPY_SEG_STRICT(cs);
  94
  95         err |= __get_user(tmpflags, &sc->flags);
  96         regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
  97         regs->orig_ax = -1;             /* disable syscall checks */
  98
  99         err |= __get_user(buf, &sc->fpstate);
 100         err |= restore_i387_xstate(buf);
 101
 102         err |= __get_user(*pax, &sc->ax);
 103         return err;
 104 }
 105
 106 static long do_rt_sigreturn(struct pt_regs *regs)
 107 {
 108         struct rt_sigframe __user *frame;
 109         unsigned long ax;
 110         sigset_t set;
 111
 112         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 113         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 114                 goto badframe;
 115         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 116                 goto badframe;
 117
 118         sigdelsetmask(&set, ~_BLOCKABLE);
 119         spin_lock_irq(&current->sighand->siglock);
 120         current->blocked = set;
 121         recalc_sigpending();
 122         spin_unlock_irq(&current->sighand->siglock);
 123
 124         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 125                 goto badframe;
 126
 127         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
 128                 goto badframe;
 129
 130         return ax;
 131
 132 badframe:
 133         signal_fault(regs, frame, "rt_sigreturn");
 134         return 0;
 135 }
 136
 137 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 138 {
 139         return do_rt_sigreturn(regs);
 140 }
 141
 142 /*
 143  * Set up a signal frame.
 144  */
 145
 146 static inline int
 147 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
 148                 unsigned long mask, struct task_struct *me)
 149 {
 150         int err = 0;
 151
 152         err |= __put_user(regs->cs, &sc->cs);
 153         err |= __put_user(0, &sc->gs);
 154         err |= __put_user(0, &sc->fs);
 155
 156         err |= __put_user(regs->di, &sc->di);
 157         err |= __put_user(regs->si, &sc->si);
 158         err |= __put_user(regs->bp, &sc->bp);
 159         err |= __put_user(regs->sp, &sc->sp);
 160         err |= __put_user(regs->bx, &sc->bx);
 161         err |= __put_user(regs->dx, &sc->dx);
 162         err |= __put_user(regs->cx, &sc->cx);
 163         err |= __put_user(regs->ax, &sc->ax);
 164         err |= __put_user(regs->r8, &sc->r8);
 165         err |= __put_user(regs->r9, &sc->r9);
 166         err |= __put_user(regs->r10, &sc->r10);
 167         err |= __put_user(regs->r11, &sc->r11);
 168         err |= __put_user(regs->r12, &sc->r12);
 169         err |= __put_user(regs->r13, &sc->r13);
 170         err |= __put_user(regs->r14, &sc->r14);
 171         err |= __put_user(regs->r15, &sc->r15);
 172         err |= __put_user(me->thread.trap_no, &sc->trapno);
 173         err |= __put_user(me->thread.error_code, &sc->err);
 174         err |= __put_user(regs->ip, &sc->ip);
 175         err |= __put_user(regs->flags, &sc->flags);
 176         err |= __put_user(mask, &sc->oldmask);
 177         err |= __put_user(me->thread.cr2, &sc->cr2);
 178
 179         return err;
 180 }
 181
 182 /*
 183  * Determine which stack to use..
 184  */
 185
 186 static void __user *
 187 get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
 188 {
 189         unsigned long sp;
 190
 191         /* Default to using normal stack - redzone*/
 192         sp = regs->sp - 128;
 193
 194         /* This is the X/Open sanctioned signal stack switching.  */
 195         if (ka->sa.sa_flags & SA_ONSTACK) {
 196                 if (sas_ss_flags(sp) == 0)
 197                         sp = current->sas_ss_sp + current->sas_ss_size;
 198         }
 199
 200         return (void __user *)round_down(sp - size, 64);
 201 }
 202
 203 static int __setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 204                             sigset_t *set, struct pt_regs *regs)
 205 {
 206         struct rt_sigframe __user *frame;
 207         void __user *fp = NULL;
 208         int err = 0;
 209         struct task_struct *me = current;
 210
 211         if (used_math()) {
 212                 fp = get_stack(ka, regs, sig_xstate_size);
 213                 frame = (void __user *)round_down(
 214                         (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
 215
 216                 if (save_i387_xstate(fp) < 0)
 217                         return -EFAULT;
 218         } else
 219                 frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
 220
 221         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 222                 return -EFAULT;
 223
 224         if (ka->sa.sa_flags & SA_SIGINFO) {
 225                 if (copy_siginfo_to_user(&frame->info, info))
 226                         return -EFAULT;
 227         }
 228
 229         /* Create the ucontext.  */
 230         if (cpu_has_xsave)
 231                 err |= __put_user(UC_FP_XSTATE, &frame->uc.uc_flags);
 232         else
 233                 err |= __put_user(0, &frame->uc.uc_flags);
 234         err |= __put_user(0, &frame->uc.uc_link);
 235         err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 236         err |= __put_user(sas_ss_flags(regs->sp),
 237                           &frame->uc.uc_stack.ss_flags);
 238         err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
 239         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
 240         err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
 241         if (sizeof(*set) == 16) {
 242                 __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 243                 __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
 244         } else
 245                 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 246
 247         /* Set up to return from userspace.  If provided, use a stub
 248            already in userspace.  */
 249         /* x86-64 should always use SA_RESTORER. */
 250         if (ka->sa.sa_flags & SA_RESTORER) {
 251                 err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
 252         } else {
 253                 /* could use a vstub here */
 254                 return -EFAULT;
 255         }
 256
 257         if (err)
 258                 return -EFAULT;
 259
 260         /* Set up registers for signal handler */
 261         regs->di = sig;
 262         /* In case the signal handler was declared without prototypes */
 263         regs->ax = 0;
 264
 265         /* This also works for non SA_SIGINFO handlers because they expect the
 266            next argument after the signal number on the stack. */
 267         regs->si = (unsigned long)&frame->info;
 268         regs->dx = (unsigned long)&frame->uc;
 269         regs->ip = (unsigned long) ka->sa.sa_handler;
 270
 271         regs->sp = (unsigned long)frame;
 272
 273         /* Set up the CS register to run signal handlers in 64-bit mode,
 274            even if the handler happens to be interrupting 32-bit code. */
 275         regs->cs = __USER_CS;
 276
 277         return 0;
 278 }
 279
 280 /*
 281  * OK, we're invoking a handler
 282  */
 283 static int signr_convert(int sig)
 284 {
 285         return sig;
 286 }
 287
 288 #ifdef CONFIG_IA32_EMULATION
 289 #define is_ia32 test_thread_flag(TIF_IA32)
 290 #else
 291 #define is_ia32 0
 292 #endif
 293
 294 static int
 295 setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 296                sigset_t *set, struct pt_regs *regs)
 297 {
 298         int usig = signr_convert(sig);
 299         int ret;
 300
 301         /* Set up the stack frame */
 302         if (is_ia32) {
 303                 if (ka->sa.sa_flags & SA_SIGINFO)
 304                         ret = ia32_setup_rt_frame(usig, ka, info, set, regs);
 305                 else
 306                         ret = ia32_setup_frame(usig, ka, set, regs);
 307         } else
 308                 ret = __setup_rt_frame(sig, ka, info, set, regs);
 309
 310         if (ret) {
 311                 force_sigsegv(sig, current);
 312                 return -EFAULT;
 313         }
 314
 315         return ret;
 316 }
 317
 318 static int
 319 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 320               sigset_t *oldset, struct pt_regs *regs)
 321 {
 322         int ret;
 323
 324         /* Are we from a system call? */
 325         if (syscall_get_nr(current, regs) >= 0) {
 326                 /* If so, check system call restarting.. */
 327                 switch (syscall_get_error(current, regs)) {
 328                 case -ERESTART_RESTARTBLOCK:
 329                 case -ERESTARTNOHAND:
 330                         regs->ax = -EINTR;
 331                         break;
 332
 333                 case -ERESTARTSYS:
 334                         if (!(ka->sa.sa_flags & SA_RESTART)) {
 335                                 regs->ax = -EINTR;
 336                                 break;
 337                         }
 338                 /* fallthrough */
 339                 case -ERESTARTNOINTR:
 340                         regs->ax = regs->orig_ax;
 341                         regs->ip -= 2;
 342                         break;
 343                 }
 344         }
 345
 346         /*
 347          * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
 348          * flag so that register information in the sigcontext is correct.
 349          */
 350         if (unlikely(regs->flags & X86_EFLAGS_TF) &&
 351             likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 352                 regs->flags &= ~X86_EFLAGS_TF;
 353
 354         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 355
 356         if (ret)
 357                 return ret;
 358
 359 #ifdef CONFIG_X86_64
 360         /*
 361          * This has nothing to do with segment registers,
 362          * despite the name.  This magic affects uaccess.h
 363          * macros' behavior.  Reset it to the normal setting.
 364          */
 365         set_fs(USER_DS);
 366 #endif
 367
 368         /*
 369          * Clear the direction flag as per the ABI for function entry.
 370          */
 371         regs->flags &= ~X86_EFLAGS_DF;
 372
 373         /*
 374          * Clear TF when entering the signal handler, but
 375          * notify any tracer that was single-stepping it.
 376          * The tracer may want to single-step inside the
 377          * handler too.
 378          */
 379         regs->flags &= ~X86_EFLAGS_TF;
 380
 381         spin_lock_irq(&current->sighand->siglock);
 382         sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
 383         if (!(ka->sa.sa_flags & SA_NODEFER))
 384                 sigaddset(&current->blocked, sig);
 385         recalc_sigpending();
 386         spin_unlock_irq(&current->sighand->siglock);
 387
 388         tracehook_signal_handler(sig, info, ka, regs,
 389                                  test_thread_flag(TIF_SINGLESTEP));
 390
 391         return 0;
 392 }
 393
 394 #define NR_restart_syscall      \
 395         test_thread_flag(TIF_IA32) ? __NR_ia32_restart_syscall : __NR_restart_syscall
 396 /*
 397  * Note that 'init' is a special process: it doesn't get signals it doesn't
 398  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 399  * mistake.
 400  */
 401 static void do_signal(struct pt_regs *regs)
 402 {
 403         struct k_sigaction ka;
 404         siginfo_t info;
 405         int signr;
 406         sigset_t *oldset;
 407
 408         /*
 409          * We want the common case to go fast, which is why we may in certain
 410          * cases get here from kernel mode. Just return without doing anything
 411          * if so.
 412          * X86_32: vm86 regs switched out by assembly code before reaching
 413          * here, so testing against kernel CS suffices.
 414          */
 415         if (!user_mode(regs))
 416                 return;
 417
 418         if (current_thread_info()->status & TS_RESTORE_SIGMASK)
 419                 oldset = &current->saved_sigmask;
 420         else
 421                 oldset = &current->blocked;
 422
 423         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 424         if (signr > 0) {
 425                 /*
 426                  * Re-enable any watchpoints before delivering the
 427                  * signal to user space. The processor register will
 428                  * have been cleared if the watchpoint triggered
 429                  * inside the kernel.
 430                  */
 431                 if (current->thread.debugreg7)
 432                         set_debugreg(current->thread.debugreg7, 7);
 433
 434                 /* Whee! Actually deliver the signal.  */
 435                 if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 436                         /*
 437                          * A signal was successfully delivered; the saved
 438                          * sigmask will have been stored in the signal frame,
 439                          * and will be restored by sigreturn, so we can simply
 440                          * clear the TS_RESTORE_SIGMASK flag.
 441                          */
 442                         current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 443                 }
 444                 return;
 445         }
 446
 447         /* Did we come from a system call? */
 448         if (syscall_get_nr(current, regs) >= 0) {
 449                 /* Restart the system call - no handlers present */
 450                 switch (syscall_get_error(current, regs)) {
 451                 case -ERESTARTNOHAND:
 452                 case -ERESTARTSYS:
 453                 case -ERESTARTNOINTR:
 454                         regs->ax = regs->orig_ax;
 455                         regs->ip -= 2;
 456                         break;
 457
 458                 case -ERESTART_RESTARTBLOCK:
 459                         regs->ax = NR_restart_syscall;
 460                         regs->ip -= 2;
 461                         break;
 462                 }
 463         }
 464
 465         /*
 466          * If there's no signal to deliver, we just put the saved sigmask
 467          * back.
 468          */
 469         if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
 470                 current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 471                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 472         }
 473 }
 474
 475 /*
 476  * notification of userspace execution resumption
 477  * - triggered by the TIF_WORK_MASK flags
 478  */
 479 void
 480 do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
 481 {
 482 #if defined(CONFIG_X86_64) && defined(CONFIG_X86_MCE)
 483         /* notify userspace of pending MCEs */
 484         if (thread_info_flags & _TIF_MCE_NOTIFY)
 485                 mce_notify_user();
 486 #endif /* CONFIG_X86_64 && CONFIG_X86_MCE */
 487
 488         /* deal with pending signal delivery */
 489         if (thread_info_flags & _TIF_SIGPENDING)
 490                 do_signal(regs);
 491
 492         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 493                 clear_thread_flag(TIF_NOTIFY_RESUME);
 494                 tracehook_notify_resume(regs);
 495         }
 496
 497 #ifdef CONFIG_X86_32
 498         clear_thread_flag(TIF_IRET);
 499 #endif /* CONFIG_X86_32 */
 500 }
 501
 502 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 503 {
 504         struct task_struct *me = current;
 505
 506         if (show_unhandled_signals && printk_ratelimit()) {
 507                 printk(KERN_INFO
 508                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 509                        me->comm, me->pid, where, frame,
 510                        regs->ip, regs->sp, regs->orig_ax);
 511                 print_vma_addr(" in ", regs->ip);
 512                 printk(KERN_CONT "\n");
 513         }
 514
 515         force_sig(SIGSEGV, me);
 516 }