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