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