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