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  * Signal frame handlers.
  58  */
  59
  60 static inline int save_i387(struct _fpstate __user *buf)
  61 {
  62         struct task_struct *tsk = current;
  63         int err = 0;
  64
  65         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
  66                         sizeof(tsk->thread.xstate->fxsave));
  67
  68         if ((unsigned long)buf % 16)
  69                 printk("save_i387: bad fpstate %p\n", buf);
  70
  71         if (!used_math())
  72                 return 0;
  73         clear_used_math(); /* trigger finit */
  74         if (task_thread_info(tsk)->status & TS_USEDFPU) {
  75                 err = save_i387_checking((struct i387_fxsave_struct __user *)
  76                                          buf);
  77                 if (err)
  78                         return err;
  79                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
  80                 stts();
  81         } else {
  82                 if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
  83                                    sizeof(struct i387_fxsave_struct)))
  84                         return -1;
  85         }
  86         return 1;
  87 }
  88
  89 /*
  90  * This restores directly out of user space. Exceptions are handled.
  91  */
  92 static inline int restore_i387(struct _fpstate __user *buf)
  93 {
  94         struct task_struct *tsk = current;
  95         int err;
  96
  97         if (!used_math()) {
  98                 err = init_fpu(tsk);
  99                 if (err)
 100                         return err;
 101         }
 102
 103         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
 104                 clts();
 105                 task_thread_info(current)->status |= TS_USEDFPU;
 106         }
 107         return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);
 108 }
 109
 110 /*
 111  * Do a signal return; undo the signal stack.
 112  */
 113 static int
 114 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
 115                    unsigned long *pax)
 116 {
 117         unsigned int err = 0;
 118
 119         /* Always make any pending restarted system calls return -EINTR */
 120         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 121
 122 #define COPY(x)         err |= __get_user(regs->x, &sc->x)
 123
 124         COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
 125         COPY(dx); COPY(cx); COPY(ip);
 126         COPY(r8);
 127         COPY(r9);
 128         COPY(r10);
 129         COPY(r11);
 130         COPY(r12);
 131         COPY(r13);
 132         COPY(r14);
 133         COPY(r15);
 134
 135         /* Kernel saves and restores only the CS segment register on signals,
 136          * which is the bare minimum needed to allow mixed 32/64-bit code.
 137          * App's signal handler can save/restore other segments if needed. */
 138         {
 139                 unsigned cs;
 140                 err |= __get_user(cs, &sc->cs);
 141                 regs->cs = cs | 3;      /* Force into user mode */
 142         }
 143
 144         {
 145                 unsigned int tmpflags;
 146                 err |= __get_user(tmpflags, &sc->flags);
 147                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 148                 regs->orig_ax = -1;             /* disable syscall checks */
 149         }
 150
 151         {
 152                 struct _fpstate __user * buf;
 153                 err |= __get_user(buf, &sc->fpstate);
 154
 155                 if (buf) {
 156                         if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
 157                                 goto badframe;
 158                         err |= restore_i387(buf);
 159                 } else {
 160                         struct task_struct *me = current;
 161                         if (used_math()) {
 162                                 clear_fpu(me);
 163                                 clear_used_math();
 164                         }
 165                 }
 166         }
 167
 168         err |= __get_user(*pax, &sc->ax);
 169         return err;
 170
 171 badframe:
 172         return 1;
 173 }
 174
 175 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 176 {
 177         struct rt_sigframe __user *frame;
 178         sigset_t set;
 179         unsigned long ax;
 180
 181         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 182         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 183                 goto badframe;
 184         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 185                 goto badframe;
 186
 187         sigdelsetmask(&set, ~_BLOCKABLE);
 188         spin_lock_irq(&current->sighand->siglock);
 189         current->blocked = set;
 190         recalc_sigpending();
 191         spin_unlock_irq(&current->sighand->siglock);
 192
 193         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 194                 goto badframe;
 195
 196         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
 197                 goto badframe;
 198
 199         return ax;
 200
 201 badframe:
 202         signal_fault(regs,frame,"sigreturn");
 203         return 0;
 204 }
 205
 206 /*
 207  * Set up a signal frame.
 208  */
 209
 210 static inline int
 211 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
 212 {
 213         int err = 0;
 214
 215         err |= __put_user(regs->cs, &sc->cs);
 216         err |= __put_user(0, &sc->gs);
 217         err |= __put_user(0, &sc->fs);
 218
 219         err |= __put_user(regs->di, &sc->di);
 220         err |= __put_user(regs->si, &sc->si);
 221         err |= __put_user(regs->bp, &sc->bp);
 222         err |= __put_user(regs->sp, &sc->sp);
 223         err |= __put_user(regs->bx, &sc->bx);
 224         err |= __put_user(regs->dx, &sc->dx);
 225         err |= __put_user(regs->cx, &sc->cx);
 226         err |= __put_user(regs->ax, &sc->ax);
 227         err |= __put_user(regs->r8, &sc->r8);
 228         err |= __put_user(regs->r9, &sc->r9);
 229         err |= __put_user(regs->r10, &sc->r10);
 230         err |= __put_user(regs->r11, &sc->r11);
 231         err |= __put_user(regs->r12, &sc->r12);
 232         err |= __put_user(regs->r13, &sc->r13);
 233         err |= __put_user(regs->r14, &sc->r14);
 234         err |= __put_user(regs->r15, &sc->r15);
 235         err |= __put_user(me->thread.trap_no, &sc->trapno);
 236         err |= __put_user(me->thread.error_code, &sc->err);
 237         err |= __put_user(regs->ip, &sc->ip);
 238         err |= __put_user(regs->flags, &sc->flags);
 239         err |= __put_user(mask, &sc->oldmask);
 240         err |= __put_user(me->thread.cr2, &sc->cr2);
 241
 242         return err;
 243 }
 244
 245 /*
 246  * Determine which stack to use..
 247  */
 248
 249 static void __user *
 250 get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
 251 {
 252         unsigned long sp;
 253
 254         /* Default to using normal stack - redzone*/
 255         sp = regs->sp - 128;
 256
 257         /* This is the X/Open sanctioned signal stack switching.  */
 258         if (ka->sa.sa_flags & SA_ONSTACK) {
 259                 if (sas_ss_flags(sp) == 0)
 260                         sp = current->sas_ss_sp + current->sas_ss_size;
 261         }
 262
 263         return (void __user *)round_down(sp - size, 16);
 264 }
 265
 266 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 267                            sigset_t *set, struct pt_regs * regs)
 268 {
 269         struct rt_sigframe __user *frame;
 270         struct _fpstate __user *fp = NULL;
 271         int err = 0;
 272         struct task_struct *me = current;
 273
 274         if (used_math()) {
 275                 fp = get_stack(ka, regs, sizeof(struct _fpstate));
 276                 frame = (void __user *)round_down(
 277                         (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
 278
 279                 if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
 280                         goto give_sigsegv;
 281
 282                 if (save_i387(fp) < 0)
 283                         err |= -1;
 284         } else
 285                 frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
 286
 287         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 288                 goto give_sigsegv;
 289
 290         if (ka->sa.sa_flags & SA_SIGINFO) {
 291                 err |= copy_siginfo_to_user(&frame->info, info);
 292                 if (err)
 293                         goto give_sigsegv;
 294         }
 295
 296         /* Create the ucontext.  */
 297         err |= __put_user(0, &frame->uc.uc_flags);
 298         err |= __put_user(0, &frame->uc.uc_link);
 299         err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 300         err |= __put_user(sas_ss_flags(regs->sp),
 301                           &frame->uc.uc_stack.ss_flags);
 302         err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
 303         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
 304         err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
 305         if (sizeof(*set) == 16) {
 306                 __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 307                 __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
 308         } else
 309                 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 310
 311         /* Set up to return from userspace.  If provided, use a stub
 312            already in userspace.  */
 313         /* x86-64 should always use SA_RESTORER. */
 314         if (ka->sa.sa_flags & SA_RESTORER) {
 315                 err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
 316         } else {
 317                 /* could use a vstub here */
 318                 goto give_sigsegv;
 319         }
 320
 321         if (err)
 322                 goto give_sigsegv;
 323
 324         /* Set up registers for signal handler */
 325         regs->di = sig;
 326         /* In case the signal handler was declared without prototypes */
 327         regs->ax = 0;
 328
 329         /* This also works for non SA_SIGINFO handlers because they expect the
 330            next argument after the signal number on the stack. */
 331         regs->si = (unsigned long)&frame->info;
 332         regs->dx = (unsigned long)&frame->uc;
 333         regs->ip = (unsigned long) ka->sa.sa_handler;
 334
 335         regs->sp = (unsigned long)frame;
 336
 337         /* Set up the CS register to run signal handlers in 64-bit mode,
 338            even if the handler happens to be interrupting 32-bit code. */
 339         regs->cs = __USER_CS;
 340
 341         return 0;
 342
 343 give_sigsegv:
 344         force_sigsegv(sig, current);
 345         return -EFAULT;
 346 }
 347
 348 /*
 349  * Return -1L or the syscall number that @regs is executing.
 350  */
 351 static long current_syscall(struct pt_regs *regs)
 352 {
 353         /*
 354          * We always sign-extend a -1 value being set here,
 355          * so this is always either -1L or a syscall number.
 356          */
 357         return regs->orig_ax;
 358 }
 359
 360 /*
 361  * Return a value that is -EFOO if the system call in @regs->orig_ax
 362  * returned an error.  This only works for @regs from @current.
 363  */
 364 static long current_syscall_ret(struct pt_regs *regs)
 365 {
 366 #ifdef CONFIG_IA32_EMULATION
 367         if (test_thread_flag(TIF_IA32))
 368                 /*
 369                  * Sign-extend the value so (int)-EFOO becomes (long)-EFOO
 370                  * and will match correctly in comparisons.
 371                  */
 372                 return (int) regs->ax;
 373 #endif
 374         return regs->ax;
 375 }
 376
 377 /*
 378  * OK, we're invoking a handler
 379  */
 380
 381 static int
 382 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 383               sigset_t *oldset, struct pt_regs *regs)
 384 {
 385         int ret;
 386
 387         /* Are we from a system call? */
 388         if (current_syscall(regs) >= 0) {
 389                 /* If so, check system call restarting.. */
 390                 switch (current_syscall_ret(regs)) {
 391                 case -ERESTART_RESTARTBLOCK:
 392                 case -ERESTARTNOHAND:
 393                         regs->ax = -EINTR;
 394                         break;
 395
 396                 case -ERESTARTSYS:
 397                         if (!(ka->sa.sa_flags & SA_RESTART)) {
 398                                 regs->ax = -EINTR;
 399                                 break;
 400                         }
 401                 /* fallthrough */
 402                 case -ERESTARTNOINTR:
 403                         regs->ax = regs->orig_ax;
 404                         regs->ip -= 2;
 405                         break;
 406                 }
 407         }
 408
 409         /*
 410          * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
 411          * flag so that register information in the sigcontext is correct.
 412          */
 413         if (unlikely(regs->flags & X86_EFLAGS_TF) &&
 414             likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 415                 regs->flags &= ~X86_EFLAGS_TF;
 416
 417 #ifdef CONFIG_IA32_EMULATION
 418         if (test_thread_flag(TIF_IA32)) {
 419                 if (ka->sa.sa_flags & SA_SIGINFO)
 420                         ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
 421                 else
 422                         ret = ia32_setup_frame(sig, ka, oldset, regs);
 423         } else
 424 #endif
 425         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 426
 427         if (ret == 0) {
 428                 /*
 429                  * This has nothing to do with segment registers,
 430                  * despite the name.  This magic affects uaccess.h
 431                  * macros' behavior.  Reset it to the normal setting.
 432                  */
 433                 set_fs(USER_DS);
 434
 435                 /*
 436                  * Clear the direction flag as per the ABI for function entry.
 437                  */
 438                 regs->flags &= ~X86_EFLAGS_DF;
 439
 440                 /*
 441                  * Clear TF when entering the signal handler, but
 442                  * notify any tracer that was single-stepping it.
 443                  * The tracer may want to single-step inside the
 444                  * handler too.
 445                  */
 446                 regs->flags &= ~X86_EFLAGS_TF;
 447                 if (test_thread_flag(TIF_SINGLESTEP))
 448                         ptrace_notify(SIGTRAP);
 449
 450                 spin_lock_irq(&current->sighand->siglock);
 451                 sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 452                 if (!(ka->sa.sa_flags & SA_NODEFER))
 453                         sigaddset(&current->blocked,sig);
 454                 recalc_sigpending();
 455                 spin_unlock_irq(&current->sighand->siglock);
 456         }
 457
 458         return ret;
 459 }
 460
 461 /*
 462  * Note that 'init' is a special process: it doesn't get signals it doesn't
 463  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 464  * mistake.
 465  */
 466 static void do_signal(struct pt_regs *regs)
 467 {
 468         struct k_sigaction ka;
 469         siginfo_t info;
 470         int signr;
 471         sigset_t *oldset;
 472
 473         /*
 474          * We want the common case to go fast, which is why we may in certain
 475          * cases get here from kernel mode. Just return without doing anything
 476          * if so.
 477          * X86_32: vm86 regs switched out by assembly code before reaching
 478          * here, so testing against kernel CS suffices.
 479          */
 480         if (!user_mode(regs))
 481                 return;
 482
 483         if (current_thread_info()->status & TS_RESTORE_SIGMASK)
 484                 oldset = &current->saved_sigmask;
 485         else
 486                 oldset = &current->blocked;
 487
 488         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 489         if (signr > 0) {
 490                 /* Re-enable any watchpoints before delivering the
 491                  * signal to user space. The processor register will
 492                  * have been cleared if the watchpoint triggered
 493                  * inside the kernel.
 494                  */
 495                 if (current->thread.debugreg7)
 496                         set_debugreg(current->thread.debugreg7, 7);
 497
 498                 /* Whee!  Actually deliver the signal.  */
 499                 if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 500                         /*
 501                          * A signal was successfully delivered; the saved
 502                          * sigmask will have been stored in the signal frame,
 503                          * and will be restored by sigreturn, so we can simply
 504                          * clear the TS_RESTORE_SIGMASK flag.
 505                          */
 506                         current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 507                 }
 508                 return;
 509         }
 510
 511         /* Did we come from a system call? */
 512         if (current_syscall(regs) >= 0) {
 513                 /* Restart the system call - no handlers present */
 514                 switch (current_syscall_ret(regs)) {
 515                 case -ERESTARTNOHAND:
 516                 case -ERESTARTSYS:
 517                 case -ERESTARTNOINTR:
 518                         regs->ax = regs->orig_ax;
 519                         regs->ip -= 2;
 520                         break;
 521                 case -ERESTART_RESTARTBLOCK:
 522                         regs->ax = test_thread_flag(TIF_IA32) ?
 523                                         __NR_ia32_restart_syscall :
 524                                         __NR_restart_syscall;
 525                         regs->ip -= 2;
 526                         break;
 527                 }
 528         }
 529
 530         /*
 531          * If there's no signal to deliver, we just put the saved sigmask
 532          * back.
 533          */
 534         if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
 535                 current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 536                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 537         }
 538 }
 539
 540 void do_notify_resume(struct pt_regs *regs, void *unused,
 541                       __u32 thread_info_flags)
 542 {
 543 #ifdef CONFIG_X86_MCE
 544         /* notify userspace of pending MCEs */
 545         if (thread_info_flags & _TIF_MCE_NOTIFY)
 546                 mce_notify_user();
 547 #endif /* CONFIG_X86_MCE */
 548
 549         /* deal with pending signal delivery */
 550         if (thread_info_flags & _TIF_SIGPENDING)
 551                 do_signal(regs);
 552 }
 553
 554 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 555 {
 556         struct task_struct *me = current;
 557         if (show_unhandled_signals && printk_ratelimit()) {
 558                 printk("%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 559                me->comm,me->pid,where,frame,regs->ip,regs->sp,regs->orig_ax);
 560                 print_vma_addr(" in ", regs->ip);
 561                 printk("\n");
 562         }
 563
 564         force_sig(SIGSEGV, me);
 565 }