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         err = restore_fpu_checking((__force struct i387_fxsave_struct *)buf);
 108         if (unlikely(err)) {
 109                 /*
 110                  * Encountered an error while doing the restore from the
 111                  * user buffer, clear the fpu state.
 112                  */
 113                 clear_fpu(tsk);
 114                 clear_used_math();
 115         }
 116         return err;
 117 }
 118
 119 /*
 120  * Do a signal return; undo the signal stack.
 121  */
 122 static int
 123 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
 124                    unsigned long *pax)
 125 {
 126         unsigned int err = 0;
 127
 128         /* Always make any pending restarted system calls return -EINTR */
 129         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 130
 131 #define COPY(x)         err |= __get_user(regs->x, &sc->x)
 132
 133         COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
 134         COPY(dx); COPY(cx); COPY(ip);
 135         COPY(r8);
 136         COPY(r9);
 137         COPY(r10);
 138         COPY(r11);
 139         COPY(r12);
 140         COPY(r13);
 141         COPY(r14);
 142         COPY(r15);
 143
 144         /* Kernel saves and restores only the CS segment register on signals,
 145          * which is the bare minimum needed to allow mixed 32/64-bit code.
 146          * App's signal handler can save/restore other segments if needed. */
 147         {
 148                 unsigned cs;
 149                 err |= __get_user(cs, &sc->cs);
 150                 regs->cs = cs | 3;      /* Force into user mode */
 151         }
 152
 153         {
 154                 unsigned int tmpflags;
 155                 err |= __get_user(tmpflags, &sc->flags);
 156                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 157                 regs->orig_ax = -1;             /* disable syscall checks */
 158         }
 159
 160         {
 161                 struct _fpstate __user * buf;
 162                 err |= __get_user(buf, &sc->fpstate);
 163
 164                 if (buf) {
 165                         if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
 166                                 goto badframe;
 167                         err |= restore_i387(buf);
 168                 } else {
 169                         struct task_struct *me = current;
 170                         if (used_math()) {
 171                                 clear_fpu(me);
 172                                 clear_used_math();
 173                         }
 174                 }
 175         }
 176
 177         err |= __get_user(*pax, &sc->ax);
 178         return err;
 179
 180 badframe:
 181         return 1;
 182 }
 183
 184 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 185 {
 186         struct rt_sigframe __user *frame;
 187         sigset_t set;
 188         unsigned long ax;
 189
 190         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 191         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 192                 goto badframe;
 193         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 194                 goto badframe;
 195
 196         sigdelsetmask(&set, ~_BLOCKABLE);
 197         spin_lock_irq(&current->sighand->siglock);
 198         current->blocked = set;
 199         recalc_sigpending();
 200         spin_unlock_irq(&current->sighand->siglock);
 201
 202         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 203                 goto badframe;
 204
 205         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
 206                 goto badframe;
 207
 208         return ax;
 209
 210 badframe:
 211         signal_fault(regs,frame,"sigreturn");
 212         return 0;
 213 }
 214
 215 /*
 216  * Set up a signal frame.
 217  */
 218
 219 static inline int
 220 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
 221 {
 222         int err = 0;
 223
 224         err |= __put_user(regs->cs, &sc->cs);
 225         err |= __put_user(0, &sc->gs);
 226         err |= __put_user(0, &sc->fs);
 227
 228         err |= __put_user(regs->di, &sc->di);
 229         err |= __put_user(regs->si, &sc->si);
 230         err |= __put_user(regs->bp, &sc->bp);
 231         err |= __put_user(regs->sp, &sc->sp);
 232         err |= __put_user(regs->bx, &sc->bx);
 233         err |= __put_user(regs->dx, &sc->dx);
 234         err |= __put_user(regs->cx, &sc->cx);
 235         err |= __put_user(regs->ax, &sc->ax);
 236         err |= __put_user(regs->r8, &sc->r8);
 237         err |= __put_user(regs->r9, &sc->r9);
 238         err |= __put_user(regs->r10, &sc->r10);
 239         err |= __put_user(regs->r11, &sc->r11);
 240         err |= __put_user(regs->r12, &sc->r12);
 241         err |= __put_user(regs->r13, &sc->r13);
 242         err |= __put_user(regs->r14, &sc->r14);
 243         err |= __put_user(regs->r15, &sc->r15);
 244         err |= __put_user(me->thread.trap_no, &sc->trapno);
 245         err |= __put_user(me->thread.error_code, &sc->err);
 246         err |= __put_user(regs->ip, &sc->ip);
 247         err |= __put_user(regs->flags, &sc->flags);
 248         err |= __put_user(mask, &sc->oldmask);
 249         err |= __put_user(me->thread.cr2, &sc->cr2);
 250
 251         return err;
 252 }
 253
 254 /*
 255  * Determine which stack to use..
 256  */
 257
 258 static void __user *
 259 get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
 260 {
 261         unsigned long sp;
 262
 263         /* Default to using normal stack - redzone*/
 264         sp = regs->sp - 128;
 265
 266         /* This is the X/Open sanctioned signal stack switching.  */
 267         if (ka->sa.sa_flags & SA_ONSTACK) {
 268                 if (sas_ss_flags(sp) == 0)
 269                         sp = current->sas_ss_sp + current->sas_ss_size;
 270         }
 271
 272         return (void __user *)round_down(sp - size, 16);
 273 }
 274
 275 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 276                            sigset_t *set, struct pt_regs * regs)
 277 {
 278         struct rt_sigframe __user *frame;
 279         struct _fpstate __user *fp = NULL;
 280         int err = 0;
 281         struct task_struct *me = current;
 282
 283         if (used_math()) {
 284                 fp = get_stack(ka, regs, sig_xstate_size);
 285                 frame = (void __user *)round_down(
 286                         (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
 287
 288                 if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
 289                         goto give_sigsegv;
 290
 291                 if (save_i387(fp) < 0)
 292                         err |= -1;
 293         } else
 294                 frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
 295
 296         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 297                 goto give_sigsegv;
 298
 299         if (ka->sa.sa_flags & SA_SIGINFO) {
 300                 err |= copy_siginfo_to_user(&frame->info, info);
 301                 if (err)
 302                         goto give_sigsegv;
 303         }
 304
 305         /* Create the ucontext.  */
 306         err |= __put_user(0, &frame->uc.uc_flags);
 307         err |= __put_user(0, &frame->uc.uc_link);
 308         err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 309         err |= __put_user(sas_ss_flags(regs->sp),
 310                           &frame->uc.uc_stack.ss_flags);
 311         err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
 312         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
 313         err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
 314         if (sizeof(*set) == 16) {
 315                 __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 316                 __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
 317         } else
 318                 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 319
 320         /* Set up to return from userspace.  If provided, use a stub
 321            already in userspace.  */
 322         /* x86-64 should always use SA_RESTORER. */
 323         if (ka->sa.sa_flags & SA_RESTORER) {
 324                 err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
 325         } else {
 326                 /* could use a vstub here */
 327                 goto give_sigsegv;
 328         }
 329
 330         if (err)
 331                 goto give_sigsegv;
 332
 333         /* Set up registers for signal handler */
 334         regs->di = sig;
 335         /* In case the signal handler was declared without prototypes */
 336         regs->ax = 0;
 337
 338         /* This also works for non SA_SIGINFO handlers because they expect the
 339            next argument after the signal number on the stack. */
 340         regs->si = (unsigned long)&frame->info;
 341         regs->dx = (unsigned long)&frame->uc;
 342         regs->ip = (unsigned long) ka->sa.sa_handler;
 343
 344         regs->sp = (unsigned long)frame;
 345
 346         /* Set up the CS register to run signal handlers in 64-bit mode,
 347            even if the handler happens to be interrupting 32-bit code. */
 348         regs->cs = __USER_CS;
 349
 350         return 0;
 351
 352 give_sigsegv:
 353         force_sigsegv(sig, current);
 354         return -EFAULT;
 355 }
 356
 357 /*
 358  * Return -1L or the syscall number that @regs is executing.
 359  */
 360 static long current_syscall(struct pt_regs *regs)
 361 {
 362         /*
 363          * We always sign-extend a -1 value being set here,
 364          * so this is always either -1L or a syscall number.
 365          */
 366         return regs->orig_ax;
 367 }
 368
 369 /*
 370  * Return a value that is -EFOO if the system call in @regs->orig_ax
 371  * returned an error.  This only works for @regs from @current.
 372  */
 373 static long current_syscall_ret(struct pt_regs *regs)
 374 {
 375 #ifdef CONFIG_IA32_EMULATION
 376         if (test_thread_flag(TIF_IA32))
 377                 /*
 378                  * Sign-extend the value so (int)-EFOO becomes (long)-EFOO
 379                  * and will match correctly in comparisons.
 380                  */
 381                 return (int) regs->ax;
 382 #endif
 383         return regs->ax;
 384 }
 385
 386 /*
 387  * OK, we're invoking a handler
 388  */
 389
 390 static int
 391 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 392               sigset_t *oldset, struct pt_regs *regs)
 393 {
 394         int ret;
 395
 396         /* Are we from a system call? */
 397         if (current_syscall(regs) >= 0) {
 398                 /* If so, check system call restarting.. */
 399                 switch (current_syscall_ret(regs)) {
 400                 case -ERESTART_RESTARTBLOCK:
 401                 case -ERESTARTNOHAND:
 402                         regs->ax = -EINTR;
 403                         break;
 404
 405                 case -ERESTARTSYS:
 406                         if (!(ka->sa.sa_flags & SA_RESTART)) {
 407                                 regs->ax = -EINTR;
 408                                 break;
 409                         }
 410                 /* fallthrough */
 411                 case -ERESTARTNOINTR:
 412                         regs->ax = regs->orig_ax;
 413                         regs->ip -= 2;
 414                         break;
 415                 }
 416         }
 417
 418         /*
 419          * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
 420          * flag so that register information in the sigcontext is correct.
 421          */
 422         if (unlikely(regs->flags & X86_EFLAGS_TF) &&
 423             likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 424                 regs->flags &= ~X86_EFLAGS_TF;
 425
 426 #ifdef CONFIG_IA32_EMULATION
 427         if (test_thread_flag(TIF_IA32)) {
 428                 if (ka->sa.sa_flags & SA_SIGINFO)
 429                         ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
 430                 else
 431                         ret = ia32_setup_frame(sig, ka, oldset, regs);
 432         } else
 433 #endif
 434         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 435
 436         if (ret == 0) {
 437                 /*
 438                  * This has nothing to do with segment registers,
 439                  * despite the name.  This magic affects uaccess.h
 440                  * macros' behavior.  Reset it to the normal setting.
 441                  */
 442                 set_fs(USER_DS);
 443
 444                 /*
 445                  * Clear the direction flag as per the ABI for function entry.
 446                  */
 447                 regs->flags &= ~X86_EFLAGS_DF;
 448
 449                 /*
 450                  * Clear TF when entering the signal handler, but
 451                  * notify any tracer that was single-stepping it.
 452                  * The tracer may want to single-step inside the
 453                  * handler too.
 454                  */
 455                 regs->flags &= ~X86_EFLAGS_TF;
 456                 if (test_thread_flag(TIF_SINGLESTEP))
 457                         ptrace_notify(SIGTRAP);
 458
 459                 spin_lock_irq(&current->sighand->siglock);
 460                 sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 461                 if (!(ka->sa.sa_flags & SA_NODEFER))
 462                         sigaddset(&current->blocked,sig);
 463                 recalc_sigpending();
 464                 spin_unlock_irq(&current->sighand->siglock);
 465         }
 466
 467         return ret;
 468 }
 469
 470 /*
 471  * Note that 'init' is a special process: it doesn't get signals it doesn't
 472  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 473  * mistake.
 474  */
 475 static void do_signal(struct pt_regs *regs)
 476 {
 477         struct k_sigaction ka;
 478         siginfo_t info;
 479         int signr;
 480         sigset_t *oldset;
 481
 482         /*
 483          * We want the common case to go fast, which is why we may in certain
 484          * cases get here from kernel mode. Just return without doing anything
 485          * if so.
 486          * X86_32: vm86 regs switched out by assembly code before reaching
 487          * here, so testing against kernel CS suffices.
 488          */
 489         if (!user_mode(regs))
 490                 return;
 491
 492         if (current_thread_info()->status & TS_RESTORE_SIGMASK)
 493                 oldset = &current->saved_sigmask;
 494         else
 495                 oldset = &current->blocked;
 496
 497         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 498         if (signr > 0) {
 499                 /* Re-enable any watchpoints before delivering the
 500                  * signal to user space. The processor register will
 501                  * have been cleared if the watchpoint triggered
 502                  * inside the kernel.
 503                  */
 504                 if (current->thread.debugreg7)
 505                         set_debugreg(current->thread.debugreg7, 7);
 506
 507                 /* Whee!  Actually deliver the signal.  */
 508                 if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 509                         /*
 510                          * A signal was successfully delivered; the saved
 511                          * sigmask will have been stored in the signal frame,
 512                          * and will be restored by sigreturn, so we can simply
 513                          * clear the TS_RESTORE_SIGMASK flag.
 514                          */
 515                         current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 516                 }
 517                 return;
 518         }
 519
 520         /* Did we come from a system call? */
 521         if (current_syscall(regs) >= 0) {
 522                 /* Restart the system call - no handlers present */
 523                 switch (current_syscall_ret(regs)) {
 524                 case -ERESTARTNOHAND:
 525                 case -ERESTARTSYS:
 526                 case -ERESTARTNOINTR:
 527                         regs->ax = regs->orig_ax;
 528                         regs->ip -= 2;
 529                         break;
 530                 case -ERESTART_RESTARTBLOCK:
 531                         regs->ax = test_thread_flag(TIF_IA32) ?
 532                                         __NR_ia32_restart_syscall :
 533                                         __NR_restart_syscall;
 534                         regs->ip -= 2;
 535                         break;
 536                 }
 537         }
 538
 539         /*
 540          * If there's no signal to deliver, we just put the saved sigmask
 541          * back.
 542          */
 543         if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
 544                 current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 545                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 546         }
 547 }
 548
 549 void do_notify_resume(struct pt_regs *regs, void *unused,
 550                       __u32 thread_info_flags)
 551 {
 552 #ifdef CONFIG_X86_MCE
 553         /* notify userspace of pending MCEs */
 554         if (thread_info_flags & _TIF_MCE_NOTIFY)
 555                 mce_notify_user();
 556 #endif /* CONFIG_X86_MCE */
 557
 558         /* deal with pending signal delivery */
 559         if (thread_info_flags & _TIF_SIGPENDING)
 560                 do_signal(regs);
 561 }
 562
 563 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 564 {
 565         struct task_struct *me = current;
 566         if (show_unhandled_signals && printk_ratelimit()) {
 567                 printk("%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 568                me->comm,me->pid,where,frame,regs->ip,regs->sp,regs->orig_ax);
 569                 print_vma_addr(" in ", regs->ip);
 570                 printk("\n");
 571         }
 572
 573         force_sig(SIGSEGV, me);
 574 }