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