arch/x86_64/kernel/signal.c

   1 /*
   2  *  linux/arch/x86_64/kernel/signal.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
   6  *
   7  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   8  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   9  *  2000-2002   x86-64 support by Andi Kleen
  10  */
  11
  12 #include <linux/sched.h>
  13 #include <linux/mm.h>
  14 #include <linux/smp.h>
  15 #include <linux/smp_lock.h>
  16 #include <linux/kernel.h>
  17 #include <linux/signal.h>
  18 #include <linux/errno.h>
  19 #include <linux/wait.h>
  20 #include <linux/ptrace.h>
  21 #include <linux/unistd.h>
  22 #include <linux/stddef.h>
  23 #include <linux/personality.h>
  24 #include <linux/compiler.h>
  25 #include <asm/ucontext.h>
  26 #include <asm/uaccess.h>
  27 #include <asm/i387.h>
  28 #include <asm/proto.h>
  29 #include <asm/ia32_unistd.h>
  30
  31 /* #define DEBUG_SIG 1 */
  32
  33 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  34
  35 int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
  36                sigset_t *set, struct pt_regs * regs);
  37 int ia32_setup_frame(int sig, struct k_sigaction *ka,
  38             sigset_t *set, struct pt_regs * regs);
  39
  40 asmlinkage long
  41 sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
  42                 struct pt_regs *regs)
  43 {
  44         return do_sigaltstack(uss, uoss, regs->rsp);
  45 }
  46
  47
  48 /*
  49  * Do a signal return; undo the signal stack.
  50  */
  51
  52 struct rt_sigframe
  53 {
  54         char __user *pretcode;
  55         struct ucontext uc;
  56         struct siginfo info;
  57 };
  58
  59 static int
  60 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned long *prax)
  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(rdi); COPY(rsi); COPY(rbp); COPY(rsp); COPY(rbx);
  70         COPY(rdx); COPY(rcx); COPY(rip);
  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->eflags);
  92                 regs->eflags = (regs->eflags & ~0x40DD5) | (tmpflags & 0x40DD5);
  93                 regs->orig_rax = -1;            /* disable syscall checks */
  94         }
  95
  96         {
  97                 struct _fpstate __user * buf;
  98                 err |= __get_user(buf, &sc->fpstate);
  99
 100                 if (buf) {
 101                         if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
 102                                 goto badframe;
 103                         err |= restore_i387(buf);
 104                 } else {
 105                         struct task_struct *me = current;
 106                         if (used_math()) {
 107                                 clear_fpu(me);
 108                                 clear_used_math();
 109                         }
 110                 }
 111         }
 112
 113         err |= __get_user(*prax, &sc->rax);
 114         return err;
 115
 116 badframe:
 117         return 1;
 118 }
 119
 120 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 121 {
 122         struct rt_sigframe __user *frame;
 123         sigset_t set;
 124         unsigned long eax;
 125
 126         frame = (struct rt_sigframe __user *)(regs->rsp - 8);
 127         if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) {
 128                 goto badframe;
 129         }
 130         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) {
 131                 goto badframe;
 132         }
 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, &eax))
 141                 goto badframe;
 142
 143 #ifdef DEBUG_SIG
 144         printk("%d sigreturn rip:%lx rsp:%lx frame:%p rax:%lx\n",current->pid,regs.rip,regs.rsp,frame,eax);
 145 #endif
 146
 147         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->rsp) == -EFAULT)
 148                 goto badframe;
 149
 150         return eax;
 151
 152 badframe:
 153         signal_fault(regs,frame,"sigreturn");
 154         return 0;
 155 }
 156
 157 /*
 158  * Set up a signal frame.
 159  */
 160
 161 static inline int
 162 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
 163 {
 164         int err = 0;
 165
 166         err |= __put_user(regs->cs, &sc->cs);
 167         err |= __put_user(0, &sc->gs);
 168         err |= __put_user(0, &sc->fs);
 169
 170         err |= __put_user(regs->rdi, &sc->rdi);
 171         err |= __put_user(regs->rsi, &sc->rsi);
 172         err |= __put_user(regs->rbp, &sc->rbp);
 173         err |= __put_user(regs->rsp, &sc->rsp);
 174         err |= __put_user(regs->rbx, &sc->rbx);
 175         err |= __put_user(regs->rdx, &sc->rdx);
 176         err |= __put_user(regs->rcx, &sc->rcx);
 177         err |= __put_user(regs->rax, &sc->rax);
 178         err |= __put_user(regs->r8, &sc->r8);
 179         err |= __put_user(regs->r9, &sc->r9);
 180         err |= __put_user(regs->r10, &sc->r10);
 181         err |= __put_user(regs->r11, &sc->r11);
 182         err |= __put_user(regs->r12, &sc->r12);
 183         err |= __put_user(regs->r13, &sc->r13);
 184         err |= __put_user(regs->r14, &sc->r14);
 185         err |= __put_user(regs->r15, &sc->r15);
 186         err |= __put_user(me->thread.trap_no, &sc->trapno);
 187         err |= __put_user(me->thread.error_code, &sc->err);
 188         err |= __put_user(regs->rip, &sc->rip);
 189         err |= __put_user(regs->eflags, &sc->eflags);
 190         err |= __put_user(mask, &sc->oldmask);
 191         err |= __put_user(me->thread.cr2, &sc->cr2);
 192
 193         return err;
 194 }
 195
 196 /*
 197  * Determine which stack to use..
 198  */
 199
 200 static void __user *
 201 get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
 202 {
 203         unsigned long rsp;
 204
 205         /* Default to using normal stack - redzone*/
 206         rsp = regs->rsp - 128;
 207
 208         /* This is the X/Open sanctioned signal stack switching.  */
 209         if (ka->sa.sa_flags & SA_ONSTACK) {
 210                 if (sas_ss_flags(rsp) == 0)
 211                         rsp = current->sas_ss_sp + current->sas_ss_size;
 212         }
 213
 214         return (void __user *)round_down(rsp - size, 16);
 215 }
 216
 217 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 218                            sigset_t *set, struct pt_regs * regs)
 219 {
 220         struct rt_sigframe __user *frame;
 221         struct _fpstate __user *fp = NULL;
 222         int err = 0;
 223         struct task_struct *me = current;
 224
 225         if (used_math()) {
 226                 fp = get_stack(ka, regs, sizeof(struct _fpstate));
 227                 frame = (void __user *)round_down(
 228                         (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
 229
 230                 if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
 231                         goto give_sigsegv;
 232
 233                 if (save_i387(fp) < 0)
 234                         err |= -1;
 235         } else
 236                 frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
 237
 238         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 239                 goto give_sigsegv;
 240
 241         if (ka->sa.sa_flags & SA_SIGINFO) {
 242                 err |= copy_siginfo_to_user(&frame->info, info);
 243                 if (err)
 244                         goto give_sigsegv;
 245         }
 246
 247         /* Create the ucontext.  */
 248         err |= __put_user(0, &frame->uc.uc_flags);
 249         err |= __put_user(0, &frame->uc.uc_link);
 250         err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 251         err |= __put_user(sas_ss_flags(regs->rsp),
 252                           &frame->uc.uc_stack.ss_flags);
 253         err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
 254         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
 255         err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
 256         if (sizeof(*set) == 16) {
 257                 __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 258                 __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
 259         } else
 260                 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 261
 262         /* Set up to return from userspace.  If provided, use a stub
 263            already in userspace.  */
 264         /* x86-64 should always use SA_RESTORER. */
 265         if (ka->sa.sa_flags & SA_RESTORER) {
 266                 err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
 267         } else {
 268                 /* could use a vstub here */
 269                 goto give_sigsegv;
 270         }
 271
 272         if (err)
 273                 goto give_sigsegv;
 274
 275 #ifdef DEBUG_SIG
 276         printk("%d old rip %lx old rsp %lx old rax %lx\n", current->pid,regs->rip,regs->rsp,regs->rax);
 277 #endif
 278
 279         /* Set up registers for signal handler */
 280         regs->rdi = sig;
 281         /* In case the signal handler was declared without prototypes */
 282         regs->rax = 0;
 283
 284         /* This also works for non SA_SIGINFO handlers because they expect the
 285            next argument after the signal number on the stack. */
 286         regs->rsi = (unsigned long)&frame->info;
 287         regs->rdx = (unsigned long)&frame->uc;
 288         regs->rip = (unsigned long) ka->sa.sa_handler;
 289
 290         regs->rsp = (unsigned long)frame;
 291
 292         /* Set up the CS register to run signal handlers in 64-bit mode,
 293            even if the handler happens to be interrupting 32-bit code. */
 294         regs->cs = __USER_CS;
 295
 296         /* This, by contrast, has nothing to do with segment registers -
 297            see include/asm-x86_64/uaccess.h for details. */
 298         set_fs(USER_DS);
 299
 300         regs->eflags &= ~TF_MASK;
 301         if (test_thread_flag(TIF_SINGLESTEP))
 302                 ptrace_notify(SIGTRAP);
 303 #ifdef DEBUG_SIG
 304         printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
 305                 current->comm, current->pid, frame, regs->rip, frame->pretcode);
 306 #endif
 307
 308         return 0;
 309
 310 give_sigsegv:
 311         force_sigsegv(sig, current);
 312         return -EFAULT;
 313 }
 314
 315 /*
 316  * OK, we're invoking a handler
 317  */
 318
 319 static int
 320 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 321                 sigset_t *oldset, struct pt_regs *regs)
 322 {
 323         int ret;
 324
 325 #ifdef DEBUG_SIG
 326         printk("handle_signal pid:%d sig:%lu rip:%lx rsp:%lx regs=%p\n",
 327                 current->pid, sig,
 328                 regs->rip, regs->rsp, regs);
 329 #endif
 330
 331         /* Are we from a system call? */
 332         if ((long)regs->orig_rax >= 0) {
 333                 /* If so, check system call restarting.. */
 334                 switch (regs->rax) {
 335                         case -ERESTART_RESTARTBLOCK:
 336                         case -ERESTARTNOHAND:
 337                                 regs->rax = -EINTR;
 338                                 break;
 339
 340                         case -ERESTARTSYS:
 341                                 if (!(ka->sa.sa_flags & SA_RESTART)) {
 342                                         regs->rax = -EINTR;
 343                                         break;
 344                                 }
 345                                 /* fallthrough */
 346                         case -ERESTARTNOINTR:
 347                                 regs->rax = regs->orig_rax;
 348                                 regs->rip -= 2;
 349                                 break;
 350                 }
 351         }
 352
 353         /*
 354          * If TF is set due to a debugger (PT_DTRACE), clear the TF
 355          * flag so that register information in the sigcontext is
 356          * correct.
 357          */
 358         if (unlikely(regs->eflags & TF_MASK)) {
 359                 if (likely(current->ptrace & PT_DTRACE)) {
 360                         current->ptrace &= ~PT_DTRACE;
 361                         regs->eflags &= ~TF_MASK;
 362                 }
 363         }
 364
 365 #ifdef CONFIG_IA32_EMULATION
 366         if (test_thread_flag(TIF_IA32)) {
 367                 if (ka->sa.sa_flags & SA_SIGINFO)
 368                         ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
 369                 else
 370                         ret = ia32_setup_frame(sig, ka, oldset, regs);
 371         } else
 372 #endif
 373         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 374
 375         if (ret == 0) {
 376                 spin_lock_irq(&current->sighand->siglock);
 377                 sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 378                 if (!(ka->sa.sa_flags & SA_NODEFER))
 379                         sigaddset(&current->blocked,sig);
 380                 recalc_sigpending();
 381                 spin_unlock_irq(&current->sighand->siglock);
 382         }
 383
 384         return ret;
 385 }
 386
 387 /*
 388  * Note that 'init' is a special process: it doesn't get signals it doesn't
 389  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 390  * mistake.
 391  */
 392 static void do_signal(struct pt_regs *regs)
 393 {
 394         struct k_sigaction ka;
 395         siginfo_t info;
 396         int signr;
 397         sigset_t *oldset;
 398
 399         /*
 400          * We want the common case to go fast, which
 401          * is why we may in certain cases get here from
 402          * kernel mode. Just return without doing anything
 403          * if so.
 404          */
 405         if (!user_mode(regs))
 406                 return;
 407
 408         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 409                 oldset = &current->saved_sigmask;
 410         else
 411                 oldset = &current->blocked;
 412
 413         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 414         if (signr > 0) {
 415                 /* Reenable any watchpoints before delivering the
 416                  * signal to user space. The processor register will
 417                  * have been cleared if the watchpoint triggered
 418                  * inside the kernel.
 419                  */
 420                 if (current->thread.debugreg7)
 421                         set_debugreg(current->thread.debugreg7, 7);
 422
 423                 /* Whee!  Actually deliver the signal.  */
 424                 if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 425                         /* a signal was successfully delivered; the saved
 426                          * sigmask will have been stored in the signal frame,
 427                          * and will be restored by sigreturn, so we can simply
 428                          * clear the TIF_RESTORE_SIGMASK flag */
 429                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 430                 }
 431                 return;
 432         }
 433
 434         /* Did we come from a system call? */
 435         if ((long)regs->orig_rax >= 0) {
 436                 /* Restart the system call - no handlers present */
 437                 long res = regs->rax;
 438                 switch (res) {
 439                 case -ERESTARTNOHAND:
 440                 case -ERESTARTSYS:
 441                 case -ERESTARTNOINTR:
 442                         regs->rax = regs->orig_rax;
 443                         regs->rip -= 2;
 444                         break;
 445                 case -ERESTART_RESTARTBLOCK:
 446                         regs->rax = test_thread_flag(TIF_IA32) ?
 447                                         __NR_ia32_restart_syscall :
 448                                         __NR_restart_syscall;
 449                         regs->rip -= 2;
 450                         break;
 451                 }
 452         }
 453
 454         /* if there's no signal to deliver, we just put the saved sigmask
 455            back. */
 456         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 457                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 458                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 459         }
 460 }
 461
 462 void
 463 do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
 464 {
 465 #ifdef DEBUG_SIG
 466         printk("do_notify_resume flags:%x rip:%lx rsp:%lx caller:%lx pending:%lx\n",
 467                thread_info_flags, regs->rip, regs->rsp, __builtin_return_address(0),signal_pending(current));
 468 #endif
 469
 470         /* Pending single-step? */
 471         if (thread_info_flags & _TIF_SINGLESTEP) {
 472                 regs->eflags |= TF_MASK;
 473                 clear_thread_flag(TIF_SINGLESTEP);
 474         }
 475
 476         /* deal with pending signal delivery */
 477         if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))
 478                 do_signal(regs);
 479 }
 480
 481 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 482 {
 483         struct task_struct *me = current;
 484         if (exception_trace)
 485                 printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n",
 486                me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax);
 487
 488         force_sig(SIGSEGV, me);
 489 }