LXR linux/arch/x86/kernel/signal

   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/ucontext.h>
  23#include <asm/uaccess.h>
  24#include <asm/i387.h>
  25#include <asm/proto.h>
  26#include <asm/ia32_unistd.h>
  27#include <asm/mce.h>
  28
  29/* #define DEBUG_SIG 1 */
  30
  31#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  32
  33int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
  34               sigset_t *set, struct pt_regs * regs); 
  35int ia32_setup_frame(int sig, struct k_sigaction *ka,
  36            sigset_t *set, struct pt_regs * regs); 
  37
  38asmlinkage long
  39sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
  40                struct pt_regs *regs)
  41{
  42        return do_sigaltstack(uss, uoss, regs->rsp);
  43}
  44
  45
  46/*
  47 * Do a signal return; undo the signal stack.
  48 */
  49
  50struct rt_sigframe
  51{
  52        char __user *pretcode;
  53        struct ucontext uc;
  54        struct siginfo info;
  55};
  56
  57static int
  58restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned long *prax)
  59{
  60        unsigned int err = 0;
  61
  62        /* Always make any pending restarted system calls return -EINTR */
  63        current_thread_info()->restart_block.fn = do_no_restart_syscall;
  64
  65#define COPY(x)         err |= __get_user(regs->x, &sc->x)
  66
  67        COPY(rdi); COPY(rsi); COPY(rbp); COPY(rsp); COPY(rbx);
  68        COPY(rdx); COPY(rcx); COPY(rip);
  69        COPY(r8);
  70        COPY(r9);
  71        COPY(r10);
  72        COPY(r11);
  73        COPY(r12);
  74        COPY(r13);
  75        COPY(r14);
  76        COPY(r15);
  77
  78        /* Kernel saves and restores only the CS segment register on signals,
  79         * which is the bare minimum needed to allow mixed 32/64-bit code.
  80         * App's signal handler can save/restore other segments if needed. */
  81        {
  82                unsigned cs;
  83                err |= __get_user(cs, &sc->cs);
  84                regs->cs = cs | 3;      /* Force into user mode */
  85        }
  86
  87        {
  88                unsigned int tmpflags;
  89                err |= __get_user(tmpflags, &sc->eflags);
  90                regs->eflags = (regs->eflags & ~0x40DD5) | (tmpflags & 0x40DD5);
  91                regs->orig_rax = -1;            /* disable syscall checks */
  92        }
  93
  94        {
  95                struct _fpstate __user * buf;
  96                err |= __get_user(buf, &sc->fpstate);
  97
  98                if (buf) {
  99                        if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
 100                                goto badframe;
 101                        err |= restore_i387(buf);
 102                } else {
 103                        struct task_struct *me = current;
 104                        if (used_math()) {
 105                                clear_fpu(me);
 106                                clear_used_math();
 107                        }
 108                }
 109        }
 110
 111        err |= __get_user(*prax, &sc->rax);
 112        return err;
 113
 114badframe:
 115        return 1;
 116}
 117
 118asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 119{
 120        struct rt_sigframe __user *frame;
 121        sigset_t set;
 122        unsigned long eax;
 123
 124        frame = (struct rt_sigframe __user *)(regs->rsp - 8);
 125        if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) {
 126                goto badframe;
 127        } 
 128        if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) { 
 129                goto badframe;
 130        } 
 131
 132        sigdelsetmask(&set, ~_BLOCKABLE);
 133        spin_lock_irq(&current->sighand->siglock);
 134        current->blocked = set;
 135        recalc_sigpending();
 136        spin_unlock_irq(&current->sighand->siglock);
 137        
 138        if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &eax))
 139                goto badframe;
 140
 141#ifdef DEBUG_SIG
 142        printk("%d sigreturn rip:%lx rsp:%lx frame:%p rax:%lx\n",current->pid,regs->rip,regs->rsp,frame,eax);
 143#endif
 144
 145        if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->rsp) == -EFAULT)
 146                goto badframe;
 147
 148        return eax;
 149
 150badframe:
 151        signal_fault(regs,frame,"sigreturn");
 152        return 0;
 153}       
 154
 155/*
 156 * Set up a signal frame.
 157 */
 158
 159static inline int
 160setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
 161{
 162        int err = 0;
 163
 164        err |= __put_user(regs->cs, &sc->cs);
 165        err |= __put_user(0, &sc->gs);
 166        err |= __put_user(0, &sc->fs);
 167
 168        err |= __put_user(regs->rdi, &sc->rdi);
 169        err |= __put_user(regs->rsi, &sc->rsi);
 170        err |= __put_user(regs->rbp, &sc->rbp);
 171        err |= __put_user(regs->rsp, &sc->rsp);
 172        err |= __put_user(regs->rbx, &sc->rbx);
 173        err |= __put_user(regs->rdx, &sc->rdx);
 174        err |= __put_user(regs->rcx, &sc->rcx);
 175        err |= __put_user(regs->rax, &sc->rax);
 176        err |= __put_user(regs->r8, &sc->r8);
 177        err |= __put_user(regs->r9, &sc->r9);
 178        err |= __put_user(regs->r10, &sc->r10);
 179        err |= __put_user(regs->r11, &sc->r11);
 180        err |= __put_user(regs->r12, &sc->r12);
 181        err |= __put_user(regs->r13, &sc->r13);
 182        err |= __put_user(regs->r14, &sc->r14);
 183        err |= __put_user(regs->r15, &sc->r15);
 184        err |= __put_user(me->thread.trap_no, &sc->trapno);
 185        err |= __put_user(me->thread.error_code, &sc->err);
 186        err |= __put_user(regs->rip, &sc->rip);
 187        err |= __put_user(regs->eflags, &sc->eflags);
 188        err |= __put_user(mask, &sc->oldmask);
 189        err |= __put_user(me->thread.cr2, &sc->cr2);
 190
 191        return err;
 192}
 193
 194/*
 195 * Determine which stack to use..
 196 */
 197
 198static void __user *
 199get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
 200{
 201        unsigned long rsp;
 202
 203        /* Default to using normal stack - redzone*/
 204        rsp = regs->rsp - 128;
 205
 206        /* This is the X/Open sanctioned signal stack switching.  */
 207        if (ka->sa.sa_flags & SA_ONSTACK) {
 208                if (sas_ss_flags(rsp) == 0)
 209                        rsp = current->sas_ss_sp + current->sas_ss_size;
 210        }
 211
 212        return (void __user *)round_down(rsp - size, 16); 
 213}
 214
 215static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 216                           sigset_t *set, struct pt_regs * regs)
 217{
 218        struct rt_sigframe __user *frame;
 219        struct _fpstate __user *fp = NULL; 
 220        int err = 0;
 221        struct task_struct *me = current;
 222
 223        if (used_math()) {
 224                fp = get_stack(ka, regs, sizeof(struct _fpstate)); 
 225                frame = (void __user *)round_down(
 226                        (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
 227
 228                if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
 229                        goto give_sigsegv;
 230
 231                if (save_i387(fp) < 0) 
 232                        err |= -1; 
 233        } else
 234                frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
 235
 236        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 237                goto give_sigsegv;
 238
 239        if (ka->sa.sa_flags & SA_SIGINFO) { 
 240                err |= copy_siginfo_to_user(&frame->info, info);
 241                if (err)
 242                        goto give_sigsegv;
 243        }
 244                
 245        /* Create the ucontext.  */
 246        err |= __put_user(0, &frame->uc.uc_flags);
 247        err |= __put_user(0, &frame->uc.uc_link);
 248        err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 249        err |= __put_user(sas_ss_flags(regs->rsp),
 250                          &frame->uc.uc_stack.ss_flags);
 251        err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
 252        err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
 253        err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
 254        if (sizeof(*set) == 16) { 
 255                __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 256                __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]); 
 257        } else
 258                err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 259
 260        /* Set up to return from userspace.  If provided, use a stub
 261           already in userspace.  */
 262        /* x86-64 should always use SA_RESTORER. */
 263        if (ka->sa.sa_flags & SA_RESTORER) {
 264                err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
 265        } else {
 266                /* could use a vstub here */
 267                goto give_sigsegv; 
 268        }
 269
 270        if (err)
 271                goto give_sigsegv;
 272
 273#ifdef DEBUG_SIG
 274        printk("%d old rip %lx old rsp %lx old rax %lx\n", current->pid,regs->rip,regs->rsp,regs->rax);
 275#endif
 276
 277        /* Set up registers for signal handler */
 278        regs->rdi = sig;
 279        /* In case the signal handler was declared without prototypes */ 
 280        regs->rax = 0;  
 281
 282        /* This also works for non SA_SIGINFO handlers because they expect the
 283           next argument after the signal number on the stack. */
 284        regs->rsi = (unsigned long)&frame->info; 
 285        regs->rdx = (unsigned long)&frame->uc; 
 286        regs->rip = (unsigned long) ka->sa.sa_handler;
 287
 288        regs->rsp = (unsigned long)frame;
 289
 290        /* Set up the CS register to run signal handlers in 64-bit mode,
 291           even if the handler happens to be interrupting 32-bit code. */
 292        regs->cs = __USER_CS;
 293
 294        /* This, by contrast, has nothing to do with segment registers -
 295           see include/asm-x86_64/uaccess.h for details. */
 296        set_fs(USER_DS);
 297
 298        regs->eflags &= ~TF_MASK;
 299        if (test_thread_flag(TIF_SINGLESTEP))
 300                ptrace_notify(SIGTRAP);
 301#ifdef DEBUG_SIG
 302        printk("SIG deliver (%s:%d): sp=%p pc=%lx ra=%p\n",
 303                current->comm, current->pid, frame, regs->rip, frame->pretcode);
 304#endif
 305
 306        return 0;
 307
 308give_sigsegv:
 309        force_sigsegv(sig, current);
 310        return -EFAULT;
 311}
 312
 313/*
 314 * OK, we're invoking a handler
 315 */     
 316
 317static int
 318handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 319                sigset_t *oldset, struct pt_regs *regs)
 320{
 321        int ret;
 322
 323#ifdef DEBUG_SIG
 324        printk("handle_signal pid:%d sig:%lu rip:%lx rsp:%lx regs=%p\n",
 325                current->pid, sig,
 326                regs->rip, regs->rsp, regs);
 327#endif
 328
 329        /* Are we from a system call? */
 330        if ((long)regs->orig_rax >= 0) {
 331                /* If so, check system call restarting.. */
 332                switch (regs->rax) {
 333                        case -ERESTART_RESTARTBLOCK:
 334                        case -ERESTARTNOHAND:
 335                                regs->rax = -EINTR;
 336                                break;
 337
 338                        case -ERESTARTSYS:
 339                                if (!(ka->sa.sa_flags & SA_RESTART)) {
 340                                        regs->rax = -EINTR;
 341                                        break;
 342                                }
 343                                /* fallthrough */
 344                        case -ERESTARTNOINTR:
 345                                regs->rax = regs->orig_rax;
 346                                regs->rip -= 2;
 347                                break;
 348                }
 349        }
 350
 351        /*
 352         * If TF is set due to a debugger (PT_DTRACE), clear the TF
 353         * flag so that register information in the sigcontext is
 354         * correct.
 355         */
 356        if (unlikely(regs->eflags & TF_MASK)) {
 357                if (likely(current->ptrace & PT_DTRACE)) {
 358                        current->ptrace &= ~PT_DTRACE;
 359                        regs->eflags &= ~TF_MASK;
 360                }
 361        }
 362
 363#ifdef CONFIG_IA32_EMULATION
 364        if (test_thread_flag(TIF_IA32)) {
 365                if (ka->sa.sa_flags & SA_SIGINFO)
 366                        ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
 367                else
 368                        ret = ia32_setup_frame(sig, ka, oldset, regs);
 369        } else 
 370#endif
 371        ret = setup_rt_frame(sig, ka, info, oldset, regs);
 372
 373        if (ret == 0) {
 374                spin_lock_irq(&current->sighand->siglock);
 375                sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 376                if (!(ka->sa.sa_flags & SA_NODEFER))
 377                        sigaddset(&current->blocked,sig);
 378                recalc_sigpending();
 379                spin_unlock_irq(&current->sighand->siglock);
 380        }
 381
 382        return ret;
 383}
 384
 385/*
 386 * Note that 'init' is a special process: it doesn't get signals it doesn't
 387 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 388 * mistake.
 389 */
 390static void do_signal(struct pt_regs *regs)
 391{
 392        struct k_sigaction ka;
 393        siginfo_t info;
 394        int signr;
 395        sigset_t *oldset;
 396
 397        /*
 398         * We want the common case to go fast, which
 399         * is why we may in certain cases get here from
 400         * kernel mode. Just return without doing anything
 401         * if so.
 402         */
 403        if (!user_mode(regs))
 404                return;
 405
 406        if (test_thread_flag(TIF_RESTORE_SIGMASK))
 407                oldset = &current->saved_sigmask;
 408        else
 409                oldset = &current->blocked;
 410
 411        signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 412        if (signr > 0) {
 413                /* Re-enable any watchpoints before delivering the
 414                 * signal to user space. The processor register will
 415                 * have been cleared if the watchpoint triggered
 416                 * inside the kernel.
 417                 */
 418                if (current->thread.debugreg7)
 419                        set_debugreg(current->thread.debugreg7, 7);
 420
 421                /* Whee!  Actually deliver the signal.  */
 422                if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 423                        /* a signal was successfully delivered; the saved
 424                         * sigmask will have been stored in the signal frame,
 425                         * and will be restored by sigreturn, so we can simply
 426                         * clear the TIF_RESTORE_SIGMASK flag */
 427                        clear_thread_flag(TIF_RESTORE_SIGMASK);
 428                }
 429                return;
 430        }
 431
 432        /* Did we come from a system call? */
 433        if ((long)regs->orig_rax >= 0) {
 434                /* Restart the system call - no handlers present */
 435                long res = regs->rax;
 436                switch (res) {
 437                case -ERESTARTNOHAND:
 438                case -ERESTARTSYS:
 439                case -ERESTARTNOINTR:
 440                        regs->rax = regs->orig_rax;
 441                        regs->rip -= 2;
 442                        break;
 443                case -ERESTART_RESTARTBLOCK:
 444                        regs->rax = test_thread_flag(TIF_IA32) ?
 445                                        __NR_ia32_restart_syscall :
 446                                        __NR_restart_syscall;
 447                        regs->rip -= 2;
 448                        break;
 449                }
 450        }
 451
 452        /* if there's no signal to deliver, we just put the saved sigmask
 453           back. */
 454        if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 455                clear_thread_flag(TIF_RESTORE_SIGMASK);
 456                sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 457        }
 458}
 459
 460void
 461do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
 462{
 463#ifdef DEBUG_SIG
 464        printk("do_notify_resume flags:%x rip:%lx rsp:%lx caller:%p pending:%x\n",
 465               thread_info_flags, regs->rip, regs->rsp, __builtin_return_address(0),signal_pending(current)); 
 466#endif
 467               
 468        /* Pending single-step? */
 469        if (thread_info_flags & _TIF_SINGLESTEP) {
 470                regs->eflags |= TF_MASK;
 471                clear_thread_flag(TIF_SINGLESTEP);
 472        }
 473
 474#ifdef CONFIG_X86_MCE
 475        /* notify userspace of pending MCEs */
 476        if (thread_info_flags & _TIF_MCE_NOTIFY)
 477                mce_notify_user();
 478#endif /* CONFIG_X86_MCE */
 479
 480        /* deal with pending signal delivery */
 481        if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))
 482                do_signal(regs);
 483}
 484
 485void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 486{ 
 487        struct task_struct *me = current; 
 488        if (show_unhandled_signals && printk_ratelimit())
 489                printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n",
 490               me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax); 
 491
 492        force_sig(SIGSEGV, me); 
 493} 
 494