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signal.c

/* MN10300 Signal handling
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/personality.h>
#include <linux/suspend.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/fpu.h>
#include "sigframe.h"

#define DEBUG_SIG 0

#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

/*
 * atomically swap in the new signal mask, and wait for a signal.
 */
asmlinkage long sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
      mask &= _BLOCKABLE;
      spin_lock_irq(&current->sighand->siglock);
      current->saved_sigmask = current->blocked;
      siginitset(&current->blocked, mask);
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      current->state = TASK_INTERRUPTIBLE;
      schedule();
      set_thread_flag(TIF_RESTORE_SIGMASK);
      return -ERESTARTNOHAND;
}

/*
 * set signal action syscall
 */
asmlinkage long sys_sigaction(int sig,
                        const struct old_sigaction __user *act,
                        struct old_sigaction __user *oact)
{
      struct k_sigaction new_ka, old_ka;
      int ret;

      if (act) {
            old_sigset_t mask;
            if (verify_area(VERIFY_READ, act, sizeof(*act)) ||
                __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
                __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
                  return -EFAULT;
            __get_user(new_ka.sa.sa_flags, &act->sa_flags);
            __get_user(mask, &act->sa_mask);
            siginitset(&new_ka.sa.sa_mask, mask);
      }

      ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

      if (!ret && oact) {
            if (verify_area(VERIFY_WRITE, oact, sizeof(*oact)) ||
                __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
                __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
                  return -EFAULT;
            __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
            __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
      }

      return ret;
}

/*
 * set alternate signal stack syscall
 */
asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t *uoss)
{
      return do_sigaltstack(uss, uoss, __frame->sp);
}

/*
 * do a signal return; undo the signal stack.
 */
static int restore_sigcontext(struct pt_regs *regs,
                        struct sigcontext __user *sc, long *_d0)
{
      unsigned int err = 0;

      if (is_using_fpu(current))
            fpu_kill_state(current);

#define COPY(x) err |= __get_user(regs->x, &sc->x)
      COPY(d1); COPY(d2); COPY(d3);
      COPY(a0); COPY(a1); COPY(a2); COPY(a3);
      COPY(e0); COPY(e1); COPY(e2); COPY(e3);
      COPY(e4); COPY(e5); COPY(e6); COPY(e7);
      COPY(lar); COPY(lir);
      COPY(mdr); COPY(mdrq);
      COPY(mcvf); COPY(mcrl); COPY(mcrh);
      COPY(sp); COPY(pc);
#undef COPY

      {
            unsigned int tmpflags;
#ifndef CONFIG_MN10300_USING_JTAG
#define USER_EPSW (EPSW_FLAG_Z | EPSW_FLAG_N | EPSW_FLAG_C | EPSW_FLAG_V | \
               EPSW_T | EPSW_nAR)
#else
#define USER_EPSW (EPSW_FLAG_Z | EPSW_FLAG_N | EPSW_FLAG_C | EPSW_FLAG_V | \
               EPSW_nAR)
#endif
            err |= __get_user(tmpflags, &sc->epsw);
            regs->epsw = (regs->epsw & ~USER_EPSW) |
              (tmpflags & USER_EPSW);
            regs->orig_d0 = -1;           /* disable syscall checks */
      }

      {
            struct fpucontext *buf;
            err |= __get_user(buf, &sc->fpucontext);
            if (buf) {
                  if (verify_area(VERIFY_READ, buf, sizeof(*buf)))
                        goto badframe;
                  err |= fpu_restore_sigcontext(buf);
            }
      }

      err |= __get_user(*_d0, &sc->d0);
      return err;

badframe:
      return 1;
}

/*
 * standard signal return syscall
 */
asmlinkage long sys_sigreturn(void)
{
      struct sigframe __user *frame = (struct sigframe __user *) __frame->sp;
      sigset_t set;
      long d0;

      if (verify_area(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;
      if (__get_user(set.sig[0], &frame->sc.oldmask))
            goto badframe;

      if (_NSIG_WORDS > 1 &&
          __copy_from_user(&set.sig[1], &frame->extramask,
                       sizeof(frame->extramask)))
            goto badframe;

      sigdelsetmask(&set, ~_BLOCKABLE);
      spin_lock_irq(&current->sighand->siglock);
      current->blocked = set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      if (restore_sigcontext(__frame, &frame->sc, &d0))
            goto badframe;

      return d0;

badframe:
      force_sig(SIGSEGV, current);
      return 0;
}

/*
 * realtime signal return syscall
 */
asmlinkage long sys_rt_sigreturn(void)
{
      struct rt_sigframe __user *frame =
            (struct rt_sigframe __user *) __frame->sp;
      sigset_t set;
      unsigned long d0;

      if (verify_area(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;
      if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
            goto badframe;

      sigdelsetmask(&set, ~_BLOCKABLE);
      spin_lock_irq(&current->sighand->siglock);
      current->blocked = set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      if (restore_sigcontext(__frame, &frame->uc.uc_mcontext, &d0))
            goto badframe;

      if (do_sigaltstack(&frame->uc.uc_stack, NULL, __frame->sp) == -EFAULT)
            goto badframe;

      return d0;

badframe:
      force_sig(SIGSEGV, current);
      return 0;
}

/*
 * store the userspace context into a signal frame
 */
static int setup_sigcontext(struct sigcontext __user *sc,
                      struct fpucontext *fpuctx,
                      struct pt_regs *regs,
                      unsigned long mask)
{
      int tmp, err = 0;

#define COPY(x) err |= __put_user(regs->x, &sc->x)
      COPY(d0); COPY(d1); COPY(d2); COPY(d3);
      COPY(a0); COPY(a1); COPY(a2); COPY(a3);
      COPY(e0); COPY(e1); COPY(e2); COPY(e3);
      COPY(e4); COPY(e5); COPY(e6); COPY(e7);
      COPY(lar); COPY(lir);
      COPY(mdr); COPY(mdrq);
      COPY(mcvf); COPY(mcrl); COPY(mcrh);
      COPY(sp); COPY(epsw); COPY(pc);
#undef COPY

      tmp = fpu_setup_sigcontext(fpuctx);
      if (tmp < 0)
            err = 1;
      else
            err |= __put_user(tmp ? fpuctx : NULL, &sc->fpucontext);

      /* non-iBCS2 extensions.. */
      err |= __put_user(mask, &sc->oldmask);

      return err;
}

/*
 * determine which stack to use..
 */
static inline void __user *get_sigframe(struct k_sigaction *ka,
                              struct pt_regs *regs,
                              size_t frame_size)
{
      unsigned long sp;

      /* default to using normal stack */
      sp = regs->sp;

      /* this is the X/Open sanctioned signal stack switching.  */
      if (ka->sa.sa_flags & SA_ONSTACK) {
            if (!on_sig_stack(sp))
                  sp = current->sas_ss_sp + current->sas_ss_size;
      }

      return (void __user *) ((sp - frame_size) & ~7UL);
}

/*
 * set up a normal signal frame
 */
static int setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
                   struct pt_regs *regs)
{
      struct sigframe __user *frame;
      int rsig;

      frame = get_sigframe(ka, regs, sizeof(*frame));

      if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
            goto give_sigsegv;

      rsig = sig;
      if (sig < 32 &&
          current_thread_info()->exec_domain &&
          current_thread_info()->exec_domain->signal_invmap)
            rsig = current_thread_info()->exec_domain->signal_invmap[sig];

      if (__put_user(rsig, &frame->sig) < 0 ||
          __put_user(&frame->sc, &frame->psc) < 0)
            goto give_sigsegv;

      if (setup_sigcontext(&frame->sc, &frame->fpuctx, regs, set->sig[0]))
            goto give_sigsegv;

      if (_NSIG_WORDS > 1) {
            if (__copy_to_user(frame->extramask, &set->sig[1],
                           sizeof(frame->extramask)))
                  goto give_sigsegv;
      }

      /* set up to return from userspace.  If provided, use a stub already in
       * userspace */
      if (ka->sa.sa_flags & SA_RESTORER) {
            if (__put_user(ka->sa.sa_restorer, &frame->pretcode))
                  goto give_sigsegv;
      } else {
            if (__put_user((void (*)(void))frame->retcode,
                         &frame->pretcode))
                  goto give_sigsegv;
            /* this is mov $,d0; syscall 0 */
            if (__put_user(0x2c, (char *)(frame->retcode + 0)) ||
                __put_user(__NR_sigreturn, (char *)(frame->retcode + 1)) ||
                __put_user(0x00, (char *)(frame->retcode + 2)) ||
                __put_user(0xf0, (char *)(frame->retcode + 3)) ||
                __put_user(0xe0, (char *)(frame->retcode + 4)))
                  goto give_sigsegv;
            flush_icache_range((unsigned long) frame->retcode,
                           (unsigned long) frame->retcode + 5);
      }

      /* set up registers for signal handler */
      regs->sp = (unsigned long) frame;
      regs->pc = (unsigned long) ka->sa.sa_handler;
      regs->d0 = sig;
      regs->d1 = (unsigned long) &frame->sc;

      set_fs(USER_DS);

      /* the tracer may want to single-step inside the handler */
      if (test_thread_flag(TIF_SINGLESTEP))
            ptrace_notify(SIGTRAP);

#if DEBUG_SIG
      printk(KERN_DEBUG "SIG deliver %d (%s:%d): sp=%p pc=%lx ra=%p\n",
             sig, current->comm, current->pid, frame, regs->pc,
             frame->pretcode);
#endif

      return 0;

give_sigsegv:
      force_sig(SIGSEGV, current);
      return -EFAULT;
}

/*
 * set up a realtime signal frame
 */
static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                    sigset_t *set, struct pt_regs *regs)
{
      struct rt_sigframe __user *frame;
      int rsig;

      frame = get_sigframe(ka, regs, sizeof(*frame));

      if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
            goto give_sigsegv;

      rsig = sig;
      if (sig < 32 &&
          current_thread_info()->exec_domain &&
          current_thread_info()->exec_domain->signal_invmap)
            rsig = current_thread_info()->exec_domain->signal_invmap[sig];

      if (__put_user(rsig, &frame->sig) ||
          __put_user(&frame->info, &frame->pinfo) ||
          __put_user(&frame->uc, &frame->puc) ||
          copy_siginfo_to_user(&frame->info, info))
            goto give_sigsegv;

      /* create the ucontext.  */
      if (__put_user(0, &frame->uc.uc_flags) ||
          __put_user(0, &frame->uc.uc_link) ||
          __put_user((void *)current->sas_ss_sp, &frame->uc.uc_stack.ss_sp) ||
          __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags) ||
          __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size) ||
          setup_sigcontext(&frame->uc.uc_mcontext,
                       &frame->fpuctx, regs, set->sig[0]) ||
          __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)))
            goto give_sigsegv;

      /* set up to return from userspace.  If provided, use a stub already in
       * userspace */
      if (ka->sa.sa_flags & SA_RESTORER) {
            if (__put_user(ka->sa.sa_restorer, &frame->pretcode))
                  goto give_sigsegv;
      } else {
            if (__put_user((void(*)(void))frame->retcode,
                         &frame->pretcode) ||
                /* This is mov $,d0; syscall 0 */
                __put_user(0x2c, (char *)(frame->retcode + 0)) ||
                __put_user(__NR_rt_sigreturn,
                         (char *)(frame->retcode + 1)) ||
                __put_user(0x00, (char *)(frame->retcode + 2)) ||
                __put_user(0xf0, (char *)(frame->retcode + 3)) ||
                __put_user(0xe0, (char *)(frame->retcode + 4)))
                  goto give_sigsegv;

            flush_icache_range((u_long) frame->retcode,
                           (u_long) frame->retcode + 5);
      }

      /* Set up registers for signal handler */
      regs->sp = (unsigned long) frame;
      regs->pc = (unsigned long) ka->sa.sa_handler;
      regs->d0 = sig;
      regs->d1 = (long) &frame->info;

      set_fs(USER_DS);

      /* the tracer may want to single-step inside the handler */
      if (test_thread_flag(TIF_SINGLESTEP))
            ptrace_notify(SIGTRAP);

#if DEBUG_SIG
      printk(KERN_DEBUG "SIG deliver %d (%s:%d): sp=%p pc=%lx ra=%p\n",
             sig, current->comm, current->pid, frame, regs->pc,
             frame->pretcode);
#endif

      return 0;

give_sigsegv:
      force_sig(SIGSEGV, current);
      return -EFAULT;
}

/*
 * handle the actual delivery of a signal to userspace
 */
static int handle_signal(int sig,
                   siginfo_t *info, struct k_sigaction *ka,
                   sigset_t *oldset, struct pt_regs *regs)
{
      int ret;

      /* Are we from a system call? */
      if (regs->orig_d0 >= 0) {
            /* If so, check system call restarting.. */
            switch (regs->d0) {
            case -ERESTART_RESTARTBLOCK:
            case -ERESTARTNOHAND:
                  regs->d0 = -EINTR;
                  break;

            case -ERESTARTSYS:
                  if (!(ka->sa.sa_flags & SA_RESTART)) {
                        regs->d0 = -EINTR;
                        break;
                  }

                  /* fallthrough */
            case -ERESTARTNOINTR:
                  regs->d0 = regs->orig_d0;
                  regs->pc -= 2;
            }
      }

      /* Set up the stack frame */
      if (ka->sa.sa_flags & SA_SIGINFO)
            ret = setup_rt_frame(sig, ka, info, oldset, regs);
      else
            ret = setup_frame(sig, ka, oldset, regs);

      if (ret == 0) {
            spin_lock_irq(&current->sighand->siglock);
            sigorsets(&current->blocked, &current->blocked,
                    &ka->sa.sa_mask);
            if (!(ka->sa.sa_flags & SA_NODEFER))
                  sigaddset(&current->blocked, sig);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
      }

      return ret;
}

/*
 * handle a potential signal
 */
static void do_signal(struct pt_regs *regs)
{
      struct k_sigaction ka;
      siginfo_t info;
      sigset_t *oldset;
      int signr;

      /* we want the common case to go fast, which is why we may in certain
       * cases get here from kernel mode */
      if (!user_mode(regs))
            return;

      if (test_thread_flag(TIF_RESTORE_SIGMASK))
            oldset = &current->saved_sigmask;
      else
            oldset = &current->blocked;

      signr = get_signal_to_deliver(&info, &ka, regs, NULL);
      if (signr > 0) {
            if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
                  /* a signal was successfully delivered; the saved
                   * sigmask will have been stored in the signal frame,
                   * and will be restored by sigreturn, so we can simply
                   * clear the TIF_RESTORE_SIGMASK flag */
                  if (test_thread_flag(TIF_RESTORE_SIGMASK))
                        clear_thread_flag(TIF_RESTORE_SIGMASK);
            }

            return;
      }

      /* did we come from a system call? */
      if (regs->orig_d0 >= 0) {
            /* restart the system call - no handlers present */
            switch (regs->d0) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  regs->d0 = regs->orig_d0;
                  regs->pc -= 2;
                  break;

            case -ERESTART_RESTARTBLOCK:
                  regs->d0 = __NR_restart_syscall;
                  regs->pc -= 2;
                  break;
            }
      }

      /* if there's no signal to deliver, we just put the saved sigmask
       * back */
      if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
            clear_thread_flag(TIF_RESTORE_SIGMASK);
            sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
      }
}

/*
 * notification of userspace execution resumption
 * - triggered by current->work.notify_resume
 */
asmlinkage void do_notify_resume(struct pt_regs *regs, u32 thread_info_flags)
{
      /* Pending single-step? */
      if (thread_info_flags & _TIF_SINGLESTEP) {
#ifndef CONFIG_MN10300_USING_JTAG
            regs->epsw |= EPSW_T;
            clear_thread_flag(TIF_SINGLESTEP);
#else
            BUG(); /* no h/w single-step if using JTAG unit */
#endif
      }

      /* deal with pending signal delivery */
      if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
            do_signal(regs);
}

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