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signal.c

/* signal.c: FRV specific bits of signal handling
 *
 * Copyright (C) 2003-5 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 * - Derived from arch/m68k/kernel/signal.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.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/personality.h>
#include <linux/freezer.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>

#define DEBUG_SIG 0

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

struct fdpic_func_descriptor {
      unsigned long     text;
      unsigned long     GOT;
};

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
asmlinkage int 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;
}

asmlinkage int 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 (!access_ok(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 (!access_ok(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;
}

asmlinkage
int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
      return do_sigaltstack(uss, uoss, __frame->sp);
}


/*
 * Do a signal return; undo the signal stack.
 */

struct sigframe
{
      __sigrestore_t pretcode;
      int sig;
      struct sigcontext sc;
      unsigned long extramask[_NSIG_WORDS-1];
      uint32_t retcode[2];
};

struct rt_sigframe
{
      __sigrestore_t pretcode;
      int sig;
      struct siginfo __user *pinfo;
      void __user *puc;
      struct siginfo info;
      struct ucontext uc;
      uint32_t retcode[2];
};

static int restore_sigcontext(struct sigcontext __user *sc, int *_gr8)
{
      struct user_context *user = current->thread.user;
      unsigned long tbr, psr;

      tbr = user->i.tbr;
      psr = user->i.psr;
      if (copy_from_user(user, &sc->sc_context, sizeof(sc->sc_context)))
            goto badframe;
      user->i.tbr = tbr;
      user->i.psr = psr;

      restore_user_regs(user);

      user->i.syscallno = -1;       /* disable syscall checks */

      *_gr8 = user->i.gr[8];
      return 0;

 badframe:
      return 1;
}

asmlinkage int sys_sigreturn(void)
{
      struct sigframe __user *frame = (struct sigframe __user *) __frame->sp;
      sigset_t set;
      int gr8;

      if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;
      if (__get_user(set.sig[0], &frame->sc.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->sc, &gr8))
            goto badframe;
      return gr8;

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

asmlinkage int sys_rt_sigreturn(void)
{
      struct rt_sigframe __user *frame = (struct rt_sigframe __user *) __frame->sp;
      sigset_t set;
      int gr8;

      if (!access_ok(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->uc.uc_mcontext, &gr8))
            goto badframe;

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

      return gr8;

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

/*
 * Set up a signal frame
 */
static int setup_sigcontext(struct sigcontext __user *sc, unsigned long mask)
{
      save_user_regs(current->thread.user);

      if (copy_to_user(&sc->sc_context, current->thread.user, sizeof(sc->sc_context)) != 0)
            goto badframe;

      /* non-iBCS2 extensions.. */
      if (__put_user(mask, &sc->sc_oldmask) < 0)
            goto badframe;

      return 0;

 badframe:
      return 1;
}

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

      /* Default to using normal stack */
      sp = __frame->sp;

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

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

} /* end get_sigframe() */

/*****************************************************************************/
/*
 *
 */
static int setup_frame(int sig, struct k_sigaction *ka, sigset_t *set)
{
      struct sigframe __user *frame;
      int rsig;

      frame = get_sigframe(ka, 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)
            goto give_sigsegv;

      if (setup_sigcontext(&frame->sc, 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) < 0)
                  goto give_sigsegv;
      }
      else {
            /* Set up the following code on the stack:
             *    setlos      #__NR_sigreturn,gr7
             *    tira  gr0,0
             */
            if (__put_user((__sigrestore_t)frame->retcode, &frame->pretcode) ||
                __put_user(0x8efc0000|__NR_sigreturn, &frame->retcode[0]) ||
                __put_user(0xc0700000, &frame->retcode[1]))
                  goto give_sigsegv;

            flush_icache_range((unsigned long) frame->retcode,
                           (unsigned long) (frame->retcode + 2));
      }

      /* set up registers for signal handler */
      __frame->sp   = (unsigned long) frame;
      __frame->lr   = (unsigned long) &frame->retcode;
      __frame->gr8  = sig;

      if (get_personality & FDPIC_FUNCPTRS) {
            struct fdpic_func_descriptor __user *funcptr =
                  (struct fdpic_func_descriptor __user *) ka->sa.sa_handler;
            __get_user(__frame->pc, &funcptr->text);
            __get_user(__frame->gr15, &funcptr->GOT);
      } else {
            __frame->pc   = (unsigned long) ka->sa.sa_handler;
            __frame->gr15 = 0;
      }

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

      return 0;

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

} /* end setup_frame() */

/*****************************************************************************/
/*
 *
 */
static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                    sigset_t *set)
{
      struct rt_sigframe __user *frame;
      int rsig;

      frame = get_sigframe(ka, 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))
            goto give_sigsegv;

      if (copy_siginfo_to_user(&frame->info, info))
            goto give_sigsegv;

      /* Create the ucontext.  */
      if (__put_user(0, &frame->uc.uc_flags) ||
          __put_user(NULL, &frame->uc.uc_link) ||
          __put_user((void __user *)current->sas_ss_sp, &frame->uc.uc_stack.ss_sp) ||
          __put_user(sas_ss_flags(__frame->sp), &frame->uc.uc_stack.ss_flags) ||
          __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size))
            goto give_sigsegv;

      if (setup_sigcontext(&frame->uc.uc_mcontext, set->sig[0]))
            goto give_sigsegv;

      if (__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 {
            /* Set up the following code on the stack:
             *    setlos      #__NR_sigreturn,gr7
             *    tira  gr0,0
             */
            if (__put_user((__sigrestore_t)frame->retcode, &frame->pretcode) ||
                __put_user(0x8efc0000|__NR_rt_sigreturn, &frame->retcode[0]) ||
                __put_user(0xc0700000, &frame->retcode[1]))
                  goto give_sigsegv;

            flush_icache_range((unsigned long) frame->retcode,
                           (unsigned long) (frame->retcode + 2));
      }

      /* Set up registers for signal handler */
      __frame->sp  = (unsigned long) frame;
      __frame->lr   = (unsigned long) &frame->retcode;
      __frame->gr8 = sig;
      __frame->gr9 = (unsigned long) &frame->info;

      if (get_personality & FDPIC_FUNCPTRS) {
            struct fdpic_func_descriptor __user *funcptr =
                  (struct fdpic_func_descriptor __user *) ka->sa.sa_handler;
            __get_user(__frame->pc, &funcptr->text);
            __get_user(__frame->gr15, &funcptr->GOT);
      } else {
            __frame->pc   = (unsigned long) ka->sa.sa_handler;
            __frame->gr15 = 0;
      }

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

      return 0;

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

} /* end setup_rt_frame() */

/*****************************************************************************/
/*
 * OK, we're invoking a handler
 */
static int handle_signal(unsigned long sig, siginfo_t *info,
                   struct k_sigaction *ka, sigset_t *oldset)
{
      int ret;

      /* Are we from a system call? */
      if (in_syscall(__frame)) {
            /* If so, check system call restarting.. */
            switch (__frame->gr8) {
            case -ERESTART_RESTARTBLOCK:
            case -ERESTARTNOHAND:
                  __frame->gr8 = -EINTR;
                  break;

            case -ERESTARTSYS:
                  if (!(ka->sa.sa_flags & SA_RESTART)) {
                        __frame->gr8 = -EINTR;
                        break;
                  }

                  /* fallthrough */
            case -ERESTARTNOINTR:
                  __frame->gr8 = __frame->orig_gr8;
                  __frame->pc -= 4;
            }
      }

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

      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;

} /* end handle_signal() */

/*****************************************************************************/
/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
static void do_signal(void)
{
      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. Just return without doing anything
       * if so.
       */
      if (!user_mode(__frame))
            return;

      if (try_to_freeze())
            goto no_signal;

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

      signr = get_signal_to_deliver(&info, &ka, __frame, NULL);
      if (signr > 0) {
            if (handle_signal(signr, &info, &ka, oldset) == 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;
      }

no_signal:
      /* Did we come from a system call? */
      if (__frame->syscallno >= 0) {
            /* Restart the system call - no handlers present */
            switch (__frame->gr8) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  __frame->gr8 = __frame->orig_gr8;
                  __frame->pc -= 4;
                  break;

            case -ERESTART_RESTARTBLOCK:
                  __frame->gr8 = __NR_restart_syscall;
                  __frame->pc -= 4;
                  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);
      }

} /* end do_signal() */

/*****************************************************************************/
/*
 * notification of userspace execution resumption
 * - triggered by the TIF_WORK_MASK flags
 */
asmlinkage void do_notify_resume(__u32 thread_info_flags)
{
      /* pending single-step? */
      if (thread_info_flags & _TIF_SINGLESTEP)
            clear_thread_flag(TIF_SINGLESTEP);

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

} /* end do_notify_resume() */

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