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signal.c

/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * Based on linux/arch/sh/kernel/signal.c
 *  Copyright (C) 1999, 2000  Niibe Yutaka & Kaz Kojima
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/freezer.h>

#include <asm/uaccess.h>
#include <asm/ucontext.h>

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

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

struct rt_sigframe
{
      struct siginfo info;
      struct ucontext uc;
      unsigned long retcode;
};

static int
restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
      int err = 0;

#define COPY(x)         err |= __get_user(regs->x, &sc->x)
      COPY(sr);
      COPY(pc);
      COPY(lr);
      COPY(sp);
      COPY(r12);
      COPY(r11);
      COPY(r10);
      COPY(r9);
      COPY(r8);
      COPY(r7);
      COPY(r6);
      COPY(r5);
      COPY(r4);
      COPY(r3);
      COPY(r2);
      COPY(r1);
      COPY(r0);
#undef      COPY

      /*
       * Don't allow anyone to pretend they're running in supervisor
       * mode or something...
       */
      err |= !valid_user_regs(regs);

      return err;
}


asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
{
      struct rt_sigframe __user *frame;
      sigset_t set;

      frame = (struct rt_sigframe __user *)regs->sp;
      pr_debug("SIG return: frame = %p\n", frame);

      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(regs, &frame->uc.uc_mcontext))
            goto badframe;

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

      pr_debug("Context restored: pc = %08lx, lr = %08lx, sp = %08lx\n",
             regs->pc, regs->lr, regs->sp);

      return regs->r12;

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

static int
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
{
      int err = 0;

#define COPY(x)         err |= __put_user(regs->x, &sc->x)
      COPY(sr);
      COPY(pc);
      COPY(lr);
      COPY(sp);
      COPY(r12);
      COPY(r11);
      COPY(r10);
      COPY(r9);
      COPY(r8);
      COPY(r7);
      COPY(r6);
      COPY(r5);
      COPY(r4);
      COPY(r3);
      COPY(r2);
      COPY(r1);
      COPY(r0);
#undef      COPY

      return err;
}

static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize)
{
      unsigned long sp = regs->sp;

      if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
            sp = current->sas_ss_sp + current->sas_ss_size;

      return (void __user *)((sp - framesize) & ~3);
}

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 err = 0;

      frame = get_sigframe(ka, regs, sizeof(*frame));
      err = -EFAULT;
      if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
            goto out;

      /*
       * Set up the return code:
       *
       *    mov   r8, __NR_rt_sigreturn
       *    scall
       *
       * Note: This will blow up since we're using a non-executable
       * stack. Better use SA_RESTORER.
       */
#if __NR_rt_sigreturn > 127
# error __NR_rt_sigreturn must be < 127 to fit in a short mov
#endif
      err = __put_user(0x3008d733 | (__NR_rt_sigreturn << 20),
                   &frame->retcode);

      err |= copy_siginfo_to_user(&frame->info, info);

      /* Set up the ucontext */
      err |= __put_user(0, &frame->uc.uc_flags);
      err |= __put_user(NULL, &frame->uc.uc_link);
      err |= __put_user((void __user *)current->sas_ss_sp,
                    &frame->uc.uc_stack.ss_sp);
      err |= __put_user(sas_ss_flags(regs->sp),
                    &frame->uc.uc_stack.ss_flags);
      err |= __put_user(current->sas_ss_size,
                    &frame->uc.uc_stack.ss_size);
      err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
      err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

      if (err)
            goto out;

      regs->r12 = sig;
      regs->r11 = (unsigned long) &frame->info;
      regs->r10 = (unsigned long) &frame->uc;
      regs->sp = (unsigned long) frame;
      if (ka->sa.sa_flags & SA_RESTORER)
            regs->lr = (unsigned long)ka->sa.sa_restorer;
      else {
            printk(KERN_NOTICE "[%s:%d] did not set SA_RESTORER\n",
                   current->comm, current->pid);
            regs->lr = (unsigned long) &frame->retcode;
      }

      pr_debug("SIG deliver [%s:%d]: sig=%d sp=0x%lx pc=0x%lx->0x%p lr=0x%lx\n",
             current->comm, current->pid, sig, regs->sp,
             regs->pc, ka->sa.sa_handler, regs->lr);

      regs->pc = (unsigned long) ka->sa.sa_handler;

out:
      return err;
}

static inline void restart_syscall(struct pt_regs *regs)
{
      if (regs->r12 == -ERESTART_RESTARTBLOCK)
            regs->r8 = __NR_restart_syscall;
      else
            regs->r12 = regs->r12_orig;
      regs->pc -= 2;
}

static inline void
handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
            sigset_t *oldset, struct pt_regs *regs, int syscall)
{
      int ret;

      /*
       * Set up the stack frame
       */
      ret = setup_rt_frame(sig, ka, info, oldset, regs);

      /*
       * Check that the resulting registers are sane
       */
      ret |= !valid_user_regs(regs);

      /*
       * Block the signal if we were unsuccessful.
       */
      if (ret != 0 || !(ka->sa.sa_flags & SA_NODEFER)) {
            spin_lock_irq(&current->sighand->siglock);
            sigorsets(&current->blocked, &current->blocked,
                    &ka->sa.sa_mask);
            sigaddset(&current->blocked, sig);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
      }

      if (ret == 0)
            return;

      force_sigsegv(sig, current);
}

/*
 * 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.
 */
int do_signal(struct pt_regs *regs, sigset_t *oldset, int syscall)
{
      siginfo_t info;
      int signr;
      struct k_sigaction ka;

      /*
       * 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(regs))
            return 0;

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

      signr = get_signal_to_deliver(&info, &ka, regs, NULL);
      if (syscall) {
            switch (regs->r12) {
            case -ERESTART_RESTARTBLOCK:
            case -ERESTARTNOHAND:
                  if (signr > 0) {
                        regs->r12 = -EINTR;
                        break;
                  }
                  /* fall through */
            case -ERESTARTSYS:
                  if (signr > 0 && !(ka.sa.sa_flags & SA_RESTART)) {
                        regs->r12 = -EINTR;
                        break;
                  }
                  /* fall through */
            case -ERESTARTNOINTR:
                  restart_syscall(regs);
            }
      }

      if (signr == 0) {
            /* No signal to deliver -- 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);
            }
            return 0;
      }

      handle_signal(signr, &ka, &info, oldset, regs, syscall);
      return 1;
}

asmlinkage void do_notify_resume(struct pt_regs *regs, struct thread_info *ti)
{
      int syscall = 0;

      if ((sysreg_read(SR) & MODE_MASK) == MODE_SUPERVISOR)
            syscall = 1;

      if (ti->flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
            do_signal(regs, &current->blocked, syscall);
}

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