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signal.c

/*
 * Copyright (C) 2003, Axis Communications AB.
 */

#include <linux/sched.h>
#include <linux/mm.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/syscalls.h>
#include <linux/vmalloc.h>

#include <asm/io.h>
#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <arch/ptrace.h>
#include <arch/hwregs/cpu_vect.h>

extern unsigned long cris_signal_return_page;

/* Flag to check if a signal is blockable. */
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

/*
 * A syscall in CRIS is really a "break 13" instruction, which is 2
 * bytes. The registers is manipulated so upon return the instruction
 * will be executed again.
 *
 * This relies on that PC points to the instruction after the break call.
 */
#define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->erp -= 2;

/* Signal frames. */
00039 struct signal_frame {
      struct sigcontext sc;
      unsigned long extramask[_NSIG_WORDS - 1];
      unsigned char retcode[8];     /* Trampoline code. */
};

00045 struct rt_signal_frame {
      struct siginfo *pinfo;
      void *puc;
      struct siginfo info;
      struct ucontext uc;
      unsigned char retcode[8];     /* Trampoline code. */
};

void do_signal(int restart, struct pt_regs *regs);
void keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
                  struct pt_regs *regs);
/*
 * Swap in the new signal mask, and wait for a signal. Define some
 * dummy arguments to be able to reach the regs argument.
 */
int
sys_sigsuspend(old_sigset_t mask, long r11, long r12, long r13, long mof,
             long srp, struct pt_regs *regs)
{
      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;
}

int
sys_sigaction(int signal, const struct old_sigaction *act,
            struct old_sigaction *oact)
{
      int retval;
      struct k_sigaction newk;
      struct k_sigaction oldk;

      if (act) {
            old_sigset_t mask;

            if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
                __get_user(newk.sa.sa_handler, &act->sa_handler) ||
                __get_user(newk.sa.sa_restorer, &act->sa_restorer))
                  return -EFAULT;

            __get_user(newk.sa.sa_flags, &act->sa_flags);
            __get_user(mask, &act->sa_mask);
            siginitset(&newk.sa.sa_mask, mask);
      }

      retval = do_sigaction(signal, act ? &newk : NULL, oact ? &oldk : NULL);

      if (!retval && oact) {
            if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
                __put_user(oldk.sa.sa_handler, &oact->sa_handler) ||
                __put_user(oldk.sa.sa_restorer, &oact->sa_restorer))
                  return -EFAULT;

            __put_user(oldk.sa.sa_flags, &oact->sa_flags);
            __put_user(oldk.sa.sa_mask.sig[0], &oact->sa_mask);
      }

      return retval;
}

int
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
      return do_sigaltstack(uss, uoss, rdusp());
}

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

        /* Always make any pending restarted system calls return -EINTR */
      current_thread_info()->restart_block.fn = do_no_restart_syscall;

      /*
       * Restore the registers from &sc->regs. sc is already checked
       * for VERIFY_READ since the signal_frame was previously
       * checked in sys_sigreturn().
       */
      if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
            goto badframe;

      /* Make that the user-mode flag is set. */
      regs->ccs |= (1 << (U_CCS_BITNR + CCS_SHIFT));

      /* Restore the old USP. */
      err |= __get_user(old_usp, &sc->usp);
      wrusp(old_usp);

      return err;

badframe:
      return 1;
}

/* Define some dummy arguments to be able to reach the regs argument. */
asmlinkage int
sys_sigreturn(long r10, long r11, long r12, long r13, long mof, long srp,
            struct pt_regs *regs)
{
      sigset_t set;
      struct signal_frame __user *frame;
      unsigned long oldspc = regs->spc;
      unsigned long oldccs = regs->ccs;

      frame = (struct signal_frame *) rdusp();

      /*
       * Since the signal is stacked on a dword boundary, the frame
       * should be dword aligned here as well. It it's not, then the
       * user is trying some funny business.
       */
      if (((long)frame) & 3)
            goto badframe;

      if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;

      if (__get_user(set.sig[0], &frame->sc.oldmask) ||
          (_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(regs, &frame->sc))
            goto badframe;

      keep_debug_flags(oldccs, oldspc, regs);

      return regs->r10;

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

/* Define some dummy variables to be able to reach the regs argument. */
asmlinkage int
sys_rt_sigreturn(long r10, long r11, long r12, long r13, long mof, long srp,
             struct pt_regs *regs)
{
      sigset_t set;
      struct rt_signal_frame __user *frame;
      unsigned long oldspc = regs->spc;
      unsigned long oldccs = regs->ccs;

      frame = (struct rt_signal_frame *) rdusp();

      /*
       * Since the signal is stacked on a dword boundary, the frame
       * should be dword aligned here as well. It it's not, then the
       * user is trying some funny business.
       */
      if (((long)frame) & 3)
            goto badframe;

      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, rdusp()) == -EFAULT)
            goto badframe;

      keep_debug_flags(oldccs, oldspc, regs);

      return regs->r10;

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

/* Setup a signal frame. */
static int
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
             unsigned long mask)
{
      int err;
      unsigned long usp;

      err = 0;
      usp = rdusp();

      /*
       * Copy the registers. They are located first in sc, so it's
       * possible to use sc directly.
       */
      err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));

      err |= __put_user(mask, &sc->oldmask);
      err |= __put_user(usp, &sc->usp);

      return err;
}

/* Figure out where to put the new signal frame - usually on the stack. */
static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
{
      unsigned long sp;

      sp = rdusp();

      /* 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;
      }

      /* Make sure the frame is dword-aligned. */
      sp &= ~3;

      return (void __user *)(sp - frame_size);
}

/* Grab and setup a signal frame.
 *
 * Basically a lot of state-info is stacked, and arranged for the
 * user-mode program to return to the kernel using either a trampiline
 * which performs the syscall sigreturn(), or a provided user-mode
 * trampoline.
  */
static int
setup_frame(int sig, struct k_sigaction *ka,  sigset_t *set,
          struct pt_regs * regs)
{
      int err;
      unsigned long return_ip;
      struct signal_frame __user *frame;

      err = 0;
      frame = get_sigframe(ka, regs, sizeof(*frame));

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

      err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);

      if (err)
            goto give_sigsegv;

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

      if (err)
            goto give_sigsegv;

      /*
       * Set up to return from user-space. If provided, use a stub
       * already located in user-space.
       */
      if (ka->sa.sa_flags & SA_RESTORER) {
            return_ip = (unsigned long)ka->sa.sa_restorer;
      } else {
            /* Trampoline - the desired return ip is in the signal return page. */
            return_ip = cris_signal_return_page;

            /*
             * This is movu.w __NR_sigreturn, r9; break 13;
             *
             * WE DO NOT USE IT ANY MORE! It's only left here for historical
             * reasons and because gdb uses it as a signature to notice
             * signal handler stack frames.
             */
            err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
            err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
            err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
      }

      if (err)
            goto give_sigsegv;

      /*
       * Set up registers for signal handler.
       *
       * Where the code enters now.
       * Where the code enter later.
       * First argument, signo.
       */
      regs->erp = (unsigned long) ka->sa.sa_handler;
      regs->srp = return_ip;
      regs->r10 = sig;

      /* Actually move the USP to reflect the stacked frame. */
      wrusp((unsigned long)frame);

      return 0;

give_sigsegv:
      if (sig == SIGSEGV)
            ka->sa.sa_handler = SIG_DFL;

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

static int
setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
             sigset_t *set, struct pt_regs * regs)
{
      int err;
      unsigned long return_ip;
      struct rt_signal_frame __user *frame;

      err = 0;
      frame = get_sigframe(ka, regs, sizeof(*frame));

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

      /* TODO: what is the current->exec_domain stuff and invmap ? */

      err |= __put_user(&frame->info, &frame->pinfo);
      err |= __put_user(&frame->uc, &frame->puc);
      err |= copy_siginfo_to_user(&frame->info, info);

      if (err)
            goto give_sigsegv;

      /* Clear all the bits of the ucontext we don't use.  */
      err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
      err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
      err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

      if (err)
            goto give_sigsegv;

      /*
       * Set up to return from user-space. If provided, use a stub
       * already located in user-space.
       */
      if (ka->sa.sa_flags & SA_RESTORER) {
            return_ip = (unsigned long) ka->sa.sa_restorer;
      } else {
            /* Trampoline - the desired return ip is in the signal return page. */
            return_ip = cris_signal_return_page + 6;

            /*
             * This is movu.w __NR_rt_sigreturn, r9; break 13;
             *
             * WE DO NOT USE IT ANY MORE! It's only left here for historical
             * reasons and because gdb uses it as a signature to notice
             * signal handler stack frames.
             */
            err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));

            err |= __put_user(__NR_rt_sigreturn,
                          (short __user*)(frame->retcode+2));

            err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
      }

      if (err)
            goto give_sigsegv;

      /*
       * Set up registers for signal handler.
       *
       * Where the code enters now.
       * Where the code enters later.
       * First argument is signo.
       * Second argument is (siginfo_t *).
       * Third argument is unused.
       */
      regs->erp = (unsigned long) ka->sa.sa_handler;
      regs->srp = return_ip;
      regs->r10 = sig;
      regs->r11 = (unsigned long) &frame->info;
      regs->r12 = 0;

      /* Actually move the usp to reflect the stacked frame. */
      wrusp((unsigned long)frame);

      return 0;

give_sigsegv:
      if (sig == SIGSEGV)
            ka->sa.sa_handler = SIG_DFL;

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

/* Invoke a signal handler to, well, handle the signal. */
static inline int
handle_signal(int canrestart, unsigned long sig,
            siginfo_t *info, struct k_sigaction *ka,
              sigset_t *oldset, struct pt_regs * regs)
{
      int ret;

      /* Check if this got called from a system call. */
      if (canrestart) {
            /* If so, check system call restarting. */
            switch (regs->r10) {
                  case -ERESTART_RESTARTBLOCK:
                  case -ERESTARTNOHAND:
                        /*
                         * This means that the syscall should
                         * only be restarted if there was no
                         * handler for the signal, and since
                         * this point isn't reached unless
                         * there is a handler, there's no need
                         * to restart.
                         */
                        regs->r10 = -EINTR;
                        break;

                        case -ERESTARTSYS:
                        /*
                         * This means restart the syscall if
                                 * there is no handler, or the handler
                                 * was registered with SA_RESTART.
                         */
                        if (!(ka->sa.sa_flags & SA_RESTART)) {
                              regs->r10 = -EINTR;
                              break;
                        }

                        /* Fall through. */

                  case -ERESTARTNOINTR:
                        /*
                         * This means that the syscall should
                                 * be called again after the signal
                                 * handler returns.
                         */
                        RESTART_CRIS_SYS(regs);
                        break;
                }
        }

      /* 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 (ka->sa.sa_flags & SA_ONESHOT)
            ka->sa.sa_handler = SIG_DFL;

      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;
}

/*
 * 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.
 *
 * Also note that the regs structure given here as an argument, is the latest
 * pushed pt_regs. It may or may not be the same as the first pushed registers
 * when the initial usermode->kernelmode transition took place. Therefore
 * we can use user_mode(regs) to see if we came directly from kernel or user
 * mode below.
 */
void
do_signal(int canrestart, struct pt_regs *regs)
{
      int signr;
      siginfo_t info;
        struct k_sigaction ka;
      sigset_t *oldset;

      /*
       * The common case should go fast, which is why this point is
       * reached from kernel-mode. If that's the case, just return
       * without doing anything.
       */
      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) {
            /* Whee!  Actually deliver the signal.  */
            if (handle_signal(canrestart, signr, &info, &ka,
                        oldset, regs)) {
                  /* 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;
      }

      /* Got here from a system call? */
      if (canrestart) {
            /* Restart the system call - no handlers present. */
            if (regs->r10 == -ERESTARTNOHAND ||
                regs->r10 == -ERESTARTSYS ||
                regs->r10 == -ERESTARTNOINTR) {
                  RESTART_CRIS_SYS(regs);
            }

            if (regs->r10 == -ERESTART_RESTARTBLOCK){
                  regs->r10 = __NR_restart_syscall;
                  regs->erp -= 2;
            }
      }

      /* 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);
      }
}

asmlinkage void
ugdb_trap_user(struct thread_info *ti, int sig)
{
      if (((user_regs(ti)->exs & 0xff00) >> 8) != SINGLE_STEP_INTR_VECT) {
            /* Zero single-step PC if the reason we stopped wasn't a single
               step exception. This is to avoid relying on it when it isn't
               reliable. */
            user_regs(ti)->spc = 0;
      }
      /* FIXME: Filter out false h/w breakpoint hits (i.e. EDA
         not withing any configured h/w breakpoint range). Synchronize with
         what already exists for kernel debugging.  */
      if (((user_regs(ti)->exs & 0xff00) >> 8) == BREAK_8_INTR_VECT) {
            /* Break 8: subtract 2 from ERP unless in a delay slot. */
            if (!(user_regs(ti)->erp & 0x1))
                  user_regs(ti)->erp -= 2;
      }
      sys_kill(ti->task->pid, sig);
}

void
keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
             struct pt_regs *regs)
{
      if (oldccs & (1 << Q_CCS_BITNR)) {
            /* Pending single step due to single-stepping the break 13
               in the signal trampoline: keep the Q flag. */
            regs->ccs |= (1 << Q_CCS_BITNR);
            /* S flag should be set - complain if it's not. */
            if (!(oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT)))) {
                  printk("Q flag but no S flag?");
            }
            regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
            /* Assume the SPC is valid and interesting. */
            regs->spc = oldspc;

      } else if (oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT))) {
            /* If a h/w bp was set in the signal handler we need
               to keep the S flag. */
            regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
            /* Don't keep the old SPC though; if we got here due to
               a single-step, the Q flag should have been set. */
      } else if (regs->spc) {
            /* If we were single-stepping *before* the signal was taken,
               we don't want to restore that state now, because GDB will
               have forgotten all about it. */
            regs->spc = 0;
            regs->ccs &= ~(1 << (S_CCS_BITNR + CCS_SHIFT));
      }
}

/* Set up the trampolines on the signal return page. */
int __init
cris_init_signal(void)
{
      u16* data = kmalloc(PAGE_SIZE, GFP_KERNEL);

      /* This is movu.w __NR_sigreturn, r9; break 13; */
      data[0] = 0x9c5f;
      data[1] = __NR_sigreturn;
      data[2] = 0xe93d;
      /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
      data[3] = 0x9c5f;
      data[4] = __NR_rt_sigreturn;
      data[5] = 0xe93d;

      /* Map to userspace with appropriate permissions (no write access...) */
      cris_signal_return_page = (unsigned long)
          __ioremap_prot(virt_to_phys(data), PAGE_SIZE, PAGE_SIGNAL_TRAMPOLINE);

      return 0;
}

__initcall(cris_init_signal);

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