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signal.c

/*
 * arch/xtensa/kernel/signal.c
 *
 * Default platform functions.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2005, 2006 Tensilica Inc.
 * Copyright (C) 1991, 1992  Linus Torvalds
 * 1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 * Chris Zankel <chris@zankel.net>
 * Joe Taylor <joe@tensilica.com>
 */

#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/freezer.h>

#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/coprocessor.h>
#include <asm/unistd.h>

#define DEBUG_SIG  0

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

asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset);

extern struct task_struct *coproc_owners[];

extern void release_all_cp (struct task_struct *);

struct rt_sigframe
{
      struct siginfo info;
      struct ucontext uc;
      cp_state_t cpstate;
      unsigned char retcode[6];
      unsigned int window[4];
};

/* 
 * Flush register windows stored in pt_regs to stack.
 * Returns 1 for errors.
 *
 * Note that windowbase, windowstart, and wmask are not updated!
 */

int
flush_window_regs_user(struct pt_regs *regs)
{
      const unsigned long ws = regs->windowstart;
      const unsigned long wb = regs->windowbase;
      unsigned long sp = 0;
      unsigned long wm;
      int err = 1;
      int base;

      /* Return if no other frames. */

      if (regs->wmask == 1)
            return 0;

      /* Rotate windowmask and skip empty frames. */

      wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
      base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
            
      /* For call8 or call12 frames, we need the previous stack pointer. */

      if ((regs->wmask & 2) == 0)
            if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
                  goto errout;

      /* Spill frames to stack. */

      while (base < XCHAL_NUM_AREGS / 4) {

            int m = (wm >> base);
            int inc = 0;

            /* Save registers a4..a7 (call8) or a4...a11 (call12) */

            if (m & 2) {                  /* call4 */
                  inc = 1;

            } else if (m & 4) {           /* call8 */
                  if (copy_to_user((void*)(sp - 32),
                                 &regs->areg[(base + 1) * 4], 16))
                        goto errout;
                  inc = 2;

            } else if (m & 8) {     /* call12 */
                  if (copy_to_user((void*)(sp - 48),
                                 &regs->areg[(base + 1) * 4], 32))
                        goto errout;
                  inc = 3;
            }

            /* Save current frame a0..a3 under next SP */

            sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
            if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
                  goto errout;

            /* Get current stack pointer for next loop iteration. */

            sp = regs->areg[base * 4 + 1];
            base += inc;
      }

      return 0;

errout:
      return err;
}

/*
 * Note: We don't copy double exception 'regs', we have to finish double exc. 
 * first before we return to signal handler! This dbl.exc.handler might cause 
 * another double exception, but I think we are fine as the situation is the 
 * same as if we had returned to the signal handerl and got an interrupt 
 * immediately...
 */

static int
setup_sigcontext(struct sigcontext __user *sc, cp_state_t *cpstate,
             struct pt_regs *regs, unsigned long mask)
{
      int err = 0;

#define COPY(x)   err |= __put_user(regs->x, &sc->sc_##x)
      COPY(pc);
      COPY(ps);
      COPY(lbeg);
      COPY(lend);
      COPY(lcount);
      COPY(sar);
#undef COPY

      err |= flush_window_regs_user(regs);
      err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);

      // err |= __copy_to_user (sc->sc_a, regs->areg, XCHAL_NUM_AREGS * 4)

#if XCHAL_HAVE_CP
# error Coprocessors unsupported
      err |= save_cpextra(cpstate);
      err |= __put_user(err ? NULL : cpstate, &sc->sc_cpstate);
#endif
      /* non-iBCS2 extensions.. */
      err |= __put_user(mask, &sc->oldmask);

      return err;
}

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

#define COPY(x)   err |= __get_user(regs->x, &sc->sc_##x)
      COPY(pc);
      COPY(lbeg);
      COPY(lend);
      COPY(lcount);
      COPY(sar);
#undef COPY

      /* All registers were flushed to stack. Start with a prestine frame. */

      regs->wmask = 1;
      regs->windowbase = 0;
      regs->windowstart = 1;

      /* For PS, restore only PS.CALLINC.
       * Assume that all other bits are either the same as for the signal
       * handler, or the user mode value doesn't matter (e.g. PS.OWB).
       */
      err |= __get_user(ps, &sc->sc_ps);
      regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);

      /* Additional corruption checks */

      if ((regs->lcount > 0)
          && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
            err = 1;

      err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);

#if XCHAL_HAVE_CP
# error Coprocessors unsupported
      /* The signal handler may have used coprocessors in which
       * case they are still enabled.  We disable them to force a
       * reloading of the original task's CP state by the lazy
       * context-switching mechanisms of CP exception handling.
       * Also, we essentially discard any coprocessor state that the
       * signal handler created. */

      if (!err) {
        struct task_struct *tsk = current;
        release_all_cp(tsk);
        err |= __copy_from_user(tsk->thread.cpextra, sc->sc_cpstate, 
                                XTENSA_CP_EXTRA_SIZE);
      }
#endif

      regs->syscall = -1;           /* disable syscall checks */
      return err;
}



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

asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
                            long a4, long a5, struct pt_regs *regs)
{
      struct rt_sigframe __user *frame;
      sigset_t set;
      int ret;

      if (regs->depc > 64)
            panic("rt_sigreturn in double exception!\n");

      frame = (struct rt_sigframe __user *) regs->areg[1];

      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;

      ret = regs->areg[2];

      if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->areg[1]) == -EFAULT)
            goto badframe;

      return ret;

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



/*
 * Set up a signal frame.
 */

static int
gen_return_code(unsigned char *codemem)
{
      int err = 0;

      /*
       * The 12-bit immediate is really split up within the 24-bit MOVI
       * instruction.  As long as the above system call numbers fit within
       * 8-bits, the following code works fine. See the Xtensa ISA for
       * details.
       */

#if __NR_rt_sigreturn > 255
# error Generating the MOVI instruction below breaks!
#endif

#ifdef __XTENSA_EB__   /* Big Endian version */
      /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
      err |= __put_user(0x22, &codemem[0]);
      err |= __put_user(0x0a, &codemem[1]);
      err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
      /* Generate instruction:  SYSCALL */
      err |= __put_user(0x00, &codemem[3]);
      err |= __put_user(0x05, &codemem[4]);
      err |= __put_user(0x00, &codemem[5]);

#elif defined __XTENSA_EL__   /* Little Endian version */
      /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
      err |= __put_user(0x22, &codemem[0]);
      err |= __put_user(0xa0, &codemem[1]);
      err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
      /* Generate instruction:  SYSCALL */
      err |= __put_user(0x00, &codemem[3]);
      err |= __put_user(0x50, &codemem[4]);
      err |= __put_user(0x00, &codemem[5]);
#else
# error Must use compiler for Xtensa processors.
#endif

      /* Flush generated code out of the data cache */

      if (err == 0) {
            __invalidate_icache_range((unsigned long)codemem, 6UL);
            __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
      }

      return err;
}


static void setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                  sigset_t *set, struct pt_regs *regs)
{
      struct rt_sigframe *frame;
      int err = 0;
      int signal;
      unsigned long sp, ra;

      sp = regs->areg[1];

      if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
            sp = current->sas_ss_sp + current->sas_ss_size;
      }

      frame = (void *)((sp - sizeof(*frame)) & -16ul);

      if (regs->depc > 64)
            panic ("Double exception sys_sigreturn\n");

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

      signal = current_thread_info()->exec_domain
            && current_thread_info()->exec_domain->signal_invmap
            && sig < 32
            ? current_thread_info()->exec_domain->signal_invmap[sig]
            : sig;

      if (ka->sa.sa_flags & SA_SIGINFO) {
            err |= copy_siginfo_to_user(&frame->info, info);
      }

      /* Create the user context.  */

      err |= __put_user(0, &frame->uc.uc_flags);
      err |= __put_user(0, &frame->uc.uc_link);
      err |= __put_user((void *)current->sas_ss_sp,
                    &frame->uc.uc_stack.ss_sp);
      err |= __put_user(sas_ss_flags(regs->areg[1]),
                    &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, &frame->cpstate,
                          regs, set->sig[0]);
      err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

      /* Create sys_rt_sigreturn syscall in stack frame */

      err |= gen_return_code(frame->retcode);

      if (err) {
            goto give_sigsegv;
      }
            

      /* 
       * Create signal handler execution context.
       * Return context not modified until this point.
       */

      /* Set up registers for signal handler */
      start_thread(regs, (unsigned long) ka->sa.sa_handler, 
                 (unsigned long) frame);

      /* Set up a stack frame for a call4
       * Note: PS.CALLINC is set to one by start_thread
       */
      ra = (unsigned long) frame->retcode;
      regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
      regs->areg[6] = (unsigned long) signal;
      regs->areg[7] = (unsigned long) &frame->info;
      regs->areg[8] = (unsigned long) &frame->uc;

      /* Set access mode to USER_DS.  Nomenclature is outdated, but
       * functionality is used in uaccess.h
       */
      set_fs(USER_DS);

#if DEBUG_SIG
      printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
            current->comm, current->pid, signal, frame, regs->pc);
#endif

      return;

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

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */

asmlinkage long xtensa_rt_sigsuspend(sigset_t __user *unewset, 
                             size_t sigsetsize,
                             long a2, long a3, long a4, long a5, 
                             struct pt_regs *regs)
{
      sigset_t saveset, newset;

      /* XXX: Don't preclude handling different sized sigset_t's.  */
      if (sigsetsize != sizeof(sigset_t))
            return -EINVAL;

      if (copy_from_user(&newset, unewset, sizeof(newset)))
            return -EFAULT;

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

      regs->areg[2] = -EINTR;
      while (1) {
            current->state = TASK_INTERRUPTIBLE;
            schedule();
            if (do_signal(regs, &saveset))
                  return -EINTR;
      }
}

asmlinkage long xtensa_sigaltstack(const stack_t __user *uss, 
                           stack_t __user *uoss,
                           long a2, long a3, long a4, long a5,
                           struct pt_regs *regs)
{
      return do_sigaltstack(uss, uoss, regs->areg[1]);
}



/*
 * 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.
 *
 * Note that we go through the signals twice: once to check the signals that
 * the kernel can handle, and then we build all the user-level signal handling
 * stack-frames in one go after that.
 */
int do_signal(struct pt_regs *regs, sigset_t *oldset)
{
      siginfo_t info;
      int signr;
      struct k_sigaction ka;

      if (!user_mode(regs))
            return 0;

      if (try_to_freeze())
            goto no_signal;

      if (!oldset)
            oldset = &current->blocked;

      task_pt_regs(current)->icountlevel = 0;

      signr = get_signal_to_deliver(&info, &ka, regs, NULL);

      if (signr > 0) {

            /* Are we from a system call? */

            if ((signed)regs->syscall >= 0) {

                  /* If so, check system call restarting.. */

                  switch (regs->areg[2]) {
                        case -ERESTARTNOHAND:
                        case -ERESTART_RESTARTBLOCK:
                              regs->areg[2] = -EINTR;
                              break;

                        case -ERESTARTSYS:
                              if (!(ka.sa.sa_flags & SA_RESTART)) {
                                    regs->areg[2] = -EINTR;
                                    break;
                              }
                              /* fallthrough */
                        case -ERESTARTNOINTR:
                              regs->areg[2] = regs->syscall;
                              regs->pc -= 3;
                              break;

                        default:
                              /* nothing to do */
                              if (regs->areg[2] != 0)
                              break;
                  }
            }

            /* Whee!  Actually deliver the signal.  */
            /* Set up the stack frame */
            setup_frame(signr, &ka, &info, oldset, regs);

            if (ka.sa.sa_flags & SA_ONESHOT)
                  ka.sa.sa_handler = SIG_DFL;

            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, signr);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
            if (current->ptrace & PT_SINGLESTEP)
                  task_pt_regs(current)->icountlevel = 1;

            return 1;
      }

no_signal:
      /* Did we come from a system call? */
      if ((signed) regs->syscall >= 0) {
            /* Restart the system call - no handlers present */
            switch (regs->areg[2]) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  regs->areg[2] = regs->syscall;
                  regs->pc -= 3;
                  break;
            case -ERESTART_RESTARTBLOCK:
                  regs->areg[2] = __NR_restart_syscall;
                  regs->pc -= 3;
                  break;
            }
      }
      if (current->ptrace & PT_SINGLESTEP)
            task_pt_regs(current)->icountlevel = 1;
      return 0;
}


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