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signal.c

/*
 * 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) 1991, 1992  Linus Torvalds
 * Copyright (C) 1994 - 2000  Ralf Baechle
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 */
#include <linux/cache.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/personality.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/compiler.h>
#include <linux/uaccess.h>

#include <asm/abi.h>
#include <asm/asm.h>
#include <linux/bitops.h>
#include <asm/cacheflush.h>
#include <asm/fpu.h>
#include <asm/sim.h>
#include <asm/ucontext.h>
#include <asm/cpu-features.h>
#include <asm/war.h>

#include "signal-common.h"

/*
 * Horribly complicated - with the bloody RM9000 workarounds enabled
 * the signal trampolines is moving to the end of the structure so we can
 * increase the alignment without breaking software compatibility.
 */
#if ICACHE_REFILLS_WORKAROUND_WAR == 0

struct sigframe {
      u32 sf_ass[4];          /* argument save space for o32 */
      u32 sf_code[2];         /* signal trampoline */
      struct sigcontext sf_sc;
      sigset_t sf_mask;
};

struct rt_sigframe {
      u32 rs_ass[4];          /* argument save space for o32 */
      u32 rs_code[2];         /* signal trampoline */
      struct siginfo rs_info;
      struct ucontext rs_uc;
};

#else

struct sigframe {
      u32 sf_ass[4];                /* argument save space for o32 */
      u32 sf_pad[2];
      struct sigcontext sf_sc;      /* hw context */
      sigset_t sf_mask;
      u32 sf_code[8] ____cacheline_aligned;     /* signal trampoline */
};

struct rt_sigframe {
      u32 rs_ass[4];                /* argument save space for o32 */
      u32 rs_pad[2];
      struct siginfo rs_info;
      struct ucontext rs_uc;
      u32 rs_code[8] ____cacheline_aligned;     /* signal trampoline */
};

#endif

/*
 * Helper routines
 */
static int protected_save_fp_context(struct sigcontext __user *sc)
{
      int err;
      while (1) {
            lock_fpu_owner();
            own_fpu_inatomic(1);
            err = save_fp_context(sc); /* this might fail */
            unlock_fpu_owner();
            if (likely(!err))
                  break;
            /* touch the sigcontext and try again */
            err = __put_user(0, &sc->sc_fpregs[0]) |
                  __put_user(0, &sc->sc_fpregs[31]) |
                  __put_user(0, &sc->sc_fpc_csr);
            if (err)
                  break;      /* really bad sigcontext */
      }
      return err;
}

static int protected_restore_fp_context(struct sigcontext __user *sc)
{
      int err, tmp;
      while (1) {
            lock_fpu_owner();
            own_fpu_inatomic(0);
            err = restore_fp_context(sc); /* this might fail */
            unlock_fpu_owner();
            if (likely(!err))
                  break;
            /* touch the sigcontext and try again */
            err = __get_user(tmp, &sc->sc_fpregs[0]) |
                  __get_user(tmp, &sc->sc_fpregs[31]) |
                  __get_user(tmp, &sc->sc_fpc_csr);
            if (err)
                  break;      /* really bad sigcontext */
      }
      return err;
}

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

      err |= __put_user(regs->cp0_epc, &sc->sc_pc);

      err |= __put_user(0, &sc->sc_regs[0]);
      for (i = 1; i < 32; i++)
            err |= __put_user(regs->regs[i], &sc->sc_regs[i]);

#ifdef CONFIG_CPU_HAS_SMARTMIPS
      err |= __put_user(regs->acx, &sc->sc_acx);
#endif
      err |= __put_user(regs->hi, &sc->sc_mdhi);
      err |= __put_user(regs->lo, &sc->sc_mdlo);
      if (cpu_has_dsp) {
            err |= __put_user(mfhi1(), &sc->sc_hi1);
            err |= __put_user(mflo1(), &sc->sc_lo1);
            err |= __put_user(mfhi2(), &sc->sc_hi2);
            err |= __put_user(mflo2(), &sc->sc_lo2);
            err |= __put_user(mfhi3(), &sc->sc_hi3);
            err |= __put_user(mflo3(), &sc->sc_lo3);
            err |= __put_user(rddsp(DSP_MASK), &sc->sc_dsp);
      }

      used_math = !!used_math();
      err |= __put_user(used_math, &sc->sc_used_math);

      if (used_math) {
            /*
             * Save FPU state to signal context. Signal handler
             * will "inherit" current FPU state.
             */
            err |= protected_save_fp_context(sc);
      }
      return err;
}

int fpcsr_pending(unsigned int __user *fpcsr)
{
      int err, sig = 0;
      unsigned int csr, enabled;

      err = __get_user(csr, fpcsr);
      enabled = FPU_CSR_UNI_X | ((csr & FPU_CSR_ALL_E) << 5);
      /*
       * If the signal handler set some FPU exceptions, clear it and
       * send SIGFPE.
       */
      if (csr & enabled) {
            csr &= ~enabled;
            err |= __put_user(csr, fpcsr);
            sig = SIGFPE;
      }
      return err ?: sig;
}

static int
check_and_restore_fp_context(struct sigcontext __user *sc)
{
      int err, sig;

      err = sig = fpcsr_pending(&sc->sc_fpc_csr);
      if (err > 0)
            err = 0;
      err |= protected_restore_fp_context(sc);
      return err ?: sig;
}

int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
      unsigned int used_math;
      unsigned long treg;
      int err = 0;
      int i;

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

      err |= __get_user(regs->cp0_epc, &sc->sc_pc);

#ifdef CONFIG_CPU_HAS_SMARTMIPS
      err |= __get_user(regs->acx, &sc->sc_acx);
#endif
      err |= __get_user(regs->hi, &sc->sc_mdhi);
      err |= __get_user(regs->lo, &sc->sc_mdlo);
      if (cpu_has_dsp) {
            err |= __get_user(treg, &sc->sc_hi1); mthi1(treg);
            err |= __get_user(treg, &sc->sc_lo1); mtlo1(treg);
            err |= __get_user(treg, &sc->sc_hi2); mthi2(treg);
            err |= __get_user(treg, &sc->sc_lo2); mtlo2(treg);
            err |= __get_user(treg, &sc->sc_hi3); mthi3(treg);
            err |= __get_user(treg, &sc->sc_lo3); mtlo3(treg);
            err |= __get_user(treg, &sc->sc_dsp); wrdsp(treg, DSP_MASK);
      }

      for (i = 1; i < 32; i++)
            err |= __get_user(regs->regs[i], &sc->sc_regs[i]);

      err |= __get_user(used_math, &sc->sc_used_math);
      conditional_used_math(used_math);

      if (used_math) {
            /* restore fpu context if we have used it before */
            if (!err)
                  err = check_and_restore_fp_context(sc);
      } else {
            /* signal handler may have used FPU.  Give it up. */
            lose_fpu(0);
      }

      return err;
}

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->regs[29];

      /*
       * FPU emulator may have it's own trampoline active just
       * above the user stack, 16-bytes before the next lowest
       * 16 byte boundary.  Try to avoid trashing it.
       */
      sp -= 32;

      /* This is the X/Open sanctioned signal stack switching.  */
      if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags (sp) == 0))
            sp = current->sas_ss_sp + current->sas_ss_size;

      return (void __user *)((sp - frame_size) & (ICACHE_REFILLS_WORKAROUND_WAR ? ~(cpu_icache_line_size()-1) : ALMASK));
}

int install_sigtramp(unsigned int __user *tramp, unsigned int syscall)
{
      int err;

      /*
       * Set up the return code ...
       *
       *         li      v0, __NR__foo_sigreturn
       *         syscall
       */

      err = __put_user(0x24020000 + syscall, tramp + 0);
      err |= __put_user(0x0000000c         , tramp + 1);
      if (ICACHE_REFILLS_WORKAROUND_WAR) {
            err |= __put_user(0, tramp + 2);
            err |= __put_user(0, tramp + 3);
            err |= __put_user(0, tramp + 4);
            err |= __put_user(0, tramp + 5);
            err |= __put_user(0, tramp + 6);
            err |= __put_user(0, tramp + 7);
      }
      flush_cache_sigtramp((unsigned long) tramp);

      return err;
}

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

#ifdef CONFIG_TRAD_SIGNALS
asmlinkage int sys_sigsuspend(nabi_no_regargs struct pt_regs regs)
{
      sigset_t newset;
      sigset_t __user *uset;

      uset = (sigset_t __user *) regs.regs[4];
      if (copy_from_user(&newset, uset, sizeof(sigset_t)))
            return -EFAULT;
      sigdelsetmask(&newset, ~_BLOCKABLE);

      spin_lock_irq(&current->sighand->siglock);
      current->saved_sigmask = current->blocked;
      current->blocked = newset;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

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

asmlinkage int sys_rt_sigsuspend(nabi_no_regargs struct pt_regs regs)
{
      sigset_t newset;
      sigset_t __user *unewset;
      size_t sigsetsize;

      /* XXX Don't preclude handling different sized sigset_t's.  */
      sigsetsize = regs.regs[5];
      if (sigsetsize != sizeof(sigset_t))
            return -EINVAL;

      unewset = (sigset_t __user *) regs.regs[4];
      if (copy_from_user(&newset, unewset, sizeof(newset)))
            return -EFAULT;
      sigdelsetmask(&newset, ~_BLOCKABLE);

      spin_lock_irq(&current->sighand->siglock);
      current->saved_sigmask = current->blocked;
      current->blocked = newset;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

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

#ifdef CONFIG_TRAD_SIGNALS
asmlinkage int sys_sigaction(int sig, const struct sigaction __user *act,
      struct sigaction __user *oact)
{
      struct k_sigaction new_ka, old_ka;
      int ret;
      int err = 0;

      if (act) {
            old_sigset_t mask;

            if (!access_ok(VERIFY_READ, act, sizeof(*act)))
                  return -EFAULT;
            err |= __get_user(new_ka.sa.sa_handler, &act->sa_handler);
            err |= __get_user(new_ka.sa.sa_flags, &act->sa_flags);
            err |= __get_user(mask, &act->sa_mask.sig[0]);
            if (err)
                  return -EFAULT;

            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)))
                  return -EFAULT;
            err |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
            err |= __put_user(old_ka.sa.sa_handler, &oact->sa_handler);
            err |= __put_user(old_ka.sa.sa_mask.sig[0], oact->sa_mask.sig);
            err |= __put_user(0, &oact->sa_mask.sig[1]);
            err |= __put_user(0, &oact->sa_mask.sig[2]);
            err |= __put_user(0, &oact->sa_mask.sig[3]);
            if (err)
                  return -EFAULT;
      }

      return ret;
}
#endif

asmlinkage int sys_sigaltstack(nabi_no_regargs struct pt_regs regs)
{
      const stack_t __user *uss = (const stack_t __user *) regs.regs[4];
      stack_t __user *uoss = (stack_t __user *) regs.regs[5];
      unsigned long usp = regs.regs[29];

      return do_sigaltstack(uss, uoss, usp);
}

#ifdef CONFIG_TRAD_SIGNALS
asmlinkage void sys_sigreturn(nabi_no_regargs struct pt_regs regs)
{
      struct sigframe __user *frame;
      sigset_t blocked;
      int sig;

      frame = (struct sigframe __user *) regs.regs[29];
      if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;
      if (__copy_from_user(&blocked, &frame->sf_mask, sizeof(blocked)))
            goto badframe;

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

      sig = restore_sigcontext(&regs, &frame->sf_sc);
      if (sig < 0)
            goto badframe;
      else if (sig)
            force_sig(sig, current);

      /*
       * Don't let your children do this ...
       */
      __asm__ __volatile__(
            "move\t$29, %0\n\t"
            "j\tsyscall_exit"
            :/* no outputs */
            :"r" (&regs));
      /* Unreached */

badframe:
      force_sig(SIGSEGV, current);
}
#endif /* CONFIG_TRAD_SIGNALS */

asmlinkage void sys_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
{
      struct rt_sigframe __user *frame;
      sigset_t set;
      stack_t st;
      int sig;

      frame = (struct rt_sigframe __user *) regs.regs[29];
      if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;
      if (__copy_from_user(&set, &frame->rs_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);

      sig = restore_sigcontext(&regs, &frame->rs_uc.uc_mcontext);
      if (sig < 0)
            goto badframe;
      else if (sig)
            force_sig(sig, current);

      if (__copy_from_user(&st, &frame->rs_uc.uc_stack, sizeof(st)))
            goto badframe;
      /* It is more difficult to avoid calling this function than to
         call it and ignore errors.  */
      do_sigaltstack((stack_t __user *)&st, NULL, regs.regs[29]);

      /*
       * Don't let your children do this ...
       */
      __asm__ __volatile__(
            "move\t$29, %0\n\t"
            "j\tsyscall_exit"
            :/* no outputs */
            :"r" (&regs));
      /* Unreached */

badframe:
      force_sig(SIGSEGV, current);
}

#ifdef CONFIG_TRAD_SIGNALS
static int setup_frame(struct k_sigaction * ka, struct pt_regs *regs,
      int signr, sigset_t *set)
{
      struct sigframe __user *frame;
      int err = 0;

      frame = get_sigframe(ka, regs, sizeof(*frame));
      if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
            goto give_sigsegv;

      err |= install_sigtramp(frame->sf_code, __NR_sigreturn);

      err |= setup_sigcontext(regs, &frame->sf_sc);
      err |= __copy_to_user(&frame->sf_mask, set, sizeof(*set));
      if (err)
            goto give_sigsegv;

      /*
       * Arguments to signal handler:
       *
       *   a0 = signal number
       *   a1 = 0 (should be cause)
       *   a2 = pointer to struct sigcontext
       *
       * $25 and c0_epc point to the signal handler, $29 points to the
       * struct sigframe.
       */
      regs->regs[ 4] = signr;
      regs->regs[ 5] = 0;
      regs->regs[ 6] = (unsigned long) &frame->sf_sc;
      regs->regs[29] = (unsigned long) frame;
      regs->regs[31] = (unsigned long) frame->sf_code;
      regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;

      DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
             current->comm, current->pid,
             frame, regs->cp0_epc, regs->regs[31]);
      return 0;

give_sigsegv:
      force_sigsegv(signr, current);
      return -EFAULT;
}
#endif

static int setup_rt_frame(struct k_sigaction * ka, struct pt_regs *regs,
      int signr, sigset_t *set, siginfo_t *info)
{
      struct rt_sigframe __user *frame;
      int err = 0;

      frame = get_sigframe(ka, regs, sizeof(*frame));
      if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
            goto give_sigsegv;

      err |= install_sigtramp(frame->rs_code, __NR_rt_sigreturn);

      /* Create siginfo.  */
      err |= copy_siginfo_to_user(&frame->rs_info, info);

      /* Create the ucontext.  */
      err |= __put_user(0, &frame->rs_uc.uc_flags);
      err |= __put_user(NULL, &frame->rs_uc.uc_link);
      err |= __put_user((void __user *)current->sas_ss_sp,
                        &frame->rs_uc.uc_stack.ss_sp);
      err |= __put_user(sas_ss_flags(regs->regs[29]),
                        &frame->rs_uc.uc_stack.ss_flags);
      err |= __put_user(current->sas_ss_size,
                        &frame->rs_uc.uc_stack.ss_size);
      err |= setup_sigcontext(regs, &frame->rs_uc.uc_mcontext);
      err |= __copy_to_user(&frame->rs_uc.uc_sigmask, set, sizeof(*set));

      if (err)
            goto give_sigsegv;

      /*
       * Arguments to signal handler:
       *
       *   a0 = signal number
       *   a1 = 0 (should be cause)
       *   a2 = pointer to ucontext
       *
       * $25 and c0_epc point to the signal handler, $29 points to
       * the struct rt_sigframe.
       */
      regs->regs[ 4] = signr;
      regs->regs[ 5] = (unsigned long) &frame->rs_info;
      regs->regs[ 6] = (unsigned long) &frame->rs_uc;
      regs->regs[29] = (unsigned long) frame;
      regs->regs[31] = (unsigned long) frame->rs_code;
      regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;

      DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
             current->comm, current->pid,
             frame, regs->cp0_epc, regs->regs[31]);

      return 0;

give_sigsegv:
      force_sigsegv(signr, current);
      return -EFAULT;
}

struct mips_abi mips_abi = {
#ifdef CONFIG_TRAD_SIGNALS
      .setup_frame      = setup_frame,
#endif
      .setup_rt_frame   = setup_rt_frame,
      .restart    = __NR_restart_syscall
};

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

      switch(regs->regs[0]) {
      case ERESTART_RESTARTBLOCK:
      case ERESTARTNOHAND:
            regs->regs[2] = EINTR;
            break;
      case ERESTARTSYS:
            if (!(ka->sa.sa_flags & SA_RESTART)) {
                  regs->regs[2] = EINTR;
                  break;
            }
      /* fallthrough */
      case ERESTARTNOINTR:          /* Userland will reload $v0.  */
            regs->regs[7] = regs->regs[26];
            regs->cp0_epc -= 8;
      }

      regs->regs[0] = 0;            /* Don't deal with this again.  */

      if (sig_uses_siginfo(ka))
            ret = current->thread.abi->setup_rt_frame(ka, regs, sig, oldset, info);
      else
            ret = current->thread.abi->setup_frame(ka, regs, sig, oldset);

      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;
}

static void do_signal(struct pt_regs *regs)
{
      struct k_sigaction ka;
      sigset_t *oldset;
      siginfo_t info;
      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(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(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;
      }

      /*
       * Who's code doesn't conform to the restartable syscall convention
       * dies here!!!  The li instruction, a single machine instruction,
       * must directly be followed by the syscall instruction.
       */
      if (regs->regs[0]) {
            if (regs->regs[2] == ERESTARTNOHAND ||
                regs->regs[2] == ERESTARTSYS ||
                regs->regs[2] == ERESTARTNOINTR) {
                  regs->regs[7] = regs->regs[26];
                  regs->cp0_epc -= 8;
            }
            if (regs->regs[2] == ERESTART_RESTARTBLOCK) {
                  regs->regs[2] = current->thread.abi->restart;
                  regs->regs[7] = regs->regs[26];
                  regs->cp0_epc -= 4;
            }
            regs->regs[0] = 0;      /* Don't deal with this again.  */
      }

      /*
       * 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 the TIF_WORK_MASK flags
 */
asmlinkage void do_notify_resume(struct pt_regs *regs, void *unused,
      __u32 thread_info_flags)
{
      /* deal with pending signal delivery */
      if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
            do_signal(regs);
}

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