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signal.c

/*
 * Architecture-specific signal handling support.
 *
 * Copyright (C) 1999-2004 Hewlett-Packard Co
 *    David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * Derived from i386 and Alpha versions.
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <linux/unistd.h>
#include <linux/wait.h>

#include <asm/intrinsics.h>
#include <asm/uaccess.h>
#include <asm/rse.h>
#include <asm/sigcontext.h>

#include "sigframe.h"

#define DEBUG_SIG 0
#define STACK_ALIGN     16          /* minimal alignment for stack pointer */
#define _BLOCKABLE      (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

#if _NSIG_WORDS > 1
# define PUT_SIGSET(k,u)      __copy_to_user((u)->sig, (k)->sig, sizeof(sigset_t))
# define GET_SIGSET(k,u)      __copy_from_user((k)->sig, (u)->sig, sizeof(sigset_t))
#else
# define PUT_SIGSET(k,u)      __put_user((k)->sig[0], &(u)->sig[0])
# define GET_SIGSET(k,u)      __get_user((k)->sig[0], &(u)->sig[0])
#endif

asmlinkage long
sys_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, long arg2,
             long arg3, long arg4, long arg5, long arg6, long arg7,
             struct pt_regs regs)
{
      return do_sigaltstack(uss, uoss, regs.r12);
}

static long
restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr)
{
      unsigned long ip, flags, nat, um, cfm, rsc;
      long err;

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

      /* restore scratch that always needs gets updated during signal delivery: */
      err  = __get_user(flags, &sc->sc_flags);
      err |= __get_user(nat, &sc->sc_nat);
      err |= __get_user(ip, &sc->sc_ip);              /* instruction pointer */
      err |= __get_user(cfm, &sc->sc_cfm);
      err |= __get_user(um, &sc->sc_um);              /* user mask */
      err |= __get_user(rsc, &sc->sc_ar_rsc);
      err |= __get_user(scr->pt.ar_unat, &sc->sc_ar_unat);
      err |= __get_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr);
      err |= __get_user(scr->pt.ar_pfs, &sc->sc_ar_pfs);
      err |= __get_user(scr->pt.pr, &sc->sc_pr);            /* predicates */
      err |= __get_user(scr->pt.b0, &sc->sc_br[0]);         /* b0 (rp) */
      err |= __get_user(scr->pt.b6, &sc->sc_br[6]);         /* b6 */
      err |= __copy_from_user(&scr->pt.r1, &sc->sc_gr[1], 8);     /* r1 */
      err |= __copy_from_user(&scr->pt.r8, &sc->sc_gr[8], 4*8);   /* r8-r11 */
      err |= __copy_from_user(&scr->pt.r12, &sc->sc_gr[12], 2*8); /* r12-r13 */
      err |= __copy_from_user(&scr->pt.r15, &sc->sc_gr[15], 8);   /* r15 */

      scr->pt.cr_ifs = cfm | (1UL << 63);
      scr->pt.ar_rsc = rsc | (3 << 2); /* force PL3 */

      /* establish new instruction pointer: */
      scr->pt.cr_iip = ip & ~0x3UL;
      ia64_psr(&scr->pt)->ri = ip & 0x3;
      scr->pt.cr_ipsr = (scr->pt.cr_ipsr & ~IA64_PSR_UM) | (um & IA64_PSR_UM);

      scr->scratch_unat = ia64_put_scratch_nat_bits(&scr->pt, nat);

      if (!(flags & IA64_SC_FLAG_IN_SYSCALL)) {
            /* Restore most scratch-state only when not in syscall. */
            err |= __get_user(scr->pt.ar_ccv, &sc->sc_ar_ccv);          /* ar.ccv */
            err |= __get_user(scr->pt.b7, &sc->sc_br[7]);               /* b7 */
            err |= __get_user(scr->pt.r14, &sc->sc_gr[14]);             /* r14 */
            err |= __copy_from_user(&scr->pt.ar_csd, &sc->sc_ar25, 2*8); /* ar.csd & ar.ssd */
            err |= __copy_from_user(&scr->pt.r2, &sc->sc_gr[2], 2*8);   /* r2-r3 */
            err |= __copy_from_user(&scr->pt.r16, &sc->sc_gr[16], 16*8);      /* r16-r31 */
      }

      if ((flags & IA64_SC_FLAG_FPH_VALID) != 0) {
            struct ia64_psr *psr = ia64_psr(&scr->pt);

            err |= __copy_from_user(current->thread.fph, &sc->sc_fr[32], 96*16);
            psr->mfh = 0;     /* drop signal handler's fph contents... */
            preempt_disable();
            if (psr->dfh)
                  ia64_drop_fpu(current);
            else {
                  /* We already own the local fph, otherwise psr->dfh wouldn't be 0.  */
                  __ia64_load_fpu(current->thread.fph);
                  ia64_set_local_fpu_owner(current);
            }
            preempt_enable();
      }
      return err;
}

int
copy_siginfo_to_user (siginfo_t __user *to, siginfo_t *from)
{
      if (!access_ok(VERIFY_WRITE, to, sizeof(siginfo_t)))
            return -EFAULT;
      if (from->si_code < 0) {
            if (__copy_to_user(to, from, sizeof(siginfo_t)))
                  return -EFAULT;
            return 0;
      } else {
            int err;

            /*
             * If you change siginfo_t structure, please be sure this code is fixed
             * accordingly.  It should never copy any pad contained in the structure
             * to avoid security leaks, but must copy the generic 3 ints plus the
             * relevant union member.
             */
            err = __put_user(from->si_signo, &to->si_signo);
            err |= __put_user(from->si_errno, &to->si_errno);
            err |= __put_user((short)from->si_code, &to->si_code);
            switch (from->si_code >> 16) {
                  case __SI_FAULT >> 16:
                  err |= __put_user(from->si_flags, &to->si_flags);
                  err |= __put_user(from->si_isr, &to->si_isr);
                  case __SI_POLL >> 16:
                  err |= __put_user(from->si_addr, &to->si_addr);
                  err |= __put_user(from->si_imm, &to->si_imm);
                  break;
                  case __SI_TIMER >> 16:
                  err |= __put_user(from->si_tid, &to->si_tid);
                  err |= __put_user(from->si_overrun, &to->si_overrun);
                  err |= __put_user(from->si_ptr, &to->si_ptr);
                  break;
                  case __SI_RT >> 16:     /* Not generated by the kernel as of now.  */
                  case __SI_MESGQ >> 16:
                  err |= __put_user(from->si_uid, &to->si_uid);
                  err |= __put_user(from->si_pid, &to->si_pid);
                  err |= __put_user(from->si_ptr, &to->si_ptr);
                  break;
                  case __SI_CHLD >> 16:
                  err |= __put_user(from->si_utime, &to->si_utime);
                  err |= __put_user(from->si_stime, &to->si_stime);
                  err |= __put_user(from->si_status, &to->si_status);
                  default:
                  err |= __put_user(from->si_uid, &to->si_uid);
                  err |= __put_user(from->si_pid, &to->si_pid);
                  break;
            }
            return err;
      }
}

long
ia64_rt_sigreturn (struct sigscratch *scr)
{
      extern char ia64_strace_leave_kernel, ia64_leave_kernel;
      struct sigcontext __user *sc;
      struct siginfo si;
      sigset_t set;
      long retval;

      sc = &((struct sigframe __user *) (scr->pt.r12 + 16))->sc;

      /*
       * When we return to the previously executing context, r8 and r10 have already
       * been setup the way we want them.  Indeed, if the signal wasn't delivered while
       * in a system call, we must not touch r8 or r10 as otherwise user-level state
       * could be corrupted.
       */
      retval = (long) &ia64_leave_kernel;
      if (test_thread_flag(TIF_SYSCALL_TRACE)
          || test_thread_flag(TIF_SYSCALL_AUDIT))
            /*
             * strace expects to be notified after sigreturn returns even though the
             * context to which we return may not be in the middle of a syscall.
             * Thus, the return-value that strace displays for sigreturn is
             * meaningless.
             */
            retval = (long) &ia64_strace_leave_kernel;

      if (!access_ok(VERIFY_READ, sc, sizeof(*sc)))
            goto give_sigsegv;

      if (GET_SIGSET(&set, &sc->sc_mask))
            goto give_sigsegv;

      sigdelsetmask(&set, ~_BLOCKABLE);

      spin_lock_irq(&current->sighand->siglock);
      {
            current->blocked = set;
            recalc_sigpending();
      }
      spin_unlock_irq(&current->sighand->siglock);

      if (restore_sigcontext(sc, scr))
            goto give_sigsegv;

#if DEBUG_SIG
      printk("SIG return (%s:%d): sp=%lx ip=%lx\n",
             current->comm, current->pid, scr->pt.r12, scr->pt.cr_iip);
#endif
      /*
       * It is more difficult to avoid calling this function than to
       * call it and ignore errors.
       */
      do_sigaltstack(&sc->sc_stack, NULL, scr->pt.r12);
      return retval;

  give_sigsegv:
      si.si_signo = SIGSEGV;
      si.si_errno = 0;
      si.si_code = SI_KERNEL;
      si.si_pid = task_pid_vnr(current);
      si.si_uid = current_uid();
      si.si_addr = sc;
      force_sig_info(SIGSEGV, &si, current);
      return retval;
}

/*
 * This does just the minimum required setup of sigcontext.
 * Specifically, it only installs data that is either not knowable at
 * the user-level or that gets modified before execution in the
 * trampoline starts.  Everything else is done at the user-level.
 */
static long
setup_sigcontext (struct sigcontext __user *sc, sigset_t *mask, struct sigscratch *scr)
{
      unsigned long flags = 0, ifs, cfm, nat;
      long err = 0;

      ifs = scr->pt.cr_ifs;

      if (on_sig_stack((unsigned long) sc))
            flags |= IA64_SC_FLAG_ONSTACK;
      if ((ifs & (1UL << 63)) == 0)
            /* if cr_ifs doesn't have the valid bit set, we got here through a syscall */
            flags |= IA64_SC_FLAG_IN_SYSCALL;
      cfm = ifs & ((1UL << 38) - 1);
      ia64_flush_fph(current);
      if ((current->thread.flags & IA64_THREAD_FPH_VALID)) {
            flags |= IA64_SC_FLAG_FPH_VALID;
            err = __copy_to_user(&sc->sc_fr[32], current->thread.fph, 96*16);
      }

      nat = ia64_get_scratch_nat_bits(&scr->pt, scr->scratch_unat);

      err |= __put_user(flags, &sc->sc_flags);
      err |= __put_user(nat, &sc->sc_nat);
      err |= PUT_SIGSET(mask, &sc->sc_mask);
      err |= __put_user(cfm, &sc->sc_cfm);
      err |= __put_user(scr->pt.cr_ipsr & IA64_PSR_UM, &sc->sc_um);
      err |= __put_user(scr->pt.ar_rsc, &sc->sc_ar_rsc);
      err |= __put_user(scr->pt.ar_unat, &sc->sc_ar_unat);        /* ar.unat */
      err |= __put_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr);        /* ar.fpsr */
      err |= __put_user(scr->pt.ar_pfs, &sc->sc_ar_pfs);
      err |= __put_user(scr->pt.pr, &sc->sc_pr);                  /* predicates */
      err |= __put_user(scr->pt.b0, &sc->sc_br[0]);               /* b0 (rp) */
      err |= __put_user(scr->pt.b6, &sc->sc_br[6]);               /* b6 */
      err |= __copy_to_user(&sc->sc_gr[1], &scr->pt.r1, 8);       /* r1 */
      err |= __copy_to_user(&sc->sc_gr[8], &scr->pt.r8, 4*8);           /* r8-r11 */
      err |= __copy_to_user(&sc->sc_gr[12], &scr->pt.r12, 2*8);   /* r12-r13 */
      err |= __copy_to_user(&sc->sc_gr[15], &scr->pt.r15, 8);           /* r15 */
      err |= __put_user(scr->pt.cr_iip + ia64_psr(&scr->pt)->ri, &sc->sc_ip);

      if (!(flags & IA64_SC_FLAG_IN_SYSCALL)) {
            /* Copy scratch regs to sigcontext if the signal didn't interrupt a syscall. */
            err |= __put_user(scr->pt.ar_ccv, &sc->sc_ar_ccv);          /* ar.ccv */
            err |= __put_user(scr->pt.b7, &sc->sc_br[7]);               /* b7 */
            err |= __put_user(scr->pt.r14, &sc->sc_gr[14]);             /* r14 */
            err |= __copy_to_user(&sc->sc_ar25, &scr->pt.ar_csd, 2*8); /* ar.csd & ar.ssd */
            err |= __copy_to_user(&sc->sc_gr[2], &scr->pt.r2, 2*8);           /* r2-r3 */
            err |= __copy_to_user(&sc->sc_gr[16], &scr->pt.r16, 16*8);  /* r16-r31 */
      }
      return err;
}

/*
 * Check whether the register-backing store is already on the signal stack.
 */
static inline int
rbs_on_sig_stack (unsigned long bsp)
{
      return (bsp - current->sas_ss_sp < current->sas_ss_size);
}

static long
force_sigsegv_info (int sig, void __user *addr)
{
      unsigned long flags;
      struct siginfo si;

      if (sig == SIGSEGV) {
            /*
             * Acquiring siglock around the sa_handler-update is almost
             * certainly overkill, but this isn't a
             * performance-critical path and I'd rather play it safe
             * here than having to debug a nasty race if and when
             * something changes in kernel/signal.c that would make it
             * no longer safe to modify sa_handler without holding the
             * lock.
             */
            spin_lock_irqsave(&current->sighand->siglock, flags);
            current->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
            spin_unlock_irqrestore(&current->sighand->siglock, flags);
      }
      si.si_signo = SIGSEGV;
      si.si_errno = 0;
      si.si_code = SI_KERNEL;
      si.si_pid = task_pid_vnr(current);
      si.si_uid = current_uid();
      si.si_addr = addr;
      force_sig_info(SIGSEGV, &si, current);
      return 0;
}

static long
setup_frame (int sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *set,
           struct sigscratch *scr)
{
      extern char __kernel_sigtramp[];
      unsigned long tramp_addr, new_rbs = 0, new_sp;
      struct sigframe __user *frame;
      long err;

      new_sp = scr->pt.r12;
      tramp_addr = (unsigned long) __kernel_sigtramp;
      if (ka->sa.sa_flags & SA_ONSTACK) {
            int onstack = sas_ss_flags(new_sp);

            if (onstack == 0) {
                  new_sp = current->sas_ss_sp + current->sas_ss_size;
                  /*
                   * We need to check for the register stack being on the
                   * signal stack separately, because it's switched
                   * separately (memory stack is switched in the kernel,
                   * register stack is switched in the signal trampoline).
                   */
                  if (!rbs_on_sig_stack(scr->pt.ar_bspstore))
                        new_rbs = ALIGN(current->sas_ss_sp,
                                    sizeof(long));
            } else if (onstack == SS_ONSTACK) {
                  unsigned long check_sp;

                  /*
                   * If we are on the alternate signal stack and would
                   * overflow it, don't. Return an always-bogus address
                   * instead so we will die with SIGSEGV.
                   */
                  check_sp = (new_sp - sizeof(*frame)) & -STACK_ALIGN;
                  if (!likely(on_sig_stack(check_sp)))
                        return force_sigsegv_info(sig, (void __user *)
                                            check_sp);
            }
      }
      frame = (void __user *) ((new_sp - sizeof(*frame)) & -STACK_ALIGN);

      if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
            return force_sigsegv_info(sig, frame);

      err  = __put_user(sig, &frame->arg0);
      err |= __put_user(&frame->info, &frame->arg1);
      err |= __put_user(&frame->sc, &frame->arg2);
      err |= __put_user(new_rbs, &frame->sc.sc_rbs_base);
      err |= __put_user(0, &frame->sc.sc_loadrs);     /* initialize to zero */
      err |= __put_user(ka->sa.sa_handler, &frame->handler);

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

      err |= __put_user(current->sas_ss_sp, &frame->sc.sc_stack.ss_sp);
      err |= __put_user(current->sas_ss_size, &frame->sc.sc_stack.ss_size);
      err |= __put_user(sas_ss_flags(scr->pt.r12), &frame->sc.sc_stack.ss_flags);
      err |= setup_sigcontext(&frame->sc, set, scr);

      if (unlikely(err))
            return force_sigsegv_info(sig, frame);

      scr->pt.r12 = (unsigned long) frame - 16; /* new stack pointer */
      scr->pt.ar_fpsr = FPSR_DEFAULT;                 /* reset fpsr for signal handler */
      scr->pt.cr_iip = tramp_addr;
      ia64_psr(&scr->pt)->ri = 0;               /* start executing in first slot */
      ia64_psr(&scr->pt)->be = 0;               /* force little-endian byte-order */
      /*
       * Force the interruption function mask to zero.  This has no effect when a
       * system-call got interrupted by a signal (since, in that case, scr->pt_cr_ifs is
       * ignored), but it has the desirable effect of making it possible to deliver a
       * signal with an incomplete register frame (which happens when a mandatory RSE
       * load faults).  Furthermore, it has no negative effect on the getting the user's
       * dirty partition preserved, because that's governed by scr->pt.loadrs.
       */
      scr->pt.cr_ifs = (1UL << 63);

      /*
       * Note: this affects only the NaT bits of the scratch regs (the ones saved in
       * pt_regs), which is exactly what we want.
       */
      scr->scratch_unat = 0; /* ensure NaT bits of r12 is clear */

#if DEBUG_SIG
      printk("SIG deliver (%s:%d): sig=%d sp=%lx ip=%lx handler=%p\n",
             current->comm, current->pid, sig, scr->pt.r12, frame->sc.sc_ip, frame->handler);
#endif
      return 1;
}

static long
handle_signal (unsigned long sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *oldset,
             struct sigscratch *scr)
{
      if (!setup_frame(sig, ka, info, oldset, scr))
            return 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);

      /*
       * Let tracing know that we've done the handler setup.
       */
      tracehook_signal_handler(sig, info, ka, &scr->pt,
                         test_thread_flag(TIF_SINGLESTEP));

      return 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.
 */
void
ia64_do_signal (struct sigscratch *scr, long in_syscall)
{
      struct k_sigaction ka;
      sigset_t *oldset;
      siginfo_t info;
      long restart = in_syscall;
      long errno = scr->pt.r8;

      /*
       * In the ia64_leave_kernel code path, 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(&scr->pt))
            return;

      if (current_thread_info()->status & TS_RESTORE_SIGMASK)
            oldset = &current->saved_sigmask;
      else
            oldset = &current->blocked;

      /*
       * This only loops in the rare cases of handle_signal() failing, in which case we
       * need to push through a forced SIGSEGV.
       */
      while (1) {
            int signr = get_signal_to_deliver(&info, &ka, &scr->pt, NULL);

            /*
             * get_signal_to_deliver() may have run a debugger (via notify_parent())
             * and the debugger may have modified the state (e.g., to arrange for an
             * inferior call), thus it's important to check for restarting _after_
             * get_signal_to_deliver().
             */
            if ((long) scr->pt.r10 != -1)
                  /*
                   * A system calls has to be restarted only if one of the error codes
                   * ERESTARTNOHAND, ERESTARTSYS, or ERESTARTNOINTR is returned.  If r10
                   * isn't -1 then r8 doesn't hold an error code and we don't need to
                   * restart the syscall, so we can clear the "restart" flag here.
                   */
                  restart = 0;

            if (signr <= 0)
                  break;

            if (unlikely(restart)) {
                  switch (errno) {
                        case ERESTART_RESTARTBLOCK:
                        case ERESTARTNOHAND:
                        scr->pt.r8 = EINTR;
                        /* note: scr->pt.r10 is already -1 */
                        break;

                        case ERESTARTSYS:
                        if ((ka.sa.sa_flags & SA_RESTART) == 0) {
                              scr->pt.r8 = EINTR;
                              /* note: scr->pt.r10 is already -1 */
                              break;
                        }
                        case ERESTARTNOINTR:
                        ia64_decrement_ip(&scr->pt);
                        restart = 0; /* don't restart twice if handle_signal() fails... */
                  }
            }

            /*
             * Whee!  Actually deliver the signal.  If the delivery failed, we need to
             * continue to iterate in this loop so we can deliver the SIGSEGV...
             */
            if (handle_signal(signr, &ka, &info, oldset, scr)) {
                  /*
                   * 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 TS_RESTORE_SIGMASK flag.
                   */
                  current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
                  return;
            }
      }

      /* Did we come from a system call? */
      if (restart) {
            /* Restart the system call - no handlers present */
            if (errno == ERESTARTNOHAND || errno == ERESTARTSYS || errno == ERESTARTNOINTR
                || errno == ERESTART_RESTARTBLOCK)
            {
                  /*
                   * Note: the syscall number is in r15 which is saved in
                   * pt_regs so all we need to do here is adjust ip so that
                   * the "break" instruction gets re-executed.
                   */
                  ia64_decrement_ip(&scr->pt);
                  if (errno == ERESTART_RESTARTBLOCK)
                        scr->pt.r15 = __NR_restart_syscall;
            }
      }

      /* if there's no signal to deliver, we just put the saved sigmask
       * back */
      if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
            current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
            sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
      }
}

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