Pull bugzilla-5653 into release branch

[mirror_ubuntu-jammy-kernel.git] / arch / ia64 / kernel / 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/config.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <linux/unistd.h>
#include <linux/wait.h>

#include <asm/ia32.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

long
ia64_rt_sigsuspend (sigset_t __user *uset, size_t sigsetsize, struct sigscratch *scr)
{
        sigset_t oldset, set;

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

        if (!access_ok(VERIFY_READ, uset, sigsetsize))
                return -EFAULT;

        if (GET_SIGSET(&set, uset))
                return -EFAULT;

        sigdelsetmask(&set, ~_BLOCKABLE);

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

        /*
         * The return below usually returns to the signal handler.  We need to
         * pre-set the correct error code here to ensure that the right values
         * get saved in sigcontext by ia64_do_signal.
         */
        scr->pt.r8 = EINTR;
        scr->pt.r10 = -1;

        while (1) {
                current->state = TASK_INTERRUPTIBLE;
                schedule();
                if (ia64_do_signal(&oldset, scr, 1))
                        return -EINTR;
        }
}

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);

                __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 = current->pid;
        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;

        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;
                __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) {
                /* Clear scratch registers if the signal interrupted a system call. */
                err |= __put_user(0, &sc->sc_ar_ccv);                           /* ar.ccv */
                err |= __put_user(0, &sc->sc_br[7]);                            /* b7 */
                err |= __put_user(0, &sc->sc_gr[14]);                           /* r14 */
                err |= __clear_user(&sc->sc_ar25, 2*8);                 /* ar.csd & ar.ssd */
                err |= __clear_user(&sc->sc_gr[2], 2*8);                        /* r2-r3 */
                err |= __clear_user(&sc->sc_gr[16], 16*8);                      /* r16-r31 */
        } else {
                /* 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 = current->pid;
        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) && sas_ss_flags(new_sp) == 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 = (current->sas_ss_sp + sizeof(long) - 1) & ~(sizeof(long) - 1);
        }
        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 (IS_IA32_PROCESS(&scr->pt)) {
                /* send signal to IA-32 process */
                if (!ia32_setup_frame1(sig, ka, info, oldset, &scr->pt))
                        return 0;
        } else
                /* send signal to IA-64 process */
                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);
        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.
 */
long
ia64_do_signal (sigset_t *oldset, struct sigscratch *scr, long in_syscall)
{
        struct k_sigaction ka;
        siginfo_t info;
        long restart = in_syscall;
        long errno = scr->pt.r8;
#       define ERR_CODE(c)      (IS_IA32_PROCESS(&scr->pt) ? -(c) : (c))

        /*
         * 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 0;

        if (!oldset)
                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 (IS_IA32_PROCESS(&scr->pt)) {
                        if (in_syscall) {
                                if (errno >= 0)
                                        restart = 0;
                                else
                                        errno = -errno;
                        }
                } else 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 = ERR_CODE(EINTR);
                                /* note: scr->pt.r10 is already -1 */
                                break;

                              case ERESTARTSYS:
                                if ((ka.sa.sa_flags & SA_RESTART) == 0) {
                                        scr->pt.r8 = ERR_CODE(EINTR);
                                        /* note: scr->pt.r10 is already -1 */
                                        break;
                                }
                              case ERESTARTNOINTR:
                                if (IS_IA32_PROCESS(&scr->pt)) {
                                        scr->pt.r8 = scr->pt.r1;
                                        scr->pt.cr_iip -= 2;
                                } else
                                        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))
                        return 1;
        }

        /* 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)
                {
                        if (IS_IA32_PROCESS(&scr->pt)) {
                                scr->pt.r8 = scr->pt.r1;
                                scr->pt.cr_iip -= 2;
                                if (errno == ERESTART_RESTARTBLOCK)
                                        scr->pt.r8 = 0; /* x86 version of __NR_restart_syscall */
                        } else {
                                /*
                                 * 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;
                        }
                }
        }
        return 0;
}