signal.c

Go to the documentation of this file.

/*
 * Architecture-specific signal handling support.
 *
 * Copyright (C) 1999-2004 Hewlett-Packard Co
 *  David Mosberger-Tang <[email protected]>
 *
 * 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 */

#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;

    set_current_blocked(&set);

    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 = from_kuid_munged(current_user_ns(), 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 = from_kuid_munged(current_user_ns(), 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,
           struct sigscratch *scr)
{
    if (!setup_frame(sig, ka, info, sigmask_to_save(), scr))
        return 0;

    signal_delivered(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;
    siginfo_t info;
    long restart = in_syscall;
    long errno = scr->pt.r8;

    /*
     * 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, scr))
            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 */
    restore_saved_sigmask();
}