signal.c

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/*
 * Signal support for Hexagon processor
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/linkage.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <asm/registers.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
#include <asm/uaccess.h>
#include <asm/ucontext.h>
#include <asm/cacheflush.h>
#include <asm/signal.h>
#include <asm/vdso.h>

struct rt_sigframe {
    unsigned long tramp[2];
    struct siginfo info;
    struct ucontext uc;
};

static void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
              size_t frame_size)
{
    unsigned long sp = regs->r29;

    /* Switch to signal stack if appropriate */
    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) & ~(sizeof(long long) - 1));
}

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

    err |= copy_to_user(&sc->sc_regs.r0, &regs->r00,
                32*sizeof(unsigned long));

    err |= __put_user(regs->sa0, &sc->sc_regs.sa0);
    err |= __put_user(regs->lc0, &sc->sc_regs.lc0);
    err |= __put_user(regs->sa1, &sc->sc_regs.sa1);
    err |= __put_user(regs->lc1, &sc->sc_regs.lc1);
    err |= __put_user(regs->m0, &sc->sc_regs.m0);
    err |= __put_user(regs->m1, &sc->sc_regs.m1);
    err |= __put_user(regs->usr, &sc->sc_regs.usr);
    err |= __put_user(regs->preds, &sc->sc_regs.p3_0);
    err |= __put_user(regs->gp, &sc->sc_regs.gp);
    err |= __put_user(regs->ugp, &sc->sc_regs.ugp);

    tmp = pt_elr(regs); err |= __put_user(tmp, &sc->sc_regs.pc);
    tmp = pt_cause(regs); err |= __put_user(tmp, &sc->sc_regs.cause);
    tmp = pt_badva(regs); err |= __put_user(tmp, &sc->sc_regs.badva);

    return err;
}

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

    err |= copy_from_user(&regs->r00, &sc->sc_regs.r0,
                  32 * sizeof(unsigned long));

    err |= __get_user(regs->sa0, &sc->sc_regs.sa0);
    err |= __get_user(regs->lc0, &sc->sc_regs.lc0);
    err |= __get_user(regs->sa1, &sc->sc_regs.sa1);
    err |= __get_user(regs->lc1, &sc->sc_regs.lc1);
    err |= __get_user(regs->m0, &sc->sc_regs.m0);
    err |= __get_user(regs->m1, &sc->sc_regs.m1);
    err |= __get_user(regs->usr, &sc->sc_regs.usr);
    err |= __get_user(regs->preds, &sc->sc_regs.p3_0);
    err |= __get_user(regs->gp, &sc->sc_regs.gp);
    err |= __get_user(regs->ugp, &sc->sc_regs.ugp);

    err |= __get_user(tmp, &sc->sc_regs.pc); pt_set_elr(regs, tmp);

    return err;
}

/*
 * Setup signal stack frame with siginfo structure
 */
static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
              sigset_t *set,  struct pt_regs *regs)
{
    int err = 0;
    struct rt_sigframe __user *frame;
    struct hexagon_vdso *vdso = current->mm->context.vdso;

    frame = get_sigframe(ka, regs, sizeof(struct rt_sigframe));

    if (!access_ok(VERIFY_WRITE, frame, sizeof(struct rt_sigframe)))
        goto    sigsegv;

    if (copy_siginfo_to_user(&frame->info, info))
        goto    sigsegv;

    /* The on-stack signal trampoline is no longer executed;
     * however, the libgcc signal frame unwinding code checks for
     * the presence of these two numeric magic values.
     */
    err |= __put_user(0x7800d166, &frame->tramp[0]);
    err |= __put_user(0x5400c004, &frame->tramp[1]);
    err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
    if (err)
        goto sigsegv;

    /* Load r0/r1 pair with signumber/siginfo pointer... */
    regs->r0100 = ((unsigned long long)((unsigned long)&frame->info) << 32)
        | (unsigned long long)signr;
    regs->r02 = (unsigned long) &frame->uc;
    regs->r31 = (unsigned long) vdso->rt_signal_trampoline;
    pt_psp(regs) = (unsigned long) frame;
    pt_set_elr(regs, (unsigned long)ka->sa.sa_handler);

    return 0;

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

/*
 * Setup invocation of signal handler
 */
static void handle_signal(int sig, siginfo_t *info, struct k_sigaction *ka,
             struct pt_regs *regs)
{
    /*
     * If we're handling a signal that aborted a system call,
     * set up the error return value before adding the signal
     * frame to the stack.
     */

    if (regs->syscall_nr >= 0) {
        switch (regs->r00) {
        case -ERESTART_RESTARTBLOCK:
        case -ERESTARTNOHAND:
            regs->r00 = -EINTR;
            break;
        case -ERESTARTSYS:
            if (!(ka->sa.sa_flags & SA_RESTART)) {
                regs->r00 = -EINTR;
                break;
            }
            /* Fall through */
        case -ERESTARTNOINTR:
            regs->r06 = regs->syscall_nr;
            pt_set_elr(regs, pt_elr(regs) - 4);
            regs->r00 = regs->restart_r0;
            break;
        default:
            break;
        }
    }

    /*
     * Set up the stack frame; not doing the SA_SIGINFO thing.  We
     * only set up the rt_frame flavor.
     */
    /* If there was an error on setup, no signal was delivered. */
    if (setup_rt_frame(sig, ka, info, sigmask_to_save(), regs) < 0)
        return;

    signal_delivered(sig, info, ka, regs,
            test_thread_flag(TIF_SINGLESTEP));
}

/*
 * Called from return-from-event code.
 */
static void do_signal(struct pt_regs *regs)
{
    struct k_sigaction sigact;
    siginfo_t info;
    int signo;

    if (!user_mode(regs))
        return;

    signo = get_signal_to_deliver(&info, &sigact, regs, NULL);

    if (signo > 0) {
        handle_signal(signo, &info, &sigact, regs);
        return;
    }

    /*
     * If we came from a system call, handle the restart.
     */
    if (regs->syscall_nr >= 0) {
        switch (regs->r00) {
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
            regs->r06 = regs->syscall_nr;
            break;
        case -ERESTART_RESTARTBLOCK:
            regs->r06 = __NR_restart_syscall;
            break;
        default:
            goto no_restart;
        }
        pt_set_elr(regs, pt_elr(regs) - 4);
        regs->r00 = regs->restart_r0;
    }

no_restart:
    /* If there's no signal to deliver, put the saved sigmask back */
    restore_saved_sigmask();
}

void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
{
    if (thread_info_flags & _TIF_SIGPENDING)
        do_signal(regs);

    if (thread_info_flags & _TIF_NOTIFY_RESUME) {
        clear_thread_flag(TIF_NOTIFY_RESUME);
        tracehook_notify_resume(regs);
    }
}

/*
 * Architecture-specific wrappers for signal-related system calls
 */
asmlinkage int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
    struct pt_regs *regs = current_thread_info()->regs;

    return do_sigaltstack(uss, uoss, regs->r29);
}

asmlinkage int sys_rt_sigreturn(void)
{
    struct pt_regs *regs = current_thread_info()->regs;
    struct rt_sigframe __user *frame;
    sigset_t blocked;

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

    frame = (struct rt_sigframe __user *)pt_psp(regs);
    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&blocked, &frame->uc.uc_sigmask, sizeof(blocked)))
        goto badframe;

    set_current_blocked(&blocked);

    if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
        goto badframe;

    /* Restore the user's stack as well */
    pt_psp(regs) = regs->r29;

    /*
     * Leave a trace in the stack frame that this was a sigreturn.
     * If the system call is to replay, we've already restored the
     * number in the GPR slot and it will be regenerated on the
     * new system call trap entry. Note that if restore_sigcontext()
     * did something other than a bulk copy of the pt_regs struct,
     * we could avoid this assignment by simply not overwriting
     * regs->syscall_nr.
     */
    regs->syscall_nr = __NR_rt_sigreturn;

    /*
     * If we were meticulous, we'd only call this if we knew that
     * we were actually going to use an alternate stack, and we'd
     * consider any error to be fatal.  What we do here, in common
     * with many other architectures, is call it blindly and only
     * consider the -EFAULT return case to be proof of a problem.
     */
    if (do_sigaltstack(&frame->uc.uc_stack, NULL, pt_psp(regs)) == -EFAULT)
        goto badframe;

    return 0;

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