signal.c

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/*
 *  linux/arch/cris/kernel/signal.c
 *
 *  Based on arch/i386/kernel/signal.c by
 *     Copyright (C) 1991, 1992  Linus Torvalds
 *     1997-11-28  Modified for POSIX.1b signals by Richard Henderson *
 *
 *  Ideas also taken from arch/arm.
 *
 *  Copyright (C) 2000-2007 Axis Communications AB
 *
 *  Authors:  Bjorn Wesen ([email protected])
 *
 */

#include <linux/sched.h>
#include <linux/mm.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/stddef.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <arch/system.h>

#define DEBUG_SIG 0

/* a syscall in Linux/CRIS is a break 13 instruction which is 2 bytes */
/* manipulate regs so that upon return, it will be re-executed */

/* We rely on that pc points to the instruction after "break 13", so the
 * library must never do strange things like putting it in a delay slot.
 */
#define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->irp -= 2;

void do_signal(int canrestart, struct pt_regs *regs);

/*
 * Atomically swap in the new signal mask, and wait for a signal.  Define
 * dummy arguments to be able to reach the regs argument.  (Note that this
 * arrangement relies on old_sigset_t occupying one register.)
 */
int sys_sigsuspend(old_sigset_t mask)
{
    sigset_t blocked;
    siginitset(&blocked, mask);
    return sigsuspend(&blocked);
}

int sys_sigaction(int sig, const struct old_sigaction __user *act,
    struct old_sigaction *oact)
{
    struct k_sigaction new_ka, old_ka;
    int ret;

    if (act) {
        old_sigset_t mask;
        if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
            __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
            __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
             __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
             __get_user(mask, &act->sa_mask))
            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)) ||
            __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
            __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
            __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
            __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
            return -EFAULT;
    }

    return ret;
}

int sys_sigaltstack(const stack_t *uss, stack_t __user *uoss)
{
    return do_sigaltstack(uss, uoss, rdusp());
}


/*
 * Do a signal return; undo the signal stack.
 */

struct sigframe {
    struct sigcontext sc;
    unsigned long extramask[_NSIG_WORDS-1];
    unsigned char retcode[8];  /* trampoline code */
};

struct rt_sigframe {
    struct siginfo *pinfo;
    void *puc;
    struct siginfo info;
    struct ucontext uc;
    unsigned char retcode[8];  /* trampoline code */
};


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

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

    /* restore the regs from &sc->regs (same as sc, since regs is first)
     * (sc is already checked for VERIFY_READ since the sigframe was
     *  checked in sys_sigreturn previously)
     */

    if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
                goto badframe;

    /* make sure the U-flag is set so user-mode cannot fool us */

    regs->dccr |= 1 << 8;

    /* restore the old USP as it was before we stacked the sc etc.
     * (we cannot just pop the sigcontext since we aligned the sp and
     *  stuff after pushing it)
     */

    err |= __get_user(old_usp, &sc->usp);

    wrusp(old_usp);

    /* TODO: the other ports use regs->orig_XX to disable syscall checks
     * after this completes, but we don't use that mechanism. maybe we can
     * use it now ?
     */

    return err;

badframe:
    return 1;
}

/* Define dummy arguments to be able to reach the regs argument.  */

asmlinkage int sys_sigreturn(long r10, long r11, long r12, long r13, long mof,
                             long srp, struct pt_regs *regs)
{
    struct sigframe __user *frame = (struct sigframe *)rdusp();
    sigset_t set;

        /*
         * Since we stacked the signal on a dword boundary,
         * then frame should be dword aligned here.  If it's
         * not, then the user is trying to mess with us.
         */
        if (((long)frame) & 3)
                goto badframe;

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__get_user(set.sig[0], &frame->sc.oldmask)
        || (_NSIG_WORDS > 1
        && __copy_from_user(&set.sig[1], frame->extramask,
                    sizeof(frame->extramask))))
        goto badframe;

    set_current_blocked(&set);

    if (restore_sigcontext(regs, &frame->sc))
        goto badframe;

    /* TODO: SIGTRAP when single-stepping as in arm ? */

    return regs->r10;

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

/* Define dummy arguments to be able to reach the regs argument.  */

asmlinkage int sys_rt_sigreturn(long r10, long r11, long r12, long r13,
                                long mof, long srp, struct pt_regs *regs)
{
    struct rt_sigframe __user *frame = (struct rt_sigframe *)rdusp();
    sigset_t set;

        /*
         * Since we stacked the signal on a dword boundary,
         * then frame should be dword aligned here.  If it's
         * not, then the user is trying to mess with us.
         */
        if (((long)frame) & 3)
                goto badframe;

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
        goto badframe;

    set_current_blocked(&set);

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

    if (do_sigaltstack(&frame->uc.uc_stack, NULL, rdusp()) == -EFAULT)
        goto badframe;

    return regs->r10;

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

/*
 * Set up a signal frame.
 */

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

    /* copy the regs. they are first in sc so we can use sc directly */

    err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));

        /* Set the frametype to CRIS_FRAME_NORMAL for the execution of
           the signal handler. The frametype will be restored to its previous
           value in restore_sigcontext. */
        regs->frametype = CRIS_FRAME_NORMAL;

    /* then some other stuff */

    err |= __put_user(mask, &sc->oldmask);

    err |= __put_user(usp, &sc->usp);

    return err;
}

/* Figure out where we want to put the new signal frame
 * - usually on the stack. */

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

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

    /* make sure the frame is dword-aligned */

    sp &= ~3;

    return (void __user*)(sp - frame_size);
}

/* grab and setup a signal frame.
 *
 * basically we stack a lot of state info, and arrange for the
 * user-mode program to return to the kernel using either a
 * trampoline which performs the syscall sigreturn, or a provided
 * user-mode trampoline.
 */

static int setup_frame(int sig, struct k_sigaction *ka,
               sigset_t *set, struct pt_regs *regs)
{
    struct sigframe __user *frame;
    unsigned long return_ip;
    int err = 0;

    frame = get_sigframe(ka, regs, sizeof(*frame));

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        goto give_sigsegv;

    err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
    if (err)
        goto give_sigsegv;

    if (_NSIG_WORDS > 1) {
        err |= __copy_to_user(frame->extramask, &set->sig[1],
                      sizeof(frame->extramask));
    }
    if (err)
        goto give_sigsegv;

    /* Set up to return from userspace.  If provided, use a stub
       already in userspace.  */
    if (ka->sa.sa_flags & SA_RESTORER) {
        return_ip = (unsigned long)ka->sa.sa_restorer;
    } else {
        /* trampoline - the desired return ip is the retcode itself */
        return_ip = (unsigned long)&frame->retcode;
        /* This is movu.w __NR_sigreturn, r9; break 13; */
        err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
        err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
        err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
    }

    if (err)
        goto give_sigsegv;

    /* Set up registers for signal handler */

    regs->irp = (unsigned long) ka->sa.sa_handler;  /* what we enter NOW   */
    regs->srp = return_ip;                          /* what we enter LATER */
    regs->r10 = sig;                                /* first argument is signo */

    /* actually move the usp to reflect the stacked frame */

    wrusp((unsigned long)frame);

    return 0;

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

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

    frame = get_sigframe(ka, regs, sizeof(*frame));

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        goto give_sigsegv;

    err |= __put_user(&frame->info, &frame->pinfo);
    err |= __put_user(&frame->uc, &frame->puc);
    err |= copy_siginfo_to_user(&frame->info, info);
    if (err)
        goto give_sigsegv;

    /* Clear all the bits of the ucontext we don't use.  */
        err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));

    err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);

    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (err)
        goto give_sigsegv;

    /* Set up to return from userspace.  If provided, use a stub
       already in userspace.  */
    if (ka->sa.sa_flags & SA_RESTORER) {
        return_ip = (unsigned long)ka->sa.sa_restorer;
    } else {
        /* trampoline - the desired return ip is the retcode itself */
        return_ip = (unsigned long)&frame->retcode;
        /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
        err |= __put_user(0x9c5f, (short __user *)(frame->retcode+0));
        err |= __put_user(__NR_rt_sigreturn,
            (short __user *)(frame->retcode+2));
        err |= __put_user(0xe93d, (short __user *)(frame->retcode+4));
    }

    if (err)
        goto give_sigsegv;

    /* TODO what is the current->exec_domain stuff and invmap ? */

    /* Set up registers for signal handler */

    /* What we enter NOW   */
    regs->irp = (unsigned long) ka->sa.sa_handler;
    /* What we enter LATER */
    regs->srp = return_ip;
    /* First argument is signo */
    regs->r10 = sig;
    /* Second argument is (siginfo_t *) */
    regs->r11 = (unsigned long)&frame->info;
    /* Third argument is unused */
    regs->r12 = 0;

    /* Actually move the usp to reflect the stacked frame */
    wrusp((unsigned long)frame);

    return 0;

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

/*
 * OK, we're invoking a handler
 */

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

    /* Are we from a system call? */
    if (canrestart) {
        /* If so, check system call restarting.. */
        switch (regs->r10) {
        case -ERESTART_RESTARTBLOCK:
        case -ERESTARTNOHAND:
            /* ERESTARTNOHAND means that the syscall should
             * only be restarted if there was no handler for
             * the signal, and since we only get here if there
             * is a handler, we don't restart */
            regs->r10 = -EINTR;
            break;
        case -ERESTARTSYS:
            /* ERESTARTSYS means to restart the syscall if
             * there is no handler or the handler was
             * registered with SA_RESTART */
            if (!(ka->sa.sa_flags & SA_RESTART)) {
                regs->r10 = -EINTR;
                break;
            }
        /* fallthrough */
        case -ERESTARTNOINTR:
            /* ERESTARTNOINTR means that the syscall should
             * be called again after the signal handler returns. */
            RESTART_CRIS_SYS(regs);
        }
    }

    /* Set up the stack frame */
    if (ka->sa.sa_flags & SA_SIGINFO)
        ret = setup_rt_frame(sig, ka, info, oldset, regs);
    else
        ret = setup_frame(sig, ka, oldset, regs);

    if (ret == 0)
        signal_delivered(sig, info, ka, regs, 0);
}

/*
 * 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.
 *
 * Also note that the regs structure given here as an argument, is the latest
 * pushed pt_regs. It may or may not be the same as the first pushed registers
 * when the initial usermode->kernelmode transition took place. Therefore
 * we can use user_mode(regs) to see if we came directly from kernel or user
 * mode below.
 */

void do_signal(int canrestart, struct pt_regs *regs)
{
    siginfo_t info;
    int signr;
        struct k_sigaction ka;

    /*
     * 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;

    signr = get_signal_to_deliver(&info, &ka, regs, NULL);
    if (signr > 0) {
        /* Whee!  Actually deliver the signal.  */
        handle_signal(canrestart, signr, &info, &ka, regs);
        return;
    }

    /* Did we come from a system call? */
    if (canrestart) {
        /* Restart the system call - no handlers present */
        if (regs->r10 == -ERESTARTNOHAND ||
            regs->r10 == -ERESTARTSYS ||
            regs->r10 == -ERESTARTNOINTR) {
            RESTART_CRIS_SYS(regs);
        }
        if (regs->r10 == -ERESTART_RESTARTBLOCK) {
            regs->r9 = __NR_restart_syscall;
            regs->irp -= 2;
        }
    }

    /* if there's no signal to deliver, we just put the saved sigmask
     * back */
    restore_saved_sigmask();
}