signal.c

Go to the documentation of this file.

/*
 * arch/xtensa/kernel/signal.c
 *
 * Default platform functions.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2005, 2006 Tensilica Inc.
 * Copyright (C) 1991, 1992  Linus Torvalds
 * 1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 * Chris Zankel <[email protected]>
 * Joe Taylor <[email protected]>
 */

#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/tracehook.h>

#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/coprocessor.h>
#include <asm/unistd.h>

#define DEBUG_SIG  0

extern struct task_struct *coproc_owners[];

struct rt_sigframe
{
    struct siginfo info;
    struct ucontext uc;
    struct {
        xtregs_opt_t opt;
        xtregs_user_t user;
#if XTENSA_HAVE_COPROCESSORS
        xtregs_coprocessor_t cp;
#endif
    } xtregs;
    unsigned char retcode[6];
    unsigned int window[4];
};

/* 
 * Flush register windows stored in pt_regs to stack.
 * Returns 1 for errors.
 */

int
flush_window_regs_user(struct pt_regs *regs)
{
    const unsigned long ws = regs->windowstart;
    const unsigned long wb = regs->windowbase;
    unsigned long sp = 0;
    unsigned long wm;
    int err = 1;
    int base;

    /* Return if no other frames. */

    if (regs->wmask == 1)
        return 0;

    /* Rotate windowmask and skip empty frames. */

    wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
    base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
        
    /* For call8 or call12 frames, we need the previous stack pointer. */

    if ((regs->wmask & 2) == 0)
        if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
            goto errout;

    /* Spill frames to stack. */

    while (base < XCHAL_NUM_AREGS / 4) {

        int m = (wm >> base);
        int inc = 0;

        /* Save registers a4..a7 (call8) or a4...a11 (call12) */

        if (m & 2) {            /* call4 */
            inc = 1;

        } else if (m & 4) {     /* call8 */
            if (copy_to_user((void*)(sp - 32),
                       &regs->areg[(base + 1) * 4], 16))
                goto errout;
            inc = 2;

        } else if (m & 8) { /* call12 */
            if (copy_to_user((void*)(sp - 48),
                       &regs->areg[(base + 1) * 4], 32))
                goto errout;
            inc = 3;
        }

        /* Save current frame a0..a3 under next SP */

        sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
        if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
            goto errout;

        /* Get current stack pointer for next loop iteration. */

        sp = regs->areg[base * 4 + 1];
        base += inc;
    }

    regs->wmask = 1;
    regs->windowstart = 1 << wb;

    return 0;

errout:
    return err;
}

/*
 * Note: We don't copy double exception 'regs', we have to finish double exc. 
 * first before we return to signal handler! This dbl.exc.handler might cause 
 * another double exception, but I think we are fine as the situation is the 
 * same as if we had returned to the signal handerl and got an interrupt 
 * immediately...
 */

static int
setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
{
    struct sigcontext __user *sc = &frame->uc.uc_mcontext;
    struct thread_info *ti = current_thread_info();
    int err = 0;

#define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
    COPY(pc);
    COPY(ps);
    COPY(lbeg);
    COPY(lend);
    COPY(lcount);
    COPY(sar);
#undef COPY

    err |= flush_window_regs_user(regs);
    err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
    err |= __put_user(0, &sc->sc_xtregs);

    if (err)
        return err;

#if XTENSA_HAVE_COPROCESSORS
    coprocessor_flush_all(ti);
    coprocessor_release_all(ti);
    err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
                  sizeof (frame->xtregs.cp));
#endif
    err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
                  sizeof (xtregs_opt_t));
    err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
                  sizeof (xtregs_user_t));

    err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);

    return err;
}

static int
restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
{
    struct sigcontext __user *sc = &frame->uc.uc_mcontext;
    struct thread_info *ti = current_thread_info();
    unsigned int err = 0;
    unsigned long ps;

#define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
    COPY(pc);
    COPY(lbeg);
    COPY(lend);
    COPY(lcount);
    COPY(sar);
#undef COPY

    /* All registers were flushed to stack. Start with a prestine frame. */

    regs->wmask = 1;
    regs->windowbase = 0;
    regs->windowstart = 1;

    regs->syscall = -1;     /* disable syscall checks */

    /* For PS, restore only PS.CALLINC.
     * Assume that all other bits are either the same as for the signal
     * handler, or the user mode value doesn't matter (e.g. PS.OWB).
     */
    err |= __get_user(ps, &sc->sc_ps);
    regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);

    /* Additional corruption checks */

    if ((regs->lcount > 0)
        && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
        err = 1;

    err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);

    if (err)
        return err;

    /* The signal handler may have used coprocessors in which
     * case they are still enabled.  We disable them to force a
     * reloading of the original task's CP state by the lazy
     * context-switching mechanisms of CP exception handling.
     * Also, we essentially discard any coprocessor state that the
     * signal handler created. */

#if XTENSA_HAVE_COPROCESSORS
    coprocessor_release_all(ti);
    err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
                sizeof (frame->xtregs.cp));
#endif
    err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
                sizeof (xtregs_user_t));
    err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
                sizeof (xtregs_opt_t));

    return err;
}


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

asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
                    long a4, long a5, struct pt_regs *regs)
{
    struct rt_sigframe __user *frame;
    sigset_t set;
    int ret;

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

    if (regs->depc > 64)
        panic("rt_sigreturn in double exception!\n");

    frame = (struct rt_sigframe __user *) regs->areg[1];

    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))
        goto badframe;

    ret = regs->areg[2];

    if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->areg[1]) == -EFAULT)
        goto badframe;

    return ret;

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



/*
 * Set up a signal frame.
 */

static int
gen_return_code(unsigned char *codemem)
{
    int err = 0;

    /*
     * The 12-bit immediate is really split up within the 24-bit MOVI
     * instruction.  As long as the above system call numbers fit within
     * 8-bits, the following code works fine. See the Xtensa ISA for
     * details.
     */

#if __NR_rt_sigreturn > 255
# error Generating the MOVI instruction below breaks!
#endif

#ifdef __XTENSA_EB__   /* Big Endian version */
    /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
    err |= __put_user(0x22, &codemem[0]);
    err |= __put_user(0x0a, &codemem[1]);
    err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
    /* Generate instruction:  SYSCALL */
    err |= __put_user(0x00, &codemem[3]);
    err |= __put_user(0x05, &codemem[4]);
    err |= __put_user(0x00, &codemem[5]);

#elif defined __XTENSA_EL__   /* Little Endian version */
    /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
    err |= __put_user(0x22, &codemem[0]);
    err |= __put_user(0xa0, &codemem[1]);
    err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
    /* Generate instruction:  SYSCALL */
    err |= __put_user(0x00, &codemem[3]);
    err |= __put_user(0x50, &codemem[4]);
    err |= __put_user(0x00, &codemem[5]);
#else
# error Must use compiler for Xtensa processors.
#endif

    /* Flush generated code out of the data cache */

    if (err == 0) {
        __invalidate_icache_range((unsigned long)codemem, 6UL);
        __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
    }

    return err;
}


static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
               sigset_t *set, struct pt_regs *regs)
{
    struct rt_sigframe *frame;
    int err = 0;
    int signal;
    unsigned long sp, ra;

    sp = regs->areg[1];

    if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
        sp = current->sas_ss_sp + current->sas_ss_size;
    }

    frame = (void *)((sp - sizeof(*frame)) & -16ul);

    if (regs->depc > 64)
        panic ("Double exception sys_sigreturn\n");

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

    signal = current_thread_info()->exec_domain
        && current_thread_info()->exec_domain->signal_invmap
        && sig < 32
        ? current_thread_info()->exec_domain->signal_invmap[sig]
        : sig;

    if (ka->sa.sa_flags & SA_SIGINFO) {
        err |= copy_siginfo_to_user(&frame->info, info);
    }

    /* Create the user context.  */

    err |= __put_user(0, &frame->uc.uc_flags);
    err |= __put_user(0, &frame->uc.uc_link);
    err |= __put_user((void *)current->sas_ss_sp,
              &frame->uc.uc_stack.ss_sp);
    err |= __put_user(sas_ss_flags(regs->areg[1]),
              &frame->uc.uc_stack.ss_flags);
    err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
    err |= setup_sigcontext(frame, regs);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (ka->sa.sa_flags & SA_RESTORER) {
        ra = (unsigned long)ka->sa.sa_restorer;
    } else {

        /* Create sys_rt_sigreturn syscall in stack frame */

        err |= gen_return_code(frame->retcode);

        if (err) {
            goto give_sigsegv;
        }
        ra = (unsigned long) frame->retcode;
    }

    /* 
     * Create signal handler execution context.
     * Return context not modified until this point.
     */

    /* Set up registers for signal handler */
    start_thread(regs, (unsigned long) ka->sa.sa_handler, 
             (unsigned long) frame);

    /* Set up a stack frame for a call4
     * Note: PS.CALLINC is set to one by start_thread
     */
    regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
    regs->areg[6] = (unsigned long) signal;
    regs->areg[7] = (unsigned long) &frame->info;
    regs->areg[8] = (unsigned long) &frame->uc;

    /* Set access mode to USER_DS.  Nomenclature is outdated, but
     * functionality is used in uaccess.h
     */
    set_fs(USER_DS);

#if DEBUG_SIG
    printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
        current->comm, current->pid, signal, frame, regs->pc);
#endif

    return 0;

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

asmlinkage long xtensa_sigaltstack(const stack_t __user *uss, 
                   stack_t __user *uoss,
                       long a2, long a3, long a4, long a5,
                   struct pt_regs *regs)
{
    return do_sigaltstack(uss, uoss, regs->areg[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.
 *
 * Note that we go through the signals twice: once to check the signals that
 * the kernel can handle, and then we build all the user-level signal handling
 * stack-frames in one go after that.
 */
static void do_signal(struct pt_regs *regs)
{
    siginfo_t info;
    int signr;
    struct k_sigaction ka;

    task_pt_regs(current)->icountlevel = 0;

    signr = get_signal_to_deliver(&info, &ka, regs, NULL);

    if (signr > 0) {
        int ret;

        /* Are we from a system call? */

        if ((signed)regs->syscall >= 0) {

            /* If so, check system call restarting.. */

            switch (regs->areg[2]) {
                case -ERESTARTNOHAND:
                case -ERESTART_RESTARTBLOCK:
                    regs->areg[2] = -EINTR;
                    break;

                case -ERESTARTSYS:
                    if (!(ka.sa.sa_flags & SA_RESTART)) {
                        regs->areg[2] = -EINTR;
                        break;
                    }
                    /* fallthrough */
                case -ERESTARTNOINTR:
                    regs->areg[2] = regs->syscall;
                    regs->pc -= 3;
                    break;

                default:
                    /* nothing to do */
                    if (regs->areg[2] != 0)
                    break;
            }
        }

        /* Whee!  Actually deliver the signal.  */
        /* Set up the stack frame */
        ret = setup_frame(signr, &ka, &info, sigmask_to_save(), regs);
        if (ret)
            return;

        signal_delivered(signr, &info, &ka, regs, 0);
        if (current->ptrace & PT_SINGLESTEP)
            task_pt_regs(current)->icountlevel = 1;

        return;
    }

    /* Did we come from a system call? */
    if ((signed) regs->syscall >= 0) {
        /* Restart the system call - no handlers present */
        switch (regs->areg[2]) {
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
            regs->areg[2] = regs->syscall;
            regs->pc -= 3;
            break;
        case -ERESTART_RESTARTBLOCK:
            regs->areg[2] = __NR_restart_syscall;
            regs->pc -= 3;
            break;
        }
    }

    /* If there's no signal to deliver, we just restore the saved mask.  */
    restore_saved_sigmask();

    if (current->ptrace & PT_SINGLESTEP)
        task_pt_regs(current)->icountlevel = 1;
    return;
}

void do_notify_resume(struct pt_regs *regs)
{
    if (test_thread_flag(TIF_SIGPENDING))
        do_signal(regs);

    if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
        tracehook_notify_resume(regs);
}