/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2000 by Sun Microsystems, Inc.
 * All rights reserved.
 */
/*
 * Copyright 2018 Joyent, Inc.
 */

#include <mdb/mdb_modapi.h>
#include <mdb/mdb_ctf.h>
#include "ctxop.h"

struct ctxop_walk_state {
        uintptr_t       cws_head;
        uint_t          cws_next_offset;
};

int
ctxop_walk_init(mdb_walk_state_t *wsp)
{
        struct ctxop_walk_state *priv;
        int offset;
        uintptr_t addr;

        if (wsp->walk_addr == 0) {
                mdb_warn("must specify thread for ctxop walk\n");
                return (WALK_ERR);
        }

        offset = mdb_ctf_offsetof_by_name("kthread_t", "t_ctx");
        if (offset == -1)
                return (WALK_ERR);

        if (mdb_vread(&addr, sizeof (addr),
            wsp->walk_addr + offset) != sizeof (addr)) {
                mdb_warn("failed to read thread %p", wsp->walk_addr);
                return (WALK_ERR);
        }

        /* No further work for threads with a NULL t_ctx */
        if (addr == 0) {
                wsp->walk_data = NULL;
                return (WALK_DONE);
        }

        /* rely on CTF for the offset of the 'next' pointer */
        offset = mdb_ctf_offsetof_by_name("struct ctxop", "next");
        if (offset == -1)
                return (WALK_ERR);

        priv = mdb_alloc(sizeof (*priv), UM_SLEEP);
        priv->cws_head = addr;
        priv->cws_next_offset = (uint_t)offset;

        wsp->walk_data = priv;
        wsp->walk_addr = addr;
        return (WALK_NEXT);
}

int
ctxop_walk_step(mdb_walk_state_t *wsp)
{
        struct ctxop_walk_state *priv = wsp->walk_data;
        uintptr_t next;
        int status;

        if (mdb_vread(&next, sizeof (next),
            wsp->walk_addr + priv->cws_next_offset) == -1) {
                mdb_warn("failed to read ctxop`next at %p",
                    wsp->walk_addr + priv->cws_next_offset);
                return (WALK_DONE);
        }

        status = wsp->walk_callback(wsp->walk_addr, NULL, wsp->walk_cbdata);

        if (status == WALK_NEXT) {
                /*
                 * If a NULL terminator or a loop back to the head element is
                 * encountered, the walk is done.
                 */
                if (next == 0 || next == priv->cws_head) {
                        status = WALK_DONE;
                }
        }

        wsp->walk_addr = next;
        return (status);
}

void
ctxop_walk_fini(mdb_walk_state_t *wsp)
{
        struct ctxop_walk_state *priv = wsp->walk_data;

        if (priv != NULL) {
                mdb_free(priv, sizeof (*priv));
        }
}