/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

#if !defined(__linux__)
#error This module is currently only implemented for Linux.
#endif

#include "httpd.h"
#include "http_config.h"

#include <fcntl.h>
#include <unistd.h>
#include <execinfo.h>

static char *log_fname;

static void bt_show_backtrace(int sig)
{
    char msgbuf[128];
    size_t size;
    void *array[20];
    extern int main();
    int logfd;
    time_t now;
    char msg_prefix[40];
    char *newline;

    time(&now);
    ap_snprintf(msg_prefix, sizeof msg_prefix,
                "[%s pid %ld",
                asctime(localtime(&now)),
                (long)getpid());
    newline = strchr(msg_prefix, '\n'); /* dang asctime() */
    if (newline) {                      /* silly we are */
        *newline = ']';
    }

    if (log_fname) {
        logfd = open(log_fname, O_WRONLY|O_APPEND|O_CREAT, 0644);
        if (logfd == -1) {
            logfd = 2; /* unix, so fd 2 is the web server error log */
            ap_snprintf(msgbuf, sizeof msgbuf,
                        "%s error %d opening %s\n",
                        msg_prefix, errno, log_fname);
            write(logfd, msgbuf, strlen(msgbuf));
        }
    }
    else {
        logfd = 2;
    }
    
    ap_snprintf(msgbuf, sizeof msgbuf,
                "%s backtrace for signal %d\n",
                msg_prefix, sig);
    write(logfd, msgbuf, strlen(msgbuf));

    /* the address of main() can be useful if we're on old 
     * glibc and get only addresses for stack frames... knowing
     * where main() is then is a useful clue
     */
    ap_snprintf(msgbuf, sizeof msgbuf,
                "%s main() is at %pp\n",
                msg_prefix,
                main);/* don't you DARE put parens after "main" */
    write(logfd, msgbuf, strlen(msgbuf));

    size = backtrace(array, sizeof array / sizeof array[0]);
    backtrace_symbols_fd(array, size, logfd);
    ap_snprintf(msgbuf, sizeof msgbuf,
                "%s end of backtrace\n",
                msg_prefix);
    write(logfd, msgbuf, strlen(msgbuf));
    close(logfd);
}

static void bt_exception_hook(ap_exception_info_t *ei)
{
    bt_show_backtrace(ei->sig);
}

static void bt_init(server_rec *s, pool *p)
{
    ap_add_fatal_exception_hook(bt_exception_hook);
}

static const char *bt_cmd_file(cmd_parms *cmd, void *dconf, char *fname)
{
    log_fname = ap_pstrdup(cmd->pool, fname);
    return NULL;
}

static const command_rec bt_command_table[] = {
    {
        "BTFile", bt_cmd_file, NULL, RSRC_CONF, TAKE1, "the filename of the mod_backtrace_13 logfile"
    }
    ,
    {
        NULL
    }
};

module MODULE_VAR_EXPORT backtrace_13_module = {
    STANDARD_MODULE_STUFF,
    bt_init,                    /* initializer */
    NULL,                       /* dir config creater */
    NULL,                       /* dir merger --- default is to override */
    NULL,                       /* server config */
    NULL,                       /* merge server config */
    bt_command_table,           /* command table */
    NULL,                       /* handlers */
    NULL,                       /* filename translation */
    NULL,                       /* check_user_id */
    NULL,                       /* check auth */
    NULL,                       /* check access */
    NULL,                       /* type_checker */
    NULL,                       /* fixups */
    NULL,                       /* logger */
    NULL,                       /* header parser */
    NULL,                       /* child init */
    NULL,                       /* child exit */
    NULL                        /* post read request */
};