libdtrace/common/dlink_common.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 2012 by Delphix. All rights reserved.
 */

/*
 * Common functions for helper provider loading both compiled into the
 * executable via drti.o and dtrace(1M) -G, and the libdaudit.so library.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <dlink.h>

/*
 * In Solaris 10 GA, the only mechanism for communicating helper information
 * is through the DTrace helper pseudo-device node in /devices; there is
 * no /dev link. Because of this, USDT providers and helper actions don't
 * work inside of non-global zones. This issue was addressed by adding
 * the /dev and having this initialization code use that /dev link. If the
 * /dev link doesn't exist it falls back to looking for the /devices node
 * as this code may be embedded in a binary which runs on Solaris 10 GA.
 */
const char *devname = "/dev/dtrace/helper";
static const char *olddevname = "/devices/pseudo/dtrace@0:helper";

static boolean_t dof_init_debug = B_FALSE;

void
dprintf(int debug, const char *fmt, ...)
{
    va_list ap;

    if (debug && !dof_init_debug)
        return;

    va_start(ap, fmt);

    (void) fprintf(stderr, "dtrace DOF: ");

    (void) vfprintf(stderr, fmt, ap);

    if (fmt[strlen(fmt) - 1] != '\n')
        (void) fprintf(stderr, ": %s\n", strerror(errno));

    va_end(ap);
}

/*
 * Users may set the following environment variable to affect the way
 * helper initialization takes place:
 *
 *  DTRACE_DOF_INIT_DEBUG       enable debugging output
 *  DTRACE_DOF_INIT_DISABLE     disable helper loading
 *  DTRACE_DOF_INIT_DEVNAME     set the path to the helper node
 */
void
dtrace_link_init(void)
{
    if (getenv("DTRACE_DOF_INIT_DEBUG") != NULL)
        dof_init_debug = B_TRUE;
}

void
dtrace_link_dof(dof_hdr_t *dof, Lmid_t lmid, const char *name, uintptr_t addr)
{
    const char *modname;
    const char *p;
#ifdef _LP64
    Elf64_Ehdr *elf;
#else
    Elf32_Ehdr *elf;
#endif
    dof_helper_t dh;
    int fd;

    if (getenv("DTRACE_DOF_INIT_DISABLE") != NULL)
        return;

    if ((modname = strrchr(name, '/')) == NULL)
        modname = name;
    else
        modname++;

    if (dof->dofh_ident[DOF_ID_MAG0] != DOF_MAG_MAG0 ||
        dof->dofh_ident[DOF_ID_MAG1] != DOF_MAG_MAG1 ||
        dof->dofh_ident[DOF_ID_MAG2] != DOF_MAG_MAG2 ||
        dof->dofh_ident[DOF_ID_MAG3] != DOF_MAG_MAG3) {
        dprintf(0, ".SUNW_dof section corrupt for %s\n", modname);
        return;
    }

    elf = (void *)addr;

    dh.dofhp_dof = (uintptr_t)dof;
    dh.dofhp_addr = elf->e_type == ET_DYN ? addr : 0;

    if (lmid == LM_ID_BASE) {
        (void) snprintf(dh.dofhp_mod, sizeof (dh.dofhp_mod),
            "%s", modname);
    } else {
        (void) snprintf(dh.dofhp_mod, sizeof (dh.dofhp_mod),
            "LM%lu`%s", lmid, modname);
    }

    if ((p = getenv("DTRACE_DOF_INIT_DEVNAME")) != NULL)
        devname = p;

    if ((fd = open64(devname, O_RDWR)) < 0) {
        dprintf(1, "failed to open helper device %s", devname);

        /*
         * If the device path wasn't explicitly set, try again with
         * the old device path.
         */
        if (p != NULL)
            return;

        devname = olddevname;

        if ((fd = open64(devname, O_RDWR)) < 0) {
            dprintf(1, "failed to open helper device %s", devname);
            return;
        }
    }

    if (ioctl(fd, DTRACEHIOC_ADDDOF, &dh) == -1) {
        dprintf(1, "DTrace ioctl failed for DOF at %p in %s", dof,
            name);
    } else {
        dprintf(1, "DTrace ioctl succeeded for DOF at %p in %s\n", dof,
            name);
    }
    (void) close(fd);
}