libdtrace/common/drti.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.
 */

#include <unistd.h>
#include <fcntl.h>
#include <dlfcn.h>
#include <link.h>
#include <sys/dtrace.h>

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.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.
 *
 * 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
 */

static const char *devname = "/dev/dtrace/helper";
static const char *olddevname = "/devices/pseudo/dtrace@0:helper";

static const char *modname; /* Name of this load object */
static int gen;         /* DOF helper generation */
extern dof_hdr_t __SUNW_dof;    /* DOF defined in the .SUNW_dof section */
static boolean_t dof_init_debug = B_FALSE;  /* From DTRACE_DOF_INIT_DEBUG */

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

    if (debug && !dof_init_debug)
        return;

    va_start(ap, fmt);

    if (modname == NULL)
        (void) fprintf(stderr, "dtrace DOF: ");
    else
        (void) fprintf(stderr, "dtrace DOF %s: ", modname);

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

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

    va_end(ap);
}

#pragma init(dtrace_dof_init)
static void
dtrace_dof_init(void)
{
    dof_hdr_t *dof = &__SUNW_dof;
#ifdef _LP64
    Elf64_Ehdr *elf;
#else
    Elf32_Ehdr *elf;
#endif
    dof_helper_t dh;
    Link_map *lmp;
    Lmid_t lmid;
    int fd;
    const char *p;

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

    if (getenv("DTRACE_DOF_INIT_DEBUG") != NULL)
        dof_init_debug = B_TRUE;

    if (dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &lmp) == -1 || lmp == NULL) {
        dprintf(1, "couldn't discover module name or address\n");
        return;
    }

    if (dlinfo(RTLD_SELF, RTLD_DI_LMID, &lmid) == -1) {
        dprintf(1, "couldn't discover link map ID\n");
        return;
    }

    if ((modname = strrchr(lmp->l_name, '/')) == NULL)
        modname = lmp->l_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\n");
        return;
    }

    elf = (void *)lmp->l_addr;

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

    if (lmid == 0) {
        (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 ((gen = ioctl(fd, DTRACEHIOC_ADDDOF, &dh)) == -1)
        dprintf(1, "DTrace ioctl failed for DOF at %p", dof);
    else
        dprintf(1, "DTrace ioctl succeeded for DOF at %p\n", dof);

    (void) close(fd);
}

#pragma fini(dtrace_dof_fini)
static void
dtrace_dof_fini(void)
{
    int fd;

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

    if ((gen = ioctl(fd, DTRACEHIOC_REMOVE, gen)) == -1)
        dprintf(1, "DTrace ioctl failed to remove DOF (%d)\n", gen);
    else
        dprintf(1, "DTrace ioctl removed DOF (%d)\n", gen);

    (void) close(fd);
}