lib/libtnfctl/internal.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.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * Implements the routines that are needed only for internal process
 * control.
 */

#ifndef DEBUG
#define NDEBUG  1
#endif

#include "tnfctl_int.h"
#include "kernel_int.h"
#include "dbg.h"

#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <link.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/param.h>
#include <sys/procfs.h>
#include <assert.h>
#include <dlfcn.h>

static int inprocess_read(void *ignore,
    uintptr_t addr, void *buf, size_t size);
static int inprocess_write(void *ignore,
    uintptr_t addr, void *buf, size_t size);
static pid_t inprocess_getpid(void *ignore);
static tnfctl_errcode_t inprocess_get_dtdebug(void *hndl, uintptr_t *ret_val);
static int inprocess_loadobj_iter(void *opq, tnfctl_ind_obj_f *obj_func,
                    void *cd);

/*
 * Cause interposition on dlclose() and dlopen()
 */
#pragma weak dlclose = _tnfctl_dlclose

#pragma weak dlopen = _tnfctl_dlopen

/*
 * The lock used to protect the _tnfctl_internal_tracing_flag variable.
 *
 */
mutex_t     _tnfctl_internalguard_lock = DEFAULTMUTEX;
boolean_t   _tnfctl_internal_tracing_flag = 0;
pid_t       _tnfctl_externally_traced_pid = NOPID;

/*
 * Returns a pointer to a tnfctl handle that can do in process probe control.
 */
tnfctl_errcode_t
tnfctl_internal_open(tnfctl_handle_t **ret_val)
{
    tnfctl_handle_t *hdl;
    tnfctl_errcode_t    prexstat;
    uintptr_t       dbgaddr;

    /* allocate hdl and zero fill */
    hdl = calloc(1, sizeof (*hdl));
    if (hdl == NULL) {
        return (TNFCTL_ERR_ALLOCFAIL);
    }

    hdl->mode = INTERNAL_MODE;
    hdl->called_exit = B_FALSE;

    /* plug in inprocess call back functions */
    hdl->p_read = inprocess_read;
    hdl->p_write = inprocess_write;
    hdl->p_obj_iter = inprocess_loadobj_iter;
    hdl->p_getpid = inprocess_getpid;

    /*
     * get the address of DT_DEBUG and store it in proc_p
     * (the handle on the same process is the dbg address)
     */
    prexstat = inprocess_get_dtdebug(hdl, &dbgaddr);
    if (prexstat) {
        free(hdl);
        return (prexstat);
    }
    hdl->proc_p = (void *) dbgaddr;

    /* initialize state in handle */
    prexstat = _tnfctl_set_state(hdl);
    if (prexstat) {
        free(hdl);
        return (prexstat);
    }
    /* see if process is already being traced */
    prexstat = _tnfctl_internal_getlock();
    if (prexstat) {
        free(hdl);
        return (prexstat);
    }
    *ret_val = hdl;
    return (TNFCTL_ERR_NONE);
}

/*
 * reads a block of memory from the same address space.
 */
static int
inprocess_read(void *ignore, uintptr_t addr, void *buf, size_t size)
{

    DBG_TNF_PROBE_2(inprocess_read_1, "libtnfctl", "sunw%verbosity 3;",
        tnf_long, num_bytes, size,
        tnf_opaque, from_address, addr);

    (void) memcpy(buf, (void *) addr, size);
    return (0);
}

/*
 * writes a block of memory to the same address space.
 */
static int
inprocess_write(void *ignore, uintptr_t addr, void *buf, size_t size)
{

    DBG_TNF_PROBE_2(inprocess_write_1, "libtnfctl", "sunw%verbosity 3;",
        tnf_long, num_bytes, size,
        tnf_opaque, to_address, addr);

    (void) memcpy((void *)addr, buf, size);
    return (0);
}

/*
 * returns the pid of the process.
 */
static pid_t
inprocess_getpid(void *ignore)
{
    return (getpid());
}
extern Elf3264_Dyn _DYNAMIC;

/*
 * returns the address of the DT_DEBUG field in the _DYNAMIC array
 * of the same address space.
 */
static tnfctl_errcode_t
inprocess_get_dtdebug(void *hndl, uintptr_t *ret_val)
{
    Elf3264_Dyn     *dyn = &_DYNAMIC;
    Elf3264_Dyn *dp;

    for (dp = dyn; dp->d_tag != DT_NULL; dp++) {
        if (dp->d_tag == DT_DEBUG) {
            *ret_val = (uintptr_t) dp;
            return (TNFCTL_ERR_NONE);
        }
    }
    return (TNFCTL_ERR_INTERNAL);
}

#define PROCFORMAT  "/proc/%d"

/*
 * iterate over all loadobjects in the same address space calling the
 * callback function "obj_func".
 */
static int
inprocess_loadobj_iter(void *opq, tnfctl_ind_obj_f *obj_func, void *cd)
{
    Elf3264_Dyn *dtdebug = opq;
    struct r_debug  *r_dbg;
    struct link_map *lmap;
    char        path[MAXPATHLEN];
    int     procfd;
    tnfctl_ind_obj_info_t   loadobj;
    int     retval = 0; /* sucessful return */

    DBG_TNF_PROBE_0(inprocess_loadobj_iter_start, "libtnfctl",
            "start inprocess_loadobj_iter; sunw%verbosity 1");

    r_dbg = (struct r_debug *)dtdebug->d_un.d_ptr;

    DBG_TNF_PROBE_1(inprocess_loadobj_iter_1, "libtnfctl",
        "sunw%verbosity 1",
        tnf_string, link_map_state,
        (r_dbg->r_state == RT_CONSISTENT) ? "RT_CONSISTENT" :
            (r_dbg->r_state == RT_ADD) ? "RT_ADD" : "RT_DELETE");

    /* bail if link map is not consistent */
    if (r_dbg->r_state != RT_CONSISTENT)
        return (1);

    (void) sprintf(path, PROCFORMAT, (int) getpid());

    /*
     * opening /proc readonly, so debuggers can still run
     * We use /proc in order to get fd on the object.
     */
    procfd = open(path, O_RDONLY);
    if (procfd == -1)
        return (1);

    for (lmap = r_dbg->r_map; lmap; lmap = lmap->l_next) {
        loadobj.text_base = lmap->l_addr;
        loadobj.data_base = lmap->l_addr;
        loadobj.objname = lmap->l_name;
        /*
         * client of this interface should deal with -1 for objfd,
         * so no error checking is needed on this ioctl
         */
        loadobj.objfd = ioctl(procfd, PIOCOPENM, &(lmap->l_addr));

        retval = obj_func(opq, &loadobj, cd);

        /* close the fd */
        if (loadobj.objfd != -1)
            close(loadobj.objfd);

        /* check for error */
        if (retval == 1)
            goto end_of_func;
    }

end_of_func:
    close(procfd);

    DBG_TNF_PROBE_0(inprocess_loadobj_iter_end, "libtnfctl",
            "end inprocess_loadobj_iter; sunw%verbosity 1");
    return (retval);
}

/*
 * The lock that prevents a thread from accessing our cached library list
 * and a dlopen or dlclose happening at the same time in another thread.
 */
mutex_t     _tnfctl_lmap_lock = DEFAULTMUTEX;

/*
 * The flag that indicates that the library list has changed via a
 * dlopen or dlclose.
 */
boolean_t   _tnfctl_libs_changed = B_FALSE;

/*
 * Thread id of the owner of the lock in order to implement a
 * recursive lock i.e. no deadlock if the same thread tries to lock
 * a lock it already holds.
 */
static thread_t lock_holder = 0;    /* XXX - no tid with 0 */
NOTE(MUTEX_PROTECTS_DATA(warlock::lmap_lock, lock_holder))
NOTE(DATA_READABLE_WITHOUT_LOCK(lock_holder))

/*
 * In the routines below, we will appear to use a different lock if we
 * are running lock_lint/warlock.  We define a macro to represent whichever
 * lock is appropriate.
 */
#if defined(__lock_lint)
#define LMAP_LOCK   (&warlock_kludge->lmap_lock)
#else
#define LMAP_LOCK   (&_tnfctl_lmap_lock)
#endif

/*
 * dlclose interposition with a recursive lock so that a .fini section
 * can recursively call dlopen or dlclose while holding _tnfctl_lmap_lock
 * This interposition serializes access to rtld's loadobject list and
 * also updates the flag _tnfctl_libs_changed to indicate a change in
 * the library list.  This flag is checked by operations that update
 * probes so that it can sync up with the new library list and potential
 * new/deleted probes.
 */
int
_tnfctl_dlclose(void *handle)
{
    static int (*real_dlclose)(void *handle) = NULL;
    int retval;
    thread_t tid;

    if (real_dlclose == NULL) {
        real_dlclose = (int (*)(void *)) dlsym(RTLD_NEXT, "dlclose");
    }
    assert(real_dlclose);

    if (mutex_trylock(LMAP_LOCK) != 0) {
        /* don't have lock */
        tid = thr_self();
        if (tid == lock_holder) {
            /* recursive dlopen/dlclose by same thread */
            return ((*real_dlclose)(handle));
        }
        /* not a recursive dlopen/dlclose - wait on lock */
        mutex_lock(LMAP_LOCK);
    }

    /* lock is held now */
    lock_holder = thr_self();
    retval = (*real_dlclose)(handle);

    /*
     * reset lock_holder so that if _tnfctl_lmap_lock is held by some
     * other part of the code, we don't assume it is a recursive
     * dlopen/dlclose
     */
    lock_holder = 0;
    _tnfctl_libs_changed = B_TRUE;
    mutex_unlock(LMAP_LOCK);

    return (retval);
}

/*
 * dlopen interposition with a recursive lock so that a .init section
 * can recursively call dlopen or dlclose while holding _tnfctl_lmap_lock
 * This interposition serializes access to rtld's loadobject list and
 * also updates the flag _tnfctl_libs_changed to indicate a change in
 * the library list.  This flag is checked by operations that update
 * probes so that it can sync up with the new library list and potential
 * new/deleted probes.
 */
void *
_tnfctl_dlopen(const char *pathname, int mode)
{
    static void * (*real_dlopen)(const char *, int) = NULL;
    void *retval;
    thread_t tid;

    if (real_dlopen == NULL) {
        real_dlopen = (void * (*)(const char *, int))
                    dlsym(RTLD_NEXT, "dlopen");
    }
    assert(real_dlopen);

    if (mutex_trylock(LMAP_LOCK) != 0) {
        /* don't have lock */
        tid = thr_self();
        if (tid == lock_holder) {
            /* recursive dlopen/dlclose by same thread */
            return ((*real_dlopen)(pathname, mode));
        }
        /* not a recursive dlopen/dlclose - wait on lock */
        mutex_lock(LMAP_LOCK);
    }

    /* lock is held now */
    lock_holder = thr_self();
    retval = (*real_dlopen)(pathname, mode);

    /*
     * reset lock_holder so that if _tnfctl_lmap_lock is held by some
     * other part of the code, we don't assume it is a recursive
     * dlopen/dlclose
     */
    lock_holder = 0;
    _tnfctl_libs_changed = B_TRUE;
    mutex_unlock(LMAP_LOCK);

    return (retval);
}

tnfctl_errcode_t
_tnfctl_internal_getlock()
{
    mutex_lock(&_tnfctl_internalguard_lock);
    if (_tnfctl_internal_tracing_flag == 1) {
    /* internal trace control active */
    mutex_unlock(&_tnfctl_internalguard_lock);
    return (TNFCTL_ERR_BUSY);
    }
    _tnfctl_internal_tracing_flag = 1;
    if (_tnfctl_externally_traced_pid == getpid()) {
    /* external trace control is active */
    _tnfctl_internal_tracing_flag = 0;
    mutex_unlock(&_tnfctl_internalguard_lock);
    return (TNFCTL_ERR_BUSY);
    }
    DBG((void) fprintf(stderr, "_tnfctl_internal_getlock: ok to trace %d\n",
    getpid()));
    mutex_unlock(&_tnfctl_internalguard_lock);
    return (TNFCTL_ERR_NONE);
}


#ifdef __lock_lint

/*
 * dummy function for lock_lint (warlock) static lock analysis.
 */
int
warlock_dummy()
{
    int (*fp)();

    return ((*fp)());
}

#endif