newlinker/debug_map.c

/*
 * Copyright (C) 2008, 2009 The Android Open source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS 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
 * COPYRIGHT OWNER OR 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.
 */

#include <pthread.h>
#include <stddef.h>

#include "linker.h"
#include "debug_map.h"

/*
 * This function is an empty stub where GDB locates a breakpoint to get notified
 * about linker activity.
 */
void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(void);

static struct link_map* r_debug_tail = NULL;
static pthread_mutex_t _r_debug_lock = PTHREAD_MUTEX_INITIALIZER;

// Cast rtld_db_dlactivity to Elf64_Addr on x86-64 NaCl.
#if defined(ANDROID_X86_64_LINKER) && defined(__native_client__)
struct r_debug _r_debug = {
  1,
  NULL,
  (Elf64_Addr) &rtld_db_dlactivity,
  RT_CONSISTENT,
  0
};
#else
struct r_debug _r_debug = {
  1,
  NULL,
  &rtld_db_dlactivity,
  RT_CONSISTENT,
  0
};
#endif

void insert_soinfo_into_debug_map(struct soinfo * info) {
    // Copy the necessary fields into the debug structure.
    struct link_map* map = &(info->linkmap);
    map->l_addr = info->base;
    map->l_name = (char*) info->name;
    map->l_ld = (uintptr_t)info->dynamic;

    /* Stick the new library at the end of the list.
     * gdb tends to care more about libc than it does
     * about leaf libraries, and ordering it this way
     * reduces the back-and-forth over the wire.
     */
    if (r_debug_tail) {
        r_debug_tail->l_next = map;
        map->l_prev = r_debug_tail;
        map->l_next = 0;
    } else {
        _r_debug.r_map = map;
        map->l_prev = 0;
        map->l_next = 0;
    }
    r_debug_tail = map;
}

void remove_soinfo_from_debug_map(struct soinfo* info) {
    struct link_map* map = &(info->linkmap);

    if (r_debug_tail == map) {
        r_debug_tail = map->l_prev;
    }

    if (map->l_prev) {
        map->l_prev->l_next = map->l_next;
    }
    if (map->l_next) {
        map->l_next->l_prev = map->l_prev;
    }
}

void notify_gdb_of_load(struct soinfo* info) {
#if !defined(__native_client__)
    if (info->flags & FLAG_EXE) {
        // GDB already knows about the main executable
        return;
    }
#endif

    pthread_mutex_lock(&_r_debug_lock);

    _r_debug.r_state = RT_ADD;
    rtld_db_dlactivity();

    insert_soinfo_into_debug_map(info);

    _r_debug.r_state = RT_CONSISTENT;
    rtld_db_dlactivity();

    pthread_mutex_unlock(&_r_debug_lock);
}

void notify_gdb_of_unload(struct soinfo* info) {
    if (info->flags & FLAG_EXE) {
        // GDB already knows about the main executable
        return;
    }

    pthread_mutex_lock(&_r_debug_lock);

    _r_debug.r_state = RT_DELETE;
    rtld_db_dlactivity();

    remove_soinfo_from_debug_map(info);

    _r_debug.r_state = RT_CONSISTENT;
    rtld_db_dlactivity();

    pthread_mutex_unlock(&_r_debug_lock);
}

void notify_gdb_of_libraries()
{
    _r_debug.r_state = RT_ADD;
    rtld_db_dlactivity();
    _r_debug.r_state = RT_CONSISTENT;
    rtld_db_dlactivity();
}