module.c

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/*
 * Copyright (c) 2008 Jiri Svoboda
 * 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <adt/list.h>
#include <loader/pcb.h>

#include <rtld/rtld.h>
#include <rtld/rtld_debug.h>
#include <rtld/dynamic.h>
#include <rtld/rtld_arch.h>
#include <rtld/module.h>
#include <elf_load.h>

void module_process_relocs(module_t *m)
{
        DPRINTF("module_process_relocs('%s')\n", m->dyn.soname);

        /* Do not relocate twice. */
        if (m->relocated) return;

        module_process_pre_arch(m);

        if (m->dyn.plt_rel == DT_REL) {
                DPRINTF("table type DT_REL\n");
                if (m->dyn.rel != NULL) {
                        DPRINTF("non-empty\n");
                        rel_table_process(m, m->dyn.rel, m->dyn.rel_sz);
                }
                /* FIXME: this seems wrong */
                if (m->dyn.jmp_rel != NULL) {
                DPRINTF("table type jmp-rel\n");
                        DPRINTF("non-empty\n");
                        rel_table_process(m, m->dyn.jmp_rel, m->dyn.plt_rel_sz);
                }
        } else { /* (m->dyn.plt_rel == DT_RELA) */
                DPRINTF("table type DT_RELA\n");
                if (m->dyn.rela != NULL) {
                        DPRINTF("non-empty\n");
                        rela_table_process(m, m->dyn.rela, m->dyn.rela_sz);
                }
        }

        m->relocated = true;
}

module_t *module_find(const char *name)
{
        link_t *head = &runtime_env->modules_head;

        link_t *cur;
        module_t *m;
        const char *p, *soname;

        DPRINTF("module_find('%s')\n", name);

        /*
         * If name contains slashes, treat it as a pathname and
         * construct soname by chopping off the path. Otherwise
         * treat it as soname.
         */
        p = str_rchr(name, '/');
        soname = p ? (p + 1) : name;

        /* Traverse list of all modules. Not extremely fast, but simple */
        DPRINTF("head = %p\n", head);
        for (cur = head->next; cur != head; cur = cur->next) {
                DPRINTF("cur = %p\n", cur);
                m = list_get_instance(cur, module_t, modules_link);
                if (str_cmp(m->dyn.soname, soname) == 0) {
                        return m; /* Found */
                }
        }
        
        return NULL; /* Not found */
}

#define NAME_BUF_SIZE 64

module_t *module_load(const char *name)
{
        elf_info_t info;
        char name_buf[NAME_BUF_SIZE];
        module_t *m;
        int rc;
        
        m = malloc(sizeof(module_t));
        if (!m) {
                printf("malloc failed\n");
                exit(1);
        }

        if (str_size(name) > NAME_BUF_SIZE - 2) {
                printf("soname too long. increase NAME_BUF_SIZE\n");
                exit(1);
        }

        /* Prepend soname with '/lib/' */
        str_cpy(name_buf, NAME_BUF_SIZE, "/lib/");
        str_cpy(name_buf + 5, NAME_BUF_SIZE - 5, name);

        /* FIXME: need to real allocation of address space */
        m->bias = runtime_env->next_bias;
        runtime_env->next_bias += 0x100000;

        DPRINTF("filename:'%s'\n", name_buf);
        DPRINTF("load '%s' at 0x%x\n", name_buf, m->bias);

        rc = elf_load_file(name_buf, m->bias, ELDF_RW, &info);
        if (rc != EE_OK) {
                printf("Failed to load '%s'\n", name_buf);
                exit(1);
        }

        if (info.dynamic == NULL) {
                printf("Error: '%s' is not a dynamically-linked object.\n",
                    name_buf);
                exit(1);
        }

        /* Pending relocation. */
        m->relocated = false;

        DPRINTF("parse dynamic section\n");
        /* Parse ELF .dynamic section. Store info to m->dyn. */
        dynamic_parse(info.dynamic, m->bias, &m->dyn);

        /* Insert into the list of loaded modules */
        list_append(&m->modules_link, &runtime_env->modules_head);

        return m;
}

void module_load_deps(module_t *m)
{
        elf_dyn_t *dp;
        char *dep_name;
        module_t *dm;
        size_t n, i;

        DPRINTF("module_load_deps('%s')\n", m->dyn.soname);

        /* Count direct dependencies */
        
        dp = m->dyn.dynamic;
        n = 0;

        while (dp->d_tag != DT_NULL) {
                if (dp->d_tag == DT_NEEDED) ++n;
                ++dp;
        }

        /* Create an array of pointers to direct dependencies */

        m->n_deps = n;

        if (n == 0) {
                /* There are no dependencies, so we are done. */
                m->deps = NULL;
                return;
        }

        m->deps = malloc(n * sizeof(module_t *));
        if (!m->deps) {
                printf("malloc failed\n");
                exit(1);
        }

        i = 0; /* Current dependency index */
        dp = m->dyn.dynamic;

        while (dp->d_tag != DT_NULL) {
                if (dp->d_tag == DT_NEEDED) {
                        dep_name = m->dyn.str_tab + dp->d_un.d_val;

                        DPRINTF("%s needs %s\n", m->dyn.soname, dep_name);
                        dm = module_find(dep_name);
                        if (!dm) {
                                dm = module_load(dep_name);
                                module_load_deps(dm);
                        }

                        /* Save into deps table */
                        m->deps[i++] = dm;
                }
                ++dp;
        }
}

void modules_process_relocs(module_t *start)
{
        link_t *head = &runtime_env->modules_head;

        link_t *cur;
        module_t *m;

        for (cur = head->next; cur != head; cur = cur->next) {
                m = list_get_instance(cur, module_t, modules_link);

                /* Skip rtld, since it has already been processed */
                if (m != &runtime_env->rtld) {
                        module_process_relocs(m);
                }
        }
}

void modules_untag(void)
{
        link_t *head = &runtime_env->modules_head;

        link_t *cur;
        module_t *m;

        for (cur = head->next; cur != head; cur = cur->next) {
                m = list_get_instance(cur, module_t, modules_link);
                m->bfs_tag = false;
        }
}

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