source: mainline/uspace/lib/c/generic/rtld/module.c

/*
 * Copyright (c) 2024 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.
 */

/** @addtogroup rtld
 * @brief
 * @{
 */
/**
 * @file
 */

#include <align.h>
#include <adt/list.h>
#include <elf/elf_load.h>
#include <errno.h>
#include <loader/pcb.h>
#include <stdalign.h>
#include <stdio.h>
#include <stdlib.h>
#include <str.h>
#include <macros.h>

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

#include "../private/libc.h"

/** Create the "entrypoint" module, of the program executable
 *
 * @param p_info Program ELF file info
 * @param rtld Run-time dynamic linker
 * @param rmodule Place to store pointer to new module or @c NULL
 * @return EOK on success, ENOMEM if out of memory
 */
errno_t module_create_entrypoint(elf_finfo_t *p_info, rtld_t *rtld, module_t **rmodule)
{
        module_t *module;
        bool is_dynamic = p_info->dynamic != NULL;
        DPRINTF("module_create_entrypoint\n");

        module = calloc(1, sizeof(module_t));
        if (module == NULL)
                return ENOMEM;

        uintptr_t bias = elf_get_bias(p_info->base);

        /*
         * First we need to process dynamic sections of the executable
         * program and insert it into the module graph.
         */
        if (is_dynamic) {
                DPRINTF("Parse program .dynamic section at %p\n", p_info->dynamic);
                dynamic_parse(p_info->dynamic, bias, &module->dyn);
        } else {
                DPRINTF("Executable is not dynamically linked\n");
        }

        module->bias = bias;
        module->id = rtld_get_next_id(rtld);
        module->dyn.soname = "[program]";

        module->rtld = rtld;
        module->exec = true;
        module->local = !is_dynamic;

        module->tdata = p_info->tls.tdata;
        module->tdata_size = p_info->tls.tdata_size;
        module->tbss_size = p_info->tls.tbss_size;
        module->tls_align = p_info->tls.tls_align;

        DPRINTF("prog tdata at %p size %zu, tbss size %zu\n",
            module->tdata, module->tdata_size, module->tbss_size);

        list_append(&module->modules_link, &rtld->modules);

        if (rmodule != NULL)
                *rmodule = module;
        return EOK;
}

/** (Eagerly) process all relocation tables in a module.
 *
 * Currently works as if LD_BIND_NOW was specified.
 */
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);

        /* jmp_rel table */
        if (m->dyn.jmp_rel != NULL) {
                DPRINTF("jmp_rel table\n");
                if (m->dyn.plt_rel == DT_REL) {
                        DPRINTF("jmp_rel table type DT_REL\n");
                        rel_table_process(m, m->dyn.jmp_rel, m->dyn.plt_rel_sz);
                } else {
                        assert(m->dyn.plt_rel == DT_RELA);
                        DPRINTF("jmp_rel table type DT_RELA\n");
                        rela_table_process(m, m->dyn.jmp_rel, m->dyn.plt_rel_sz);
                }
        }

        /* rel table */
        if (m->dyn.rel != NULL) {
                DPRINTF("rel table\n");
                rel_table_process(m, m->dyn.rel, m->dyn.rel_sz);
        }

        /* rela table */
        if (m->dyn.rela != NULL) {
                DPRINTF("rela table\n");
                rela_table_process(m, m->dyn.rela, m->dyn.rela_sz);
        }

        m->relocated = true;
}

/** Find module structure by soname/pathname.
 *
 * Used primarily to see if a module has already been loaded.
 * Modules are compared according to their soname, i.e. possible
 * path components are ignored.
 */
module_t *module_find(rtld_t *rtld, const char *name)
{
        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 */
        list_foreach(rtld->modules, modules_link, module_t, m) {
                DPRINTF("m = %p\n", m);
                if (str_cmp(m->dyn.soname, soname) == 0) {
                        return m; /* Found */
                }
        }

        return NULL; /* Not found */
}

#define NAME_BUF_SIZE 64

/** Load a module.
 *
 * Currently this trivially tries to load '/<name>'.
 */
module_t *module_load(rtld_t *rtld, const char *name, mlflags_t flags)
{
        elf_finfo_t info;
        char name_buf[NAME_BUF_SIZE];
        module_t *m;
        errno_t rc;

        m = calloc(1, sizeof(module_t));
        if (m == NULL) {
                DPRINTF("malloc failed\n");
                goto error;
        }

        m->rtld = rtld;
        m->id = rtld_get_next_id(rtld);

        if ((flags & mlf_local) != 0)
                m->local = true;

        if (str_size(name) > NAME_BUF_SIZE - 2) {
                DPRINTF("soname too long. increase NAME_BUF_SIZE\n");
                goto error;
        }

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

        DPRINTF("filename:'%s'\n", name_buf);

        rc = elf_load_file_name(name_buf, RTLD_MODULE_LDF, &info);
        if (rc != EOK) {
                DPRINTF("Failed to load '%s'\n", name_buf);
                goto error;
        }

        m->bias = elf_get_bias(info.base);

        DPRINTF("loaded '%s' at 0x%zx\n", name_buf, m->bias);

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

        /* 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, &rtld->modules);

        /* Copy TLS info */
        m->tdata = info.tls.tdata;
        m->tdata_size = info.tls.tdata_size;
        m->tbss_size = info.tls.tbss_size;
        m->tls_align = info.tls.tls_align;

        DPRINTF("tdata at %p size %zu, tbss size %zu\n",
            m->tdata, m->tdata_size, m->tbss_size);

        return m;

error:
        if (m)
                free(m);

        return NULL;
}

/** Load all modules on which m (transitively) depends.
 */
errno_t module_load_deps(module_t *m, mlflags_t flags)
{
        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 EOK;
        }

        m->deps = malloc(n * sizeof(module_t *));
        if (!m->deps) {
                DPRINTF("malloc failed\n");
                return ENOMEM;
        }

        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(m->rtld, dep_name);
                        if (!dm) {
                                dm = module_load(m->rtld, dep_name, flags);
                                if (!dm) {
                                        return EINVAL;
                                }

                                errno_t rc = module_load_deps(dm, flags);
                                if (rc != EOK) {
                                        return rc;
                                }
                        }

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

        return EOK;
}

/** Find module structure by ID. */
module_t *module_by_id(rtld_t *rtld, unsigned long id)
{
        list_foreach(rtld->modules, modules_link, module_t, m) {
                if (m->id == id)
                        return m;
        }

        return NULL;
}

/** Process relocations in modules.
 *
 * Processes relocations in @a start and all its dependencies.
 * Modules that have already been relocated are unaffected.
 *
 * @param       start   The module where to start from.
 */
void modules_process_relocs(rtld_t *rtld, module_t *start)
{
        list_foreach(rtld->modules, modules_link, module_t, m) {
                /*
                 * Skip rtld module, since it has already been processed.
                 * Skip start / main program -- leave it for later
                 */
                if (m != &rtld->rtld && m != start) {
                        module_process_relocs(m);
                }
        }

        /*
         * Now that shared libraries have been processed and their variables
         * are thus initialized, we can process the main program,
         * which may contain COPY relocations that copy value from shared
         * library variables to instances of those variables defined
         * in the main program.
         */
        module_process_relocs(start);
}

void modules_process_tls(rtld_t *rtld)
{
#ifdef CONFIG_TLS_VARIANT_1
        rtld->tls_size = sizeof(tcb_t);
        rtld->tls_align = alignof(tcb_t);

        list_foreach(rtld->modules, modules_link, module_t, m) {
                list_append(&m->imodules_link, &rtld->imodules);
                rtld->tls_align = max(rtld->tls_align, m->tls_align);

                rtld->tls_size = ALIGN_UP(rtld->tls_size, m->tls_align);
                m->tpoff = rtld->tls_size;
                rtld->tls_size += m->tdata_size + m->tbss_size;
        }

#else
        rtld->tls_size = 0;
        rtld->tls_align = alignof(tcb_t);

        list_foreach(rtld->modules, modules_link, module_t, m) {
                list_append(&m->imodules_link, &rtld->imodules);
                rtld->tls_align = max(rtld->tls_align, m->tls_align);

                /*
                 * We are allocating spans "backwards", here,
                 * as described in U. Drepper's paper.
                 */
                rtld->tls_size += m->tdata_size + m->tbss_size;
                rtld->tls_size = ALIGN_UP(rtld->tls_size, m->tls_align);
                m->tpoff = -(ptrdiff_t) rtld->tls_size;
        }

        /*
         * We are in negative offsets. In order for the alignments to
         * be correct, "zero" offset (i.e. the total size) must be aligned
         * to the strictest alignment present.
         */
        rtld->tls_size = ALIGN_UP(rtld->tls_size, rtld->tls_align);

        /*
         * Space for the TCB.
         * Later, the TLS zero offset is equal to the pointer to tcb_t, so
         * adding the sizeof(tcb_t) block AFTER we calculated the alignment
         * of the remainder above is correct.
         */
        rtld->tls_size += sizeof(tcb_t);
#endif
}

/** Clear BFS tags of all modules.
 */
void modules_untag(rtld_t *rtld)
{
        list_foreach(rtld->modules, modules_link, module_t, m) {
                m->bfs_tag = false;
        }
}

/** @}
 */