dynamic.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 <rtld/elf_dyn.h>
#include <rtld/dynamic.h>
#include <rtld/rtld.h>
#include <rtld/rtld_debug.h>

void dynamic_parse(elf_dyn_t *dyn_ptr, size_t bias, dyn_info_t *info)
{
        elf_dyn_t *dp = dyn_ptr;

        void *d_ptr;
        elf_word d_val;

        elf_word soname_idx;
        elf_word rpath_idx;

        DPRINTF("memset\n");
        memset(info, 0, sizeof(dyn_info_t));

        soname_idx = 0;
        rpath_idx = 0;

        DPRINTF("pass 1\n");
        while (dp->d_tag != DT_NULL) {
                d_ptr = (void *)((uint8_t *)dp->d_un.d_ptr + bias);
                d_val = dp->d_un.d_val;
                DPRINTF("tag=%u ptr=0x%x val=%u\n", (unsigned)dp->d_tag,
                        (unsigned)d_ptr, (unsigned)d_val);

                switch (dp->d_tag) {

                case DT_PLTRELSZ:       info->plt_rel_sz = d_val; break;
                case DT_PLTGOT:         info->plt_got = d_ptr; break;
                case DT_HASH:           info->hash = d_ptr; break;
                case DT_STRTAB:         info->str_tab = d_ptr; break;
                case DT_SYMTAB:         info->sym_tab = d_ptr; break;
                case DT_RELA:           info->rela = d_ptr; break;
                case DT_RELASZ:         info->rela_sz = d_val; break;
                case DT_RELAENT:        info->rela_ent = d_val; break;
                case DT_STRSZ:          info->str_sz = d_val; break;
                case DT_SYMENT:         info->sym_ent = d_val; break;
                case DT_INIT:           info->init = d_ptr; break;
                case DT_FINI:           info->fini = d_ptr; break;
                case DT_SONAME:         soname_idx = d_val; break;
                case DT_RPATH:          rpath_idx = d_val; break;
                case DT_SYMBOLIC:       info->symbolic = true; break;
                case DT_REL:            info->rel = d_ptr; break;
                case DT_RELSZ:          info->rel_sz = d_val; break;
                case DT_RELENT:         info->rel_ent = d_val; break;
                case DT_PLTREL:         info->plt_rel = d_val; break;
                case DT_TEXTREL:        info->text_rel = true; break;
                case DT_JMPREL:         info->jmp_rel = d_ptr; break;
                case DT_BIND_NOW:       info->bind_now = true; break;

                default:
                        if (dp->d_tag >= DT_LOPROC && dp->d_tag <= DT_HIPROC)
                                dyn_parse_arch(dp, bias, info);
                        break;
                }

                ++dp;
        }

        info->soname = info->str_tab + soname_idx;
        info->rpath = info->str_tab + rpath_idx;

        /* This will be useful for parsing dependencies later */
        info->dynamic = dyn_ptr;

        DPRINTF("str_tab=0x%x, soname_idx=0x%x, soname=0x%x\n",
                (uintptr_t)info->soname, soname_idx, (uintptr_t)info->soname);
        DPRINTF("soname='%s'\n", info->soname);
        DPRINTF("rpath='%s'\n", info->rpath);
        DPRINTF("hash=0x%x\n", (uintptr_t)info->hash);
        DPRINTF("dt_rela=0x%x\n", (uintptr_t)info->rela);
        DPRINTF("dt_rela_sz=0x%x\n", (uintptr_t)info->rela_sz);
        DPRINTF("dt_rel=0x%x\n", (uintptr_t)info->rel);
        DPRINTF("dt_rel_sz=0x%x\n", (uintptr_t)info->rel_sz);

        /*
         * Now that we have a pointer to the string table,
         * we can parse DT_NEEDED fields (which contain offsets into it).
         */

        DPRINTF("pass 2\n");
        dp = dyn_ptr;
        while (dp->d_tag != DT_NULL) {
                d_val = dp->d_un.d_val;

                switch (dp->d_tag) {
                case DT_NEEDED:
                        /* Assume just for now there's only one dependency */
                        info->needed = info->str_tab + d_val;
                        DPRINTF("needed:'%s'\n", info->needed);
                        break;

                default: break;
                }

                ++dp;
        }
}

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