reloc.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 <libarch/rtld/elf_dyn.h>
#include <rtld/symbol.h>
#include <rtld/rtld.h>
#include <rtld/rtld_debug.h>
#include <rtld/rtld_arch.h>

void module_process_pre_arch(module_t *m)
{
        /* Unused */
}


void rel_table_process(module_t *m, elf_rel_t *rt, size_t rt_size)
{
        unsigned i;

        size_t rt_entries;
        size_t r_offset;
        elf_word r_info;
        unsigned rel_type;
        elf_word sym_idx;
        uint32_t sym_addr;
        
        elf_symbol_t *sym_table;
        elf_symbol_t *sym;
        uint32_t *r_ptr;
        uint32_t sym_size;
        char *str_tab;
        
        elf_symbol_t *sym_def;
        module_t *dest;

        DPRINTF("parse relocation table\n");

        sym_table = m->dyn.sym_tab;
        rt_entries = rt_size / sizeof(elf_rel_t);
        str_tab = m->dyn.str_tab;

        DPRINTF("address: 0x%x, entries: %d\n", (uintptr_t)rt, rt_entries);
        
        for (i = 0; i < rt_entries; ++i) {
//              DPRINTF("symbol %d: ", i);
                r_offset = rt[i].r_offset;
                r_info = rt[i].r_info;

                sym_idx = ELF32_R_SYM(r_info);
                sym = &sym_table[sym_idx];

/*              DPRINTF("name '%s', value 0x%x, size 0x%x\n",
                    str_tab + sym->st_name,
                    sym->st_value,
                    sym->st_size);
*/
                rel_type = ELF32_R_TYPE(r_info);
                r_ptr = (uint32_t *)(r_offset + m->bias);

                if (sym->st_name != 0) {
//                      DPRINTF("rel_type: %x, rel_offset: 0x%x\n", rel_type, r_offset);
                        sym_def = symbol_def_find(str_tab + sym->st_name,
                            m, &dest);
//                      DPRINTF("dest name: '%s'\n", dest->dyn.soname);
//                      DPRINTF("dest bias: 0x%x\n", dest->bias);
                        if (sym_def) {
                                sym_addr = (uint32_t)
                                    symbol_get_addr(sym_def, dest);
//                              DPRINTF("symbol definition found, addr=0x%x\n", sym_addr);
                        } else {
                                printf("Definition of '%s' not found.\n",
                                    str_tab + sym->st_name);
                                continue;
                        }
                } else {
                        sym_addr = 0;
                        sym_def = NULL;
                }

                switch (rel_type) {
                case R_386_GLOB_DAT:
                case R_386_JUMP_SLOT:
                        DPRINTF("fixup R_386_GLOB_DAT/JUMP_SLOT (b+v)\n");
                        *r_ptr = sym_addr;
                        break;

                case R_386_32:
                        DPRINTF("fixup R_386_32 (b+v+a)\n");
                        *r_ptr += sym_addr;
                        break;

                case R_386_PC32:
                        DPRINTF("fixup R_386_PC32 (b+v+a-p)\n");
                        *r_ptr += sym_addr - (uint32_t) r_ptr;
                        break;

                case R_386_COPY:
                        /*
                         * Copy symbol data from shared object to specified
                         * location.
                         */
                        DPRINTF("fixup R_386_COPY (s)\n");
                        sym_size = sym->st_size;
                        if (sym_size != sym_def->st_size) {
                                printf("Warning: Mismatched symbol sizes.\n");
                                /* Take the lower value. */
                                if (sym_size > sym_def->st_size)
                                        sym_size = sym_def->st_size;
                        }
                        memcpy(r_ptr, (const void *)sym_addr, sym_size);
                        break;
                        
                case R_386_RELATIVE:
                        DPRINTF("fixup R_386_RELATIVE (b+a)\n");
                        *r_ptr += m->bias;
                        break;

                case R_386_TLS_DTPMOD32:
                        /*
                         * We can ignore this as long as the only module
                         * with TLS variables is libc.so.
                         */
                        DPRINTF("Ignoring R_386_TLS_DTPMOD32\n");
                        break;

                default:
                        printf("Error: Unknown relocation type %d\n",
                            rel_type);
                        exit(1);
                }

        }

}

void rela_table_process(module_t *m, elf_rela_t *rt, size_t rt_size)
{
        /* Unused */
        (void)m; (void)rt; (void)rt_size;
}

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