510 lines
12 KiB
C
510 lines
12 KiB
C
/* $NetBSD: elf.c,v 1.19 2006/07/08 05:49:01 ross Exp $ */
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/*
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* Copyright (c) 1998 Johan Danielsson <joda@pdc.kth.se>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: elf.c,v 1.19 2006/07/08 05:49:01 ross Exp $");
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#include <sys/param.h>
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#if defined(__alpha__) || defined(__arch64__) || defined(__x86_64__)
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#ifndef _LP64
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#error Temporary sanity check failed. Tell ross@netbsd.org
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#endif
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#endif
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#ifdef _LP64
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#define ELFSIZE 64
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#else
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#define ELFSIZE 32
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#endif
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#include <sys/exec_elf.h>
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#ifndef ELF_HDR_SIZE
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#define ELF_HDR_SIZE sizeof(Elf_Ehdr)
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#endif
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#include <sys/lkm.h>
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#include <err.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include "modload.h"
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char *strtab;
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static void
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read_section_header(int fd, Elf_Ehdr *ehdr, int num, Elf_Shdr *shdr)
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{
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if (lseek(fd, ehdr->e_shoff + num * ehdr->e_shentsize, SEEK_SET) < 0)
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err(1, "lseek");
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if (read(fd, shdr, sizeof(*shdr)) != sizeof(*shdr))
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err(1, "read");
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}
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struct elf_section {
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char *name; /* name of section; points into string table */
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unsigned long type; /* type of section */
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void *addr; /* load address of section */
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off_t offset; /* offset in file */
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size_t size; /* size of section */
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size_t align;
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struct elf_section *next;
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};
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/* adds the section `s' at the correct (sorted by address) place in
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the list pointed to by head; *head may be NULL */
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static void
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add_section(struct elf_section **head, struct elf_section *s)
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{
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struct elf_section *p, **q;
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q = head;
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p = *head;
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while (1) {
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if (p == NULL || p->addr > s->addr) {
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s->next = p;
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*q = s;
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return;
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}
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q = &p->next;
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p = p->next;
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}
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}
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/* make a linked list of all sections containing ALLOCatable data */
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static void
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read_sections(int fd, Elf_Ehdr *ehdr, char *shstrtab, struct elf_section **head)
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{
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int i;
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Elf_Shdr shdr;
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*head = NULL;
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/* scan through section headers */
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for (i = 0; i < ehdr->e_shnum; i++) {
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struct elf_section *s;
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read_section_header(fd, ehdr, i, &shdr);
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if (shdr.sh_size == 0)
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continue;
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if (((shdr.sh_flags & SHF_ALLOC) == 0)
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&& (shdr.sh_type != SHT_STRTAB)
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&& (shdr.sh_type != SHT_SYMTAB)
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&& (shdr.sh_type != SHT_DYNSYM)) {
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/* skip non-ALLOC sections */
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continue;
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}
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s = malloc(sizeof(*s));
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if (s == NULL)
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errx(1, "failed to allocate %lu bytes", (u_long)sizeof(*s));
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s->name = shstrtab + shdr.sh_name;
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s->type = shdr.sh_type;
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s->addr = (void *)shdr.sh_addr;
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s->offset = shdr.sh_offset;
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s->size = shdr.sh_size;
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s->align = shdr.sh_addralign;
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add_section(head, s);
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}
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}
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/* get the symbol table sections and free the rest of them */
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static void
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get_symtab(struct elf_section **symtb)
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{
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struct elf_section *head, *cur, *prev;
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head = NULL;
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prev = NULL;
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cur = *symtb;
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while (cur) {
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if ((cur->type == SHT_SYMTAB) || (cur->type == SHT_DYNSYM)) {
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if (head == NULL) {
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head = cur;
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}
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if (prev != NULL) {
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prev->next = cur;
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}
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prev = cur;
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cur = cur->next;
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} else {
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struct elf_section *p = cur;
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cur = cur->next;
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p->next = NULL;
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free(p);
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}
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}
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if (prev) {
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prev->next = NULL;
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}
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*symtb = head;
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}
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/* free a list of section headers */
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static void
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free_sections(struct elf_section *head)
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{
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while (head) {
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struct elf_section *p = head;
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head = head->next;
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free(p);
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}
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}
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/* read section header's string table */
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static char *
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read_shstring_table(int fd, Elf_Ehdr *ehdr)
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{
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Elf_Shdr shdr;
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char *shstrtab;
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read_section_header(fd, ehdr, ehdr->e_shstrndx, &shdr);
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shstrtab = malloc(shdr.sh_size);
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if (shstrtab == NULL)
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errx(1, "failed to allocate %lu bytes", (u_long)shdr.sh_size);
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if (lseek(fd, shdr.sh_offset, SEEK_SET) < 0)
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err(1, "lseek");
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if (read(fd, shstrtab, shdr.sh_size) != shdr.sh_size)
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err(1, "read");
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return shstrtab;
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}
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/* read string table */
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static char *
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read_string_table(int fd, struct elf_section *head, int *strtablen)
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{
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char *string_table=NULL;
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while (head) {
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if ((strcmp(head->name, ".strtab") == 0 )
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&& (head->type == SHT_STRTAB)) {
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string_table = malloc(head->size);
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if (string_table == NULL)
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errx(1, "failed to allocate %lu bytes",
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(u_long)head->size);
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if (lseek(fd, head->offset, SEEK_SET) < 0)
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err(1, "lseek");
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if (read(fd, string_table, head->size) != head->size)
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err(1, "read");
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*strtablen = head->size;
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break;
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} else {
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head = head->next;
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}
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}
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return string_table;
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}
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static int
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read_elf_header(int fd, Elf_Ehdr *ehdr)
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{
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ssize_t n;
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n = read(fd, ehdr, sizeof(*ehdr));
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if (n < 0)
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err(1, "failed reading %lu bytes", (u_long)sizeof(*ehdr));
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if (n != sizeof(*ehdr)) {
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if (debug)
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warnx("failed to read %lu bytes", (u_long)sizeof(*ehdr));
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return -1;
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}
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if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0 ||
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ehdr->e_ident[EI_CLASS] != ELFCLASS)
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errx(4, "not in ELF%u format", ELFSIZE);
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if (ehdr->e_ehsize != ELF_HDR_SIZE)
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errx(4, "file has ELF%u identity, but wrong header size",
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ELFSIZE);
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return 0;
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}
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/* offset of data segment; this is horrible, but keeps the size of the
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module to a minimum */
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static ssize_t data_offset;
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/* return size needed by the module */
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int
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elf_mod_sizes(int fd,
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size_t *modsize,
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int *strtablen,
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struct lmc_resrv *resrvp,
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struct stat *sp)
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{
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Elf_Ehdr ehdr;
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ssize_t off = 0;
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size_t data_hole = 0;
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char *shstrtab, *strtb;
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struct elf_section *head, *s;
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if (read_elf_header(fd, &ehdr) < 0)
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return -1;
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shstrtab = read_shstring_table(fd, &ehdr);
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read_sections(fd, &ehdr, shstrtab, &head);
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for (s = head; s; s = s->next) {
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if ((s->type == SHT_STRTAB) && (s->type == SHT_SYMTAB)
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&& (s->type == SHT_DYNSYM)) {
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continue;
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}
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if (debug)
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fprintf(stderr,
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"%s: addr = %p size = %#lx align = %#lx\n",
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s->name, s->addr, (u_long)s->size, (u_long)s->align);
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/* XXX try to get rid of the hole before the data
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section that GNU-ld likes to put there */
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if (strcmp(s->name, ".data") == 0 && s->addr > (void *)off) {
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#define ROUND(V, S) (((V) + (S) - 1) & ~((S) - 1))
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data_offset = ROUND(off, s->align);
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if (debug)
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fprintf(stderr, ".data section forced to "
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"offset %p (was %p)\n",
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(void *)data_offset,
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s->addr);
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/* later remove size of compressed hole from off */
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data_hole = (ssize_t)s->addr - data_offset;
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}
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off = (ssize_t)s->addr + s->size;
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}
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off -= data_hole;
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/* XXX round to pagesize? */
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*modsize = ROUND(off, sysconf(_SC_PAGESIZE));
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free(shstrtab);
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/* get string table length */
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strtb = read_string_table(fd, head, strtablen);
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free(strtb);
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/* get symbol table sections */
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resrvp->sym_symsize = 0;
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if (symtab) {
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struct elf_section *st;
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get_symtab(&head);
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for(st = head; st; st = st->next)
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resrvp->sym_symsize += st->size;
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resrvp->sym_size = resrvp->sym_symsize + *strtablen;
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} else
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resrvp->sym_size = 0;
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free_sections(head);
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return (0);
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}
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/*
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* Expected linker options:
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*
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* -R executable to link against
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* -e entry point
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* -o output file
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* -Ttext address to link text segment to in hex (assumes it's
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* a page boundary)
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* -Tdata address to link data segment to in hex
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* <target> object file
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* -T ldscript linker script (on some archs)
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*/
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#define LINKCMD "ld -R %s -e %s -o %s -Ttext %p %s"
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#define LINKCMD2 "ld -R %s -e %s -o %s -Ttext %p -Tdata %p %s"
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#define LINKSCRIPTCMD "ld -T %s -R %s -e %s -o %s -Ttext %p %s"
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#define LINKSCRIPTCMD2 "ld -T %s -R %s -e %s -o %s -Ttext %p -Tdata %p %s"
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/* make a link command; XXX if data_offset above is non-zero, force
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data address to be at start of text + offset */
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void
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elf_linkcmd(char **cmdp,
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const char *kernel,
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const char *entry,
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const char *outfile,
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const void *address,
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const char *object,
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const char *ldscript)
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{
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if (ldscript == NULL) {
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if (data_offset == 0)
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asprintf(cmdp, LINKCMD, kernel, entry,
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outfile, address, object);
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else
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asprintf(cmdp, LINKCMD2, kernel, entry,
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outfile, address,
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(const char *)address + data_offset,
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object);
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} else {
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if (data_offset == 0)
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asprintf(cmdp, LINKSCRIPTCMD, ldscript, kernel,
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entry, outfile, address, object);
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else
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asprintf(cmdp, LINKSCRIPTCMD2, ldscript, kernel,
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entry, outfile, address,
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(const char *)address + data_offset,
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object);
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}
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if (cmdp == NULL)
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err(1, "malloc");
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}
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/* load a pre-linked module; returns entry point */
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void *
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elf_mod_load(int fd)
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{
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Elf_Ehdr ehdr;
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size_t zero_size = 0;
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size_t b;
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ssize_t n;
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char *shstrtab;
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struct elf_section *head, *s;
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char buf[10 * BUFSIZ];
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void *addr = NULL;
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if (read_elf_header(fd, &ehdr) < 0)
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return NULL;
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shstrtab = read_shstring_table(fd, &ehdr);
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read_sections(fd, &ehdr, shstrtab, &head);
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for (s = head; s; s = s->next) {
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if ((s->type != SHT_STRTAB) && (s->type != SHT_SYMTAB)
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&& (s->type != SHT_DYNSYM)) {
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if (debug)
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fprintf(stderr, "loading `%s': addr = %p, "
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"size = %#lx\n",
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s->name, s->addr, (u_long)s->size);
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if (s->type == SHT_NOBITS) {
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/* skip some space */
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zero_size += s->size;
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} else {
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if (addr != NULL) {
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/* if there is a gap in the prelinked
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module, transfer some empty
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space... */
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zero_size += (char *)s->addr
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- (char *)addr;
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}
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if (zero_size) {
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loadspace(zero_size);
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zero_size = 0;
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}
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b = s->size;
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if (lseek(fd, s->offset, SEEK_SET) == -1)
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err(1, "lseek");
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while (b) {
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n = read(fd, buf, MIN(b, sizeof(buf)));
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if (n == 0)
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errx(1, "unexpected EOF");
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if (n < 0)
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err(1, "read");
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loadbuf(buf, n);
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b -= n;
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}
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addr = (char *)s->addr + s->size;
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}
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}
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}
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if (zero_size)
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loadspace(zero_size);
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free_sections(head);
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free(shstrtab);
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return (void *)ehdr.e_entry;
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}
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void
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elf_mod_symload(int strtablen)
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{
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Elf_Ehdr ehdr;
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char *shstrtab;
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struct elf_section *head, *s;
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char *symbuf, *strbuf;
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/*
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* Seek to the text offset to start loading...
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*/
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if (lseek(modfd, 0, SEEK_SET) == -1)
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err(12, "lseek");
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if (read_elf_header(modfd, &ehdr) < 0)
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return;
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shstrtab = read_shstring_table(modfd, &ehdr);
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read_sections(modfd, &ehdr, shstrtab, &head);
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for (s = head; s; s = s->next) {
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struct elf_section *p = s;
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if ((p->type == SHT_SYMTAB) || (p->type == SHT_DYNSYM)) {
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if (debug)
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fprintf(stderr, "loading `%s': addr = %p, "
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"size = %#lx\n",
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s->name, s->addr, (u_long)s->size);
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/*
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* Seek to the file offset to start loading it...
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*/
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if (lseek(modfd, p->offset, SEEK_SET) == -1)
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err(12, "lseek");
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symbuf = malloc(p->size);
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if (symbuf == 0)
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err(13, "malloc");
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if (read(modfd, symbuf, p->size) != p->size)
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err(14, "read");
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loadsym(symbuf, p->size);
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free(symbuf);
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}
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}
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for (s = head; s; s = s->next) {
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struct elf_section *p = s;
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if ((p->type == SHT_STRTAB)
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&& (strcmp(p->name, ".strtab") == 0 )) {
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if (debug)
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fprintf(stderr, "loading `%s': addr = %p, "
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"size = %#lx\n",
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s->name, s->addr, (u_long)s->size);
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/*
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* Seek to the file offset to start loading it...
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*/
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if (lseek(modfd, p->offset, SEEK_SET) == -1)
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err(12, "lseek");
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strbuf = malloc(p->size);
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if (strbuf == 0)
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err(13, "malloc");
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if (read(modfd, strbuf, p->size) != p->size)
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err(14, "read");
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loadsym(strbuf, p->size);
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free(strbuf);
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}
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}
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free(shstrtab);
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free_sections(head);
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return;
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}
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