mirror of
git://projects.qi-hardware.com/openwrt-xburst.git
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328 lines
8.3 KiB
C
328 lines
8.3 KiB
C
/* http://www.muppetlabs.com/~breadbox/software/elfkickers.html */
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/* sstrip: Copyright (C) 1999-2001 by Brian Raiter, under the GNU
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* General Public License. No warranty. See COPYING for details.
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*/
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#define __MIPSEL__ 1
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#define _MIPS_SZLONG 32
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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 <errno.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <elf.h>
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#include <linux/bitops.h>
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typedef signed char s8;
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typedef unsigned char u8;
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typedef signed short s16;
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typedef unsigned short u16;
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typedef signed int s32;
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typedef unsigned int u32;
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typedef signed long long s64;
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typedef unsigned long long u64;
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#include <asm/elf.h>
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#ifndef TRUE
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#define TRUE 1
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#define FALSE 0
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#endif
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#if ELF_CLASS == ELFCLASS32
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#define Elf_Ehdr Elf32_Ehdr
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#define Elf_Phdr Elf32_Phdr
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#else
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#define Elf_Ehdr Elf64_Ehdr
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#define Elf_Phdr Elf64_Phdr
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#endif
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/* The name of the program.
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*/
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static char const *progname;
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/* The name of the current file.
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*/
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static char const *filename;
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/* A simple error-handling function. FALSE is always returned for the
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* convenience of the caller.
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*/
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static int err(char const *errmsg)
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{
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fprintf(stderr, "%s: %s: %s\n", progname, filename, errmsg);
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return FALSE;
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}
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/* A macro for I/O errors: The given error message is used only when
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* errno is not set.
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*/
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#define ferr(msg) (err(errno ? strerror(errno) : (msg)))
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/* readelfheader() reads the ELF header into our global variable, and
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* checks to make sure that this is in fact a file that we should be
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* munging.
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*/
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static int readelfheader(int fd, Elf_Ehdr *ehdr)
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{
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errno = 0;
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if (read(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
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return ferr("missing or incomplete ELF header.");
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/* Check the ELF signature.
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*/
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if (!(ehdr->e_ident[EI_MAG0] == ELFMAG0 &&
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ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
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ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
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ehdr->e_ident[EI_MAG3] == ELFMAG3))
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return err("missing ELF signature.");
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/* Compare the file's class and endianness with the program's.
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*/
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if (ehdr->e_ident[EI_DATA] != ELF_DATA)
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return err("ELF file has different endianness.");
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if (ehdr->e_ident[EI_CLASS] != ELF_CLASS)
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return err("ELF file has different word size.");
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/* Check the target architecture.
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*/
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if (ehdr->e_machine != ELF_ARCH)
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return err("ELF file created for different architecture.");
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/* Verify the sizes of the ELF header and the program segment
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* header table entries.
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*/
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if (ehdr->e_ehsize != sizeof(Elf_Ehdr))
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return err("unrecognized ELF header size.");
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if (ehdr->e_phentsize != sizeof(Elf_Phdr))
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return err("unrecognized program segment header size.");
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/* Finally, check the file type.
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*/
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if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
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return err("not an executable or shared-object library.");
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return TRUE;
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}
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/* readphdrtable() loads the program segment header table into memory.
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*/
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static int readphdrtable(int fd, Elf_Ehdr const *ehdr, Elf_Phdr **phdrs)
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{
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size_t size;
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if (!ehdr->e_phoff || !ehdr->e_phnum)
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return err("ELF file has no program header table.");
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size = ehdr->e_phnum * sizeof **phdrs;
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if (!(*phdrs = malloc(size)))
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return err("Out of memory!");
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errno = 0;
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if (read(fd, *phdrs, size) != (ssize_t)size)
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return ferr("missing or incomplete program segment header table.");
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return TRUE;
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}
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/* getmemorysize() determines the offset of the last byte of the file
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* that is referenced by an entry in the program segment header table.
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* (Anything in the file after that point is not used when the program
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* is executing, and thus can be safely discarded.)
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*/
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static int getmemorysize(Elf_Ehdr const *ehdr, Elf_Phdr const *phdrs,
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unsigned long *newsize)
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{
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Elf32_Phdr const *phdr;
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unsigned long size, n;
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int i;
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/* Start by setting the size to include the ELF header and the
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* complete program segment header table.
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*/
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size = ehdr->e_phoff + ehdr->e_phnum * sizeof *phdrs;
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if (size < sizeof *ehdr)
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size = sizeof *ehdr;
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/* Then keep extending the size to include whatever data the
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* program segment header table references.
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*/
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for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
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if (phdr->p_type != PT_NULL) {
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n = phdr->p_offset + phdr->p_filesz;
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if (n > size)
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size = n;
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}
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}
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*newsize = size;
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return TRUE;
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}
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/* truncatezeros() examines the bytes at the end of the file's
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* size-to-be, and reduces the size to exclude any trailing zero
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* bytes.
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*/
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static int truncatezeros(int fd, unsigned long *newsize)
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{
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unsigned char contents[1024];
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unsigned long size, n;
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size = *newsize;
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do {
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n = sizeof contents;
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if (n > size)
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n = size;
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if (lseek(fd, size - n, SEEK_SET) == (off_t)-1)
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return ferr("cannot seek in file.");
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if (read(fd, contents, n) != (ssize_t)n)
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return ferr("cannot read file contents");
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while (n && !contents[--n])
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--size;
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} while (size && !n);
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/* Sanity check.
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*/
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if (!size)
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return err("ELF file is completely blank!");
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*newsize = size;
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return TRUE;
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}
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/* modifyheaders() removes references to the section header table if
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* it was stripped, and reduces program header table entries that
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* included truncated bytes at the end of the file.
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*/
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static int modifyheaders(Elf_Ehdr *ehdr, Elf_Phdr *phdrs,
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unsigned long newsize)
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{
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Elf32_Phdr *phdr;
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int i;
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/* If the section header table is gone, then remove all references
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* to it in the ELF header.
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*/
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if (ehdr->e_shoff >= newsize) {
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ehdr->e_shoff = 0;
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ehdr->e_shnum = 0;
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ehdr->e_shentsize = 0;
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ehdr->e_shstrndx = 0;
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}
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/* The program adjusts the file size of any segment that was
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* truncated. The case of a segment being completely stripped out
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* is handled separately.
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*/
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for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
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if (phdr->p_offset >= newsize) {
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phdr->p_offset = newsize;
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phdr->p_filesz = 0;
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} else if (phdr->p_offset + phdr->p_filesz > newsize) {
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phdr->p_filesz = newsize - phdr->p_offset;
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}
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}
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return TRUE;
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}
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/* commitchanges() writes the new headers back to the original file
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* and sets the file to its new size.
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*/
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static int commitchanges(int fd, Elf_Ehdr const *ehdr, Elf_Phdr *phdrs,
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unsigned long newsize)
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{
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size_t n;
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/* Save the changes to the ELF header, if any.
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*/
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if (lseek(fd, 0, SEEK_SET))
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return ferr("could not rewind file");
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errno = 0;
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if (write(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
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return err("could not modify file");
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/* Save the changes to the program segment header table, if any.
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*/
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if (lseek(fd, ehdr->e_phoff, SEEK_SET) == (off_t)-1) {
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err("could not seek in file.");
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goto warning;
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}
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n = ehdr->e_phnum * sizeof *phdrs;
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if (write(fd, phdrs, n) != (ssize_t)n) {
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err("could not write to file");
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goto warning;
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}
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/* Eleventh-hour sanity check: don't truncate before the end of
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* the program segment header table.
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*/
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if (newsize < ehdr->e_phoff + n)
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newsize = ehdr->e_phoff + n;
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/* Chop off the end of the file.
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*/
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if (ftruncate(fd, newsize)) {
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err("could not resize file");
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goto warning;
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}
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return TRUE;
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warning:
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return err("ELF file may have been corrupted!");
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}
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/* main() loops over the cmdline arguments, leaving all the real work
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* to the other functions.
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*/
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int main(int argc, char *argv[])
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{
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int fd;
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Elf_Ehdr ehdr;
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Elf_Phdr *phdrs;
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unsigned long newsize;
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char **arg;
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int failures = 0;
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if (argc < 2 || argv[1][0] == '-') {
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printf("Usage: sstrip FILE...\n"
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"sstrip discards all nonessential bytes from an executable.\n\n"
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"Version 2.0 Copyright (C) 2000,2001 Brian Raiter.\n"
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"This program is free software, licensed under the GNU\n"
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"General Public License. There is absolutely no warranty.\n");
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return EXIT_SUCCESS;
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}
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progname = argv[0];
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for (arg = argv + 1 ; *arg != NULL ; ++arg) {
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filename = *arg;
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fd = open(*arg, O_RDWR);
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if (fd < 0) {
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ferr("can't open");
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++failures;
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continue;
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}
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if (!(readelfheader(fd, &ehdr) &&
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readphdrtable(fd, &ehdr, &phdrs) &&
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getmemorysize(&ehdr, phdrs, &newsize) &&
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truncatezeros(fd, &newsize) &&
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modifyheaders(&ehdr, phdrs, newsize) &&
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commitchanges(fd, &ehdr, phdrs, newsize)))
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++failures;
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close(fd);
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}
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return failures ? EXIT_FAILURE : EXIT_SUCCESS;
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}
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