linux c elf文件格式操作之sstrip源码（支持cygwin编译）

202年的strip.c 支持linux 32位系统的elf32

/* sstrip: Copyright (C) 1999-2001 by Brian Raiter, under the GNU
* General Public License. No warranty. See COPYING for details.
*/

#include        <stdio.h>
#include        <stdlib.h>
#include        <string.h>
#include        <errno.h>
#include        <unistd.h>
#include        <fcntl.h>
#include        <elf.h>
//#include        <asm/elf.h>

//asm/elf.h
#define EM_linux_i386 3
#define EM_ARM 40

#define EF_ARM_APCS26 0x08
#define EF_ARM_SOFT_FLOAT 0x200
#define EF_ARM_EABI_MASK 0xFF000000

#define R_ARM_NONE 0
#define R_ARM_PC24 1
#define R_ARM_ABS32 2
#define R_ARM_CALL 28
#define R_ARM_JUMP24 29

#define ELF_CLASS ELFCLASS32
#ifdef __ARMEB__
#define ELF_DATA ELFDATA2MSB
#else
#define ELF_DATA ELFDATA2LSB
#endif

#define ELF_ARCH EM_linux_i386

#ifndef TRUE
#define TRUE            1
#define FALSE           0
#endif

#if ELF_CLASS == ELFCLASS32
#define Elf_Ehdr        Elf32_Ehdr
#define Elf_Phdr        Elf32_Phdr
#else
#define Elf_Ehdr        Elf64_Ehdr
#define Elf_Phdr        Elf64_Phdr
#endif

/* The name of the program.
*/
static char const      *progname;

/* The name of the current file.
*/
static char const      *filename;

/* A simple error-handling function. FALSE is always returned for the
* convenience of the caller.
*/
static int err(char const *errmsg)
{
fprintf(stderr, "%s: %s: %s\n", progname, filename, errmsg);
return FALSE;
}

/* A macro for I/O errors: The given error message is used only when
* errno is not set.
*/
#define ferr(msg)       (err(errno ? strerror(errno) : (msg)))

/* readelfheader() reads the ELF header into our global variable, and
* checks to make sure that this is in fact a file that we should be
* munging.
*/
static int readelfheader(int fd, Elf_Ehdr *ehdr)
{
errno = 0;
if (read(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
return ferr("missing or incomplete ELF header.");

/* Check the ELF signature.
*/
if (!(ehdr->e_ident[EI_MAG0] == ELFMAG0 &&
ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
ehdr->e_ident[EI_MAG3] == ELFMAG3))
return err("missing ELF signature.");

/* Compare the file's class and endianness with the program's.
*/
if (ehdr->e_ident[EI_DATA] != ELF_DATA)
return err("ELF file has different endianness.");
if (ehdr->e_ident[EI_CLASS] != ELF_CLASS)
return err("ELF file has different word size.");

/* Check the target architecture.
*/
if (ehdr->e_machine != ELF_ARCH)
{
printf("==%d\n",ehdr->e_machine);
return err("ELF file created for different architecture.");
}

/* Verify the sizes of the ELF header and the program segment
* header table entries.
*/
if (ehdr->e_ehsize != sizeof(Elf_Ehdr))
return err("unrecognized ELF header size.");
if (ehdr->e_phentsize != sizeof(Elf_Phdr))
return err("unrecognized program segment header size.");

/* Finally, check the file type.
*/
if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
return err("not an executable or shared-object library.");

return TRUE;
}

/* readphdrtable() loads the program segment header table into memory.
*/
static int readphdrtable(int fd, Elf_Ehdr const *ehdr, Elf_Phdr **phdrs)
{
size_t      size;

if (!ehdr->e_phoff || !ehdr->e_phnum)
return err("ELF file has no program header table.");

size = ehdr->e_phnum * sizeof **phdrs;
if (!(*phdrs = malloc(size)))
return err("Out of memory!");

errno = 0;
if (read(fd, *phdrs, size) != (ssize_t)size)
return ferr("missing or incomplete program segment header table.");

return TRUE;
}

/* getmemorysize() determines the offset of the last byte of the file
* that is referenced by an entry in the program segment header table.
* (Anything in the file after that point is not used when the program
* is executing, and thus can be safely discarded.)
*/
static int getmemorysize(Elf_Ehdr const *ehdr, Elf_Phdr const *phdrs,
unsigned long *newsize)
{
Elf32_Phdr const   *phdr;
unsigned long       size, n;
int                 i;

/* Start by setting the size to include the ELF header and the
* complete program segment header table.
*/
size = ehdr->e_phoff + ehdr->e_phnum * sizeof *phdrs;
if (size < sizeof *ehdr)
size = sizeof *ehdr;

/* Then keep extending the size to include whatever data the
* program segment header table references.
*/
for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
if (phdr->p_type != PT_NULL) {
n = phdr->p_offset + phdr->p_filesz;
if (n > size)
size = n;
}
}

*newsize = size;
return TRUE;
}

/* truncatezeros() examines the bytes at the end of the file's
* size-to-be, and reduces the size to exclude any trailing zero
* bytes.
*/
static int truncatezeros(int fd, unsigned long *newsize)
{
unsigned char       contents[1024];
unsigned long       size, n;

size = *newsize;
do {
n = sizeof contents;
if (n > size)
n = size;
if (lseek(fd, size - n, SEEK_SET) == (off_t)-1)
return ferr("cannot seek in file.");
if (read(fd, contents, n) != (ssize_t)n)
return ferr("cannot read file contents");
while (n && !contents[--n])
--size;
} while (size && !n);

/* Sanity check.
*/
if (!size)
return err("ELF file is completely blank!");

*newsize = size;
return TRUE;
}

/* modifyheaders() removes references to the section header table if
* it was stripped, and reduces program header table entries that
* included truncated bytes at the end of the file.
*/
static int modifyheaders(Elf_Ehdr *ehdr, Elf_Phdr *phdrs,
unsigned long newsize)
{
Elf32_Phdr *phdr;
int         i;

/* If the section header table is gone, then remove all references
* to it in the ELF header.
*/
if (ehdr->e_shoff >= newsize) {
ehdr->e_shoff = 0;
ehdr->e_shnum = 0;
ehdr->e_shentsize = 0;
ehdr->e_shstrndx = 0;
}

/* The program adjusts the file size of any segment that was
* truncated. The case of a segment being completely stripped out
* is handled separately.
*/
for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
if (phdr->p_offset >= newsize) {
phdr->p_offset = newsize;
phdr->p_filesz = 0;
} else if (phdr->p_offset + phdr->p_filesz > newsize) {
phdr->p_filesz = newsize - phdr->p_offset;
}
}

return TRUE;
}

/* commitchanges() writes the new headers back to the original file
* and sets the file to its new size.
*/
static int commitchanges(int fd, Elf_Ehdr const *ehdr, Elf_Phdr *phdrs,
unsigned long newsize)
{
size_t      n;

/* Save the changes to the ELF header, if any.
*/
if (lseek(fd, 0, SEEK_SET))
return ferr("could not rewind file");
errno = 0;
if (write(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
return err("could not modify file");

/* Save the changes to the program segment header table, if any.
*/
if (lseek(fd, ehdr->e_phoff, SEEK_SET) == (off_t)-1) {
err("could not seek in file.");
goto warning;
}
n = ehdr->e_phnum * sizeof *phdrs;
if (write(fd, phdrs, n) != (ssize_t)n) {
err("could not write to file");
goto warning;
}

/* Eleventh-hour sanity check: don't truncate before the end of
* the program segment header table.
*/
if (newsize < ehdr->e_phoff + n)
newsize = ehdr->e_phoff + n;

/* Chop off the end of the file.
*/
if (ftruncate(fd, newsize)) {
err("could not resize file");
goto warning;
}

return TRUE;

warning:
return err("ELF file may have been corrupted!");
}

/* main() loops over the cmdline arguments, leaving all the real work
* to the other functions.
*/
int main(int argc, char *argv[])
{
int                 fd;
Elf_Ehdr            ehdr;
Elf_Phdr           *phdrs;
unsigned long       newsize;
char              **arg;
int                 failures = 0;

if (argc < 2 || argv[1][0] == '-') {
printf("Usage: sstrip FILE...\n"
"sstrip discards all nonessential bytes from an executable.\n\n"
"Version 2.0 Copyright (C) 2000,2001 Brian Raiter.\n"
"This program is free software, licensed under the GNU\n"
"General Public License. There is absolutely no warranty.\n");
return EXIT_SUCCESS;
}

progname = argv[0];

for (arg = argv + 1 ; *arg != NULL ; ++arg) {
filename = *arg;

fd = open(*arg, O_RDWR);
if (fd < 0) {
ferr("can't open");
++failures;
continue;
}

if (!(readelfheader(fd, &ehdr)                  &&
readphdrtable(fd, &ehdr, &phdrs)          &&
getmemorysize(&ehdr, phdrs, &newsize)     &&
truncatezeros(fd, &newsize)               &&
modifyheaders(&ehdr, phdrs, newsize)      &&
commitchanges(fd, &ehdr, phdrs, newsize)))
++failures;

close(fd);
}

return failures ? EXIT_FAILURE : EXIT_SUCCESS;
}

/*
vi:ts=8:et:nowrap
*/

支持elf64

/* sstrip: Copyright (C) 1999-2001 by Brian Raiter, under the GNU
* General Public License. No warranty. See COPYING for details.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <elf.h>

//asm/elf.h
#define EM_linux_x64 62
#define EM_ARM 40

#define ELF_CLASS ELFCLASS64

#ifdef __ARMEB__
#define ELF_DATA ELFDATA2MSB
#else
#define ELF_DATA ELFDATA2LSB
#endif

#define ELF_ARCH EM_linux_x64

#ifndef TRUE
#define TRUE 1
#define FALSE 0
#endif

#if 0
#define Elf_Ehdr Elf32_Ehdr
#define Elf_Phdr Elf32_Phdr
#else
#define Elf_Ehdr Elf64_Ehdr
#define Elf_Phdr Elf64_Phdr
#endif

/* The name of the program.
*/
static char const *progname;

/* The name of the current file.
*/
static char const *filename;

/* A simple error-handling function. FALSE is always returned for the
* convenience of the caller.
*/
static int err(char const *errmsg)
{
fprintf(stderr, "%s: %s: %s\n", progname, filename, errmsg);
return FALSE;
}

/* A macro for I/O errors: The given error message is used only when
* errno is not set.
*/
#define ferr(msg) (err(errno ? strerror(errno) : (msg)))

/* readelfheader() reads the ELF header into our global variable, and
* checks to make sure that this is in fact a file that we should be
* munging.
*/
static int readelfheader(int fd, Elf_Ehdr *ehdr)
{
errno = 0;
if (read(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
return ferr("missing or incomplete ELF header.");

/* Check the ELF signature.
*/
if (!(ehdr->e_ident[EI_MAG0] == ELFMAG0 &&
ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
ehdr->e_ident[EI_MAG3] == ELFMAG3))
return err("missing ELF signature.");

/* Compare the file's class and endianness with the program's.
*/
if (ehdr->e_ident[EI_DATA] != ELF_DATA)
return err("ELF file has different endianness.");
if (ehdr->e_ident[EI_CLASS] != ELF_CLASS)
return err("ELF file has different word size.");

/* Check the target architecture.
*/
if (ehdr->e_machine != ELF_ARCH)
{
printf("==%d\n",ehdr->e_machine);
return err("ELF file created for different architecture.");
}

/* Verify the sizes of the ELF header and the program segment
* header table entries.
*/
if (ehdr->e_ehsize != sizeof(Elf_Ehdr))
return err("unrecognized ELF header size.");
if (ehdr->e_phentsize != sizeof(Elf_Phdr))
return err("unrecognized program segment header size.");

/* Finally, check the file type.
*/
if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
return err("not an executable or shared-object library.");

return TRUE;
}

/* readphdrtable() loads the program segment header table into memory.
*/
static int readphdrtable(int fd, Elf_Ehdr const *ehdr, Elf_Phdr **phdrs)
{
size_t size;

if (!ehdr->e_phoff || !ehdr->e_phnum)
return err("ELF file has no program header table.");

size = ehdr->e_phnum * sizeof **phdrs;
if (!(*phdrs = malloc(size)))
return err("Out of memory!");

errno = 0;
if (read(fd, *phdrs, size) != (ssize_t)size)
return ferr("missing or incomplete program segment header table.");

return TRUE;
}

/* getmemorysize() determines the offset of the last byte of the file
* that is referenced by an entry in the program segment header table.
* (Anything in the file after that point is not used when the program
* is executing, and thus can be safely discarded.)
*/
static int getmemorysize(Elf_Ehdr const *ehdr, Elf_Phdr const *phdrs,
unsigned long *newsize)
{
Elf64_Phdr const *phdr;
unsigned long size, n;
int i;

/* Start by setting the size to include the ELF header and the
* complete program segment header table.
*/
size = ehdr->e_phoff + ehdr->e_phnum * sizeof *phdrs;
if (size < sizeof *ehdr)
size = sizeof *ehdr;

/* Then keep extending the size to include whatever data the
* program segment header table references.
*/
for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
if (phdr->p_type != PT_NULL) {
n = phdr->p_offset + phdr->p_filesz;
if (n > size)
size = n;
}
}

*newsize = size;
return TRUE;
}

/* truncatezeros() examines the bytes at the end of the file's
* size-to-be, and reduces the size to exclude any trailing zero
* bytes.
*/
static int truncatezeros(int fd, unsigned long *newsize)
{
unsigned char contents[1024];
unsigned long size, n;

size = *newsize;
do {
n = sizeof contents;
if (n > size)
n = size;
if (lseek(fd, size - n, SEEK_SET) == (off_t)-1)
return ferr("cannot seek in file.");
if (read(fd, contents, n) != (ssize_t)n)
return ferr("cannot read file contents");
while (n && !contents[--n])
--size;
} while (size && !n);

/* Sanity check.
*/
if (!size)
return err("ELF file is completely blank!");

*newsize = size;
return TRUE;
}

/* modifyheaders() removes references to the section header table if
* it was stripped, and reduces program header table entries that
* included truncated bytes at the end of the file.
*/
static int modifyheaders(Elf_Ehdr *ehdr, Elf_Phdr *phdrs,
unsigned long newsize)
{
Elf32_Phdr *phdr;
int i;

/* If the section header table is gone, then remove all references
* to it in the ELF header.
*/
if (ehdr->e_shoff >= newsize) {
ehdr->e_shoff = 0;
ehdr->e_shnum = 0;
ehdr->e_shentsize = 0;
ehdr->e_shstrndx = 0;
}

/* The program adjusts the file size of any segment that was
* truncated. The case of a segment being completely stripped out
* is handled separately.
*/
for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
if (phdr->p_offset >= newsize) {
phdr->p_offset = newsize;
phdr->p_filesz = 0;
} else if (phdr->p_offset + phdr->p_filesz > newsize) {
phdr->p_filesz = newsize - phdr->p_offset;
}
}

return TRUE;
}

/* commitchanges() writes the new headers back to the original file
* and sets the file to its new size.
*/
static int commitchanges(int fd, Elf_Ehdr const *ehdr, Elf_Phdr *phdrs,
unsigned long newsize)
{
size_t n;

/* Save the changes to the ELF header, if any.
*/
if (lseek(fd, 0, SEEK_SET))
return ferr("could not rewind file");
errno = 0;
if (write(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
return err("could not modify file");

/* Save the changes to the program segment header table, if any.
*/
if (lseek(fd, ehdr->e_phoff, SEEK_SET) == (off_t)-1) {
err("could not seek in file.");
goto warning;
}
n = ehdr->e_phnum * sizeof *phdrs;
if (write(fd, phdrs, n) != (ssize_t)n) {
err("could not write to file");
goto warning;
}

/* Eleventh-hour sanity check: don't truncate before the end of
* the program segment header table.
*/
if (newsize < ehdr->e_phoff + n)
newsize = ehdr->e_phoff + n;

/* Chop off the end of the file.
*/
if (ftruncate(fd, newsize)) {
err("could not resize file");
goto warning;
}

return TRUE;

warning:
return err("ELF file may have been corrupted!");
}

/* main() loops over the cmdline arguments, leaving all the real work
* to the other functions.
*/
int main(int argc, char *argv[])
{
int fd;
Elf_Ehdr ehdr;
Elf_Phdr *phdrs;
unsigned long newsize;
char **arg;
int failures = 0;

if (argc < 2 || argv[1][0] == '-') {
printf("Usage: sstrip FILE...\n"
"sstrip discards all nonessential bytes from an executable.\n\n"
"Version 2.0 Copyright (C) 2000,2001 Brian Raiter.\n"
"This program is free software, licensed under the GNU\n"
"General Public License. There is absolutely no warranty.\n");
return EXIT_SUCCESS;
}

progname = argv[0];

for (arg = argv + 1 ; *arg != NULL ; ++arg) {
filename = *arg;

fd = open(*arg, O_RDWR);
if (fd < 0) {
ferr("can't open");
++failures;
continue;
}

if (!(readelfheader(fd, &ehdr) &&
readphdrtable(fd, &ehdr, &phdrs) &&
getmemorysize(&ehdr, phdrs, &newsize) &&
truncatezeros(fd, &newsize) &&
modifyheaders(&ehdr, phdrs, newsize) &&
commitchanges(fd, &ehdr, phdrs, newsize)))
++failures;

close(fd);
}

return failures ? EXIT_FAILURE : EXIT_SUCCESS;
}

/*
vi:ts=8:et:nowrap
*/


2013年源码

/* http://www.muppetlabs.com/~breadbox/software/elfkickers.html */

/* sstrip: Copyright (C) 1999-2001 by Brian Raiter, under the GNU
* General Public License. No warranty. See COPYING for details.
*
* Aug 23, 2004 Hacked by Manuel Novoa III <mjn3@codepoet.org> to
* handle targets of different endianness and/or elf class, making
* it more useful in a cross-devel environment.
*/

/* ============== original README ===================
*
* sstrip is a small utility that removes the contents at the end of an
* ELF file that are not part of the program's memory image.
*
* Most ELF executables are built with both a program header table and a
* section header table. However, only the former is required in order
* for the OS to load, link and execute a program. sstrip attempts to
* extract the ELF header, the program header table, and its contents,
* leaving everything else in the bit bucket. It can only remove parts of
* the file that occur at the end, after the parts to be saved. However,
* this almost always includes the section header table, and occasionally
* a few random sections that are not used when running a program.
*
* It should be noted that the GNU bfd library is (understandably)
* dependent on the section header table as an index to the file's
* contents. Thus, an executable file that has no section header table
* cannot be used with gdb, objdump, or any other program based upon the
* bfd library, at all. In fact, the program will not even recognize the
* file as a valid executable. (This limitation is noted in the source
* code comments for bfd, and is marked "FIXME", so this may change at
* some future date. However, I would imagine that it is a pretty
* low-priority item, as executables without a section header table are
* rare in the extreme.) This probably also explains why strip doesn't
* offer the option to do this.
*
* Shared library files may also have their section header table removed.
* Such a library will still function; however, it will no longer be
* possible for a compiler to link a new program against it.
*
* As an added bonus, sstrip also tries to removes trailing zero bytes
* from the end of the file. (This normally cannot be done with an
* executable that has a section header table.)
*
* sstrip is a very simplistic program. It depends upon the common
* practice of putting the parts of the file that contribute to the
* memory image at the front, and the remaining material at the end. This
* permits it to discard the latter material without affecting file
* offsets and memory addresses in what remains. Of course, the ELF
* standard permits files to be organized in almost any order, so if a
* pathological linker decided to put its section headers at the top,
* sstrip would be useless on such executables.
*/

#include    <stdio.h>
#include    <stdlib.h>
#include    <string.h>
#include    <errno.h>
#include    <unistd.h>
#include    <fcntl.h>
#include    <elf.h>
#include    <endian.h>
#include    <byteswap.h>

#ifndef TRUE
#define TRUE        1
#define FALSE       0
#endif

/* The name of the program.
*/
static char const   *progname;

/* The name of the current file.
*/
static char const   *filename;

/* A simple error-handling function. FALSE is always returned for the
* convenience of the caller.
*/
static int err(char const *errmsg)
{
fprintf(stderr, "%s: %s: %s\n", progname, filename, errmsg);
return FALSE;
}

/* A flag to signal the need for endian reversal.
*/
static int do_reverse_endian;

/* Get a value from the elf header, compensating for endianness.
*/
#define EGET(X) \
(__extension__ ({ \
uint64_t __res; \
if (!do_reverse_endian) { \
__res = (X); \
} else if (sizeof(X) == 1) { \
__res = (X); \
} else if (sizeof(X) == 2) { \
__res = bswap_16((X)); \
} else if (sizeof(X) == 4) { \
__res = bswap_32((X)); \
} else if (sizeof(X) == 8) { \
__res = bswap_64((X)); \
} else { \
fprintf(stderr, "%s: %s: EGET failed for size %ld\n", \
progname, filename, (long) sizeof(X)); \
exit(EXIT_FAILURE); \
} \
__res; \
}))

/* Set a value 'Y' in the elf header to 'X', compensating for endianness.
*/
#define ESET(Y,X) \
do if (!do_reverse_endian) { \
Y = (X); \
} else if (sizeof(Y) == 1) { \
Y = (X); \
} else if (sizeof(Y) == 2) { \
Y = bswap_16((uint16_t)(X)); \
} else if (sizeof(Y) == 4) { \
Y = bswap_32((uint32_t)(X)); \
} else if (sizeof(Y) == 8) { \
Y = bswap_64((uint64_t)(X)); \
} else { \
fprintf(stderr, "%s: %s: ESET failed for size %ld\n", \
progname, filename, (long) sizeof(Y)); \
exit(EXIT_FAILURE); \
} while (0)

/* A macro for I/O errors: The given error message is used only when
* errno is not set.
*/
#define ferr(msg)   (err(errno ? strerror(errno) : (msg)))

#define HEADER_FUNCTIONS(CLASS) \
\
/* readelfheader() reads the ELF header into our global variable, and \
* checks to make sure that this is in fact a file that we should be \
* munging. \
*/ \
static int readelfheader ## CLASS (int fd, Elf ## CLASS ## _Ehdr *ehdr) \
{ \
if (read(fd, ((char *)ehdr)+EI_NIDENT, sizeof(*ehdr) - EI_NIDENT) \
!= (ssize_t)sizeof(*ehdr) - EI_NIDENT) \
return ferr("missing or incomplete ELF header."); \
\
/* Verify the sizes of the ELF header and the program segment \
* header table entries. \
*/ \
if (EGET(ehdr->e_ehsize) != sizeof(Elf ## CLASS ## _Ehdr)) \
return err("unrecognized ELF header size."); \
if (EGET(ehdr->e_phentsize) != sizeof(Elf ## CLASS ## _Phdr)) \
return err("unrecognized program segment header size."); \
\
/* Finally, check the file type. \
*/ \
if (EGET(ehdr->e_type) != ET_EXEC && EGET(ehdr->e_type) != ET_DYN) \
return err("not an executable or shared-object library."); \
\
return TRUE; \
} \
\
/* readphdrtable() loads the program segment header table into memory. \
*/ \
static int readphdrtable ## CLASS (int fd, Elf ## CLASS ## _Ehdr const *ehdr, \
Elf ## CLASS ## _Phdr **phdrs) \
{ \
size_t  size; \
\
if (!EGET(ehdr->e_phoff) || !EGET(ehdr->e_phnum) \
)       return err("ELF file has no program header table."); \
\
size = EGET(ehdr->e_phnum) * sizeof **phdrs; \
if (!(*phdrs = malloc(size))) \
return err("Out of memory!"); \
\
errno = 0; \
if (read(fd, *phdrs, size) != (ssize_t)size) \
return ferr("missing or incomplete program segment header table."); \
\
return TRUE; \
} \
\
/* getmemorysize() determines the offset of the last byte of the file \
* that is referenced by an entry in the program segment header table. \
* (Anything in the file after that point is not used when the program \
* is executing, and thus can be safely discarded.) \
*/ \
static int getmemorysize ## CLASS (Elf ## CLASS ## _Ehdr const *ehdr, \
Elf ## CLASS ## _Phdr const *phdrs, \
unsigned long *newsize) \
{ \
Elf ## CLASS ## _Phdr const   *phdr; \
unsigned long   size, n; \
size_t          i; \
\
/* Start by setting the size to include the ELF header and the \
* complete program segment header table. \
*/ \
size = EGET(ehdr->e_phoff) + EGET(ehdr->e_phnum) * sizeof *phdrs; \
if (size < sizeof *ehdr) \
size = sizeof *ehdr; \
\
/* Then keep extending the size to include whatever data the \
* program segment header table references. \
*/ \
for (i = 0, phdr = phdrs ; i < EGET(ehdr->e_phnum) ; ++i, ++phdr) { \
if (EGET(phdr->p_type) != PT_NULL) { \
n = EGET(phdr->p_offset) + EGET(phdr->p_filesz); \
if (n > size) \
size = n; \
} \
} \
\
*newsize = size; \
return TRUE; \
} \
\
/* modifyheaders() removes references to the section header table if \
* it was stripped, and reduces program header table entries that \
* included truncated bytes at the end of the file. \
*/ \
static int modifyheaders ## CLASS (Elf ## CLASS ## _Ehdr *ehdr, \
Elf ## CLASS ## _Phdr *phdrs, \
unsigned long newsize) \
{ \
Elf ## CLASS ## _Phdr *phdr; \
size_t  i; \
\
/* If the section header table is gone, then remove all references \
* to it in the ELF header. \
*/ \
if (EGET(ehdr->e_shoff) >= newsize) { \
ESET(ehdr->e_shoff,0); \
ESET(ehdr->e_shnum,0); \
ESET(ehdr->e_shentsize,sizeof(Elf ## CLASS ## _Shdr)); \
ESET(ehdr->e_shstrndx,0); \
} \
\
/* The program adjusts the file size of any segment that was \
* truncated. The case of a segment being completely stripped out \
* is handled separately. \
*/ \
for (i = 0, phdr = phdrs ; i < EGET(ehdr->e_phnum) ; ++i, ++phdr) { \
if (EGET(phdr->p_offset) >= newsize) { \
ESET(phdr->p_offset,newsize); \
ESET(phdr->p_filesz,0); \
} else if (EGET(phdr->p_offset) + EGET(phdr->p_filesz) > newsize) { \
newsize -= EGET(phdr->p_offset); \
ESET(phdr->p_filesz, newsize); \
} \
} \
\
return TRUE; \
} \
\
/* commitchanges() writes the new headers back to the original file \
* and sets the file to its new size. \
*/ \
static int commitchanges ## CLASS (int fd, Elf ## CLASS ## _Ehdr const *ehdr, \
Elf ## CLASS ## _Phdr *phdrs, \
unsigned long newsize) \
{ \
size_t  n; \
\
/* Save the changes to the ELF header, if any. \
*/ \
if (lseek(fd, 0, SEEK_SET)) \
return ferr("could not rewind file"); \
errno = 0; \
if (write(fd, ehdr, sizeof *ehdr) != (ssize_t)sizeof *ehdr) \
return err("could not modify file"); \
\
/* Save the changes to the program segment header table, if any. \
*/ \
if (lseek(fd, EGET(ehdr->e_phoff), SEEK_SET) == (off_t)-1) { \
err("could not seek in file."); \
goto warning; \
} \
n = EGET(ehdr->e_phnum) * sizeof *phdrs; \
if (write(fd, phdrs, n) != (ssize_t)n) { \
err("could not write to file"); \
goto warning; \
} \
\
/* Eleventh-hour sanity check: don't truncate before the end of \
* the program segment header table. \
*/ \
if (newsize < EGET(ehdr->e_phoff) + n) \
newsize = EGET(ehdr->e_phoff) + n; \
\
/* Chop off the end of the file. \
*/ \
if (ftruncate(fd, newsize)) { \
err("could not resize file"); \
goto warning; \
} \
\
return TRUE; \
\
warning: \
return err("ELF file may have been corrupted!"); \
}

/* First elements of Elf32_Ehdr and Elf64_Ehdr are common.
*/
static int readelfheaderident(int fd, Elf32_Ehdr *ehdr)
{
errno = 0;
if (read(fd, ehdr, EI_NIDENT) != EI_NIDENT)
return ferr("missing or incomplete ELF header.");

/* Check the ELF signature.
*/
if (!(ehdr->e_ident[EI_MAG0] == ELFMAG0 &&
ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
ehdr->e_ident[EI_MAG3] == ELFMAG3))
{
err("missing ELF signature.");
return -1;
}

/* Compare the file's class and endianness with the program's.
*/
#if __BYTE_ORDER == __LITTLE_ENDIAN
if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB) {
do_reverse_endian = 0;
} else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) {
/*      fprintf(stderr, "ELF file has different endianness.\n"); */
do_reverse_endian = 1;
}
#elif __BYTE_ORDER == __BIG_ENDIAN
if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB) {
/*      fprintf(stderr, "ELF file has different endianness.\n"); */
do_reverse_endian = 1;
} else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) {
do_reverse_endian = 0;
}
#else
#error unkown endianness
#endif
else {
err("Unsupported endianness");
return -1;
}

/* Check the target architecture.
*/
/*   if (EGET(ehdr->e_machine) != ELF_ARCH) { */
/*      /\* return err("ELF file created for different architecture."); *\/ */
/*      fprintf(stderr, "ELF file created for different architecture.\n"); */
/*  } */
return ehdr->e_ident[EI_CLASS];
}

HEADER_FUNCTIONS(32)

HEADER_FUNCTIONS(64)

/* truncatezeros() examines the bytes at the end of the file's
* size-to-be, and reduces the size to exclude any trailing zero
* bytes.
*/
static int truncatezeros(int fd, unsigned long *newsize)
{
unsigned char   contents[1024];
unsigned long   size, n;

size = *newsize;
do {
n = sizeof contents;
if (n > size)
n = size;
if (lseek(fd, size - n, SEEK_SET) == (off_t)-1)
return ferr("cannot seek in file.");
if (read(fd, contents, n) != (ssize_t)n)
return ferr("cannot read file contents");
while (n && !contents[--n])
--size;
} while (size && !n);

/* Sanity check.
*/
if (!size)
return err("ELF file is completely blank!");

*newsize = size;
return TRUE;
}

/* main() loops over the cmdline arguments, leaving all the real work
* to the other functions.
*/
int main(int argc, char *argv[])
{
int             fd;
union {
Elf32_Ehdr  ehdr32;
Elf64_Ehdr  ehdr64;
} e;
union {
Elf32_Phdr  *phdrs32;
Elf64_Phdr  *phdrs64;
} p;
unsigned long   newsize;
char            **arg;
int             failures = 0;

if (argc < 2 || argv[1][0] == '-') {
printf("Usage: sstrip FILE...\n"
"sstrip discards all nonessential bytes from an executable.\n\n"
"Version 2.0-X Copyright (C) 2000,2001 Brian Raiter.\n"
"Cross-devel hacks Copyright (C) 2004 Manuel Novoa III.\n"
"This program is free software, licensed under the GNU\n"
"General Public License. There is absolutely no warranty.\n");
return EXIT_SUCCESS;
}

progname = argv[0];

for (arg = argv + 1 ; *arg != NULL ; ++arg) {
filename = *arg;

fd = open(*arg, O_RDWR);
if (fd < 0) {
ferr("can't open");
++failures;
continue;
}

switch (readelfheaderident(fd, &e.ehdr32)) {
case ELFCLASS32:
if (!(readelfheader32(fd, &e.ehdr32)                    &&
readphdrtable32(fd, &e.ehdr32, &p.phdrs32)        &&
getmemorysize32(&e.ehdr32, p.phdrs32, &newsize)   &&
truncatezeros(fd, &newsize)                       &&
modifyheaders32(&e.ehdr32, p.phdrs32, newsize)    &&
commitchanges32(fd, &e.ehdr32, p.phdrs32, newsize)))
++failures;
break;
case ELFCLASS64:
if (!(readelfheader64(fd, &e.ehdr64)                    &&
readphdrtable64(fd, &e.ehdr64, &p.phdrs64)        &&
getmemorysize64(&e.ehdr64, p.phdrs64, &newsize)   &&
truncatezeros(fd, &newsize)                       &&
modifyheaders64(&e.ehdr64, p.phdrs64, newsize)    &&
commitchanges64(fd, &e.ehdr64, p.phdrs64, newsize)))
++failures;
break;
default:
++failures;
break;
}
close(fd);
}

return failures ? EXIT_FAILURE : EXIT_SUCCESS;
}

/*
vi:ts=4:et:nowrap
*/