--- /dev/null
+/* 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 %d\n", \
+ progname, filename, 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 %d\n", \
+ progname, filename, 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) \
+ != 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; \
+ int 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; \
+ int 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,0); \
+ 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) != 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;
+}
projects / buildroot.git / commitdiff