sstrip

git-svn-id: svn://svn.openwrt.org/openwrt/trunk/openwrt@282 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/openwrt/openwrt.mk

@@ -144,9 +144,23 @@ openwrt-addpattern: $(OPENWRT_ADDPATTERN_TARGET)
 openwrt-addpattern-clean: 
 	rm $(OPENWRT_ADDPATTERN_TARGET)
 
+# sstrip tool
+OPENWRT_SSTRIP_SOURCE=package/openwrt/sstrip.c
+OPENWRT_SSTRIP_TARGET=$(STAGING_DIR)/bin/sstrip
+
+$(OPENWRT_SSTRIP_TARGET):
+		$(CC) -o $(OPENWRT_SSTRIP_TARGET) $(OPENWRT_SSTRIP_SOURCE)
+
+openwrt-sstrip: $(OPENWRT_SSTRIP_TARGET)
+
+openwrt-sstrip-clean:
+	rm $(OPENWRT_SSTRIP_TARGET)
+
+STRIP=$(OPENWRT_SSTRIP_TARGET)
+
 linksys:	linksys-shared linksys-nvram linksys-wlconf
 
-openwrt:	linksys openwrt-mtd openwrt-trx openwrt-addpattern openwrt-jffs2root
+openwrt:	linksys openwrt-mtd openwrt-trx openwrt-addpattern openwrt-jffs2root openwrt-sstrip-clean
 
 openwrt-dirclean: linksys-shared-dirclean linksys-nvram-dirclean linksys-wlconf-dirclean
 

package/openwrt/sstrip.c

@@ -0,0 +1,483 @@
+/* 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>
+#ifdef __FreeBSD__
+/**
+ * This seems to work on FreeBSD 5.3, should
+ * work on all newer versions as well. I have
+ * no idea if it will work on versions < 5.3
+ *
+ * Joe Estock (guru) <jestock at nutextonline.com>
+ */
+#include <sys/endian.h>
+#define bswap_64 __bswap64
+#define bswap_32 __bswap32
+#define bswap_16 __bswap16
+#else
+#include	<endian.h>
+#include	<byteswap.h>
+#endif /* defined(__FreeBSD__) */
+
+
+#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;
+}