libelf_open.c

/*-
 * Copyright (c) 2006,2008-2011 Joseph Koshy
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <errno.h>
#include <libelf.h>
#include <stdlib.h>
#include <unistd.h>

#include "_libelf.h"

#if	ELFTC_HAVE_MMAP
#include <sys/mman.h>
#endif

ELFTC_VCSID("$Id: libelf_open.c 3007 2014-03-22 08:10:14Z jkoshy $");

#define	_LIBELF_INITSIZE	(64*1024)

/*
 * Read from a device file, pipe or socket.
 */
static void *
_libelf_read_special_file(int fd, size_t *fsz)
{
	ssize_t readsz;
	size_t bufsz, datasz;
	unsigned char *buf, *t;

	datasz = 0;
	readsz = 0;
	bufsz = _LIBELF_INITSIZE;
	if ((buf = malloc(bufsz)) == NULL)
		goto resourceerror;

	/*
	 * Read data from the file descriptor till we reach EOF, or
	 * till an error is encountered.
	 */
	do {
		/* Check if we need to expand the data buffer. */
		if (datasz == bufsz) {
			bufsz *= 2;
			if ((t = realloc(buf, bufsz)) == NULL)
				goto resourceerror;
			buf = t;
		}

		do {
			assert(bufsz - datasz > 0);
			t = buf + datasz;
			if ((readsz = read(fd, t, bufsz - datasz)) <= 0)
				break;
			datasz += (size_t) readsz;
		} while (datasz < bufsz);

	} while (readsz > 0);

	if (readsz < 0) {
		LIBELF_SET_ERROR(IO, errno);
		goto error;
	}

	assert(readsz == 0);

	/*
	 * Free up extra buffer space.
	 */
	if (bufsz > datasz) {
		if (datasz > 0) {
			if ((t = realloc(buf, datasz)) == NULL)
				goto resourceerror;
			buf = t;
		} else {	/* Zero bytes read. */
			LIBELF_SET_ERROR(ARGUMENT, 0);
			free(buf);
			buf = NULL;
		}
	}

	*fsz = datasz;
	return (buf);

resourceerror:
	LIBELF_SET_ERROR(RESOURCE, 0);
error:
	if (buf != NULL)
		free(buf);
	return (NULL);
}

/*
 * Read the contents of the file referenced by the file descriptor
 * 'fd'.
 */

Elf *
_libelf_open_object(int fd, Elf_Cmd c, int reporterror)
{
	Elf *e;
	void *m;
	mode_t mode;
	size_t fsize;
	struct stat sb;
	unsigned int flags;

	assert(c == ELF_C_READ || c == ELF_C_RDWR || c == ELF_C_WRITE);

	if (fstat(fd, &sb) < 0) {
		LIBELF_SET_ERROR(IO, errno);
		return (NULL);
	}

	mode = sb.st_mode;
	fsize = (size_t) sb.st_size;

	/*
	 * Reject unsupported file types.
	 */
	if (!S_ISREG(mode) && !S_ISCHR(mode) && !S_ISFIFO(mode) &&
	    !S_ISSOCK(mode)) {
		LIBELF_SET_ERROR(ARGUMENT, 0);
		return (NULL);
	}

	/*
	 * For ELF_C_WRITE mode, allocate and return a descriptor.
	 */
	if (c == ELF_C_WRITE) {
		if ((e = _libelf_allocate_elf()) != NULL) {
			_libelf_init_elf(e, ELF_K_ELF);
			e->e_byteorder = LIBELF_PRIVATE(byteorder);
			e->e_fd = fd;
			e->e_cmd = c;
			if (!S_ISREG(mode))
				e->e_flags |= LIBELF_F_SPECIAL_FILE;
		}

		return (e);
	}


	/*
	 * ELF_C_READ and ELF_C_RDWR mode.
	 */
	m = NULL;
	flags = 0;
	if (S_ISREG(mode)) {

		/*
		 * Reject zero length files.
		 */
		if (fsize == 0) {
			LIBELF_SET_ERROR(ARGUMENT, 0);
			return (NULL);
		}

#if	ELFTC_HAVE_MMAP
		/*
		 * Always map regular files in with 'PROT_READ'
		 * permissions.
		 *
		 * For objects opened in ELF_C_RDWR mode, when
		 * elf_update(3) is called, we remove this mapping,
		 * write file data out using write(2), and map the new
		 * contents back.
		 */
		m = mmap(NULL, fsize, PROT_READ, MAP_PRIVATE, fd, (off_t) 0);

		if (m == MAP_FAILED)
			m = NULL;
		else
			flags = LIBELF_F_RAWFILE_MMAP;
#endif

		/*
		 * Fallback to a read() if the call to mmap() failed,
		 * or if mmap() is not available.
		 */
		if (m == NULL) {
			if ((m = malloc(fsize)) == NULL) {
				LIBELF_SET_ERROR(RESOURCE, 0);
				return (NULL);
			}

			if (read(fd, m, fsize) != (ssize_t) fsize) {
				LIBELF_SET_ERROR(IO, errno);
				free(m);
				return (NULL);
			}

			flags = LIBELF_F_RAWFILE_MALLOC;
		}
	} else if ((m = _libelf_read_special_file(fd, &fsize)) != NULL)
		flags = LIBELF_F_RAWFILE_MALLOC | LIBELF_F_SPECIAL_FILE;
	else
		return (NULL);

	if ((e = _libelf_memory(m, fsize, reporterror)) == NULL) {
		assert((flags & LIBELF_F_RAWFILE_MALLOC) ||
		    (flags & LIBELF_F_RAWFILE_MMAP));
		if (flags & LIBELF_F_RAWFILE_MALLOC)
			free(m);
#if	ELFTC_HAVE_MMAP
		else
			(void) munmap(m, fsize);
#endif
		return (NULL);
	}

	/* ar(1) archives aren't supported in RDWR mode. */
	if (c == ELF_C_RDWR && e->e_kind == ELF_K_AR) {
		(void) elf_end(e);
		LIBELF_SET_ERROR(ARGUMENT, 0);
		return (NULL);
	}

	e->e_flags |= flags;
	e->e_fd = fd;
	e->e_cmd = c;

	return (e);
}