Loader/tools/elf.c

/* $Id$ */
/* Copyright (c) 2010 Pierre Pronchery <khorben@defora.org> */
/* This file is part of DeforaOS System Loader */
/* This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. */



/* macros */
# undef ELFFUNC
# undef ELFTYPE
#if ELFSIZE == 32
# define ELFFUNC(func) _do_ ## func ## 32
# define ELFTYPE(type) Elf ## 32 ## _ ## type
#elif ELFSIZE == 64
# define ELFFUNC(func) _do_ ## func ## 64
# define ELFTYPE(type) Elf ## 64 ## _ ## type
#else
# error ELFSIZE is not defined
#endif


/* prototypes */
static int ELFFUNC(ldd)(char const * filename, FILE * fp, ELFTYPE(Ehdr) * ehdr);


/* functions */
/* ldd */
static int ELFFUNC(ldd)(char const * filename, FILE * fp, ELFTYPE(Ehdr) * ehdr);
static int ELFFUNC(phdr)(char const * filename, FILE * fp, ELFTYPE(Ehdr) * ehdr,
		ELFTYPE(Phdr) * phdr);
static int ELFFUNC(phdr_dyn)(char const * filename, FILE * fp,
		ELFTYPE(Ehdr) * ehdr, ELFTYPE(Phdr) * phdr, ELFTYPE(Dyn) * dyn);
static char * ELFFUNC(string)(char const * filename, FILE * fp,
		ELFTYPE(Ehdr) * ehdr, ELFTYPE(Addr) addr, ELFTYPE(Addr) index);

static int ELFFUNC(ldd)(char const * filename, FILE * fp, ELFTYPE(Ehdr) * ehdr)
{
	int ret;
	ELFTYPE(Phdr) * phdr;

	if(ehdr->e_phnum == 0)
		return -_error(filename, "No program header found", 1);
	if(ehdr->e_phentsize != sizeof(*phdr))
		return -_error(filename, "Unexpected program header size", 1);
	if(fseek(fp, ehdr->e_phoff, SEEK_SET) != 0)
		return -_error(filename, strerror(errno), 1);
	if((phdr = malloc(sizeof(*phdr) * ehdr->e_phnum)) == NULL)
		return -_error(filename, strerror(errno), 1);
	ret = ELFFUNC(phdr)(filename, fp, ehdr, phdr);
	free(phdr);
	return ret;
}

static int ELFFUNC(phdr)(char const * filename, FILE * fp, ELFTYPE(Ehdr) * ehdr,
		ELFTYPE(Phdr) * phdr)
{
	int ret = 0;
	size_t i;
	ELFTYPE(Dyn) * dyn;

	if(fread(phdr, sizeof(*phdr), ehdr->e_phnum, fp) != ehdr->e_phnum)
	{
		if(ferror(fp) != 0)
			ret = -_error(filename, strerror(errno), 1);
		else
			ret = -_error(filename, "Corrupted ELF file", 1);
		return ret;
	}
	printf("%s:\n", filename);
	for(i = 0; i < ehdr->e_phnum; i++)
	{
		if(phdr[i].p_type != PT_DYNAMIC)
			continue;
		if(fseek(fp, phdr[i].p_offset, SEEK_SET) != 0)
		{
			ret |= -_error(filename, strerror(errno), 1);
			continue;
		}
		if((dyn = malloc(phdr[i].p_filesz)) == NULL)
		{
			ret |= -_error(filename, strerror(errno), 1);
			continue;
		}
		if(fread(dyn, phdr[i].p_filesz, 1, fp) == 1)
			ret = ELFFUNC(phdr_dyn)(filename, fp, ehdr, &phdr[i],
					dyn);
		else
		{
			if(ferror(fp) != 0)
				ret |= -_error(filename, strerror(errno), 1);
			else
				ret |= -_error(filename, "Corrupted ELF file",
						1);
		}
		free(dyn);
	}
	return ret;
}

static int ELFFUNC(phdr_dyn)(char const * filename, FILE * fp,
		ELFTYPE(Ehdr) * ehdr, ELFTYPE(Phdr) * phdr, ELFTYPE(Dyn) * dyn)
{
	ssize_t s = -1;
	ssize_t r = -1;
	size_t i;
	char * p;

	for(i = 0; (i + 1) * sizeof(*dyn) < phdr->p_filesz; i++)
	{
		if(dyn[i].d_tag == DT_NULL)
			break;
		if(dyn[i].d_tag == DT_STRTAB)
			s = i;
		else if(dyn[i].d_tag == DT_RPATH)
			r = i;
	}
	if(s < 0)
		return -_error(filename, "Missing string section", 1);
#ifdef DEBUG
	fprintf(stderr, "DEBUG: %s() strtab=%ld\n", __func__, s);
#endif
	for(i = 0; (i + 1) * sizeof(*dyn) < phdr->p_filesz; i++)
	{
		if(dyn[i].d_tag == DT_NULL)
			break;
		if(dyn[i].d_tag != DT_NEEDED)
			continue;
		if((p = ELFFUNC(string)(filename, fp, ehdr, dyn[s].d_un.d_ptr,
						dyn[i].d_un.d_val)) == NULL)
			continue;
		printf("\t%s\n", p);
		/* FIXME display the full filename and address */
		free(p);
	}
	return 0;
}

static char * ELFFUNC(string)(char const * filename, FILE * fp,
		ELFTYPE(Ehdr) * ehdr, ELFTYPE(Addr) addr, ELFTYPE(Addr) index)
{
	char * ret;
	size_t i;
	ELFTYPE(Shdr) shdr;
	char * p = NULL;

	if(fseek(fp, ehdr->e_shoff, SEEK_SET) != 0)
	{
		_error(filename, strerror(errno), 1);
		return NULL;
	}
	for(i = 0; i < ehdr->e_shnum; i++)
	{
		if(fread(&shdr, sizeof(shdr), 1, fp) != 1)
		{
			if(ferror(fp) != 0)
				_error(filename, strerror(errno), 1);
			else
				_error(filename, "Corrupted ELF file", 1);
			break;
		}
		if(shdr.sh_type != SHT_STRTAB)
			continue;
		if(shdr.sh_addr != addr)
			continue;
		if(fseek(fp, shdr.sh_offset, SEEK_SET) != 0
				|| (p = malloc(shdr.sh_size)) == NULL)
		{
			_error(filename, strerror(errno), 1);
			break;
		}
		if(fread(p, sizeof(*p), shdr.sh_size, fp) != shdr.sh_size)
		{
			if(ferror(fp) != 0)
				_error(filename, strerror(errno), 1);
			else
				_error(filename, "Corrupted ELF file", 1);
			break;
		}
		for(i = index; i < shdr.sh_size; i++)
		{
			if(p[i] != '\0')
				continue;
			if((ret = strdup(&p[index])) == NULL)
				_error(filename, strerror(errno), 1);
			free(p);
			return ret;
		}
		break;
	}
	free(p);
	return NULL;
}