elfinterp.c

ucLinux is a very good embeded sytem. Most of company use this as their development OS.

/* vi: set sw=4 ts=4: */
/* x86_64 ELF shared library loader suppport
 *
 * Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald,
 *                              David Engel, Hongjiu Lu and Mitch D'Souza
 * Copyright (C) 2001-2004 Erik Andersen
 *
 * 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. The name of the above contributors may not be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE 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 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 "ldso.h"

/* Program to load an ELF binary on a linux system, and run it.
   References to symbols in sharable libraries can be resolved by either
   an ELF sharable library or a linux style of shared library. */

/* Disclaimer:  I have never seen any AT&T source code for SVr4, nor have
   I ever taken any courses on internals.  This program was developed using
   information available through the book "UNIX SYSTEM V RELEASE 4,
   Programmers guide: Ansi C and Programming Support Tools", which did
   a more than adequate job of explaining everything required to get this
   working. */

extern int _dl_linux_resolve(void);

unsigned long
_dl_linux_resolver(struct elf_resolve *tpnt, int reloc_entry)
{
	int reloc_type;
	ELF_RELOC *this_reloc;
	char *strtab;
	ElfW(Sym) *symtab;
	int symtab_index;
	char *rel_addr;
	char *new_addr;
	char **got_addr;
	ElfW(Addr) instr_addr;
	char *symname;

	rel_addr = (char *)tpnt->dynamic_info[DT_JMPREL];
	this_reloc = (ELF_RELOC *)(rel_addr + reloc_entry);
	reloc_type = ELF_R_TYPE(this_reloc->r_info);
	symtab_index = ELF_R_SYM(this_reloc->r_info);

	symtab = (ElfW(Sym) *)tpnt->dynamic_info[DT_SYMTAB];
	strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
	symname = strtab + symtab[symtab_index].st_name;

	if (unlikely(reloc_type != R_X86_64_JUMP_SLOT)) {
		_dl_dprintf(2, "%s: Incorrect relocation type in jump relocations\n",
		            _dl_progname);
		_dl_exit(1);
	}

	/* Address of the jump instruction to fix up. */
	instr_addr = (this_reloc->r_offset + tpnt->loadaddr);
	got_addr = (char **)instr_addr;

	/* Get the address of the GOT entry. */
	new_addr = _dl_find_hash(symname, tpnt->symbol_scope, tpnt, ELF_RTYPE_CLASS_PLT);
	if (unlikely(!new_addr)) {
		_dl_dprintf(2, "%s: Can't resolve symbol '%s'\n", _dl_progname, symname);
		_dl_exit(1);
	}

#if defined (__SUPPORT_LD_DEBUG__)
	if ((unsigned long)got_addr < 0x40000000) {
		if (_dl_debug_bindings) {
			_dl_dprintf(_dl_debug_file, "\nresolve function: %s", symname);
			if (_dl_debug_detail)
				_dl_dprintf(_dl_debug_file,
				            "\tpatched: %x ==> %x @ %x\n",
				            *got_addr, new_addr, got_addr);
		}
	}
	if (!_dl_debug_nofixups)
#endif
		*got_addr = new_addr;

	return (unsigned long)new_addr;
}

static int
_dl_parse(struct elf_resolve *tpnt, struct dyn_elf *scope,
	  unsigned long rel_addr, unsigned long rel_size,
	  int (*reloc_fnc)(struct elf_resolve *tpnt, struct dyn_elf *scope,
			   ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab))
{
	unsigned int i;
	char *strtab;
	ElfW(Sym) *symtab;
	ELF_RELOC *rpnt;
	int symtab_index;

	/* Parse the relocation information. */
	rpnt = (ELF_RELOC *)rel_addr;
	rel_size /= sizeof(ELF_RELOC);

	symtab = (ElfW(Sym) *)tpnt->dynamic_info[DT_SYMTAB];
	strtab = (char *)tpnt->dynamic_info[DT_STRTAB];

	for (i = 0; i < rel_size; i++, rpnt++) {
		int res;

		symtab_index = ELF_R_SYM(rpnt->r_info);

		debug_sym(symtab, strtab, symtab_index);
		debug_reloc(symtab, strtab, rpnt);

		res = reloc_fnc(tpnt, scope, rpnt, symtab, strtab);

		if (res == 0)
			continue;

		_dl_dprintf(2, "\n%s: ", _dl_progname);

		if (symtab_index)
			_dl_dprintf(2, "symbol '%s': ",
				    strtab + symtab[symtab_index].st_name);

		if (unlikely(res < 0)) {
			int reloc_type = ELF_R_TYPE(rpnt->r_info);

			_dl_dprintf(2, "can't handle reloc type "
#if defined (__SUPPORT_LD_DEBUG__)
				    "%s\n", _dl_reltypes(reloc_type));
#else
				    "%x\n", reloc_type);
#endif
			_dl_exit(-res);
		} else if (unlikely(res > 0)) {
			_dl_dprintf(2, "can't resolve symbol\n");
			return res;
		}
	}

	return 0;
}

static int
_dl_do_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
	     ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
{
	int reloc_type;
	int symtab_index;
	char *symname;
	ElfW(Addr) *reloc_addr;
	ElfW(Addr) symbol_addr;
#if defined (__SUPPORT_LD_DEBUG__)
	ElfW(Addr) old_val;
#endif

	reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + (unsigned long)rpnt->r_offset);
	reloc_type = ELF_R_TYPE(rpnt->r_info);
	symtab_index = ELF_R_SYM(rpnt->r_info);
	symbol_addr = 0;
	symname = strtab + symtab[symtab_index].st_name;

	if (symtab_index) {
		symbol_addr = (ElfW(Addr))_dl_find_hash(symname, scope, tpnt,
							    elf_machine_type_class(reloc_type));
		/*
		 * We want to allow undefined references to weak symbols - this
		 * might have been intentional.  We should not be linking local
		 * symbols here, so all bases should be covered.
		 */
		if (unlikely(!symbol_addr && ELF_ST_BIND(symtab[symtab_index].st_info) != STB_WEAK)) {
			_dl_dprintf(2, "%s: can't resolve symbol '%s'\n", _dl_progname, symname);
			_dl_exit(1);
		};
	}

#if defined (__SUPPORT_LD_DEBUG__)
	old_val = *reloc_addr;
#endif

	switch (reloc_type) {
		case R_X86_64_NONE:
			break;

		case R_X86_64_64:
			*reloc_addr = symbol_addr + rpnt->r_addend;
			break;

		case R_X86_64_PC32:
			*reloc_addr = symbol_addr + rpnt->r_addend - rpnt->r_offset;
			break;

		case R_X86_64_GLOB_DAT:
		case R_X86_64_JUMP_SLOT:
			*reloc_addr = symbol_addr;
			break;

		/* handled by elf_machine_relative()
		case R_X86_64_RELATIVE:
			*reloc_addr = map->l_addr + rpnt->r_addend;
			break;
		*/
#if 0
		case R_X86_64_DTPMOD64:
			break;
		case R_X86_64_DTPOFF64:
			*reloc_addr = symbol_addr + rpnt->r_addend;
			break;
		case R_X86_64_TPOFF64:
			*reloc_addr = symbol_addr + rpnt->r_addend;
			break;
		case R_X86_64_32:
			*reloc_addr = symbol_addr + rpnt->r_addend;
			break;

#endif
		case R_X86_64_COPY:
			if (symbol_addr) {
#if defined (__SUPPORT_LD_DEBUG__)
				if (_dl_debug_move)
					_dl_dprintf(_dl_debug_file,
						    "\t%s move %d bytes from %x to %x\n",
						    symname, symtab[symtab_index].st_size,
						    symbol_addr, reloc_addr);
#endif

				_dl_memcpy((char *)reloc_addr,
					   (char *)symbol_addr,
					   symtab[symtab_index].st_size);
			} else
				_dl_dprintf(_dl_debug_file, "no symbol_addr to copy !?\n");
			break;

		default:
			return -1;	/* Calls _dl_exit(1). */
	}

#if defined (__SUPPORT_LD_DEBUG__)
	if (_dl_debug_reloc && _dl_debug_detail)
		_dl_dprintf(_dl_debug_file, "\tpatched: %x ==> %x @ %x\n",
			    old_val, *reloc_addr, reloc_addr);
#endif

	return 0;
}

#if 0
static int
_dl_do_lazy_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
		  ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
{
	int reloc_type;
	int symtab_index;
	ElfW(Addr) *reloc_addr;
#if defined (__SUPPORT_LD_DEBUG__)
	ElfW(Addr) old_val;
#endif

	(void)scope;
	symtab_index = ELF_R_SYM(rpnt->r_info);
	(void)strtab;

	reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + rpnt->r_offset);
	reloc_type = ELF_R_TYPE(rpnt->r_info);

#if defined (__SUPPORT_LD_DEBUG__)
	old_val = *reloc_addr;
#endif

	switch (reloc_type) {
		case R_X86_64_NONE:
			break;
		case R_X86_64_JUMP_SLOT:
			*reloc_addr = tpnt->loadaddr + symtab[symtab_index].st_value;
			break;
		default:
			_dl_exit(1);
	}

#if defined (__SUPPORT_LD_DEBUG__)
	if (_dl_debug_reloc && _dl_debug_detail)
		_dl_dprintf(_dl_debug_file, "\tpatched_lazy: %x ==> %x @ %x\n",
			    old_val, *reloc_addr, reloc_addr);
#endif

	return 0;
}
#endif

void
_dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
				      unsigned long rel_addr,
				      unsigned long rel_size)
{
	_dl_parse_relocation_information(rpnt, rel_addr, rel_size);
/*	jump slot isnt working
	(void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
*/
}

int
_dl_parse_relocation_information(struct dyn_elf *rpnt,
				 unsigned long rel_addr,
				 unsigned long rel_size)
{
	return _dl_parse(rpnt->dyn, rpnt->dyn->symbol_scope, rel_addr, rel_size, _dl_do_reloc);
}