elfinterp.c

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

/* vi: set sw=8 ts=8: */
/*
 * ldso/ldso/sh64/elfinterp.c
 *
 * SuperH (sh64) ELF shared library loader suppport
 *
 * Copyright (C) 2003, 2004, 2005  Paul Mundt <[e-mail]>
 *
 * 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.
 */

/* 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;
	Elf32_Sym *symtab;
	int symtab_index;
	char *rel_addr;
	char *new_addr;
	char **got_addr;
	unsigned long instr_addr;
	char *symname;

	rel_addr = (char *)tpnt->dynamic_info[DT_JMPREL];

	this_reloc = (ELF_RELOC *)(intptr_t)(rel_addr + reloc_entry);
	reloc_type = ELF32_R_TYPE(this_reloc->r_info);
	symtab_index = ELF32_R_SYM(this_reloc->r_info);

	symtab = (Elf32_Sym *)(intptr_t)tpnt->dynamic_info[DT_SYMTAB];
	strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
	symname = strtab + symtab[symtab_index].st_name;

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

	/* Address of jump instruction to fix up */
	instr_addr = ((unsigned long)this_reloc->r_offset +
			(unsigned long)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);
	}

#ifdef __SUPPORT_LD_DEBUG__
	if ((unsigned long)got_addr < 0x20000000) {
		if (_dl_debug_bindings) {
			_dl_dprintf(_dl_debug_file, "\nresolve function: %s",
				    symname);

			if (_dl_debug_detail)
				_dl_dprintf(_dl_debug_file,
					    "\n\tpatched %x ==> %x @ %x\n",
					    *got_addr, new_addr, got_addr);
		}
	}

	if (!_dl_debug_nofixups)
		*got_addr = new_addr;
#else
	*got_addr = new_addr;
#endif

	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, Elf32_Sym *symtab,
				      char *strtab))
{
	unsigned int i;
	char *strtab;
	Elf32_Sym *symtab;
	ELF_RELOC *rpnt;
	int symtab_index;

	/* Now parse the relocation information */
	rpnt = (ELF_RELOC *)(intptr_t)rel_addr;
	rel_size = rel_size / sizeof(ELF_RELOC);

	symtab = (Elf32_Sym *)(intptr_t)tpnt->dynamic_info[DT_SYMTAB];
	strtab = (char *)tpnt->dynamic_info[DT_STRTAB];

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

		symtab_index = ELF32_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 = ELF32_R_TYPE(rpnt->r_info);

			_dl_dprintf(2, "can't handle reloc type "
#ifdef __SUPPORT_LD_DEBUG__
					"%s\n", _dl_reltypes(reloc_type)
#else
					"%x\n", reloc_type
#endif
			);

			_dl_exit(-res);
		}
		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, Elf32_Sym *symtab, char *strtab)
{
        int reloc_type;
	int symtab_index, lsb;
	char *symname;
	unsigned long *reloc_addr;
	unsigned long symbol_addr;
#ifdef __SUPPORT_LD_DEBUG__
	unsigned long old_val;
#endif

	reloc_type   = ELF32_R_TYPE(rpnt->r_info);
	symtab_index = ELF32_R_SYM(rpnt->r_info);
	symbol_addr  = 0;
	lsb          = !!(symtab[symtab_index].st_other & STO_SH5_ISA32);
	symname      = strtab + symtab[symtab_index].st_name;
	reloc_addr   = (unsigned long *)(intptr_t)
		(tpnt->loadaddr + (unsigned long)rpnt->r_offset);

	if (symtab_index) {
		int stb;

		symbol_addr = (unsigned long)_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.
		 */
		stb = ELF32_ST_BIND(symtab[symtab_index].st_info);

		if (stb != STB_WEAK && !symbol_addr) {
			_dl_dprintf (2, "%s: can't resolve symbol '%s'\n",
				     _dl_progname, strtab + symtab[symtab_index].st_name);
			_dl_exit (1);
		}
	}

#ifdef __SUPPORT_LD_DEBUG__
	old_val = *reloc_addr;
#endif

	switch (reloc_type) {
	case R_SH_NONE:
		break;
	case R_SH_COPY:
		_dl_memcpy((char *)reloc_addr,
			   (char *)symbol_addr, symtab[symtab_index].st_size);
		break;
	case R_SH_DIR32:
	case R_SH_GLOB_DAT:
	case R_SH_JMP_SLOT:
		*reloc_addr = (symbol_addr + rpnt->r_addend) | lsb;
		break;
	case R_SH_REL32:
		*reloc_addr = symbol_addr + rpnt->r_addend -
			(unsigned long)reloc_addr;
		break;
	case R_SH_RELATIVE:
		*reloc_addr = (unsigned long)tpnt->loadaddr + rpnt->r_addend;
		break;
	case R_SH_RELATIVE_LOW16:
	case R_SH_RELATIVE_MEDLOW16:
	    {
		unsigned long word, value;

		word = (unsigned long)reloc_addr & ~0x3fffc00;
		value = (unsigned long)tpnt->loadaddr + rpnt->r_addend;

		if (reloc_type == R_SH_RELATIVE_MEDLOW16)
			value >>= 16;

		word |= (value & 0xffff) << 10;
		*reloc_addr = word;

		break;
	    }
	case R_SH_IMM_LOW16:
	case R_SH_IMM_MEDLOW16:
	    {
		unsigned long word, value;

		word = (unsigned long)reloc_addr & ~0x3fffc00;
		value = (symbol_addr + rpnt->r_addend) | lsb;

		if (reloc_type == R_SH_IMM_MEDLOW16)
			value >>= 16;

		word |= (value & 0xffff) << 10;
		*reloc_addr = word;

		break;
	    }
	case R_SH_IMM_LOW16_PCREL:
	case R_SH_IMM_MEDLOW16_PCREL:
	    {
		unsigned long word, value;

		word = (unsigned long)reloc_addr & ~0x3fffc00;
		value = symbol_addr + rpnt->r_addend -
			(unsigned long)reloc_addr;

		if (reloc_type == R_SH_IMM_MEDLOW16_PCREL)
			value >>= 16;

		word |= (value & 0xffff) << 10;
		*reloc_addr = word;

		break;
	    }
	default:
		return -1; /*call _dl_exit(1) */
	}

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

	return 0;
}

static int _dl_do_lazy_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
			     ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab)
{
	int reloc_type, symtab_index, lsb;
	unsigned long *reloc_addr;
#ifdef __SUPPORT_LD_DEBUG__
	unsigned long old_val;
#endif

	reloc_type   = ELF32_R_TYPE(rpnt->r_info);
	symtab_index = ELF32_R_SYM(rpnt->r_info);
	lsb          = !!(symtab[symtab_index].st_other & STO_SH5_ISA32);
	reloc_addr   = (unsigned long *)(intptr_t)
		(tpnt->loadaddr + (unsigned long)rpnt->r_offset);

#ifdef __SUPPORT_LD_DEBUG__
	old_val = *reloc_addr;
#endif

	switch (reloc_type) {
	case R_SH_NONE:
		break;
	case R_SH_JMP_SLOT:
		*reloc_addr += (unsigned long)tpnt->loadaddr | lsb;
		break;
	default:
		return -1; /*call _dl_exit(1) */
	}

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

	return 0;
}

void _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
	unsigned long rel_addr, unsigned long rel_size)
{
	(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);
}