elfinterp.c

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

		PPC_SYNC;
		PPC_ICBI(reloc_addr);
	};
}

int _dl_parse_relocation_information(struct elf_resolve *tpnt, 
	unsigned long rel_addr, unsigned long rel_size, int type)
{
	int i;
	char *strtab;
	int reloc_type;
	int goof = 0;
	Elf32_Sym *symtab;
	ELF_RELOC *rpnt;
	unsigned long *reloc_addr;
	unsigned long symbol_addr;
	int symtab_index;
	unsigned long addend;
	unsigned long *plt;

	DPRINTF("_dl_parse_relocation_information(tpnt=%x, rel_addr=%x, rel_size=%x, type=%d)\n",
		tpnt,rel_addr,rel_size,type);

	/* Now parse the relocation information */

	rpnt = (ELF_RELOC *) (rel_addr + tpnt->loadaddr);
	rel_size = rel_size / sizeof(ELF_RELOC);

	symtab = (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
	strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
	plt = (unsigned long *)(tpnt->dynamic_info[DT_PLTGOT] + tpnt->loadaddr);

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

		reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
		reloc_type = ELF32_R_TYPE(rpnt->r_info);
		symtab_index = ELF32_R_SYM(rpnt->r_info);
		addend = rpnt->r_addend;
		symbol_addr = 0;

		if (!symtab_index && tpnt->libtype == program_interpreter)
			continue;

		if (symtab_index) {

			if (tpnt->libtype == program_interpreter &&
				_dl_symbol(strtab + symtab[symtab_index].st_name))
				continue;

			symbol_addr = (unsigned long) _dl_find_hash(strtab + symtab[symtab_index].st_name, 
					tpnt->symbol_scope,
					(reloc_type == R_PPC_JMP_SLOT ? tpnt : NULL), symbolrel);

			/*
			 * 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 (!symbol_addr &&
				ELF32_ST_BIND(symtab[symtab_index].st_info) == STB_GLOBAL) {
				_dl_dprintf(2, "%s: can't resolve symbol '%s'\n", 
					_dl_progname, strtab + symtab[symtab_index].st_name);
				goof++;
			}
		}
		debug_sym(symtab,strtab,symtab_index);

		switch (reloc_type) {
		case R_PPC_NONE:
			break;
		case R_PPC_REL24:
#if 0
			{
			int delta = symbol_addr - (unsigned long)reloc_addr;
			if(delta<<6>>6 != delta){
				_dl_dprintf(2,"R_PPC_REL24: Reloc out of range\n");
				_dl_exit(1);
			}
			*reloc_addr &= 0xfc000003;
			*reloc_addr |= delta&0x03fffffc;
			}
			break;
#else
			_dl_dprintf(2, "%s: symbol '%s' is type R_PPC_REL24\n\tCompile shared libraries with -fPIC!\n",
					_dl_progname, strtab + symtab[symtab_index].st_name);
			_dl_exit(1);
#endif
		case R_PPC_RELATIVE:
			*reloc_addr = (unsigned long)tpnt->loadaddr + addend;
			break;
		case R_PPC_ADDR32:
			*reloc_addr += symbol_addr;
			break;
		case R_PPC_ADDR16_HA:
			/* XXX is this correct? */
			*(short *)reloc_addr += (symbol_addr+0x8000)>>16;
			break;
		case R_PPC_ADDR16_HI:
			*(short *)reloc_addr += symbol_addr>>16;
			break;
		case R_PPC_ADDR16_LO:
			*(short *)reloc_addr += symbol_addr;
			break;
		case R_PPC_JMP_SLOT:
			{
			unsigned long targ_addr = (unsigned long)*reloc_addr;
			int delta = targ_addr - (unsigned long)reloc_addr;
			if(delta<<6>>6 == delta){
				*reloc_addr = OPCODE_B(delta);
			}else if (targ_addr <= 0x01fffffc || targ_addr >= 0xfe000000){
				*reloc_addr = OPCODE_BA (targ_addr);
			}else{
	{
	int delta;
	int index;
	
	delta = (unsigned long)(plt+PLT_TRAMPOLINE_ENTRY_WORDS+2)
		- (unsigned long)(reloc_addr+1);

	index = ((unsigned long)reloc_addr -
		(unsigned long)(plt+PLT_INITIAL_ENTRY_WORDS))
		/sizeof(unsigned long);
	index /= 2;
	DPRINTF("        index %x delta %x\n",index,delta);
	reloc_addr[0] = OPCODE_LI(11,index*4);
	reloc_addr[1] = OPCODE_B(delta);
	}
			}
			break;
			}
		case R_PPC_GLOB_DAT:
			*reloc_addr += symbol_addr;
			break;
		case R_PPC_COPY:
			// handled later
			break;
		default:
			_dl_dprintf(2, "%s: can't handle reloc type ", _dl_progname);
#if defined (__SUPPORT_LD_DEBUG__)
			_dl_dprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
			if (symtab_index)
				_dl_dprintf(2, "'%s'\n", strtab + symtab[symtab_index].st_name);
			_dl_exit(1);
		};

		/* instructions were modified */
		PPC_DCBST(reloc_addr);
		PPC_SYNC;
		PPC_ICBI(reloc_addr);

		DPRINTF("reloc_addr %x: %x\n",reloc_addr,*reloc_addr);
	};
	return goof;
}


/* This is done as a separate step, because there are cases where
   information is first copied and later initialized.  This results in
   the wrong information being copied.  Someone at Sun was complaining about
   a bug in the handling of _COPY by SVr4, and this may in fact be what he
   was talking about.  Sigh. */

/* No, there are cases where the SVr4 linker fails to emit COPY relocs
   at all */

int _dl_parse_copy_information(struct dyn_elf *xpnt, unsigned long rel_addr, 
	unsigned long rel_size, int type)
{
	int i;
	char *strtab;
	int reloc_type;
	int goof = 0;
	Elf32_Sym *symtab;
	ELF_RELOC *rpnt;
	unsigned long *reloc_addr;
	unsigned long symbol_addr;
	struct elf_resolve *tpnt;
	int symtab_index;

	DPRINTF("parse_copy xpnt=%x rel_addr=%x rel_size=%x type=%d\n",
		(int)xpnt,rel_addr,rel_size,type);

	/* Now parse the relocation information */

	tpnt = xpnt->dyn;

	rpnt = (ELF_RELOC *) (rel_addr + tpnt->loadaddr);
	rel_size = rel_size / sizeof(ELF_RELOC);

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

	for (i = 0; i < rel_size; i++, rpnt++) {
		reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
		reloc_type = ELF32_R_TYPE(rpnt->r_info);
		if (reloc_type != R_PPC_COPY)
			continue;

		debug_reloc(rpnt);

		symtab_index = ELF32_R_SYM(rpnt->r_info);
		symbol_addr = 0;
		if (!symtab_index && tpnt->libtype == program_interpreter)
			continue;
		if (symtab_index) {

			if (tpnt->libtype == program_interpreter &&
				_dl_symbol(strtab + symtab[symtab_index].st_name))
				continue;

			symbol_addr = (unsigned long) _dl_find_hash(strtab + 
				symtab[symtab_index].st_name, xpnt->next, 
				NULL, copyrel);
			if (!symbol_addr) {
				_dl_dprintf(2, "%s: can't resolve symbol '%s'\n", 
					_dl_progname, strtab + symtab[symtab_index].st_name);
				goof++;
			};
		};

		debug_sym(symtab,strtab,symtab_index);

		DPRINTF("copy: to=%x from=%x size=%x\n",
			symtab[symtab_index].st_value, 
			symbol_addr, symtab[symtab_index].st_size);

		if (!goof) {
			_dl_memcpy((char *) symtab[symtab_index].st_value, 
				(char *) symbol_addr,
				symtab[symtab_index].st_size);
		}
	};
	return goof;
}


#ifdef unused
static void fixup_jmpslot(unsigned long reloc_addr, unsigned long targ_addr)
{
	int delta = targ_addr - reloc_addr;
	int index;
	
	if(delta<<6>>6 == delta){
		*reloc_addr = OPCODE_B(delta);
	}else if (targ_addr <= 0x01fffffc || targ_addr >= 0xfe000000){
		*reloc_addr = OPCODE_BA (targ_addr);
	}else{
		delta = (unsigned long)(plt+PLT_TRAMPOLINE_ENTRY_WORDS+2)
			- (unsigned long)(reloc_addr+1);

		index = ((unsigned long)reloc_addr -
			(unsigned long)(plt+PLT_INITIAL_ENTRY_WORDS))
			/sizeof(unsigned long);
		index /= 2;

		DPRINTF("        index %x delta %x\n",index,delta);

		reloc_addr[0] = OPCODE_LI(11,index*4);
		reloc_addr[1] = OPCODE_B(delta);
	}
}
#endif


#ifdef __SUPPORT_LD_DEBUG__
static void debug_sym(Elf32_Sym *symtab,char *strtab,int symtab_index)
{
	if (_dl_debug_symbols) {
		if(symtab_index){
			_dl_dprintf(2, "sym: name=%s value=%x size=%x info=%x other=%x shndx=%x\n",
					strtab + symtab[symtab_index].st_name,
					symtab[symtab_index].st_value,
					symtab[symtab_index].st_size,
					symtab[symtab_index].st_info,
					symtab[symtab_index].st_other,
					symtab[symtab_index].st_shndx);
		}else{
			_dl_dprintf(2, "sym: null\n");
		}
	}
}

static void debug_reloc(ELF_RELOC *rpnt)
{
	if (_dl_debug_reloc) {
		_dl_dprintf(2, "reloc: offset=%x type=%x sym=%x addend=%x\n",
				rpnt->r_offset,
				ELF32_R_TYPE(rpnt->r_info),
				ELF32_R_SYM(rpnt->r_info),
				rpnt->r_addend);
	}
}

#endif