C++ ELF_ST_BIND函数代码示例

static void compute_unresolved_hash(struct elf_info *elf)
{

	Elf_Sym *sym;
	ksym_hash_t *hash_values = elf->undef_hash.start;

	if (!hash_values)
		/* .undef.hash section is not present */
		return;

	for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
		if (sym->st_shndx == SHN_UNDEF) {
			/* undefined symbol */
			if (ELF_ST_BIND(sym->st_info) != STB_GLOBAL &&
			    ELF_ST_BIND(sym->st_info) != STB_WEAK)
				continue;
			else {
				/* GLOBAL or WEAK undefined symbols */
				*hash_values = gnu_hash((unsigned char *)
						(elf->strtab + sym->st_name));
				/*
				 * The hash_values array stored into the
				 * .undef.hash section that is ordered as the
				 * undefined symbols of the .symtab
				 */
				hash_values++;
			}
		}
	}
}

/*
 * Convert an Elf_Sym into an nlist structure.  This fills in only the
 * n_value and n_type members.
 */
static void
elf_sym_to_nlist(struct nlist *nl, Elf_Sym *s, Elf_Shdr *shdr, int shnum)
{
	nl->n_value = s->st_value;

	switch (s->st_shndx) {
	case SHN_UNDEF:
	case SHN_COMMON:
		nl->n_type = N_UNDF;
		break;
	case SHN_ABS:
		nl->n_type = ELF_ST_TYPE(s->st_info) == STT_FILE ?
		    N_FN : N_ABS;
		break;
	default:
		if (s->st_shndx >= shnum)
			nl->n_type = N_UNDF;
		else {
			Elf_Shdr *sh = shdr + s->st_shndx;

			nl->n_type = sh->sh_type == SHT_PROGBITS ?
			    (sh->sh_flags & SHF_WRITE ? N_DATA : N_TEXT) :
			    (sh->sh_type == SHT_NOBITS ? N_BSS : N_UNDF);
		}
		break;
	}

	if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
	    ELF_ST_BIND(s->st_info) == STB_WEAK)
		nl->n_type |= N_EXT;
}

static void
link_elf_reloc_local(linker_file_t lf)
{
	elf_file_t ef = (elf_file_t)lf;
	const Elf_Rel *rellim;
	const Elf_Rel *rel;
	const Elf_Rela *relalim;
	const Elf_Rela *rela;
	const Elf_Sym *sym;
	Elf_Addr base;
	int i;
	Elf_Size symidx;

	link_elf_fix_link_set(ef);

	/* Perform relocations without addend if there are any: */
	for (i = 0; i < ef->nreltab; i++) {
		rel = ef->reltab[i].rel;
		if (rel == NULL)
			panic("lost a reltab!");
		rellim = rel + ef->reltab[i].nrel;
		base = findbase(ef, ef->reltab[i].sec);
		if (base == 0)
			panic("lost base for reltab");
		for ( ; rel < rellim; rel++) {
			symidx = ELF_R_SYM(rel->r_info);
			if (symidx >= ef->ddbsymcnt)
				continue;
			sym = ef->ddbsymtab + symidx;
			/* Only do local relocs */
			if (ELF_ST_BIND(sym->st_info) != STB_LOCAL)
				continue;
			elf_reloc_local(lf, base, rel, ELF_RELOC_REL,
			    elf_obj_lookup);
		}
	}

	/* Perform relocations with addend if there are any: */
	for (i = 0; i < ef->nrelatab; i++) {
		rela = ef->relatab[i].rela;
		if (rela == NULL)
			panic("lost a relatab!");
		relalim = rela + ef->relatab[i].nrela;
		base = findbase(ef, ef->relatab[i].sec);
		if (base == 0)
			panic("lost base for relatab");
		for ( ; rela < relalim; rela++) {
			symidx = ELF_R_SYM(rela->r_info);
			if (symidx >= ef->ddbsymcnt)
				continue;
			sym = ef->ddbsymtab + symidx;
			/* Only do local relocs */
			if (ELF_ST_BIND(sym->st_info) != STB_LOCAL)
				continue;
			elf_reloc_local(lf, base, rela, ELF_RELOC_RELA,
			    elf_obj_lookup);
		}
	}
}

static bool
wantsym(const Elf_Sym *sym, const char *strtab)
{
    int type;
    int bind;

    type = ELF_ST_TYPE(sym->st_info);
    bind = ELF_ST_BIND(sym->st_info);

    if (type != STT_FUNC || (aflag && bind == STB_LOCAL))
#if 0
 ||
      (uflag && strchr(strtab + sym->st_name, '.') != NULL))
#endif
	return 0;

#ifdef __arm__
    /* ignore what gas calls "mapping symbols" */
    {
	const char *c = strtab + sym->st_name;
	if (c[0] == '$')
	    return 0;
    }
#endif

    return 1;
}

Elf32_Sym *mips_elf_find_address(struct mips_cpu *pcpu, Elf32_Addr addr)
{
	Elf32_Shdr *shsymtab = pcpu->shsymtab;
	unsigned    n = shsymtab->sh_size / shsymtab->sh_entsize;
	Elf32_Addr  min = (unsigned)-1;
	Elf32_Sym  *ret = NULL;
	unsigned    i;

	if((shsymtab->sh_offset  + shsymtab->sh_size > pcpu->elfsz)
	|| (addr >= pcpu->memsz))
		return NULL;
	
	for(i = 0; i < n; i++) {
		Elf32_Sym  *sym = get_sym(pcpu->elf, pcpu->elfsz, shsymtab, i);

		if(!sym)
			return NULL;
		if((ELF_ST_BIND(sym->st_info) != STB_GLOBAL) ||
				(ELF_ST_TYPE(sym->st_info) >= STT_SECTION))
			continue;
		
		if(sym->st_value <= addr) {
			Elf32_Addr diff = addr - sym->st_value;
			
			if(diff < min) {
				min = diff;
				ret = sym;
				if(diff == 0)
					break;
			}
		}
	}
	return ret;
}

int sym7(void)
{
	if(ELF_ST_TYPE(orcSYM->st_info) != STT_FILE)
		return 0;

	if(mode & REL)
		if(rand() % 2)
			return 0;

	unsigned char st_info = orcSYM->st_info;
	Elf_Section st_shndx;

	if(rand() % 2)
		do
			st_info = ELF_ST_INFO(rand() & 0x0f, STT_FILE);
		while(ELF_ST_BIND(st_info) == STB_LOCAL);

	if(rand() % 4 < 3){
		while((st_shndx = rand() % orcHDR->e_shnum))
			if(st_shndx != SHN_ABS)
				break;
	} else
		while((st_shndx = getElf_Section()))
			if(st_shndx != SHN_ABS)
				break;

	orcSYM->st_info  = st_info;
	orcSYM->st_shndx = st_shndx;

	fprintf(logfp, "(SYM[%d]->st_info = 0x%.2x,", entry, orcSYM->st_info);
	fprintf(logfp, " st_shndx = 0x%x)", orcSYM->st_shndx);

	return 1;
}

    bool
    generic_get_symbol( Elf_Xword index,
                        std::string& name, Elf64_Addr& value,
                        Elf_Xword& size,
                        unsigned char& bind, unsigned char& type,
                        Elf_Half& section_index,
                        unsigned char& other ) const
    {
        bool ret = false;

        if ( index < get_symbols_num() ) {
            const T* pSym = reinterpret_cast<const T*>(
                symbol_section->get_data() +
                    index * symbol_section->get_entry_size() );

            const endianess_convertor& convertor = elf_file.get_convertor();

            section* string_section = elf_file.sections[get_string_table_index()];
            string_section_accessor str_reader( string_section );
            const char* pStr = str_reader.get_string( convertor( pSym->st_name ) );
            if ( 0 != pStr ) {
                name = pStr;
            }
            value   = convertor( pSym->st_value );
            size    = convertor( pSym->st_size );
            bind    = ELF_ST_BIND( pSym->st_info );
            type    = ELF_ST_TYPE( pSym->st_info );
            section_index = convertor( pSym->st_shndx );
            other   = pSym->st_other;

            ret = true;
        }

        return ret;
    }

/*
 * Symbol lookup function that can be used when the symbol index is known (ie
 * in relocations). It uses the symbol index instead of doing a fully fledged
 * hash table based lookup when such is valid. For example for local symbols.
 * This is not only more efficient, it's also more correct. It's not always
 * the case that the symbol can be found through the hash table.
 */
static Elf_Addr
elf_obj_lookup(linker_file_t lf, Elf_Size symidx, int deps)
{
	elf_file_t ef = (elf_file_t)lf;
	Elf_Sym *sym;
	const char *symbol;
	Elf_Addr ret;

	/* Don't even try to lookup the symbol if the index is bogus. */
	if (symidx >= ef->ddbsymcnt)
		return (0);

	sym = ef->ddbsymtab + symidx;

	/* Quick answer if there is a definition included. */
	if (sym->st_shndx != SHN_UNDEF)
		return (sym->st_value);

	/* If we get here, then it is undefined and needs a lookup. */
	switch (ELF_ST_BIND(sym->st_info)) {
	case STB_LOCAL:
		/* Local, but undefined? huh? */
		return (0);

	case STB_GLOBAL:
		/* Relative to Data or Function name */
		symbol = ef->ddbstrtab + sym->st_name;

		/* Force a lookup failure if the symbol name is bogus. */
		if (*symbol == 0)
			return (0);
		ret = ((Elf_Addr)linker_file_lookup_symbol(lf, symbol, deps));

		/*
		 * Cache global lookups during module relocation. The failure
		 * case is particularly expensive for callers, who must scan
		 * through the entire globals table doing strcmp(). Cache to
		 * avoid doing such work repeatedly.
		 *
		 * After relocation is complete, undefined globals will be
		 * restored to SHN_UNDEF in elf_obj_cleanup_globals_cache(),
		 * above.
		 */
		if (ret != 0) {
			sym->st_shndx = SHN_FBSD_CACHED;
			sym->st_value = ret;
		}
		return (ret);

	case STB_WEAK:
		printf("link_elf_obj: Weak symbols not supported\n");
		return (0);

	default:
		return (0);
	}
}

/*
 * kobj_sym_lookup:
 *
 *	Symbol lookup function to be used when the symbol index
 *	is known (ie during relocation).
 */
uintptr_t
kobj_sym_lookup(kobj_t ko, uintptr_t symidx)
{
	const Elf_Sym *sym;
	const char *symbol;
	int error;
	u_long addr;

	/* Don't even try to lookup the symbol if the index is bogus. */
	if (symidx >= ko->ko_symcnt)
		return 0;

	sym = ko->ko_symtab + symidx;

	/* Quick answer if there is a definition included. */
	if (sym->st_shndx != SHN_UNDEF) {
		return sym->st_value;
	}

	/* If we get here, then it is undefined and needs a lookup. */
	switch (ELF_ST_BIND(sym->st_info)) {
	case STB_LOCAL:
		/* Local, but undefined? huh? */
		kobj_error("local symbol undefined");
		return 0;

	case STB_GLOBAL:
		/* Relative to Data or Function name */
		symbol = ko->ko_strtab + sym->st_name;

		/* Force a lookup failure if the symbol name is bogus. */
		if (*symbol == 0) {
			kobj_error("bad symbol name");
			return 0;
		}

		/*
		 * Don't need to lock, as it is known that the symbol
		 * tables aren't going to change (we hold module_lock).
		 */
		error = ksyms_getval(NULL, symbol, &addr, KSYMS_ANY);
		if (error != 0) {
			kobj_error("symbol `%s' not found", symbol);
			return (uintptr_t)0;
		}
		return (uintptr_t)addr;

	case STB_WEAK:
		kobj_error("weak symbols not supported\n");
		return 0;

	default:
		return 0;
	}
}

static void parse_elf_symbols(uintptr_t mem, size_t size, Phdr_t *load,
		struct vdso_symtable *t, uintptr_t dynsymbol_names,
		Hash_t *hash, Dyn_t *dyn_symtab)
{
	const char *vdso_symbols[VDSO_SYMBOL_MAX] = {
		ARCH_VDSO_SYMBOLS
	};
	const size_t vdso_symbol_length = sizeof(t->symbols[0].name);

	Hash_t nbucket, nchain;
	Hash_t *bucket, *chain;

	unsigned int i, j, k;
	uintptr_t addr;

	nbucket = hash[0];
	nchain = hash[1];
	bucket = &hash[2];
	chain = &hash[nbucket + 2];

	pr_debug("nbucket %lx nchain %lx bucket %lx chain %lx\n",
		 (long)nbucket, (long)nchain, (unsigned long)bucket, (unsigned long)chain);

	for (i = 0; i < VDSO_SYMBOL_MAX; i++) {
		const char * symbol = vdso_symbols[i];
		k = elf_hash((const unsigned char *)symbol);

		for (j = bucket[k % nbucket]; j < nchain && chain[j] != STN_UNDEF; j = chain[j]) {
			addr = mem + dyn_symtab->d_un.d_ptr - load->p_vaddr;
			Sym_t *sym;
			char *name;

			addr += sizeof(Sym_t)*j;
			if (__ptr_struct_oob(addr, sizeof(Sym_t), mem, size))
				continue;
			sym = (void *)addr;

			if (ELF_ST_TYPE(sym->st_info) != STT_FUNC &&
			    ELF_ST_BIND(sym->st_info) != STB_GLOBAL)
				continue;

			addr = dynsymbol_names + sym->st_name;
			if (__ptr_struct_oob(addr, vdso_symbol_length, mem, size))
				continue;
			name = (void *)addr;

			if (std_strncmp(name, symbol, vdso_symbol_length))
				continue;

			memcpy(t->symbols[i].name, name, vdso_symbol_length);
			t->symbols[i].offset = (unsigned long)sym->st_value - load->p_vaddr;
			break;
		}
	}
}

static int simplify_symbols(struct secthdr *sechdrs,
			    unsigned int symindex,
			    const char *strtab,
			    unsigned int versindex,
			    unsigned int pcpuindex, struct module *mod)
{
	struct symtab_s *sym = (void *)sechdrs[symindex].sh_addr;
	unsigned long secbase;
	unsigned int i, n = sechdrs[symindex].sh_size / sizeof(struct symtab_s);
	int ret = 0;
	const struct kernel_symbol *ksym;
	for (i = 1; i < n; i++) {
		switch (sym[i].st_shndx) {
		case SHN_COMMON:
			/* We compiled with -fno-common.  These are not supposed to happen.  */
			kprintf("simplify_symbols: Common symbol: %s\n",
				strtab + sym[i].st_name);
			kprintf("%s: please compile with -fno-common\n",
				mod->name);
			ret = -1;
			break;
		case SHN_ABS:
			/* Don't need to do anything */
			kprintf("simplify_symbols: Absolute symbol: 0x%08lx\n",
				(long)sym[i].st_value);
			break;
		case SHN_UNDEF:
			ksym =
			    resolve_symbol(sechdrs, versindex,
					   strtab + sym[i].st_name, mod);
			/* Ok if resolved.  */
			if (ksym) {
				sym[i].st_value = ksym->value;
				break;
			}
			/* Ok if weak. */
			if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
				break;
			kprintf("simplify_symbols: Unknown symbol %s\n",
				strtab + sym[i].st_name);
			ret = -1;
			break;
		default:
			if (sym[i].st_shndx == pcpuindex)
				secbase = (unsigned long)mod->percpu;
			else
				secbase = sechdrs[sym[i].st_shndx].sh_addr;
			sym[i].st_value += secbase;
			break;
		}
	}
	return ret;
}

static bool
wantsym(const Elf_Sym *sym, const char *strtab)
{
    int type;
    int bind;

    type = ELF_ST_TYPE(sym->st_info);
    bind = ELF_ST_BIND(sym->st_info);

    if (type != STT_FUNC ||
      (aflag && bind == STB_LOCAL) ||
      (uflag && strchr(strtab + sym->st_name, '.') != NULL))
	return 0;

    return 1;
}

static Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
					    const char *name)
{
	Elf_Sym *syms;
	Elf_Shdr *sechdrs;
	Elf_Ehdr *ehdr;
	int i, k;
	const char *strtab;

	if (!pi->sechdrs || !pi->ehdr)
		return NULL;

	sechdrs = pi->sechdrs;
	ehdr = pi->ehdr;

	for (i = 0; i < ehdr->e_shnum; i++) {
		if (sechdrs[i].sh_type != SHT_SYMTAB)
			continue;

		if (sechdrs[i].sh_link >= ehdr->e_shnum)
			/* Invalid strtab section number */
			continue;
		strtab = (char *)sechdrs[sechdrs[i].sh_link].sh_offset;
		syms = (Elf_Sym *)sechdrs[i].sh_offset;

		/* Go through symbols for a match */
		for (k = 0; k < sechdrs[i].sh_size/sizeof(Elf_Sym); k++) {
			if (ELF_ST_BIND(syms[k].st_info) != STB_GLOBAL)
				continue;

			if (strcmp(strtab + syms[k].st_name, name) != 0)
				continue;

			if (syms[k].st_shndx == SHN_UNDEF ||
			    syms[k].st_shndx >= ehdr->e_shnum) {
				pr_debug("Symbol: %s has bad section index %d.\n",
						name, syms[k].st_shndx);
				return NULL;
			}

			/* Found the symbol we are looking for */
			return &syms[k];
		}
	}

	return NULL;
}

void* dlsym(void* handle, const char* symbol) {
  ScopedPthreadMutexLocker locker(&g_dl_mutex);

#if !defined(__LP64__)
  if (handle == NULL) {
    __bionic_format_dlerror("dlsym library handle is null", NULL);
    return NULL;
  }
#endif

  if (symbol == NULL) {
    __bionic_format_dlerror("dlsym symbol name is null", NULL);
    return NULL;
  }

  soinfo* found = NULL;
  ElfW(Sym)* sym = NULL;
  if (handle == RTLD_DEFAULT) {
    sym = dlsym_linear_lookup(symbol, &found, NULL);
  } else if (handle == RTLD_NEXT) {
    void* caller_addr = __builtin_return_address(0);
    soinfo* si = find_containing_library(caller_addr);

    sym = NULL;
    if (si && si->next) {
      sym = dlsym_linear_lookup(symbol, &found, si->next);
    }
  } else {
    found = reinterpret_cast<soinfo*>(handle);
    sym = dlsym_handle_lookup(found, symbol);
  }

  if (sym != NULL) {
    unsigned bind = ELF_ST_BIND(sym->st_info);

    if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
      return reinterpret_cast<void*>(sym->st_value + found->load_bias);
    }

    __bionic_format_dlerror("symbol found but not global", symbol);
    return NULL;
  } else {
    __bionic_format_dlerror("undefined symbol", symbol);
    return NULL;
  }
}

/*
 * kobj_checkdup:
 *
 *	Scan symbol table for duplicates.
 */
static int
kobj_checkdup(kobj_t ko)
{
	unsigned long rval;
	Elf_Sym *sym, *ms;
	const char *name;
	bool dup;

	dup = false;
	for (ms = (sym = ko->ko_symtab) + ko->ko_symcnt; sym < ms; sym++) {
		/* Check validity of the symbol. */
		if (ELF_ST_BIND(sym->st_info) != STB_GLOBAL ||
		    sym->st_name == 0)
			continue;

		/* Check if the symbol already exists */
		name = ko->ko_strtab + sym->st_name;
		if (ksyms_getval(NULL, name, &rval, KSYMS_EXTERN) != 0) {
			continue;
		}

		/* Check (and complain) about differing values */
		if (sym->st_value == rval || sym->st_shndx == SHN_UNDEF) {
			continue;
		}
		if (strcmp(name, "_bss_start") == 0 ||
		    strcmp(name, "__bss_start") == 0 ||
		    strcmp(name, "_bss_end__") == 0 ||
		    strcmp(name, "__bss_end__") == 0 ||
		    strcmp(name, "_edata") == 0 ||
		    strcmp(name, "_end") == 0 ||
		    strcmp(name, "__end") == 0 ||
		    strcmp(name, "__end__") == 0 ||
		    strncmp(name, "__start_link_set_", 17) == 0 ||
		    strncmp(name, "__stop_link_set_", 16)) {
		    	continue;
		}
		kobj_error("global symbol `%s' redefined\n", name);
		dup = true;
	}

	return dup ? EEXIST : 0;
}