insmod.c

来自「手机嵌入式Linux下可用的busybox源码」· C语言 代码 · 共 2,778 行 · 第 1/5 页

#endif
	  	pe->inited = 1;
	  }

      /* relative distance to target */
      v -= dot;
      /* if the target is too far away.... */
      if ((int)v < -0x02000000 || (int)v >= 0x02000000) {
	    /* go via the plt */
	    v = plt + pe->offset - dot;
	  }
      if (v & 3)
	    ret = obj_reloc_dangerous;

      /* merge the offset into the instruction. */
#if defined(__arm__)
      /* Convert to words. */
      v >>= 2;

      *loc = (*loc & ~0x00ffffff) | ((v + *loc) & 0x00ffffff);
#endif
#if defined(__powerpc__)
      *loc = (*loc & ~0x03fffffc) | (v & 0x03fffffc);
#endif
      break;
#endif /* BB_USE_PLT_ENTRIES */

#if defined(BB_USE_GOT_ENTRIES)
	  bb_use_got:

		assert(isym != NULL);
        /* needs an entry in the .got: set it, once */
		if (!isym->gotent.inited) {
			isym->gotent.inited = 1;
			*(ElfW(Addr) *) (ifile->got->contents + isym->gotent.offset) = v;
		}
        /* make the reloc with_respect_to_.got */
#if defined(__sh__)
		*loc += isym->gotent.offset + rel->r_addend;
#elif defined(__i386__) || defined(__arm__) || defined(__mc68000__)
		*loc += isym->gotent.offset;
#endif
		break;

#endif /* BB_USE_GOT_ENTRIES */
	}

	return ret;
}

#if defined(BB_USE_LIST) 

static int arch_list_add(ElfW(RelM) *rel, struct arch_list_entry **list,
			  int offset, int size)
{
	struct arch_list_entry *pe;

	for (pe = *list; pe != NULL; pe = pe->next) {
		if (pe->addend == rel->r_addend) {
			break;
		}
	}

	if (pe == NULL) {
		pe = xmalloc(sizeof(struct arch_list_entry));
		pe->next = *list;
		pe->addend = rel->r_addend;
		pe->offset = offset;
		pe->inited = 0;
		*list = pe;
		return size;
	}
	return 0;
}

#endif

#if defined(BB_USE_SINGLE) 

static int arch_single_init(ElfW(RelM) *rel, struct arch_single_entry *single,
			     int offset, int size)
{
	if (single->allocated == 0) {
		single->allocated = 1;
		single->offset = offset;
		single->inited = 0;
		return size;
	}
	return 0;
}

#endif

#if defined(BB_USE_GOT_ENTRIES) || defined(BB_USE_PLT_ENTRIES)

static struct obj_section *arch_xsect_init(struct obj_file *f, char *name, 
					   int offset, int size)
{
	struct obj_section *myrelsec = obj_find_section(f, name);

	if (offset == 0) {
		offset += size;
	}

	if (myrelsec) {
		obj_extend_section(myrelsec, offset);
	} else {
		myrelsec = obj_create_alloced_section(f, name, 
						      size, offset);
		assert(myrelsec);
	}

	return myrelsec;
}

#endif

static void arch_create_got(struct obj_file *f)
{
#if defined(BB_USE_GOT_ENTRIES) || defined(BB_USE_PLT_ENTRIES)
	struct arch_file *ifile = (struct arch_file *) f;
	int i;
#if defined(BB_USE_GOT_ENTRIES)
	int got_offset = 0, got_needed = 0, got_allocate;
#endif
#if defined(BB_USE_PLT_ENTRIES)
	int plt_offset = 0, plt_needed = 0, plt_allocate;
#endif
    struct obj_section *relsec, *symsec, *strsec;
	ElfW(RelM) *rel, *relend;
	ElfW(Sym) *symtab, *extsym;
	const char *strtab, *name;
	struct arch_symbol *intsym;

	for (i = 0; i < f->header.e_shnum; ++i) {
		relsec = f->sections[i];

		if (relsec->header.sh_type != SHT_RELM)
			continue;

		symsec = f->sections[relsec->header.sh_link];
		strsec = f->sections[symsec->header.sh_link];

		rel = (ElfW(RelM) *) relsec->contents;
		relend = rel + (relsec->header.sh_size / sizeof(ElfW(RelM)));
		symtab = (ElfW(Sym) *) symsec->contents;
		strtab = (const char *) strsec->contents;

		for (; rel < relend; ++rel) {
			extsym = &symtab[ELF32_R_SYM(rel->r_info)];
			
#if defined(BB_USE_GOT_ENTRIES)
			got_allocate = 0;
#endif
#if defined(BB_USE_PLT_ENTRIES)
			plt_allocate = 0;
#endif

			switch (ELF32_R_TYPE(rel->r_info)) {

#if defined(__arm__)

			case R_ARM_PC24:
			case R_ARM_PLT32:
				plt_allocate = 1;
				break;

			case R_ARM_GOTOFF:
			case R_ARM_GOTPC:
				got_needed = 1;
				continue;

			case R_ARM_GOT32:
				got_allocate = 1;
				break;

#elif defined(__i386__)

			case R_386_GOTPC:
			case R_386_GOTOFF:
				got_needed = 1;
				continue;

			case R_386_GOT32:
				got_allocate = 1;
				break;

#elif defined(__powerpc__)

			case R_PPC_REL24:
				plt_allocate = 1;
				break;

#elif defined(__mc68000__)

			case R_68K_GOT32:
				got_allocate = 1;
				break;

			case R_68K_GOTOFF:
				got_needed = 1;
				continue;

#elif defined(__sh__)

			case R_SH_GOT32:
				got_allocate = 1; 
				break;

			case R_SH_GOTPC:
			case R_SH_GOTOFF:
				got_needed = 1;
				continue;

#endif
			default:
				continue;
			}

			if (extsym->st_name != 0) {
				name = strtab + extsym->st_name;
			} else {
				name = f->sections[extsym->st_shndx]->name;
			}
			intsym = (struct arch_symbol *) obj_find_symbol(f, name);
#if defined(BB_USE_GOT_ENTRIES)
			if (got_allocate) {
				got_offset += arch_single_init(
					rel, &intsym->gotent, 
					got_offset, BB_GOT_ENTRY_SIZE);

				got_needed = 1;
			}
#endif
#if defined(BB_USE_PLT_ENTRIES)
			if (plt_allocate) {
#if defined(BB_USE_PLT_LIST) 
				plt_offset += arch_list_add(
					rel, &intsym->pltent, 
					plt_offset, BB_PLT_ENTRY_SIZE);
#else
				plt_offset += arch_single_init(
					rel, &intsym->pltent, 
					plt_offset, BB_PLT_ENTRY_SIZE);
#endif
				plt_needed = 1;
			}
#endif
		}
	}

#if defined(BB_USE_GOT_ENTRIES)
	if (got_needed) {
		ifile->got = arch_xsect_init(f, ".got", got_offset,
					    BB_GOT_ENTRY_SIZE);
	}
#endif

#if defined(BB_USE_PLT_ENTRIES)
	if (plt_needed) {
		ifile->plt = arch_xsect_init(f, ".plt", plt_offset,
					    BB_PLT_ENTRY_SIZE);
	}
#endif

#endif /* defined(BB_USE_GOT_ENTRIES) || defined(BB_USE_PLT_ENTRIES) */
}

#ifdef BB_FEATURE_NEW_MODULE_INTERFACE
static int arch_init_module(struct obj_file *f, struct new_module *mod)
{
	return 1;
}
#endif


/*======================================================================*/

/* Standard ELF hash function.  */
static inline unsigned long obj_elf_hash_n(const char *name, unsigned long n)
{
	unsigned long h = 0;
	unsigned long g;
	unsigned char ch;

	while (n > 0) {
		ch = *name++;
		h = (h << 4) + ch;
		if ((g = (h & 0xf0000000)) != 0) {
			h ^= g >> 24;
			h &= ~g;
		}
		n--;
	}
	return h;
}

static unsigned long obj_elf_hash(const char *name)
{
	return obj_elf_hash_n(name, strlen(name));
}

#ifdef BB_FEATURE_INSMOD_VERSION_CHECKING
/* String comparison for non-co-versioned kernel and module.  */

static int ncv_strcmp(const char *a, const char *b)
{
	size_t alen = strlen(a), blen = strlen(b);

	if (blen == alen + 10 && b[alen] == '_' && b[alen + 1] == 'R')
		return strncmp(a, b, alen);
	else if (alen == blen + 10 && a[blen] == '_' && a[blen + 1] == 'R')
		return strncmp(a, b, blen);
	else
		return strcmp(a, b);
}

/* String hashing for non-co-versioned kernel and module.  Here
   we are simply forced to drop the crc from the hash.  */

static unsigned long ncv_symbol_hash(const char *str)
{
	size_t len = strlen(str);
	if (len > 10 && str[len - 10] == '_' && str[len - 9] == 'R')
		len -= 10;
	return obj_elf_hash_n(str, len);
}

static void
obj_set_symbol_compare(struct obj_file *f,
					   int (*cmp) (const char *, const char *),
					   unsigned long (*hash) (const char *))
{
	if (cmp)
		f->symbol_cmp = cmp;
	if (hash) {
		struct obj_symbol *tmptab[HASH_BUCKETS], *sym, *next;
		int i;

		f->symbol_hash = hash;

		memcpy(tmptab, f->symtab, sizeof(tmptab));
		memset(f->symtab, 0, sizeof(f->symtab));

		for (i = 0; i < HASH_BUCKETS; ++i)
			for (sym = tmptab[i]; sym; sym = next) {
				unsigned long h = hash(sym->name) % HASH_BUCKETS;
				next = sym->next;
				sym->next = f->symtab[h];
				f->symtab[h] = sym;
			}
	}
}

#endif							/* BB_FEATURE_INSMOD_VERSION_CHECKING */

static struct obj_symbol *
obj_add_symbol(struct obj_file *f, const char *name,
								  unsigned long symidx, int info,
								  int secidx, ElfW(Addr) value,
								  unsigned long size)
{
	struct obj_symbol *sym;
	unsigned long hash = f->symbol_hash(name) % HASH_BUCKETS;
	int n_type = ELFW(ST_TYPE) (info);
	int n_binding = ELFW(ST_BIND) (info);

	for (sym = f->symtab[hash]; sym; sym = sym->next)
		if (f->symbol_cmp(sym->name, name) == 0) {
			int o_secidx = sym->secidx;
			int o_info = sym->info;
			int o_type = ELFW(ST_TYPE) (o_info);
			int o_binding = ELFW(ST_BIND) (o_info);

			/* A redefinition!  Is it legal?  */

			if (secidx == SHN_UNDEF)
				return sym;
			else if (o_secidx == SHN_UNDEF)
				goto found;
			else if (n_binding == STB_GLOBAL && o_binding == STB_LOCAL) {
				/* Cope with local and global symbols of the same name
				   in the same object file, as might have been created
				   by ld -r.  The only reason locals are now seen at this
				   level at all is so that we can do semi-sensible things
				   with parameters.  */

				struct obj_symbol *nsym, **p;

				nsym = arch_new_symbol();
				nsym->next = sym->next;
				nsym->ksymidx = -1;

				/* Excise the old (local) symbol from the hash chain.  */
				for (p = &f->symtab[hash]; *p != sym; p = &(*p)->next)
					continue;
				*p = sym = nsym;
				goto found;
			} else if (n_binding == STB_LOCAL) {
				/* Another symbol of the same name has already been defined.
				   Just add this to the local table.  */
				sym = arch_new_symbol();
				sym->next = NULL;
				sym->ksymidx = -1;
				f->local_symtab[symidx] = sym;
				goto found;
			} else if (n_binding == STB_WEAK)
				return sym;
			else if (o_binding == STB_WEAK)
				goto found;
			/* Don't unify COMMON symbols with object types the programmer
			   doesn't expect.  */
			else if (secidx == SHN_COMMON
					 && (o_type == STT_NOTYPE || o_type == STT_OBJECT))
				return sym;
			else if (o_secidx == SHN_COMMON
					 && (n_type == STT_NOTYPE || n_type == STT_OBJECT))
				goto found;
			else {
				/* Don't report an error if the symbol is coming from
				   the kernel or some external module.  */
				if (secidx <= SHN_HIRESERVE)
					error_msg("%s multiply defined", name);
				return sym;
			}
		}

	/* Completely new symbol.  */
	sym = arch_new_symbol();
	sym->next = f->symtab[hash];
	f->symtab[hash] = sym;
	sym->ksymidx = -1;

	if (ELFW(ST_BIND)(info) == STB_LOCAL && symidx != -1) {
		if (symidx >= f->local_symtab_size)
			error_msg("local symbol %s with index %ld exceeds local_symtab_size %ld",
					name, (long) symidx, (long) f->local_symtab_size);
		else
			f->local_symtab[symidx] = sym;
	}

  found:
	sym->name = name;
	sym->value = value;
	sym->size = size;
	sym->secidx = secidx;
	sym->info = info;

	return sym;
}

static struct obj_symbol *
obj_find_symbol(struct obj_file *f, const char *name)
{
	struct obj_symbol *sym;
	unsigned long hash = f->symbol_hash(name) % HASH_BUCKETS;

	for (sym = f->symtab[hash]; sym; sym = sym->next)
		if (f->symbol_cmp(sym->name, name) == 0)
			return sym;

	return NULL;
}

static ElfW(Addr)
	obj_symbol_final_value(struct obj_file * f, struct obj_symbol * sym)
{
	if (sym) {
		if (sym->secidx >= SHN_LORESERVE)
			return sym->value;

		return sym->value + f->sections[sym->secidx]->header.sh_addr;
	} else {
		/* As a special case, a NULL sym has value zero.  */
		return 0;
	}
}

static struct obj_section *obj_find_section(struct obj_file *f, const char *name)
{
	int i, n = f->header.e_shnum;

	for (i = 0; i < n; ++i)
		if (strcmp(f->sections[i]->name, name) == 0)
			return f->sections[i];

	return NULL;
}

static int obj_load_order_prio(struct obj_section *a)
{
	unsigned long af, ac;

	af = a->header.sh_flags;

	ac = 0;
	if (a->name[0] != '.' || strlen(a->name) != 10 ||
		strcmp(a->name + 5, ".init"))
		ac |= 32;
	if (af & SHF_ALLOC)
		ac |= 16;
	if (!(af & SHF_WRITE))
		ac |= 8;
	if (af & SHF_EXECINSTR)
		ac |= 4;
	if (a->header.sh_type != SHT_NOBITS)
		ac |= 2;

	return ac;
}

static void
obj_insert_section_load_order(struct obj_file *f, struct obj_section *sec)
{
	struct obj_section **p;
	int prio = obj_load_order_prio(sec);
	for (p = f->load_order_search_start; *p; p = &(*p)->load_next)
		if (obj_load_order_prio(*p) < prio)
			break;
	sec->load_next = *p;
	*p = sec;
}

static struct obj_section *obj_create_alloced_section(struct obj_file *f,
											   const char *name,
											   unsigned long align,
											   unsigned long size)
{
	int newidx = f->header.e_shnum++;
	struct obj_section *sec;

	f->sections = xrealloc(f->sections, (newidx + 1) * sizeof(sec));
	f->sections[newidx] = sec = arch_new_section();

	memset(sec, 0, sizeof(*sec));
	sec->header.sh_type = SHT_PROGBITS;
	sec->header.sh_flags = SHF_WRITE | SHF_ALLOC;
	sec->header.sh_size = size;
	sec->header.sh_addralign = align;
	sec->name = name;
	sec->idx = newidx;
	if (size)
		sec->contents = xmalloc(size);

	obj_insert_section_load_order(f, sec);

	return sec;
}

static struct obj_section *obj_create_alloced_section_first(struct obj_file *f,
													 const char *name,
													 unsigned long align,
													 unsigned long size)
{
	int newidx = f->header.e_shnum++;
	struct obj_section *sec;