elf.c

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    target = (Elf_Addr)(defobj->relocbase + def->st_value);

    dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
      defobj->strtab + def->st_name, basename(obj->path),
      (void *)target, basename(defobj->path));

    /*
     * Write the new contents for the jmpslot. Note that depending on
     * architecture, the value which we need to return back to the
     * lazy binding trampoline may or may not be the target
     * address. The value returned from reloc_jmpslot() is the value
     * that the trampoline needs.
     */
    target = reloc_jmpslot(where, target, defobj, obj, rel);
    rlock_release(rtld_bind_lock, lockstate);
    return target;
}

#if 0

/*
 * Error reporting function.  Use it like printf.  If formats the message
 * into a buffer, and sets things up so that the next call to dlerror()
 * will return the message.
 */
void
_rtld_error(const char *fmt, ...)
{
    static char buf[512];
    va_list ap;

    va_start(ap, fmt);
    vsnprintf(buf, sizeof buf, fmt, ap);
    error_message = buf;
    va_end(ap);
}

/*
 * Return a dynamically-allocated copy of the current error message, if any.
 */
static char *
errmsg_save(void)
{
    return error_message == NULL ? NULL : xstrdup(error_message);
}

/*
 * Restore the current error message from a copy which was previously saved
 * by errmsg_save().  The copy is freed.
 */
static void
errmsg_restore(char *saved_msg)
{
    if (saved_msg == NULL)
	error_message = NULL;
    else {
	_rtld_error("%s", saved_msg);
	free(saved_msg);
    }
}

static const char *
basename(const char *name)
{
    const char *p = strrchr(name, '/');
    return p != NULL ? p + 1 : name;
}

static void
die(void)
{
    const char *msg = dlerror();

    if (msg == NULL)
	msg = "Fatal error";
    errx(1, "%s", msg);
}

#endif /* 0 */

/*
 * Process a shared object's DYNAMIC section, and save the important
 * information in its Obj_Entry structure.
 */
static void
digest_dynamic(Obj_Entry *obj, int early)
{
    const Elf_Dyn *dynp;
    Needed_Entry **needed_tail = &obj->needed;
    const Elf_Dyn *dyn_rpath = NULL;
    int plttype = DT_REL;

    obj->bind_now = false;
    for (dynp = obj->dynamic;  dynp->d_tag != DT_NULL;  dynp++) {
	switch (dynp->d_tag) {

	case DT_REL:
	    obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_RELSZ:
	    obj->relsize = dynp->d_un.d_val;
	    break;

	case DT_RELENT:
	    assert(dynp->d_un.d_val == sizeof(Elf_Rel));
	    break;

	case DT_JMPREL:
	    obj->pltrel = (const Elf_Rel *)
	      (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_PLTRELSZ:
	    obj->pltrelsize = dynp->d_un.d_val;
	    break;

	case DT_RELA:
	    obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_RELASZ:
	    obj->relasize = dynp->d_un.d_val;
	    break;

	case DT_RELAENT:
	    assert(dynp->d_un.d_val == sizeof(Elf_Rela));
	    break;

	case DT_PLTREL:
	    plttype = dynp->d_un.d_val;
	    assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA);
	    break;

	case DT_SYMTAB:
	    obj->symtab = (const Elf_Sym *)
	      (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_SYMENT:
	    assert(dynp->d_un.d_val == sizeof(Elf_Sym));
	    break;

	case DT_STRTAB:
	    obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_STRSZ:
	    obj->strsize = dynp->d_un.d_val;
	    break;

	case DT_HASH:
	    {
		const Elf_Hashelt *hashtab = (const Elf_Hashelt *)
		  (obj->relocbase + dynp->d_un.d_ptr);
		obj->nbuckets = hashtab[0];
		obj->nchains = hashtab[1];
		obj->buckets = hashtab + 2;
		obj->chains = obj->buckets + obj->nbuckets;
	    }
	    break;

	case DT_NEEDED:
	    if (!obj->rtld) {
		Needed_Entry *nep = NEW(Needed_Entry);
		nep->name = dynp->d_un.d_val;
		nep->obj = NULL;
		nep->next = NULL;

		*needed_tail = nep;
		needed_tail = &nep->next;
	    }
	    break;

	case DT_PLTGOT:
	    obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_TEXTREL:
	    obj->textrel = true;
	    break;

	case DT_SYMBOLIC:
	    obj->symbolic = true;
	    break;

	case DT_RPATH:
	case DT_RUNPATH:	/* XXX: process separately */
	    /*
	     * We have to wait until later to process this, because we
	     * might not have gotten the address of the string table yet.
	     */
	    dyn_rpath = dynp;
	    break;

	case DT_SONAME:
	    /* Not used by the dynamic linker. */
	    break;

	case DT_INIT:
	    obj->init = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_FINI:
	    obj->fini = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr);
	    break;

	case DT_DEBUG:
	    /* XXX - not implemented yet */
	    if (!early)
		dbg("Filling in DT_DEBUG entry");
	    ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug;
	    break;

	case DT_FLAGS:
		if (dynp->d_un.d_val & DF_ORIGIN) {
		    obj->origin_path = xmalloc(PATH_MAX);
		    if (rtld_dirname(obj->path, obj->origin_path) == -1)
			die();
		}
		if (dynp->d_un.d_val & DF_SYMBOLIC)
		    obj->symbolic = true;
		if (dynp->d_un.d_val & DF_TEXTREL)
		    obj->textrel = true;
		if (dynp->d_un.d_val & DF_BIND_NOW)
		    obj->bind_now = true;
		if (dynp->d_un.d_val & DF_STATIC_TLS)
		    ;
	    break;

	default:
	    if (!early) {
		dbg("Ignoring d_tag %ld = %#lx", (long)dynp->d_tag,
		    (long)dynp->d_tag);
	    }
	    break;
	}
    }

    obj->traced = false;

    if (plttype == DT_RELA) {
	obj->pltrela = (const Elf_Rela *) obj->pltrel;
	obj->pltrel = NULL;
	obj->pltrelasize = obj->pltrelsize;
	obj->pltrelsize = 0;
    }

    if (dyn_rpath != NULL)
	obj->rpath = obj->strtab + dyn_rpath->d_un.d_val;
}

/*
 * Process a shared object's program header.  This is used only for the
 * main program, when the kernel has already loaded the main program
 * into memory before calling the dynamic linker.  It creates and
 * returns an Obj_Entry structure.
 */
static Obj_Entry *
digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
{
    Obj_Entry *obj;
    const Elf_Phdr *phlimit = phdr + phnum;
    const Elf_Phdr *ph;
    int nsegs = 0;

    obj = obj_new();
    for (ph = phdr;  ph < phlimit;  ph++) {
	switch (ph->p_type) {

	case PT_PHDR:
	    if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
		_rtld_error("%s: invalid PT_PHDR", path);
		return NULL;
	    }
	    obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
	    obj->phsize = ph->p_memsz;
	    break;

	case PT_INTERP:
	    obj->interp = (const char *) ph->p_vaddr;
	    break;

	case PT_LOAD:
	    if (nsegs == 0) {	/* First load segment */
		obj->vaddrbase = trunc_page(ph->p_vaddr);
		obj->mapbase = (caddr_t) obj->vaddrbase;
		obj->relocbase = obj->mapbase - obj->vaddrbase;
		obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
		  obj->vaddrbase;
	    } else {		/* Last load segment */
		obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
		  obj->vaddrbase;
	    }
	    nsegs++;
	    break;

	case PT_DYNAMIC:
	    obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
	    break;

	case PT_TLS:
	    obj->tlsindex = 1;
	    obj->tlssize = ph->p_memsz;
	    obj->tlsalign = ph->p_align;
	    obj->tlsinitsize = ph->p_filesz;
	    obj->tlsinit = (void*) ph->p_vaddr;
	    break;
	}
    }
    if (nsegs < 1) {
	_rtld_error("%s: too few PT_LOAD segments", path);
	return NULL;
    }

    obj->entry = entry;
    return obj;
}

#if 0

static Obj_Entry *
dlcheck(void *handle)
{
    Obj_Entry *obj;

    for (obj = obj_list;  obj != NULL;  obj = obj->next)
	if (obj == (Obj_Entry *) handle)
	    break;

    if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
	_rtld_error("Invalid shared object handle %p", handle);
	return NULL;
    }
    return obj;
}

/*
 * If the given object is already in the donelist, return true.  Otherwise
 * add the object to the list and return false.
 */
static bool
donelist_check(DoneList *dlp, const Obj_Entry *obj)
{
    unsigned int i;

    for (i = 0;  i < dlp->num_used;  i++)
	if (dlp->objs[i] == obj)
	    return true;
    /*
     * Our donelist allocation should always be sufficient.  But if
     * our threads locking isn't working properly, more shared objects
     * could have been loaded since we allocated the list.  That should
     * never happen, but we'll handle it properly just in case it does.
     */
    if (dlp->num_used < dlp->num_alloc)
	dlp->objs[dlp->num_used++] = obj;
    return false;
}

#endif /* 0 */

/*
 * Hash function for symbol table lookup.  Don't even think about changing
 * this.  It is specified by the System V ABI.
 */
unsigned long
elf_hash(const char *name)
{
    const unsigned char *p = (const unsigned char *) name;
    unsigned long h = 0;
    unsigned long g;

    while (*p != '\0') {
	h = (h << 4) + *p++;
	if ((g = h & 0xf0000000) != 0)
	    h ^= g >> 24;
	h &= ~g;
    }
    return h;
}

#if 0

/*
 * Find the library with the given name, and return its full pathname.
 * The returned string is dynamically allocated.  Generates an error
 * message and returns NULL if the library cannot be found.
 *
 * If the second argument is non-NULL, then it refers to an already-
 * loaded shared object, whose library search path will be searched.
 *
 * The search order is:
 *   LD_LIBRARY_PATH
 *   rpath in the referencing file
 *   ldconfig hints
 *   /lib:/usr/lib
 */
static char *
find_library(const char *xname, const Obj_Entry *refobj)
{
    char *pathname;
    char *name;

    if (strchr(xname, '/') != NULL) {	/* Hard coded pathname */
	if (xname[0] != '/' && !trust) {
	    _rtld_error("Absolute pathname required for shared object \"%s\"",
	      xname);
	    return NULL;
	}
	return xstrdup(xname);
    }

    if (libmap_disable || (refobj == NULL) ||
	(name = lm_find(refobj->path, xname)) == NULL)
	name = (char *)xname;

    dbg(" Searching for \"%s\"", name);

    if ((pathname = search_library_path(name, ld_library_path)) != NULL ||
      (refobj != NULL &&
      (pathname = search_library_path(name, refobj->rpath)) != NULL) ||
      (pathname = search_library_path(name, gethints())) != NULL ||
      (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL)
	return pathname;

    if(refobj != NULL && refobj->path != NULL) {
	_rtld_error("Shared object \"%s\" not found, required by \"%s\"",
	  name, basename(refobj->path));
    } else {
	_rtld_error("Shared object \"%s\" not found", name);
    }
    return NULL;
}

#endif /* 0 */

/*
 * Given a symbol number in a referencing object, find the corresponding
 * definition of the symbol.  Returns a pointer to the symbol, or NULL if
 * no definition was found.  Returns a pointer to the Obj_Entry of the
 * defining object via the reference parameter DEFOBJ_OUT.
 */
const Elf_Sym *
find_symdef(unsigned long symnum, const Obj_Entry *refobj,
    const Obj_Entry **defobj_out, bool in_plt, SymCache *cache)
{
    const Elf_Sym *ref;
    const Elf_Sym *def;
    const Obj_Entry *defobj;
    const char *name;
    unsigned long hash;

    /*
     * If we have already found this symbol, get the information from
     * the cache.
     */
    if (symnum >= refobj->nchains)
	return NULL;	/* Bad object */
    if (cache != NULL && cache[symnum].sym != NULL) {
	*defobj_out = cache[symnum].obj;
	return cache[symnum].sym;
    }

    ref = refobj->symtab + symnum;
    name = refobj->strtab + ref->st_name;
    defobj = NULL;

    /*
     * We don't have to do a full scale lookup if the symbol is local.
     * We know it will bind to the instance in this load module; to
     * which we already have a pointer (ie ref). By not doing a lookup,
     * we not only improve performance, but it also avoids unresolvable
     * symbols when local symbols are not in the hash table. This has
     * been seen with the ia64 toolchain.
     */
    if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) {
	if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) {
	    _rtld_error("%s: Bogus symbol table entry %lu", refobj->path,
		symnum);
	}