path: root/ldso/ldso/fdpic/dl-inlines.h

/* Copyright (C) 2003, 2004 Red Hat, Inc.
 * Contributed by Alexandre Oliva <aoliva@redhat.com>
 * Copyright (C) 2006-2011 Analog Devices, Inc.
 *
 * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
 */

/* Initialize a DL_LOADADDR_TYPE given a got pointer and a complete load map. */
static __always_inline void
__dl_init_loadaddr_map(struct elf32_fdpic_loadaddr *loadaddr, Elf32_Addr dl_boot_got_pointer,
                       struct elf32_fdpic_loadmap *map)
{
	if (map->version != 0) {
		SEND_EARLY_STDERR("Invalid loadmap version number\n");
		_dl_exit(-1);
	}
	if (map->nsegs == 0) {
		SEND_EARLY_STDERR("Invalid segment count in loadmap\n");
		_dl_exit(-1);
	}
	loadaddr->got_value = (void *)dl_boot_got_pointer;
	loadaddr->map = map;
}

/*
 * Figure out how many LOAD segments there are in the given headers,
 * and allocate a block for the load map big enough for them.
 * got_value will be properly initialized later on, with INIT_GOT.
 */
static __always_inline int
__dl_init_loadaddr(struct elf32_fdpic_loadaddr *loadaddr, Elf32_Phdr *ppnt,
                   int pcnt)
{
	int count = 0, i;
	size_t size;

	for (i = 0; i < pcnt; i++)
		if (ppnt[i].p_type == PT_LOAD)
			count++;

	loadaddr->got_value = 0;

	size = sizeof(struct elf32_fdpic_loadmap) +
		(sizeof(struct elf32_fdpic_loadseg) * count);
	loadaddr->map = _dl_malloc(size);
	if (!loadaddr->map)
		_dl_exit(-1);

	loadaddr->map->version = 0;
	loadaddr->map->nsegs = 0;

	return count;
}

/* Incrementally initialize a load map. */
static __always_inline void
__dl_init_loadaddr_hdr(struct elf32_fdpic_loadaddr loadaddr, void *addr,
                       Elf32_Phdr *phdr, int maxsegs)
{
	struct elf32_fdpic_loadseg *segdata;

	if (loadaddr.map->nsegs == maxsegs)
		_dl_exit(-1);

	segdata = &loadaddr.map->segs[loadaddr.map->nsegs++];
	segdata->addr = (Elf32_Addr)addr;
	segdata->p_vaddr = phdr->p_vaddr;
	segdata->p_memsz = phdr->p_memsz;

#if defined(__SUPPORT_LD_DEBUG__)
	if (_dl_debug)
		_dl_dprintf(_dl_debug_file, "%i: mapped %x at %x, size %x\n",
			loadaddr.map->nsegs - 1,
			segdata->p_vaddr, segdata->addr, segdata->p_memsz);
#endif
}

/* Replace an existing entry in the load map. */
static __always_inline void
__dl_update_loadaddr_hdr(struct elf32_fdpic_loadaddr loadaddr, void *addr,
                         Elf32_Phdr *phdr)
{
	struct elf32_fdpic_loadseg *segdata;
	void *oldaddr;
	int i;

	for (i = 0; i < loadaddr.map->nsegs; i++)
		if (loadaddr.map->segs[i].p_vaddr == phdr->p_vaddr &&
		    loadaddr.map->segs[i].p_memsz == phdr->p_memsz)
			break;
	if (i == loadaddr.map->nsegs)
		_dl_exit(-1);

	segdata = loadaddr.map->segs + i;
	oldaddr = (void *)segdata->addr;
	_dl_munmap(oldaddr, segdata->p_memsz);
	segdata->addr = (Elf32_Addr)addr;

#if defined (__SUPPORT_LD_DEBUG__)
	if (_dl_debug)
		_dl_dprintf(_dl_debug_file, "%i: changed mapping %x at %x (old %x), size %x\n",
			loadaddr.map->nsegs - 1,
			segdata->p_vaddr, segdata->addr, oldaddr, segdata->p_memsz);
#endif
}


#ifndef __dl_loadaddr_unmap
static __always_inline void
__dl_loadaddr_unmap(struct elf32_fdpic_loadaddr loadaddr,
                    struct funcdesc_ht *funcdesc_ht)
{
	int i;

	for (i = 0; i < loadaddr.map->nsegs; i++)
		_dl_munmap((void *)loadaddr.map->segs[i].addr,
			loadaddr.map->segs[i].p_memsz);

	/*
	 * _dl_unmap is only called for dlopen()ed libraries, for which
	 * calling free() is safe, or before we've completed the initial
	 * relocation, in which case calling free() is probably pointless,
	 * but still safe.
	 */
	_dl_free(loadaddr.map);
	if (funcdesc_ht)
		htab_delete(funcdesc_ht);
}
#endif

/* Figure out whether the given address is in one of the mapped segments. */
static __always_inline int
__dl_addr_in_loadaddr(void *p, struct elf32_fdpic_loadaddr loadaddr)
{
	struct elf32_fdpic_loadmap *map = loadaddr.map;
	int c;

	for (c = 0; c < map->nsegs; c++)
		if ((void *)map->segs[c].addr <= p &&
		    (char *)p < (char *)map->segs[c].addr + map->segs[c].p_memsz)
			return 1;

	return 0;
}

/*
 * The hashcode handling code below is heavily inspired in libiberty's
 * hashtab code, but with most adaptation points and support for
 * deleting elements removed.
 *
 * Copyright (C) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
 * Contributed by Vladimir Makarov (vmakarov@cygnus.com).
 */
static __always_inline unsigned long
higher_prime_number(unsigned long n)
{
	/* These are primes that are near, but slightly smaller than, a power of two. */
	static const unsigned long primes[] = {
		7,
		13,
		31,
		61,
		127,
		251,
		509,
		1021,
		2039,
		4093,
		8191,
		16381,
		32749,
		65521,
		131071,
		262139,
		524287,
		1048573,
		2097143,
		4194301,
		8388593,
		16777213,
		33554393,
		67108859,
		134217689,
		268435399,
		536870909,
		1073741789,
		/* 4294967291 */
		((unsigned long) 2147483647) + ((unsigned long) 2147483644),
	};
	const unsigned long *low = &primes[0];
	const unsigned long *high = &primes[ARRAY_SIZE(primes)];

	while (low != high) {
		const unsigned long *mid = low + (high - low) / 2;
		if (n > *mid)
			low = mid + 1;
		else
			high = mid;
	}

#if 0
	/* If we've run out of primes, abort.  */
	if (n > *low) {
		fprintf(stderr, "Cannot find prime bigger than %lu\n", n);
		abort();
	}
#endif

	return *low;
}

struct funcdesc_ht
{
	/* Table itself */
	struct funcdesc_value **entries;

	/* Current size (in entries) of the hash table */
	size_t size;

	/* Current number of elements */
	size_t n_elements;
};

static __always_inline int
hash_pointer(const void *p)
{
	return (int) ((long)p >> 3);
}

static __always_inline struct funcdesc_ht *
htab_create(void)
{
	struct funcdesc_ht *ht = _dl_malloc(sizeof(*ht));
	size_t ent_size;

	if (!ht)
		return NULL;
	ht->size = 3;
	ent_size = sizeof(struct funcdesc_ht_value *) * ht->size;
	ht->entries = _dl_malloc(ent_size);
	if (!ht->entries)
		return NULL;

	ht->n_elements = 0;
	_dl_memset(ht->entries, 0, ent_size);

	return ht;
}

/*
 * This is only called from _dl_loadaddr_unmap, so it's safe to call
 * _dl_free().  See the discussion below.
 */
static __always_inline void
htab_delete(struct funcdesc_ht *htab)
{
	size_t i;

	for (i = htab->size - 1; i >= 0; i--)
		if (htab->entries[i])
			_dl_free(htab->entries[i]);

	_dl_free(htab->entries);
	_dl_free(htab);
}

/*
 * Similar to htab_find_slot, but without several unwanted side effects:
 *  - Does not call htab->eq_f when it finds an existing entry.
 *  - Does not change the count of elements/searches/collisions in the
 *    hash table.
 * This function also assumes there are no deleted entries in the table.
 * HASH is the hash value for the element to be inserted.
 */
static __always_inline struct funcdesc_value **
find_empty_slot_for_expand(struct funcdesc_ht *htab, int hash)
{
	size_t size = htab->size;
	unsigned int index = hash % size;
	struct funcdesc_value **slot = htab->entries + index;
	int hash2;

	if (!*slot)
		return slot;

	hash2 = 1 + hash % (size - 2);
	for (;;) {
		index += hash2;
		if (index >= size)
			index -= size;

		slot = htab->entries + index;
		if (!*slot)
			return slot;
	}
}

/*
 * The following function changes size of memory allocated for the
 * entries and repeatedly inserts the table elements.  The occupancy
 * of the table after the call will be about 50%.  Naturally the hash
 * table must already exist.  Remember also that the place of the
 * table entries is changed.  If memory allocation failures are allowed,
 * this function will return zero, indicating that the table could not be
 * expanded.  If all goes well, it will return a non-zero value.
 */
static __always_inline int
htab_expand(struct funcdesc_ht *htab)
{
	struct funcdesc_value **oentries;
	struct funcdesc_value **olimit;
	struct funcdesc_value **p;
	struct funcdesc_value **nentries;
	size_t nsize;

	oentries = htab->entries;
	olimit = oentries + htab->size;

	/*
	 * Resize only when table after removal of unused elements is either
	 * too full or too empty.
	 */
	if (htab->n_elements * 2 > htab->size)
		nsize = higher_prime_number(htab->n_elements * 2);
	else
		nsize = htab->size;

	nentries = _dl_malloc(sizeof(*nentries) * nsize);
	_dl_memset(nentries, 0, sizeof(*nentries) * nsize);
	if (nentries == NULL)
		return 0;
	htab->entries = nentries;
	htab->size = nsize;

	p = oentries;
	do {
		if (*p)
			*find_empty_slot_for_expand(htab, hash_pointer((*p)->entry_point)) = *p;
		p++;
	} while (p < olimit);

#if 0
	/*
	 * We can't tell whether this was allocated by the _dl_malloc()
	 * built into ld.so or malloc() in the main executable or libc,
	 * and calling free() for something that wasn't malloc()ed could
	 * do Very Bad Things (TM).  Take the conservative approach
	 * here, potentially wasting as much memory as actually used by
	 * the hash table, even if multiple growths occur.  That's not
	 * so bad as to require some overengineered solution that would
	 * enable us to keep track of how it was allocated.
	 */
	_dl_free(oentries);
#endif
	return 1;
}

/*
 * This function searches for a hash table slot containing an entry
 * equal to the given element.  To delete an entry, call this with
 * INSERT = 0, then call htab_clear_slot on the slot returned (possibly
 * after doing some checks).  To insert an entry, call this with
 * INSERT = 1, then write the value you want into the returned slot.
 * When inserting an entry, NULL may be returned if memory allocation
 * fails.
 */
static __always_inline struct funcdesc_value **
htab_find_slot(struct funcdesc_ht *htab, void *ptr, int insert)
{
	unsigned int index;
	int hash, hash2;
	size_t size;
	struct funcdesc_value **entry;

	if (htab->size * 3 <= htab->n_elements * 4 &&
	    htab_expand(htab) == 0)
		return NULL;

	hash = hash_pointer(ptr);

	size = htab->size;
	index = hash % size;

	entry = &htab->entries[index];
	if (!*entry)
		goto empty_entry;
	else if ((*entry)->entry_point == ptr)
		return entry;

	hash2 = 1 + hash % (size - 2);
	for (;;) {
		index += hash2;
		if (index >= size)
			index -= size;

		entry = &htab->entries[index];
		if (!*entry)
			goto empty_entry;
		else if ((*entry)->entry_point == ptr)
			return entry;
	}

 empty_entry:
	if (!insert)
		return NULL;

	htab->n_elements++;
	return entry;
}

void *
_dl_funcdesc_for (void *entry_point, void *got_value)
{
	struct elf_resolve *tpnt = ((void**)got_value)[2];
	struct funcdesc_ht *ht = tpnt->funcdesc_ht;
	struct funcdesc_value **entry;

	_dl_assert(got_value == tpnt->loadaddr.got_value);

	if (!ht) {
		ht = htab_create();
		if (!ht)
			return (void*)-1;
		tpnt->funcdesc_ht = ht;
	}

	entry = htab_find_slot(ht, entry_point, 1);
	if (*entry) {
		_dl_assert((*entry)->entry_point == entry_point);
		return _dl_stabilize_funcdesc(*entry);
	}

	*entry = _dl_malloc(sizeof(**entry));
	(*entry)->entry_point = entry_point;
	(*entry)->got_value = got_value;

	return _dl_stabilize_funcdesc(*entry);
}

static __always_inline void const *
_dl_lookup_address(void const *address)
{
	struct elf_resolve *rpnt;
	struct funcdesc_value const *fd;

	/* Make sure we don't make assumptions about its alignment.  */
	__asm__ ("" : "+r" (address));

	if ((Elf32_Addr)address & 7)
		/* It's not a function descriptor.  */
		return address;

	fd = address;

	for (rpnt = _dl_loaded_modules; rpnt; rpnt = rpnt->next) {
		if (!rpnt->funcdesc_ht)
			continue;

		if (fd->got_value != rpnt->loadaddr.got_value)
			continue;

		address = htab_find_slot(rpnt->funcdesc_ht, (void *)fd->entry_point, 0);

		if (address && *(struct funcdesc_value *const*)address == fd) {
			address = (*(struct funcdesc_value *const*)address)->entry_point;
			break;
		} else
			address = fd;
	}

	return address;
}