Commit ea2babac authored by Song Liu's avatar Song Liu Committed by Daniel Borkmann
Browse files

bpf: Simplify bpf_prog_pack_[size|mask] 

Simplify the logic that selects bpf_prog_pack_size, and always use
(PMD_SIZE * num_possible_nodes()). This is a good tradeoff, as most of
the performance benefit observed is from less direct map fragmentation [0].

Also, module_alloc(4MB) may not allocate 4MB aligned memory. Therefore,
we cannot use (ptr & bpf_prog_pack_mask) to find the correct address of
bpf_prog_pack. Fix this by checking the header address falls in the range
of pack->ptr and (pack->ptr + bpf_prog_pack_size).

  [0] https://lore.kernel.org/bpf/20220707223546.4124919-1-song@kernel.org/



Signed-off-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20220713204950.3015201-1-song@kernel.org
parent 00963a2e

kernel/bpf/core.c

+17 −54
Original line number Diff line number Diff line
@@ -825,15 +825,6 @@ struct bpf_prog_pack { 


#define BPF_PROG_SIZE_TO_NBITS(size)	(round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE)



static size_t bpf_prog_pack_size = -1;

static size_t bpf_prog_pack_mask = -1;



static int bpf_prog_chunk_count(void)

{

	WARN_ON_ONCE(bpf_prog_pack_size == -1);

	return bpf_prog_pack_size / BPF_PROG_CHUNK_SIZE;

}



static DEFINE_MUTEX(pack_mutex);

static LIST_HEAD(pack_list);
@@ -841,55 +832,33 @@ static LIST_HEAD(pack_list); 
 * CONFIG_MMU=n. Use PAGE_SIZE in these cases.

 */

#ifdef PMD_SIZE

#define BPF_HPAGE_SIZE PMD_SIZE

#define BPF_HPAGE_MASK PMD_MASK

#define BPF_PROG_PACK_SIZE (PMD_SIZE * num_possible_nodes())

#else

#define BPF_HPAGE_SIZE PAGE_SIZE

#define BPF_HPAGE_MASK PAGE_MASK

#define BPF_PROG_PACK_SIZE PAGE_SIZE

#endif



static size_t select_bpf_prog_pack_size(void)

{

	size_t size;

	void *ptr;



	size = BPF_HPAGE_SIZE * num_online_nodes();

	ptr = module_alloc(size);



	/* Test whether we can get huge pages. If not just use PAGE_SIZE

	 * packs.

	 */

	if (!ptr || !is_vm_area_hugepages(ptr)) {

		size = PAGE_SIZE;

		bpf_prog_pack_mask = PAGE_MASK;

	} else {

		bpf_prog_pack_mask = BPF_HPAGE_MASK;

	}



	vfree(ptr);

	return size;

}

#define BPF_PROG_CHUNK_COUNT (BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE)



static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_insns)

{

	struct bpf_prog_pack *pack;



	pack = kzalloc(struct_size(pack, bitmap, BITS_TO_LONGS(bpf_prog_chunk_count())),

	pack = kzalloc(struct_size(pack, bitmap, BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)),

		       GFP_KERNEL);

	if (!pack)

		return NULL;

	pack->ptr = module_alloc(bpf_prog_pack_size);

	pack->ptr = module_alloc(BPF_PROG_PACK_SIZE);

	if (!pack->ptr) {

		kfree(pack);

		return NULL;

	}

	bpf_fill_ill_insns(pack->ptr, bpf_prog_pack_size);

	bitmap_zero(pack->bitmap, bpf_prog_pack_size / BPF_PROG_CHUNK_SIZE);

	bpf_fill_ill_insns(pack->ptr, BPF_PROG_PACK_SIZE);

	bitmap_zero(pack->bitmap, BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE);

	list_add_tail(&pack->list, &pack_list);



	set_vm_flush_reset_perms(pack->ptr);

	set_memory_ro((unsigned long)pack->ptr, bpf_prog_pack_size / PAGE_SIZE);

	set_memory_x((unsigned long)pack->ptr, bpf_prog_pack_size / PAGE_SIZE);

	set_memory_ro((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);

	set_memory_x((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);

	return pack;

}
@@ -901,10 +870,7 @@ static void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insn 
	void *ptr = NULL;



	mutex_lock(&pack_mutex);

	if (bpf_prog_pack_size == -1)

		bpf_prog_pack_size = select_bpf_prog_pack_size();



	if (size > bpf_prog_pack_size) {

	if (size > BPF_PROG_PACK_SIZE) {

		size = round_up(size, PAGE_SIZE);

		ptr = module_alloc(size);

		if (ptr) {
@@ -916,9 +882,9 @@ static void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insn 
		goto out;

	}

	list_for_each_entry(pack, &pack_list, list) {

		pos = bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,

		pos = bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0,

						 nbits, 0);

		if (pos < bpf_prog_chunk_count())

		if (pos < BPF_PROG_CHUNK_COUNT)

			goto found_free_area;

	}
@@ -942,18 +908,15 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr) 
	struct bpf_prog_pack *pack = NULL, *tmp;

	unsigned int nbits;

	unsigned long pos;

	void *pack_ptr;



	mutex_lock(&pack_mutex);

	if (hdr->size > bpf_prog_pack_size) {

	if (hdr->size > BPF_PROG_PACK_SIZE) {

		module_memfree(hdr);

		goto out;

	}



	pack_ptr = (void *)((unsigned long)hdr & bpf_prog_pack_mask);



	list_for_each_entry(tmp, &pack_list, list) {

		if (tmp->ptr == pack_ptr) {

		if ((void *)hdr >= tmp->ptr && (tmp->ptr + BPF_PROG_PACK_SIZE) > (void *)hdr) {

			pack = tmp;

			break;

		}
@@ -963,14 +926,14 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr) 
		goto out;



	nbits = BPF_PROG_SIZE_TO_NBITS(hdr->size);

	pos = ((unsigned long)hdr - (unsigned long)pack_ptr) >> BPF_PROG_CHUNK_SHIFT;

	pos = ((unsigned long)hdr - (unsigned long)pack->ptr) >> BPF_PROG_CHUNK_SHIFT;



	WARN_ONCE(bpf_arch_text_invalidate(hdr, hdr->size),

		  "bpf_prog_pack bug: missing bpf_arch_text_invalidate?\n");



	bitmap_clear(pack->bitmap, pos, nbits);

	if (bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,

				       bpf_prog_chunk_count(), 0) == 0) {

	if (bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0,

				       BPF_PROG_CHUNK_COUNT, 0) == 0) {

		list_del(&pack->list);

		module_memfree(pack->ptr);

		kfree(pack);