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bpf: Simplify bpf_prog_pack_[size|mask]
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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: Song Liu <song@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20220713204950.3015201-1-song@kernel.org
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Song Liu authored and Daniel Borkmann committed Jul 22, 2022
1 parent 00963a2 commit ea2baba
Showing 1 changed file with 17 additions and 54 deletions.
71 changes: 17 additions & 54 deletions kernel/bpf/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -825,71 +825,40 @@ 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);

/* PMD_SIZE is not available in some special config, e.g. ARCH=arm with
* 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;
}

Expand All @@ -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) {
Expand All @@ -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;
}

Expand All @@ -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;
}
Expand All @@ -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);
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