diff options
-rw-r--r-- | kernel/bpf/core.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index a5ec480f9862..7ae590897b73 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -805,6 +805,133 @@ int bpf_jit_add_poke_descriptor(struct bpf_prog *prog, return slot; } +/* + * BPF program pack allocator. + * + * Most BPF programs are pretty small. Allocating a hole page for each + * program is sometime a waste. Many small bpf program also adds pressure + * to instruction TLB. To solve this issue, we introduce a BPF program pack + * allocator. The prog_pack allocator uses HPAGE_PMD_SIZE page (2MB on x86) + * to host BPF programs. + */ +#define BPF_PROG_PACK_SIZE HPAGE_PMD_SIZE +#define BPF_PROG_CHUNK_SHIFT 6 +#define BPF_PROG_CHUNK_SIZE (1 << BPF_PROG_CHUNK_SHIFT) +#define BPF_PROG_CHUNK_MASK (~(BPF_PROG_CHUNK_SIZE - 1)) +#define BPF_PROG_CHUNK_COUNT (BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE) + +struct bpf_prog_pack { + struct list_head list; + void *ptr; + unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)]; +}; + +#define BPF_PROG_MAX_PACK_PROG_SIZE HPAGE_PMD_SIZE +#define BPF_PROG_SIZE_TO_NBITS(size) (round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE) + +static DEFINE_MUTEX(pack_mutex); +static LIST_HEAD(pack_list); + +static struct bpf_prog_pack *alloc_new_pack(void) +{ + struct bpf_prog_pack *pack; + + pack = kzalloc(sizeof(*pack), GFP_KERNEL); + if (!pack) + return NULL; + pack->ptr = module_alloc(BPF_PROG_PACK_SIZE); + if (!pack->ptr) { + kfree(pack); + return NULL; + } + 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); + return pack; +} + +static void *bpf_prog_pack_alloc(u32 size) +{ + unsigned int nbits = BPF_PROG_SIZE_TO_NBITS(size); + struct bpf_prog_pack *pack; + unsigned long pos; + void *ptr = NULL; + + if (size > BPF_PROG_MAX_PACK_PROG_SIZE) { + size = round_up(size, PAGE_SIZE); + ptr = module_alloc(size); + if (ptr) { + set_vm_flush_reset_perms(ptr); + set_memory_ro((unsigned long)ptr, size / PAGE_SIZE); + set_memory_x((unsigned long)ptr, size / PAGE_SIZE); + } + return ptr; + } + mutex_lock(&pack_mutex); + list_for_each_entry(pack, &pack_list, list) { + pos = bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0, + nbits, 0); + if (pos < BPF_PROG_CHUNK_COUNT) + goto found_free_area; + } + + pack = alloc_new_pack(); + if (!pack) + goto out; + + pos = 0; + +found_free_area: + bitmap_set(pack->bitmap, pos, nbits); + ptr = (void *)(pack->ptr) + (pos << BPF_PROG_CHUNK_SHIFT); + +out: + mutex_unlock(&pack_mutex); + return ptr; +} + +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; + + if (hdr->size > BPF_PROG_MAX_PACK_PROG_SIZE) { + module_memfree(hdr); + return; + } + + pack_ptr = (void *)((unsigned long)hdr & ~(BPF_PROG_PACK_SIZE - 1)); + mutex_lock(&pack_mutex); + + list_for_each_entry(tmp, &pack_list, list) { + if (tmp->ptr == pack_ptr) { + pack = tmp; + break; + } + } + + if (WARN_ONCE(!pack, "bpf_prog_pack bug\n")) + goto out; + + nbits = BPF_PROG_SIZE_TO_NBITS(hdr->size); + pos = ((unsigned long)hdr - (unsigned long)pack_ptr) >> BPF_PROG_CHUNK_SHIFT; + + 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) { + list_del(&pack->list); + module_memfree(pack->ptr); + kfree(pack); + } +out: + mutex_unlock(&pack_mutex); +} + static atomic_long_t bpf_jit_current; /* Can be overridden by an arch's JIT compiler if it has a custom, |