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: 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

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index cfb8a50..72d0721 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -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);