libbpf: Add support for bpf_arena.

mmap() bpf_arena right after creation, since the kernel needs to
remember the address returned from mmap. This is user_vm_start.
LLVM will generate bpf_arena_cast_user() instructions where
necessary and JIT will add upper 32-bit of user_vm_start
to such pointers.

Fix up bpf_map_mmap_sz() to compute mmap size as
map->value_size * map->max_entries for arrays and
PAGE_SIZE * map->max_entries for arena.

Don't set BTF at arena creation time, since it doesn't support it.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240308010812.89848-9-alexei.starovoitov@gmail.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 567ad367e7aa7a95d4ef8830fdb3a6a995a75792..34b72207187412ba6afb975a1798db7253a86bd4 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -185,6 +185,7 @@ static const char * const map_type_name[] = {
        [BPF_MAP_TYPE_BLOOM_FILTER]             = "bloom_filter",
        [BPF_MAP_TYPE_USER_RINGBUF]             = "user_ringbuf",
        [BPF_MAP_TYPE_CGRP_STORAGE]             = "cgrp_storage",
+       [BPF_MAP_TYPE_ARENA]                    = "arena",
 };
 
 static const char * const prog_type_name[] = {
@@ -1684,7 +1685,7 @@ static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
        return map;
 }
 
-static size_t bpf_map_mmap_sz(unsigned int value_sz, unsigned int max_entries)
+static size_t array_map_mmap_sz(unsigned int value_sz, unsigned int max_entries)
 {
        const long page_sz = sysconf(_SC_PAGE_SIZE);
        size_t map_sz;
@@ -1694,6 +1695,20 @@ static size_t bpf_map_mmap_sz(unsigned int value_sz, unsigned int max_entries)
        return map_sz;
 }
 
+static size_t bpf_map_mmap_sz(const struct bpf_map *map)
+{
+       const long page_sz = sysconf(_SC_PAGE_SIZE);
+
+       switch (map->def.type) {
+       case BPF_MAP_TYPE_ARRAY:
+               return array_map_mmap_sz(map->def.value_size, map->def.max_entries);
+       case BPF_MAP_TYPE_ARENA:
+               return page_sz * map->def.max_entries;
+       default:
+               return 0; /* not supported */
+       }
+}
+
 static int bpf_map_mmap_resize(struct bpf_map *map, size_t old_sz, size_t new_sz)
 {
        void *mmaped;
@@ -1847,7 +1862,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
        pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n",
                 map->name, map->sec_idx, map->sec_offset, def->map_flags);
 
-       mmap_sz = bpf_map_mmap_sz(map->def.value_size, map->def.max_entries);
+       mmap_sz = bpf_map_mmap_sz(map);
        map->mmaped = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE,
                           MAP_SHARED | MAP_ANONYMOUS, -1, 0);
        if (map->mmaped == MAP_FAILED) {
@@ -5017,6 +5032,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
        case BPF_MAP_TYPE_SOCKHASH:
        case BPF_MAP_TYPE_QUEUE:
        case BPF_MAP_TYPE_STACK:
+       case BPF_MAP_TYPE_ARENA:
                create_attr.btf_fd = 0;
                create_attr.btf_key_type_id = 0;
                create_attr.btf_value_type_id = 0;
@@ -5261,7 +5277,19 @@ retry:
                                if (err < 0)
                                        goto err_out;
                        }
-
+                       if (map->def.type == BPF_MAP_TYPE_ARENA) {
+                               map->mmaped = mmap((void *)map->map_extra, bpf_map_mmap_sz(map),
+                                                  PROT_READ | PROT_WRITE,
+                                                  map->map_extra ? MAP_SHARED | MAP_FIXED : MAP_SHARED,
+                                                  map->fd, 0);
+                               if (map->mmaped == MAP_FAILED) {
+                                       err = -errno;
+                                       map->mmaped = NULL;
+                                       pr_warn("map '%s': failed to mmap arena: %d\n",
+                                               map->name, err);
+                                       return err;
+                               }
+                       }
                        if (map->init_slots_sz && map->def.type != BPF_MAP_TYPE_PROG_ARRAY) {
                                err = init_map_in_map_slots(obj, map);
                                if (err < 0)
@@ -8761,7 +8789,7 @@ static void bpf_map__destroy(struct bpf_map *map)
        if (map->mmaped) {
                size_t mmap_sz;
 
-               mmap_sz = bpf_map_mmap_sz(map->def.value_size, map->def.max_entries);
+               mmap_sz = bpf_map_mmap_sz(map);
                munmap(map->mmaped, mmap_sz);
                map->mmaped = NULL;
        }
@@ -9995,11 +10023,14 @@ int bpf_map__set_value_size(struct bpf_map *map, __u32 size)
                return libbpf_err(-EBUSY);
 
        if (map->mmaped) {
-               int err;
                size_t mmap_old_sz, mmap_new_sz;
+               int err;
+
+               if (map->def.type != BPF_MAP_TYPE_ARRAY)
+                       return -EOPNOTSUPP;
 
-               mmap_old_sz = bpf_map_mmap_sz(map->def.value_size, map->def.max_entries);
-               mmap_new_sz = bpf_map_mmap_sz(size, map->def.max_entries);
+               mmap_old_sz = bpf_map_mmap_sz(map);
+               mmap_new_sz = array_map_mmap_sz(size, map->def.max_entries);
                err = bpf_map_mmap_resize(map, mmap_old_sz, mmap_new_sz);
                if (err) {
                        pr_warn("map '%s': failed to resize memory-mapped region: %d\n",
@@ -13530,7 +13561,7 @@ int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
 
        for (i = 0; i < s->map_cnt; i++) {
                struct bpf_map *map = *s->maps[i].map;
-               size_t mmap_sz = bpf_map_mmap_sz(map->def.value_size, map->def.max_entries);
+               size_t mmap_sz = bpf_map_mmap_sz(map);
                int prot, map_fd = map->fd;
                void **mmaped = s->maps[i].mmaped;
 

diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index ee9b1dbea9eb877f190413044780bd17c2eeb7b1..3021881224392a52b082e02fef18e93f8b698ec5 100644 (file)
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -338,6 +338,13 @@ static int probe_map_create(enum bpf_map_type map_type)
                key_size = 0;
                max_entries = 1;
                break;
+       case BPF_MAP_TYPE_ARENA:
+               key_size        = 0;
+               value_size      = 0;
+               max_entries     = 1; /* one page */
+               opts.map_extra  = 0; /* can mmap() at any address */
+               opts.map_flags  = BPF_F_MMAPABLE;
+               break;
        case BPF_MAP_TYPE_HASH:
        case BPF_MAP_TYPE_ARRAY:
        case BPF_MAP_TYPE_PROG_ARRAY: