[PATCH bpf-next 11/16] libbpf: Add support for bpf_arena.

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

From: Alexei Starovoitov <ast@kernel.org>

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.

Use traditional map->value_size * map->max_entries to calculate mmap sz,
though it's not the best fit.

Also don't set BTF at bpf_arena creation time, since it doesn't support it.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 tools/lib/bpf/libbpf.c        | 18 ++++++++++++++++++
 tools/lib/bpf/libbpf_probes.c |  6 ++++++
 2 files changed, 24 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 01f407591a92..c5ce5946dc6d 100644
--- 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[] = {
@@ -4852,6 +4853,7 @@ 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;
@@ -4908,6 +4910,22 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 	if (map->fd == map_fd)
 		return 0;
 
+	if (def->type == BPF_MAP_TYPE_ARENA) {
+		size_t mmap_sz;
+
+		mmap_sz = bpf_map_mmap_sz(def->value_size, def->max_entries);
+		map->mmaped = mmap((void *)map->map_extra, mmap_sz, 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 bpf_arena: %d\n",
+				bpf_map__name(map), err);
+			return err;
+		}
+	}
+
 	/* Keep placeholder FD value but now point it to the BPF map object.
 	 * This way everything that relied on this map's FD (e.g., relocated
 	 * ldimm64 instructions) will stay valid and won't need adjustments.
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index ee9b1dbea9eb..cbc7f4c09060 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -338,6 +338,12 @@ 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	= sizeof(__u64);
+		value_size	= sizeof(__u64);
+		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:
-- 
2.34.1