Merge branch 'bpf-libbpf-btf-defined-maps'

Andrii Nakryiko says:

====================
This patch set implements initial version (as discussed at LSF/MM2019
conference) of a new way to specify BPF maps, relying on BTF type information,
which allows for easy extensibility, preserving forward and backward
compatibility. See details and examples in description for patch #6.

[0] contains an outline of follow up extensions to be added after this basic
set of features lands. They are useful by itself, but also allows to bring
libbpf to feature-parity with iproute2 BPF loader. That should open a path
forward for BPF loaders unification.

Patch #1 centralizes commonly used min/max macro in libbpf_internal.h.
Patch #2 extracts .BTF and .BTF.ext loading loging from elf_collect().
Patch #3 simplifies elf_collect() error-handling logic.
Patch #4 refactors map initialization logic into user-provided maps and global
data maps, in preparation to adding another way (BTF-defined maps).
Patch #5 adds support for map definitions in multiple ELF sections and
deprecates bpf_object__find_map_by_offset() API which doesn't appear to be
used anymore and makes assumption that all map definitions reside in single
ELF section.
Patch #6 splits BTF intialization from sanitization/loading into kernel to
preserve original BTF at the time of map initialization.
Patch #7 adds support for BTF-defined maps.
Patch #8 adds new test for BTF-defined map definition.
Patches #9-11 convert test BPF map definitions to use BTF way.

[0] https://lore.kernel.org/bpf/CAEf4BzbfdG2ub7gCi0OYqBrUoChVHWsmOntWAkJt47=FE+km+A@mail.gmail.com/

v1->v2:
- more BTF-sanity checks in parsing map definitions (Song);
- removed confusing usage of "attribute", switched to "field;
- split off elf_collect() refactor from btf loading refactor (Song);
- split selftests conversion into 3 patches (Stanislav):
  1. test already relying on BTF;
  2. tests w/ custom types as key/value (so benefiting from BTF);
  3. all the rest tests (integers as key/value, special maps w/o BTF support).
- smaller code improvements (Song);

rfc->v1:
- error out on unknown field by default (Stanislav, Jakub, Lorenz);
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 37 insertions, 23 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_xdp_noinline.c b/tools/testing/selftests/bpf/progs/test_xdp_noinline.c
index 4fe6aaad22a4..d2eddb5553d1 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_noinline.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_noinline.c
@@ -163,52 +163,66 @@ struct lb_stats {
 	__u64 v1;
 };
 
-struct bpf_map_def __attribute__ ((section("maps"), used)) vip_map = {
+struct {
+	__u32 type;
+	__u32 max_entries;
+	struct vip_definition *key;
+	struct vip_meta *value;
+} vip_map SEC(".maps") = {
 	.type = BPF_MAP_TYPE_HASH,
-	.key_size = sizeof(struct vip_definition),
-	.value_size = sizeof(struct vip_meta),
 	.max_entries = 512,
-	.map_flags = 0,
 };
 
-struct bpf_map_def __attribute__ ((section("maps"), used)) lru_cache = {
+struct {
+	__u32 type;
+	__u32 max_entries;
+	__u32 map_flags;
+	struct flow_key *key;
+	struct real_pos_lru *value;
+} lru_cache SEC(".maps") = {
 	.type = BPF_MAP_TYPE_LRU_HASH,
-	.key_size = sizeof(struct flow_key),
-	.value_size = sizeof(struct real_pos_lru),
 	.max_entries = 300,
 	.map_flags = 1U << 1,
 };
 
-struct bpf_map_def __attribute__ ((section("maps"), used)) ch_rings = {
+struct {
+	__u32 type;
+	__u32 max_entries;
+	__u32 *key;
+	__u32 *value;
+} ch_rings SEC(".maps") = {
 	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(__u32),
-	.value_size = sizeof(__u32),
 	.max_entries = 12 * 655,
-	.map_flags = 0,
 };
 
-struct bpf_map_def __attribute__ ((section("maps"), used)) reals = {
+struct {
+	__u32 type;
+	__u32 max_entries;
+	__u32 *key;
+	struct real_definition *value;
+} reals SEC(".maps") = {
 	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(__u32),
-	.value_size = sizeof(struct real_definition),
 	.max_entries = 40,
-	.map_flags = 0,
 };
 
-struct bpf_map_def __attribute__ ((section("maps"), used)) stats = {
+struct {
+	__u32 type;
+	__u32 max_entries;
+	__u32 *key;
+	struct lb_stats *value;
+} stats SEC(".maps") = {
 	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
-	.key_size = sizeof(__u32),
-	.value_size = sizeof(struct lb_stats),
 	.max_entries = 515,
-	.map_flags = 0,
 };
 
-struct bpf_map_def __attribute__ ((section("maps"), used)) ctl_array = {
+struct {
+	__u32 type;
+	__u32 max_entries;
+	__u32 *key;
+	struct ctl_value *value;
+} ctl_array SEC(".maps") = {
 	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(__u32),
-	.value_size = sizeof(struct ctl_value),
 	.max_entries = 16,
-	.map_flags = 0,
 };
 
 struct eth_hdr {