[PATCH 3/4] libbpf: Add support for detecting and dedup'ing a BTF archive

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

As defined by being a series of BTF raw_data concatenated that then
are combined using btf__add_btf() to then be passed to btf__dedup().

This is a simpler interface, a more involved one, maybe for pahole
would involve doing the same approach as for encoding BTF from DWARF:
create a series of threads that would load the BTF archive in parallel
to then dedup it.

Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: "Jose E. Marchesi" <jose.marchesi@oracle.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Alcock <nick.alcock@oracle.com>
Cc: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/bpf/btf.c | 38 ++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/btf.h |  3 +++
 2 files changed, 41 insertions(+)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index ee45d461d53bea9a..73a6d94eeda125e1 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1127,6 +1127,44 @@ struct btf *btf__new(const void *data, __u32 size)
 	return libbpf_ptr(btf_new(data, size, NULL, false));
 }
 
+bool btf__is_archive(const struct btf *btf)
+{
+	return btf->extra_raw_data;
+}
+
+int btf__dedup_archive(struct btf *btf, const void *data, __u32 size, const struct btf_dedup_opts *opts)
+{
+	__u32 raw_size = btf->raw_size;
+	struct btf *brother;
+	int err = 0;
+
+	while (size > raw_size) {
+		data += raw_size;
+		size -= raw_size;
+		brother = btf_new(data, size, btf->base_btf, btf->raw_data_is_mmap);
+
+		if (IS_ERR(brother)) {
+			err = PTR_ERR(brother);
+			pr_debug("%s: __btf_new() failed! %d\n", __func__, err);
+			goto out;
+		}
+
+		if (btf__add_btf(btf, brother) < 0) {
+			err = -errno;
+			pr_debug("%s: btf__add_btf() failed: %d(%s)!\n", __func__, errno, strerror(errno));
+			btf__free(brother);
+			goto out;
+		}
+
+		raw_size = brother->raw_size;
+		btf__free(brother);
+	}
+
+	err = btf__dedup(btf, opts);
+out:
+	return libbpf_err(err);
+}
+
 struct btf *btf__new_split(const void *data, __u32 size, struct btf *base_btf)
 {
 	return libbpf_ptr(btf_new(data, size, base_btf, false));
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index ccfd905f03dfe7b6..71a6b8e037f5c98b 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -258,6 +258,9 @@ struct btf_dedup_opts {
 #define btf_dedup_opts__last_field force_collisions
 
 LIBBPF_API int btf__dedup(struct btf *btf, const struct btf_dedup_opts *opts);
+LIBBPF_API int btf__dedup_archive(struct btf *btf, const void *data, __u32 size,
+				  const struct btf_dedup_opts *opts);
+LIBBPF_API bool btf__is_archive(const struct btf *btf);
 
 /**
  * @brief **btf__relocate()** will check the split BTF *btf* for references
-- 
2.50.1