Merge branch 'introduce-bpf_object__prepare'

Mykyta Yatsenko says:

====================
Introduce bpf_object__prepare

From: Mykyta Yatsenko <yatsenko@meta.com>

We are introducing a new function in the libbpf API, bpf_object__prepare,
which provides more granular control over the process of loading a
bpf_object. bpf_object__prepare performs ELF processing, relocations,
prepares final state of BPF program instructions (accessible with
bpf_program__insns()), creates and potentially pins maps, and stops short
of loading BPF programs.

There are couple of anticipated usecases for this API:
* Use BPF token for freplace programs that might need to lookup BTF of
other programs (BPF token creation can't be moved to open step, as open
step is "no privilege assumption" step so that tools like bpftool can
generate skeleton, discover the structure of BPF object, etc).
* Stopping at prepare gives users finalized BPF program
instructions (with subprogs appended, everything relocated and
finalized, etc). And that property can be taken advantage of by
veristat (and similar tools) that might want to process one program at
a time, but would like to avoid relatively slow ELF parsing and
processing; and even BPF selftests itself (RUN_TESTS part of it at
least) would benefit from this by eliminating waste of re-processing
ELF many times.
====================

Link: https://patch.msgid.link/20250303135752.158343-1-mykyta.yatsenko5@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 127 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/prepare.c b/tools/testing/selftests/bpf/prog_tests/prepare.c
new file mode 100644
index 000000000000..fb5cdad97116
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/prepare.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta */
+
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "prepare.skel.h"
+
+static bool check_prepared(struct bpf_object *obj)
+{
+	bool is_prepared = true;
+	const struct bpf_map *map;
+
+	bpf_object__for_each_map(map, obj) {
+		if (bpf_map__fd(map) < 0)
+			is_prepared = false;
+	}
+
+	return is_prepared;
+}
+
+static void test_prepare_no_load(void)
+{
+	struct prepare *skel;
+	int err;
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = &pkt_v4,
+		    .data_size_in = sizeof(pkt_v4),
+	);
+
+	skel = prepare__open();
+	if (!ASSERT_OK_PTR(skel, "prepare__open"))
+		return;
+
+	if (!ASSERT_FALSE(check_prepared(skel->obj), "not check_prepared"))
+		goto cleanup;
+
+	err = bpf_object__prepare(skel->obj);
+
+	if (!ASSERT_TRUE(check_prepared(skel->obj), "check_prepared"))
+		goto cleanup;
+
+	if (!ASSERT_OK(err, "bpf_object__prepare"))
+		goto cleanup;
+
+cleanup:
+	prepare__destroy(skel);
+}
+
+static void test_prepare_load(void)
+{
+	struct prepare *skel;
+	int err, prog_fd;
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = &pkt_v4,
+		    .data_size_in = sizeof(pkt_v4),
+	);
+
+	skel = prepare__open();
+	if (!ASSERT_OK_PTR(skel, "prepare__open"))
+		return;
+
+	if (!ASSERT_FALSE(check_prepared(skel->obj), "not check_prepared"))
+		goto cleanup;
+
+	err = bpf_object__prepare(skel->obj);
+	if (!ASSERT_OK(err, "bpf_object__prepare"))
+		goto cleanup;
+
+	err = prepare__load(skel);
+	if (!ASSERT_OK(err, "prepare__load"))
+		goto cleanup;
+
+	if (!ASSERT_TRUE(check_prepared(skel->obj), "check_prepared"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.program);
+	if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
+		goto cleanup;
+
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	if (!ASSERT_OK(err, "test_run_opts err"))
+		goto cleanup;
+
+	if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
+		goto cleanup;
+
+	ASSERT_EQ(skel->bss->err, 0, "err");
+
+cleanup:
+	prepare__destroy(skel);
+}
+
+void test_prepare(void)
+{
+	if (test__start_subtest("prepare_load"))
+		test_prepare_load();
+	if (test__start_subtest("prepare_no_load"))
+		test_prepare_no_load();
+}
diff --git a/tools/testing/selftests/bpf/progs/prepare.c b/tools/testing/selftests/bpf/progs/prepare.c
new file mode 100644
index 000000000000..1f1dd547e4ee
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/prepare.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+//#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+int err;
+
+struct {
+	__uint(type, BPF_MAP_TYPE_RINGBUF);
+	__uint(max_entries, 4096);
+} ringbuf SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u32);
+} array_map SEC(".maps");
+
+SEC("cgroup_skb/egress")
+int program(struct __sk_buff *skb)
+{
+	err = 0;
+	return 0;
+}