selftests/bpf: Add tests for names of Rust types and functions in BTF

Check that BTF with names of STRUCT, FWD, TYPEDEF and FUNC that Rust
makes is loaded and that the name of FUNC is an identifier in kallsyms.

The test is serial. Programs are not in kallsyms while bpf_jit_harden
is set and there are tests that set it for a while.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261002124714.180012-7-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

2 files changed, 84 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index 87b554067071..207341f4bd99 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -3593,6 +3593,21 @@ static struct btf_raw_test raw_tests[] = {
 	},
 	BTF_STR_SEC("\0?foo"),
 },
+{
+	.descr = "names of Rust types and functions are ok",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(NAME_NTH(1), 0, 0, 32, 4),	/* [1] */
+		BTF_STRUCT_ENC(NAME_NTH(2), 1, 4),		/* [2] */
+		BTF_MEMBER_ENC(NAME_NTH(3), 1, 0),
+		BTF_FWD_ENC(NAME_NTH(4), 0),			/* [3] */
+		BTF_TYPEDEF_ENC(NAME_NTH(5), 2),		/* [4] */
+		BTF_FUNC_PROTO_ENC(0, 1),			/* [5] */
+			BTF_FUNC_PROTO_ARG_ENC(NAME_NTH(6), 1),
+		BTF_FUNC_ENC(NAME_NTH(7), 5),			/* [6] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0u32\0Option<&str>\0__0\0*const str\0{impl#9}<[u8; 4]>\0self\0fmt<str>"),
+},
 
 {
 	.descr = "float test #1, well-formed",
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_rust.c b/tools/testing/selftests/bpf/prog_tests/btf_rust.c
new file mode 100644
index 000000000000..ce2b31087b59
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/btf_rust.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include <bpf/btf.h>
+
+#define FUNC_NAME "write_fmt<scx_simple::BpfStream>"
+#define KSYM_NAME "write_fmt_scx_simple__BpfStream_"
+
+/* The name of a function of Rust is a part of the name of the program in kallsyms */
+static void test_func_name(void)
+{
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	LIBBPF_OPTS(bpf_prog_load_opts, opts);
+	int int_id, proto_id, prog_fd = -1, i;
+	struct bpf_func_info func_info = {};
+	struct bpf_prog_info info = {};
+	unsigned long long addr;
+	__u32 len = sizeof(info);
+	char sym[128], *p = sym;
+	struct btf *btf;
+
+	btf = btf__new_empty();
+	if (!ASSERT_OK_PTR(btf, "btf"))
+		return;
+	int_id = btf__add_int(btf, "i32", 4, BTF_INT_SIGNED);
+	ASSERT_GT(int_id, 0, "int");
+	proto_id = btf__add_func_proto(btf, int_id);
+	ASSERT_GT(proto_id, 0, "proto");
+	ASSERT_OK(btf__add_func_param(btf, "ctx", int_id), "param");
+	func_info.type_id = btf__add_func(btf, FUNC_NAME, BTF_FUNC_STATIC, proto_id);
+	ASSERT_GT(func_info.type_id, 0, "func");
+	if (!ASSERT_OK(btf__load_into_kernel(btf), "btf load"))
+		goto out;
+
+	opts.prog_btf_fd = btf__fd(btf);
+	opts.func_info = &func_info;
+	opts.func_info_cnt = 1;
+	opts.func_info_rec_size = sizeof(func_info);
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns,
+				ARRAY_SIZE(insns), &opts);
+	if (!ASSERT_GE(prog_fd, 0, "prog load"))
+		goto out;
+	if (!ASSERT_OK(bpf_prog_get_info_by_fd(prog_fd, &info, &len), "prog info"))
+		goto out;
+	if (!info.jited_prog_len) {
+		test__skip();
+		goto out;
+	}
+
+	p += sprintf(p, "bpf_prog_");
+	for (i = 0; i < BPF_TAG_SIZE; i++)
+		p += sprintf(p, "%02x", info.tag[i]);
+	sprintf(p, "_%s", KSYM_NAME);
+	ASSERT_OK(kallsyms_find(sym, &addr), sym);
+out:
+	if (prog_fd >= 0)
+		close(prog_fd);
+	btf__free(btf);
+}
+
+/* Serial: programs are not in kallsyms while another test sets bpf_jit_harden */
+void serial_test_btf_rust(void)
+{
+	if (test__start_subtest("func_name"))
+		test_func_name();
+}