[RFC PATCH bpf-next 2/2] selftests/bpf: Test __ksym externs with BTF

[Hao Luo <haoluo@xxxxxxxxxx>]

Extend ksyms.c selftest to make sure BTF enables direct loads of ksyms.

Note that test is done against the kernel btf extended with kernel VARs.

Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/ksyms.c |  2 ++
 tools/testing/selftests/bpf/progs/test_ksyms.c | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c b/tools/testing/selftests/bpf/prog_tests/ksyms.c
index e3d6777226a8..0e7f3bc3b0ae 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c
@@ -65,6 +65,8 @@ void test_ksyms(void)
 	      "got %llu, exp %llu\n", data->out__btf_size, btf_size);
 	CHECK(data->out__per_cpu_start != 0, "__per_cpu_start",
 	      "got %llu, exp %llu\n", data->out__per_cpu_start, (__u64)0);
+	CHECK(data->out__rq_cpu != 0, "rq_cpu",
+	      "got %llu, exp %llu\n", data->out__rq_cpu, (__u64)0);
 
 cleanup:
 	test_ksyms__destroy(skel);
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms.c b/tools/testing/selftests/bpf/progs/test_ksyms.c
index 6c9cbb5a3bdf..e777603757e5 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2019 Facebook */
 
+#include "vmlinux.h"
 #include <stdbool.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
@@ -9,11 +10,13 @@ __u64 out__bpf_link_fops = -1;
 __u64 out__bpf_link_fops1 = -1;
 __u64 out__btf_size = -1;
 __u64 out__per_cpu_start = -1;
+__u64 out__rq_cpu = -1;
 
 extern const void bpf_link_fops __ksym;
 extern const void __start_BTF __ksym;
 extern const void __stop_BTF __ksym;
 extern const void __per_cpu_start __ksym;
+extern const void runqueues __ksym;
 /* non-existing symbol, weak, default to zero */
 extern const void bpf_link_fops1 __ksym __weak;
 
@@ -29,4 +32,15 @@ int handler(const void *ctx)
 	return 0;
 }
 
+SEC("tp_btf/sys_enter")
+int handler_tp_btf(const void *ctx)
+{
+	const struct rq *rq = &runqueues;
+
+	/* rq now points to the runqueue of cpu 0. */
+	out__rq_cpu = rq->cpu;
+
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.27.0.389.gc38d7665816-goog