selftests: bpf: Add a new test for bare tracepoints

Reuse module_attach infrastructure to add a new bare tracepoint to check
we can attach to it as a raw tracepoint.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210119122237.2426878-3-qais.yousef@arm.com

3 files changed, 32 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
index b83ea448bc79..89c6d58e5dd6 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
@@ -28,6 +28,12 @@ TRACE_EVENT(bpf_testmod_test_read,
 		  __entry->pid, __entry->comm, __entry->off, __entry->len)
 );
 
+/* A bare tracepoint with no event associated with it */
+DECLARE_TRACE(bpf_testmod_test_write_bare,
+	TP_PROTO(struct task_struct *task, struct bpf_testmod_test_write_ctx *ctx),
+	TP_ARGS(task, ctx)
+);
+
 #endif /* _BPF_TESTMOD_EVENTS_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 0b991e115d1f..141d8da687d2 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -31,9 +31,28 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
 EXPORT_SYMBOL(bpf_testmod_test_read);
 ALLOW_ERROR_INJECTION(bpf_testmod_test_read, ERRNO);
 
+noinline ssize_t
+bpf_testmod_test_write(struct file *file, struct kobject *kobj,
+		      struct bin_attribute *bin_attr,
+		      char *buf, loff_t off, size_t len)
+{
+	struct bpf_testmod_test_write_ctx ctx = {
+		.buf = buf,
+		.off = off,
+		.len = len,
+	};
+
+	trace_bpf_testmod_test_write_bare(current, &ctx);
+
+	return -EIO; /* always fail */
+}
+EXPORT_SYMBOL(bpf_testmod_test_write);
+ALLOW_ERROR_INJECTION(bpf_testmod_test_write, ERRNO);
+
 static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = {
-	.attr = { .name = "bpf_testmod", .mode = 0444, },
+	.attr = { .name = "bpf_testmod", .mode = 0666, },
 	.read = bpf_testmod_test_read,
+	.write = bpf_testmod_test_write,
 };
 
 static int bpf_testmod_init(void)
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
index b81adfedb4f6..b3892dc40111 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
@@ -11,4 +11,10 @@ struct bpf_testmod_test_read_ctx {
 	size_t len;
 };
 
+struct bpf_testmod_test_write_ctx {
+	char *buf;
+	loff_t off;
+	size_t len;
+};
+
 #endif /* _BPF_TESTMOD_H */