[PATCH bpf-next v6 19/23] selftests/bpf: add report descriptor fixup tests

[Benjamin Tissoires]

Simple report descriptor override in HID: replace part of the report
descriptor from a static definition in the bpf kernel program.

Note that this test should be run last because we disconnect/reconnect
the device, meaning that it changes the overall uhid device.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>

---

no changes in v6

changes in v5:
- amended for the new API

not in v4

changes in v3:
- added a comment to mention that this test needs to be run last

changes in v2:
- split the series by bpf/libbpf/hid/selftests and samples
---
 tools/testing/selftests/bpf/prog_tests/hid.c | 76 ++++++++++++++++++++
 tools/testing/selftests/bpf/progs/hid.c      | 53 ++++++++++++++
 2 files changed, 129 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/hid.c b/tools/testing/selftests/bpf/prog_tests/hid.c
index 19172d3e0f44..9dc5f0038472 100644
--- a/tools/testing/selftests/bpf/prog_tests/hid.c
+++ b/tools/testing/selftests/bpf/prog_tests/hid.c
@@ -9,6 +9,7 @@
 #include <dirent.h>
 #include <poll.h>
 #include <stdbool.h>
+#include <linux/hidraw.h>
 #include <linux/uhid.h>
 
 static unsigned char rdesc[] = {
@@ -769,6 +770,73 @@ static int test_hid_user_raw_request_call(int uhid_fd, int dev_id)
 	return ret;
 }
 
+/*
+ * Attach hid_rdesc_fixup to the given uhid device,
+ * retrieve and open the matching hidraw node,
+ * check that the hidraw report descriptor has been updated.
+ */
+static int test_rdesc_fixup(void)
+{
+	struct hidraw_report_descriptor rpt_desc = {0};
+	struct test_params params;
+	int err, uhid_fd, desc_size, hidraw_fd = -1, ret = -1;
+	int dev_id;
+	void *uhid_err;
+	pthread_t tid;
+	bool started = false;
+
+	dev_id = rand() % 1024;
+
+	uhid_fd = setup_uhid(dev_id);
+	if (!ASSERT_GE(uhid_fd, 0, "setup uhid"))
+		return uhid_fd;
+
+	err = prep_test(dev_id, "hid_rdesc_fixup", &params);
+	if (!ASSERT_EQ(err, 0, "prep_test(hid_rdesc_fixup)"))
+		goto cleanup;
+
+	err = uhid_start_listener(&tid, uhid_fd);
+	ASSERT_OK(err, "uhid_start_listener");
+
+	started = true;
+
+	hidraw_fd = params.hidraw_fd;
+
+	/* check that hid_rdesc_fixup() was executed */
+	ASSERT_EQ(params.skel->data->callback2_check, 0x21, "callback_check2");
+
+	/* read the exposed report descriptor from hidraw */
+	err = ioctl(hidraw_fd, HIDIOCGRDESCSIZE, &desc_size);
+	if (!ASSERT_GE(err, 0, "HIDIOCGRDESCSIZE"))
+		goto cleanup;
+
+	/* ensure the new size of the rdesc is bigger than the old one */
+	if (!ASSERT_GT(desc_size, sizeof(rdesc), "new_rdesc_size"))
+		goto cleanup;
+
+	rpt_desc.size = desc_size;
+	err = ioctl(hidraw_fd, HIDIOCGRDESC, &rpt_desc);
+	if (!ASSERT_GE(err, 0, "HIDIOCGRDESC"))
+		goto cleanup;
+
+	if (!ASSERT_EQ(rpt_desc.value[4], 0x42, "hid_rdesc_fixup"))
+		goto cleanup;
+
+	ret = 0;
+
+cleanup:
+	cleanup_test(&params);
+
+	if (started) {
+		destroy(uhid_fd);
+		pthread_join(tid, &uhid_err);
+		err = (int)(long)uhid_err;
+		CHECK_FAIL(err);
+	}
+
+	return ret;
+}
+
 void serial_test_hid_bpf(void)
 {
 	int err, uhid_fd;
@@ -799,6 +867,14 @@ void serial_test_hid_bpf(void)
 	err = test_hid_user_raw_request_call(uhid_fd, dev_id);
 	ASSERT_OK(err, "hid_user_raw_request");
 
+	/*
+	 * this test should be run last because we disconnect/reconnect
+	 * the device, meaning that it changes the overall uhid device
+	 * and messes up with the thread that reads uhid events.
+	 */
+	err = test_rdesc_fixup();
+	ASSERT_OK(err, "hid_rdesc_fixup");
+
 	destroy(uhid_fd);
 
 	pthread_join(tid, &uhid_err);
diff --git a/tools/testing/selftests/bpf/progs/hid.c b/tools/testing/selftests/bpf/progs/hid.c
index 0be319c11575..863c37ddf5ff 100644
--- a/tools/testing/selftests/bpf/progs/hid.c
+++ b/tools/testing/selftests/bpf/progs/hid.c
@@ -99,3 +99,56 @@ int hid_user_raw_request(struct hid_hw_request_syscall_args *args)
 
 	return 0;
 }
+
+static const __u8 rdesc[] = {
+	0x05, 0x01,				/* USAGE_PAGE (Generic Desktop) */
+	0x09, 0x32,				/* USAGE (Z) */
+	0x95, 0x01,				/* REPORT_COUNT (1) */
+	0x81, 0x06,				/* INPUT (Data,Var,Rel) */
+
+	0x06, 0x00, 0xff,			/* Usage Page (Vendor Defined Page 1) */
+	0x19, 0x01,				/* USAGE_MINIMUM (1) */
+	0x29, 0x03,				/* USAGE_MAXIMUM (3) */
+	0x15, 0x00,				/* LOGICAL_MINIMUM (0) */
+	0x25, 0x01,				/* LOGICAL_MAXIMUM (1) */
+	0x95, 0x03,				/* REPORT_COUNT (3) */
+	0x75, 0x01,				/* REPORT_SIZE (1) */
+	0x91, 0x02,				/* Output (Data,Var,Abs) */
+	0x95, 0x01,				/* REPORT_COUNT (1) */
+	0x75, 0x05,				/* REPORT_SIZE (5) */
+	0x91, 0x01,				/* Output (Cnst,Var,Abs) */
+
+	0x06, 0x00, 0xff,			/* Usage Page (Vendor Defined Page 1) */
+	0x19, 0x06,				/* USAGE_MINIMUM (6) */
+	0x29, 0x08,				/* USAGE_MAXIMUM (8) */
+	0x15, 0x00,				/* LOGICAL_MINIMUM (0) */
+	0x25, 0x01,				/* LOGICAL_MAXIMUM (1) */
+	0x95, 0x03,				/* REPORT_COUNT (3) */
+	0x75, 0x01,				/* REPORT_SIZE (1) */
+	0xb1, 0x02,				/* Feature (Data,Var,Abs) */
+	0x95, 0x01,				/* REPORT_COUNT (1) */
+	0x75, 0x05,				/* REPORT_SIZE (5) */
+	0x91, 0x01,				/* Output (Cnst,Var,Abs) */
+
+	0xc0,				/* END_COLLECTION */
+	0xc0,			/* END_COLLECTION */
+};
+
+SEC("?fmod_ret/hid_bpf_rdesc_fixup")
+int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hid_ctx)
+{
+	__u8 *data = hid_bpf_get_data(hid_ctx, 0 /* offset */, 4096 /* size */);
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	callback2_check = data[4];
+
+	/* insert rdesc at offset 73 */
+	__builtin_memcpy(&data[73], rdesc, sizeof(rdesc));
+
+	/* Change Usage Vendor globally */
+	data[4] = 0x42;
+
+	return sizeof(rdesc) + 73;
+}
-- 
2.36.1