[PATCH bpf-next v3 08/17] selftests/bpf: add report descriptor fixup tests

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

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@redhat.com>

---

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 | 79 ++++++++++++++++++++
 tools/testing/selftests/bpf/progs/hid.c      | 54 +++++++++++++
 2 files changed, 133 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/hid.c b/tools/testing/selftests/bpf/prog_tests/hid.c
index 9f9dd08d3232..8c8e17e7385f 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[] = {
@@ -400,6 +401,76 @@ static int test_hid_raw_event(struct hid *hid_skel, int uhid_fd, int sysfs_fd)
 	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(struct hid *hid_skel, int uhid_fd, int sysfs_fd)
+{
+	struct hidraw_report_descriptor rpt_desc = {0};
+	int err, desc_size, hidraw_ino, hidraw_fd = -1;
+	char hidraw_path[64] = {0};
+	void *uhid_err;
+	int ret = -1;
+	pthread_t tid;
+
+	/* attach the program */
+	hid_skel->links.hid_rdesc_fixup =
+		bpf_program__attach_hid(hid_skel->progs.hid_rdesc_fixup, sysfs_fd, 0);
+	if (!ASSERT_OK_PTR(hid_skel->links.hid_rdesc_fixup,
+			   "attach_hid(hid_rdesc_fixup)"))
+		return PTR_ERR(hid_skel->links.hid_rdesc_fixup);
+
+	err = uhid_start_listener(&tid, uhid_fd);
+	ASSERT_OK(err, "uhid_start_listener");
+
+	hidraw_ino = get_hidraw(hid_skel->links.hid_rdesc_fixup);
+	if (!ASSERT_GE(hidraw_ino, 0, "get_hidraw"))
+		goto cleanup;
+
+	/* open hidraw node to check the other side of the pipe */
+	sprintf(hidraw_path, "/dev/hidraw%d", hidraw_ino);
+	hidraw_fd = open(hidraw_path, O_RDWR | O_NONBLOCK);
+
+	if (!ASSERT_GE(hidraw_fd, 0, "open_hidraw"))
+		goto cleanup;
+
+	/* check that hid_rdesc_fixup() was executed */
+	ASSERT_EQ(hid_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:
+	if (hidraw_fd >= 0)
+		close(hidraw_fd);
+
+	hid__detach(hid_skel);
+
+	pthread_join(tid, &uhid_err);
+	err = (int)(long)uhid_err;
+	CHECK_FAIL(err);
+
+	return ret;
+}
+
 void serial_test_hid_bpf(void)
 {
 	struct hid *hid_skel = NULL;
@@ -434,6 +505,14 @@ void serial_test_hid_bpf(void)
 	err = test_hid_raw_event(hid_skel, uhid_fd, sysfs_fd);
 	ASSERT_OK(err, "hid");
 
+	/*
+	 * 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(hid_skel, uhid_fd, sysfs_fd);
+	ASSERT_OK(err, "hid_rdesc_fixup");
+
 cleanup:
 	hid__destroy(hid_skel);
 	destroy(uhid_fd);
diff --git a/tools/testing/selftests/bpf/progs/hid.c b/tools/testing/selftests/bpf/progs/hid.c
index a28ba19ed933..c9ce0e36e7b9 100644
--- a/tools/testing/selftests/bpf/progs/hid.c
+++ b/tools/testing/selftests/bpf/progs/hid.c
@@ -23,3 +23,57 @@ int hid_first_event(struct hid_bpf_ctx *ctx)
 
 	return 0;
 }
+
+static __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("hid/rdesc_fixup")
+int hid_rdesc_fixup(struct hid_bpf_ctx *ctx)
+{
+	__u8 *data = bpf_hid_get_data(ctx, 0 /* offset */, 4096 /* size */);
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	callback2_check = data[4];
+
+	/* insert rdesc at offset 52 */
+	__builtin_memcpy(&data[52], rdesc, sizeof(rdesc));
+	ctx->size = sizeof(rdesc) + 52;
+
+	/* Change Usage Vendor globally */
+	data[4] = 0x42;
+
+	return 0;
+}
-- 
2.35.1