[PATCH bpf-next v5 14/17] selftests/bpf: add report descriptor fixup tests

Benjamin Tissoires
2022-05-18T21:01:24Z

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 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 54c0a0fcd54d..4375c1cc00dc 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_change_report");

+ /*
+ * 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 e3444d444303..eda9306e6d7f 100644
--- a/tools/testing/selftests/bpf/progs/hid.c
+++ b/tools/testing/selftests/bpf/progs/hid.c
@@ -115,3 +115,56 @@ int hid_user_raw_request(struct hid_hw_request_syscall_args *args)

return ret;
}
+
+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