hid_device->{name,uniq,phys} are all writeable fields, we need to have
tests for them in case the verifier becomes too much strict.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

---

changes in v2:
- sashiko fixes:
  - iterate the for loop up to 5, to account for dev_id >= 1000
  - properly undef the correct macro
---
 tools/testing/selftests/hid/hid_bpf.c              | 26 ++++++++++++++++++++++
 tools/testing/selftests/hid/progs/hid.c            | 26 ++++++++++++++++++++++
 .../testing/selftests/hid/progs/hid_bpf_helpers.h  |  3 +++
 3 files changed, 55 insertions(+)

diff --git a/tools/testing/selftests/hid/hid_bpf.c b/tools/testing/selftests/hid/hid_bpf.c
index b851339308c2..069ebdbb4d1c 100644
--- a/tools/testing/selftests/hid/hid_bpf.c
+++ b/tools/testing/selftests/hid/hid_bpf.c
@@ -909,6 +909,32 @@ TEST_F(hid_bpf, test_rdesc_fixup_get_data_overflow)
 	ASSERT_EQ(self->skel->bss->get_data_overflow_check, 1);
 }
 
+TEST_F(hid_bpf, test_rdesc_fixup_change_uniq_name_phys)
+{
+	const struct test_program progs[] = {
+		{ .name = "hid_rdesc_fixup_change_uniq_name_phys" },
+	};
+	char expected[256], buf[256] = {};
+	int err;
+
+	LOAD_PROGRAMS(progs);
+
+	err = ioctl(self->hidraw_fd, HIDIOCGRAWNAME(sizeof(buf)), buf);
+	ASSERT_GE(err, 0) TH_LOG("HIDIOCGRAWNAME");
+	ASSERT_STREQ("name coming from bpf", buf);
+
+	snprintf(expected, sizeof(expected), "%d phys:coming:from:bpf", self->hid.dev_id);
+
+	err = ioctl(self->hidraw_fd, HIDIOCGRAWPHYS(sizeof(buf)), buf);
+	ASSERT_GE(err, 0) TH_LOG("HIDIOCGRAWPHYS");
+	ASSERT_STREQ(expected, buf);
+
+	err = ioctl(self->hidraw_fd, HIDIOCGRAWUNIQ(sizeof(buf)), buf);
+	ASSERT_GE(err, 0) TH_LOG("HIDIOCGRAWUNIQ");
+	ASSERT_STREQ("uniq:coming:from:bpf", buf);
+
+}
+
 static int libbpf_print_fn(enum libbpf_print_level level,
 			   const char *format, va_list args)
 {
diff --git a/tools/testing/selftests/hid/progs/hid.c b/tools/testing/selftests/hid/progs/hid.c
index b21fbb13c926..361dc7eaad22 100644
--- a/tools/testing/selftests/hid/progs/hid.c
+++ b/tools/testing/selftests/hid/progs/hid.c
@@ -255,6 +255,32 @@ struct hid_bpf_ops rdesc_fixup_get_data_overflow = {
 	.hid_rdesc_fixup = (void *)hid_rdesc_fixup_get_data_overflow,
 };
 
+SEC("?struct_ops.s/hid_rdesc_fixup")
+int BPF_PROG(hid_rdesc_fixup_change_uniq_name_phys, struct hid_bpf_ctx *hid_ctx)
+{
+#define HID_BPF_MEMCPY(target, str) \
+	__builtin_memcpy(target, str, sizeof(str))
+
+	HID_BPF_MEMCPY(hid_ctx->hid->name, "name coming from bpf");
+	HID_BPF_MEMCPY(hid_ctx->hid->uniq, "uniq:coming:from:bpf");
+	/* hid_bpf relies on a phys being a rand % 1024 */
+	for (int i = 0; i < 5; i++) {
+		if (!hid_ctx->hid->phys[i]) {
+			HID_BPF_MEMCPY(hid_ctx->hid->phys + i, " phys:coming:from:bpf");
+			break;
+		}
+	}
+
+#undef HID_BPF_MEMCPY
+
+	return 0;
+}
+
+SEC(".struct_ops.link")
+struct hid_bpf_ops rdesc_fixup_change_uniq_name_phys = {
+	.hid_rdesc_fixup = (void *)hid_rdesc_fixup_change_uniq_name_phys,
+};
+
 SEC("?struct_ops/hid_device_event")
 int BPF_PROG(hid_test_insert1, struct hid_bpf_ctx *hid_ctx, enum hid_report_type type)
 {
diff --git a/tools/testing/selftests/hid/progs/hid_bpf_helpers.h b/tools/testing/selftests/hid/progs/hid_bpf_helpers.h
index cdca912f3afd..05698793762a 100644
--- a/tools/testing/selftests/hid/progs/hid_bpf_helpers.h
+++ b/tools/testing/selftests/hid/progs/hid_bpf_helpers.h
@@ -61,6 +61,9 @@ enum hid_report_type {
 
 struct hid_device {
 	unsigned int id;
+	char name[128];
+	char phys[64];
+	char uniq[64];
 } __attribute__((preserve_access_index));
 
 struct bpf_wq {

-- 
2.55.0