kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 222 insertions, 0 deletions

diff --git a/drivers/hid/hid-uclogic-params-test.c b/drivers/hid/hid-uclogic-params-test.c
new file mode 100644
index 000000000..a30121419
--- /dev/null
+++ b/drivers/hid/hid-uclogic-params-test.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ *  HID driver for UC-Logic devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2022 José Expósito <jose.exposito89@gmail.com>
+ */
+
+#include <kunit/test.h>
+#include "./hid-uclogic-params.h"
+#include "./hid-uclogic-rdesc.h"
+
+#define MAX_STR_DESC_SIZE 14
+
+struct uclogic_parse_ugee_v2_desc_case {
+	const char *name;
+	int res;
+	const __u8 str_desc[MAX_STR_DESC_SIZE];
+	size_t str_desc_size;
+	const s32 desc_params[UCLOGIC_RDESC_PH_ID_NUM];
+	enum uclogic_params_frame_type frame_type;
+};
+
+static struct uclogic_parse_ugee_v2_desc_case uclogic_parse_ugee_v2_desc_cases[] = {
+	{
+		.name = "invalid_str_desc",
+		.res = -EINVAL,
+		.str_desc = {},
+		.str_desc_size = 0,
+		.desc_params = {},
+		.frame_type = UCLOGIC_PARAMS_FRAME_BUTTONS,
+	},
+	{
+		.name = "resolution_with_value_0",
+		.res = 0,
+		.str_desc = {
+			0x0E, 0x03,
+			0x70, 0xB2,
+			0x10, 0x77,
+			0x08,
+			0x00,
+			0xFF, 0x1F,
+			0x00, 0x00,
+		},
+		.str_desc_size = 12,
+		.desc_params = {
+			[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xB270,
+			[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] = 0x7710,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0,
+			[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] = 0x1FFF,
+			[UCLOGIC_RDESC_FRAME_PH_ID_UM] = 0x08,
+		},
+		.frame_type = UCLOGIC_PARAMS_FRAME_BUTTONS,
+	},
+	/* XP-PEN Deco L str_desc: Frame with 8 buttons */
+	{
+		.name = "frame_type_buttons",
+		.res = 0,
+		.str_desc = {
+			0x0E, 0x03,
+			0x70, 0xB2,
+			0x10, 0x77,
+			0x08,
+			0x00,
+			0xFF, 0x1F,
+			0xD8, 0x13,
+		},
+		.str_desc_size = 12,
+		.desc_params = {
+			[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xB270,
+			[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0x2320,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] = 0x7710,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0x1770,
+			[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] = 0x1FFF,
+			[UCLOGIC_RDESC_FRAME_PH_ID_UM] = 0x08,
+		},
+		.frame_type = UCLOGIC_PARAMS_FRAME_BUTTONS,
+	},
+	/* PARBLO A610 PRO str_desc: Frame with 9 buttons and dial */
+	{
+		.name = "frame_type_dial",
+		.res = 0,
+		.str_desc = {
+			0x0E, 0x03,
+			0x96, 0xC7,
+			0xF9, 0x7C,
+			0x09,
+			0x01,
+			0xFF, 0x1F,
+			0xD8, 0x13,
+		},
+		.str_desc_size = 12,
+		.desc_params = {
+			[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xC796,
+			[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0x2749,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] = 0x7CF9,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0x1899,
+			[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] = 0x1FFF,
+			[UCLOGIC_RDESC_FRAME_PH_ID_UM] = 0x09,
+		},
+		.frame_type = UCLOGIC_PARAMS_FRAME_DIAL,
+	},
+	/* XP-PEN Deco Pro S str_desc: Frame with 8 buttons and mouse */
+	{
+		.name = "frame_type_mouse",
+		.res = 0,
+		.str_desc = {
+			0x0E, 0x03,
+			0xC8, 0xB3,
+			0x34, 0x65,
+			0x08,
+			0x02,
+			0xFF, 0x1F,
+			0xD8, 0x13,
+		},
+		.str_desc_size = 12,
+		.desc_params = {
+			[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xB3C8,
+			[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0x2363,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] = 0x6534,
+			[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0x13EC,
+			[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] = 0x1FFF,
+			[UCLOGIC_RDESC_FRAME_PH_ID_UM] = 0x08,
+		},
+		.frame_type = UCLOGIC_PARAMS_FRAME_MOUSE,
+	},
+};
+
+static void uclogic_parse_ugee_v2_desc_case_desc(struct uclogic_parse_ugee_v2_desc_case *t,
+						 char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(uclogic_parse_ugee_v2_desc, uclogic_parse_ugee_v2_desc_cases,
+		  uclogic_parse_ugee_v2_desc_case_desc);
+
+static void hid_test_uclogic_parse_ugee_v2_desc(struct kunit *test)
+{
+	int res;
+	s32 desc_params[UCLOGIC_RDESC_PH_ID_NUM];
+	enum uclogic_params_frame_type frame_type;
+	const struct uclogic_parse_ugee_v2_desc_case *params = test->param_value;
+
+	res = uclogic_params_parse_ugee_v2_desc(params->str_desc,
+						params->str_desc_size,
+						desc_params,
+						ARRAY_SIZE(desc_params),
+						&frame_type);
+	KUNIT_ASSERT_EQ(test, res, params->res);
+
+	if (res)
+		return;
+
+	KUNIT_EXPECT_EQ(test,
+			params->desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM],
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM]);
+	KUNIT_EXPECT_EQ(test,
+			params->desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM],
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM]);
+	KUNIT_EXPECT_EQ(test,
+			params->desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM],
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM]);
+	KUNIT_EXPECT_EQ(test,
+			params->desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM],
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM]);
+	KUNIT_EXPECT_EQ(test,
+			params->desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM],
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM]);
+	KUNIT_EXPECT_EQ(test,
+			params->desc_params[UCLOGIC_RDESC_FRAME_PH_ID_UM],
+			desc_params[UCLOGIC_RDESC_FRAME_PH_ID_UM]);
+	KUNIT_EXPECT_EQ(test, params->frame_type, frame_type);
+}
+
+struct fake_device {
+	unsigned long quirks;
+};
+
+static void hid_test_uclogic_params_cleanup_event_hooks(struct kunit *test)
+{
+	int res, n;
+	struct hid_device *hdev;
+	struct fake_device *fake_dev;
+	struct uclogic_params p = {0, };
+
+	hdev = kunit_kzalloc(test, sizeof(struct hid_device), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, hdev);
+
+	fake_dev = kunit_kzalloc(test, sizeof(struct fake_device), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_dev);
+
+	hid_set_drvdata(hdev, fake_dev);
+
+	res = uclogic_params_ugee_v2_init_event_hooks(hdev, &p);
+	KUNIT_ASSERT_EQ(test, res, 0);
+
+	/* Check that the function can be called repeatedly */
+	for (n = 0; n < 4; n++) {
+		uclogic_params_cleanup_event_hooks(&p);
+		KUNIT_EXPECT_PTR_EQ(test, p.event_hooks, NULL);
+	}
+}
+
+static struct kunit_case hid_uclogic_params_test_cases[] = {
+	KUNIT_CASE_PARAM(hid_test_uclogic_parse_ugee_v2_desc,
+			 uclogic_parse_ugee_v2_desc_gen_params),
+	KUNIT_CASE(hid_test_uclogic_params_cleanup_event_hooks),
+	{}
+};
+
+static struct kunit_suite hid_uclogic_params_test_suite = {
+	.name = "hid_uclogic_params_test",
+	.test_cases = hid_uclogic_params_test_cases,
+};
+
+kunit_test_suite(hid_uclogic_params_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for the UC-Logic driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("José Expósito <jose.exposito89@gmail.com>");