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, 408 insertions, 0 deletions

diff --git a/net/wireless/tests/chan.c b/net/wireless/tests/chan.c
new file mode 100644
index 000000000..65eb18c49
--- /dev/null
+++ b/net/wireless/tests/chan.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for channel helper functions
+ *
+ * Copyright (C) 2023-2024, 2026 Intel Corporation
+ */
+#include <net/cfg80211.h>
+#include <kunit/test.h>
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+static struct ieee80211_channel chan_2ghz_1 = {
+	.band = NL80211_BAND_2GHZ,
+	.center_freq = 2412,
+};
+
+static struct ieee80211_channel chan_6ghz_1 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 5955,
+};
+
+static struct ieee80211_channel chan_6ghz_5 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 5975,
+};
+
+static struct ieee80211_channel chan_6ghz_105 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 6475,
+};
+
+static const struct chandef_compat_case {
+	const char *desc;
+	/* leave c1 empty for tests for identical */
+	struct cfg80211_chan_def c1, c2;
+	/* we test both ways around, so c2 should always be the compat one */
+	bool compat;
+} chandef_compat_cases[] = {
+	{
+		.desc = "identical non-HT",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_20_NOHT,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 20 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 40 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_40,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 80 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_80,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 160 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 320 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40 + 80,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "20 MHz in 320 MHz\n",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40 + 80,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "different 20 MHz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_5,
+			.center_freq1 = 5975,
+		},
+	},
+	{
+		.desc = "different primary 320 MHz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 110,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 50,
+		},
+	},
+	{
+		/* similar to previous test but one has lower BW */
+		.desc = "matching primary 160 MHz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 50,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "matching primary 160 MHz & punctured secondary 160 Mhz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 50,
+			.punctured = 0xf,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "matching primary 160 MHz & punctured matching",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0xc0,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 50,
+			.punctured = 0xc000,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "matching primary 160 MHz & punctured not matching",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x80,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 50,
+			.punctured = 0xc000,
+		},
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(chandef_compat, chandef_compat_cases, desc)
+
+static void test_chandef_compat(struct kunit *test)
+{
+	const struct chandef_compat_case *params = test->param_value;
+	const struct cfg80211_chan_def *ret, *expect;
+	struct cfg80211_chan_def c1 = params->c1;
+
+	/* tests with identical ones */
+	if (!params->c1.chan)
+		c1 = params->c2;
+
+	KUNIT_EXPECT_EQ(test, cfg80211_chandef_valid(&c1), true);
+	KUNIT_EXPECT_EQ(test, cfg80211_chandef_valid(&params->c2), true);
+
+	expect = params->compat ? &params->c2 : NULL;
+
+	ret = cfg80211_chandef_compatible(&c1, &params->c2);
+	KUNIT_EXPECT_PTR_EQ(test, ret, expect);
+
+	if (!params->c1.chan)
+		expect = &c1;
+
+	ret = cfg80211_chandef_compatible(&params->c2, &c1);
+	KUNIT_EXPECT_PTR_EQ(test, ret, expect);
+}
+
+static const struct chandef_dbe_case {
+	const char *desc;
+	struct cfg80211_chan_def c;
+	u8 dbe[3];
+	bool fails;
+	u16 cf1;
+} chandef_dbe_cases[] = {
+	{
+		.desc = "non-HT failure",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_20_NOHT,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_40,
+		.fails = true,
+	},
+	{
+		.desc = "2.4 GHz fails",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_2ghz_1,
+			.center_freq1 = 2412,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_40,
+		.fails = true,
+	},
+	{
+		.desc = "DBE narrower",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40 + 80,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_160,
+		.fails = true,
+	},
+	{
+		.desc = "DBE to 320-1",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_1,
+		.cf1 = 6425,
+	},
+	{
+		.desc = "DBE to 320-2",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_2,
+		.cf1 = 6585,
+	},
+	{
+		.desc = "bad disabled subchannel bitmap - not enough in BSS (1)",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0001,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_1 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0 */
+		.fails = true,
+	},
+	{
+		.desc = "bad disabled subchannel bitmap - too much in BSS (1)",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0001,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_1 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0x0300 */
+		.dbe[2] = 0x03,
+		.fails = true,
+	},
+	{
+		.desc = "bad disabled subchannel bitmap - not enough in BSS (2)",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0001,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_2 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0 */
+		.fails = true,
+	},
+	{
+		.desc = "bad disabled subchannel bitmap - too much in BSS (2)",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0001,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_2 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0x03 */
+		.dbe[1] = 0x03,
+		.fails = true,
+	},
+	{
+		.desc = "bad disabled subchannel bitmap - bad bitmap",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0001,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_1 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0x1100 */
+		.dbe[2] = 0x11,
+		.fails = true,
+	},
+	{
+		.desc = "good disabled subchannel bitmap (1)",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0003,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_1 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0x0300 */
+		.dbe[2] = 0x03,
+		.cf1 = 6425,
+	},
+	{
+		.desc = "good disabled subchannel bitmap (2)",
+		.c = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 30,
+			.punctured = 0x0003,
+		},
+		.dbe[0] = IEEE80211_UHR_DBE_OPER_BW_320_2 |
+			  IEEE80211_UHR_DBE_OPER_DIS_SUBCHANNEL_BITMAP_PRES,
+		/* DBE disabled subchannel bitmap == 0x0003 */
+		.dbe[1] = 0x03,
+		.cf1 = 6585,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(chandef_dbe, chandef_dbe_cases, desc)
+
+static void test_chandef_dbe(struct kunit *test)
+{
+	const struct chandef_dbe_case *params = test->param_value;
+	struct cfg80211_chan_def c = params->c;
+	int ret;
+
+	KUNIT_EXPECT_EQ(test, cfg80211_chandef_valid(&params->c), true);
+
+	ret = cfg80211_chandef_add_dbe(&c, (void *)params->dbe);
+	KUNIT_EXPECT_EQ(test, ret != 0, params->fails);
+
+	if (params->fails)
+		return;
+
+	KUNIT_EXPECT_EQ(test, c.center_freq1, params->cf1);
+}
+
+static struct kunit_case chandef_test_cases[] = {
+	KUNIT_CASE_PARAM(test_chandef_compat, chandef_compat_gen_params),
+	KUNIT_CASE_PARAM(test_chandef_dbe, chandef_dbe_gen_params),
+	{}
+};
+
+static struct kunit_suite chandef = {
+	.name = "cfg80211-chandef",
+	.test_cases = chandef_test_cases,
+};
+
+kunit_test_suite(chandef);