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, 386 insertions, 0 deletions

diff --git a/net/mac80211/tests/elems.c b/net/mac80211/tests/elems.c
new file mode 100644
index 000000000..4b13a5aad
--- /dev/null
+++ b/net/mac80211/tests/elems.c
@@ -0,0 +1,386 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for element parsing
+ *
+ * Copyright (C) 2023-2025 Intel Corporation
+ */
+#include <kunit/test.h>
+#include "../ieee80211_i.h"
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+static const struct mesh_preq_parse_test_case {
+	const char *desc;
+	u8 len;
+	bool ae_enabled;
+	u8 target_count;
+	bool result;
+} mesh_preq_parse_cases[] = {
+	{
+		.desc = "shorter than header",
+		.len = 16,
+		.ae_enabled = false,
+		.target_count = 1,
+		.result = false,
+	},
+	{
+		.desc = "too short non AE, target count is not included",
+		.len = 29,
+		.ae_enabled = false,
+		.target_count = 1,
+		.result = false,
+	},
+	{
+		.desc = "too short non AE, target count is 1",
+		.len = 36,
+		.ae_enabled = false,
+		.target_count = 1,
+		.result = false,
+	},
+	{
+		.desc = "too short AE, target count is not included",
+		.len = 35,
+		.ae_enabled = true,
+		.target_count = 1,
+		.result = false,
+	},
+	{
+		.desc = "too short AE, target count is 1",
+		.len = 42,
+		.ae_enabled = true,
+		.target_count = 1,
+		.result = false,
+	},
+	{
+		.desc = "target count is zero",
+		.len = 26,
+		.ae_enabled = false,
+		.target_count = 0,
+		.result = false,
+	},
+	{
+		.desc = "target count is 21",
+		.len = 255,
+		.ae_enabled = false,
+		.target_count = 21,
+		.result = false,
+	},
+	{
+		.desc = "non AE, target count is 1",
+		.len = 37,
+		.ae_enabled = false,
+		.target_count = 1,
+		.result = true,
+	},
+	{
+		.desc = "non AE, target count is 20",
+		.len = 246,
+		.ae_enabled = false,
+		.target_count = 20,
+		.result = true,
+	},
+	{
+		.desc = "AE, target count is 1",
+		.len = 43,
+		.ae_enabled = true,
+		.target_count = 1,
+		.result = true,
+	},
+	{
+		.desc = "AE, target count is 20",
+		.len = 252,
+		.ae_enabled = true,
+		.target_count = 20,
+		.result = true,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(mesh_preq_parse, mesh_preq_parse_cases, desc);
+
+static const struct mesh_prep_parse_test_case {
+	const char *desc;
+	u8 len;
+	bool ae_enabled;
+	bool result;
+} mesh_prep_parse_cases[] = {
+	{
+		.desc = "shorter than header",
+		.len = 12,
+		.ae_enabled = false,
+		.result = false,
+	},
+	{
+		.desc = "non AE short",
+		.len = 30,
+		.ae_enabled = false,
+		.result = false,
+	},
+	{
+		.desc = "non AE",
+		.len = 31,
+		.ae_enabled = false,
+		.result = true,
+	},
+	{
+		.desc = "AE short",
+		.len = 36,
+		.ae_enabled = true,
+		.result = false,
+	},
+	{
+		.desc = "AE",
+		.len = 37,
+		.ae_enabled = true,
+		.result = true,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(mesh_prep_parse, mesh_prep_parse_cases, desc);
+
+static const struct mesh_perr_parse_test_case {
+	const char *desc;
+	u8 len;
+	u8 number_of_dst;
+	int ae_enabled_idx;
+	bool result;
+} mesh_perr_parse_cases[] = {
+	{
+		.desc = "shorter than header",
+		.len = 1,
+		.number_of_dst = 1,
+		.ae_enabled_idx = -1,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 0",
+		.len = 2,
+		.number_of_dst = 0,
+		.ae_enabled_idx = -1,
+		.result = true,
+	},
+	{
+		.desc = "number_of_dst is 20",
+		.len = 255,
+		.number_of_dst = 20,
+		.ae_enabled_idx = -1,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 1, non AE, short",
+		.len = 14,
+		.number_of_dst = 1,
+		.ae_enabled_idx = -1,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 1, non AE",
+		.len = 15,
+		.number_of_dst = 1,
+		.ae_enabled_idx = -1,
+		.result = true,
+	},
+	{
+		.desc = "number_of_dst is 1, non AE, extra short dst header",
+		.len = 25,
+		.number_of_dst = 1,
+		.ae_enabled_idx = -1,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 1, non AE, extra dst header",
+		.len = 26,
+		.number_of_dst = 1,
+		.ae_enabled_idx = -1,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 1, AE, short",
+		.len = 20,
+		.number_of_dst = 1,
+		.ae_enabled_idx = 0,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 1, AE",
+		.len = 21,
+		.number_of_dst = 1,
+		.ae_enabled_idx = 0,
+		.result = true,
+	},
+	{
+		.desc = "number_of_dst is 19, non AE, short",
+		.len = 2 + 13 * 19 - 1,
+		.number_of_dst = 19,
+		.ae_enabled_idx = -1,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 19, non AE",
+		.len = 2 + 13 * 19,
+		.number_of_dst = 19,
+		.ae_enabled_idx = -1,
+		.result = true,
+	},
+	{
+		.desc = "number_of_dst is 19, AE, short",
+		.len = 2 + 13 * 19 + 6 - 1,
+		.number_of_dst = 19,
+		.ae_enabled_idx = 18,
+		.result = false,
+	},
+	{
+		.desc = "number_of_dst is 19, AE",
+		.len = 2 + 13 * 19 + 6,
+		.number_of_dst = 19,
+		.ae_enabled_idx = 18,
+		.result = true,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(mesh_perr_parse, mesh_perr_parse_cases, desc);
+
+
+static void mle_defrag(struct kunit *test)
+{
+	struct ieee80211_elems_parse_params parse_params = {
+		.link_id = 12,
+		.from_ap = true,
+		.mode = IEEE80211_CONN_MODE_EHT,
+		/* type is not really relevant here */
+		.type = IEEE80211_FTYPE_MGMT | IEEE80211_STYPE_BEACON,
+	};
+	struct ieee802_11_elems *parsed;
+	struct sk_buff *skb;
+	u8 *len_mle, *len_prof;
+	int i;
+
+	skb = alloc_skb(1024, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, skb);
+
+	if (skb_pad(skb, skb_tailroom(skb))) {
+		KUNIT_FAIL(test, "failed to pad skb");
+		return;
+	}
+
+	/* build a multi-link element */
+	skb_put_u8(skb, WLAN_EID_EXTENSION);
+	len_mle = skb_put(skb, 1);
+	skb_put_u8(skb, WLAN_EID_EXT_EHT_MULTI_LINK);
+
+	put_unaligned_le16(IEEE80211_ML_CONTROL_TYPE_BASIC,
+			   skb_put(skb, 2));
+	/* struct ieee80211_mle_basic_common_info */
+	skb_put_u8(skb, 7); /* includes len field */
+	skb_put_data(skb, "\x00\x00\x00\x00\x00\x00", ETH_ALEN); /* MLD addr */
+
+	/* with a STA profile inside */
+	skb_put_u8(skb, IEEE80211_MLE_SUBELEM_PER_STA_PROFILE);
+	len_prof = skb_put(skb, 1);
+	put_unaligned_le16(IEEE80211_MLE_STA_CONTROL_COMPLETE_PROFILE |
+			   parse_params.link_id,
+			   skb_put(skb, 2));
+	skb_put_u8(skb, 1); /* fake sta_info_len - includes itself */
+	/* put a bunch of useless elements into it */
+	for (i = 0; i < 20; i++) {
+		skb_put_u8(skb, WLAN_EID_SSID);
+		skb_put_u8(skb, 20);
+		skb_put(skb, 20);
+	}
+
+	/* fragment STA profile */
+	ieee80211_fragment_element(skb, len_prof,
+				   IEEE80211_MLE_SUBELEM_FRAGMENT);
+	/* fragment MLE */
+	ieee80211_fragment_element(skb, len_mle, WLAN_EID_FRAGMENT);
+
+	parse_params.start = skb->data;
+	parse_params.len = skb->len;
+	parsed = ieee802_11_parse_elems_full(&parse_params);
+	/* should return ERR_PTR or valid, not NULL */
+	KUNIT_EXPECT_NOT_NULL(test, parsed);
+
+	if (IS_ERR_OR_NULL(parsed))
+		goto free_skb;
+
+	KUNIT_EXPECT_NOT_NULL(test, parsed->ml_basic);
+	KUNIT_EXPECT_EQ(test,
+			parsed->ml_basic_len,
+			2 /* control */ +
+			7 /* common info */ +
+			2 /* sta profile element header */ +
+			3 /* sta profile header */ +
+			20 * 22 /* sta profile data */ +
+			2 /* sta profile fragment element */);
+	KUNIT_EXPECT_NOT_NULL(test, parsed->prof);
+	KUNIT_EXPECT_EQ(test,
+			parsed->sta_prof_len,
+			3 /* sta profile header */ +
+			20 * 22 /* sta profile data */);
+
+	kfree(parsed);
+free_skb:
+	kfree_skb(skb);
+}
+
+static void mesh_preq_parse(struct kunit *test)
+{
+	const struct mesh_preq_parse_test_case *params = test->param_value;
+	u8 data[64] = {};
+	struct ieee80211_mesh_hwmp_preq_top *top = (void *)data;
+	struct ieee80211_mesh_hwmp_preq_bottom *bottom;
+
+	top->flags = params->ae_enabled ? AE_F : 0;
+	bottom = ieee80211_mesh_hwmp_preq_get_bottom(data);
+	bottom->target_count = params->target_count;
+
+	KUNIT_EXPECT_EQ(test,
+			ieee80211_mesh_preq_size_ok(data, params->len),
+			params->result);
+}
+
+static void mesh_prep_parse(struct kunit *test)
+{
+	const struct mesh_prep_parse_test_case *params = test->param_value;
+	u8 data[64] = {};
+	struct ieee80211_mesh_hwmp_prep_top *top = (void *)data;
+	top->flags = params->ae_enabled ? AE_F : 0;
+
+	KUNIT_EXPECT_EQ(test,
+			ieee80211_mesh_prep_size_ok(data, params->len),
+			params->result);
+}
+
+static void mesh_perr_parse(struct kunit *test)
+{
+	const struct mesh_perr_parse_test_case *params = test->param_value;
+	u8 data[256] = {};
+	struct ieee80211_mesh_hwmp_perr *perr = (void *)data;
+
+	perr->number_of_dst = params->number_of_dst;
+	if (params->ae_enabled_idx > -1) {
+		struct ieee80211_mesh_hwmp_perr_dst *dst =
+			ieee80211_mesh_hwmp_perr_get_dst(
+				data, params->ae_enabled_idx);
+
+		dst->flags = AE_F;
+	}
+
+	KUNIT_EXPECT_EQ(test,
+			ieee80211_mesh_perr_size_ok(data, params->len),
+			params->result);
+}
+
+static struct kunit_case element_parsing_test_cases[] = {
+	KUNIT_CASE(mle_defrag),
+	KUNIT_CASE_PARAM(mesh_preq_parse, mesh_preq_parse_gen_params),
+	KUNIT_CASE_PARAM(mesh_prep_parse, mesh_prep_parse_gen_params),
+	KUNIT_CASE_PARAM(mesh_perr_parse, mesh_perr_parse_gen_params),
+	{}
+};
+
+static struct kunit_suite element_parsing = {
+	.name = "mac80211-element-parsing",
+	.test_cases = element_parsing_test_cases,
+};
+
+kunit_test_suite(element_parsing);