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, 309 insertions, 0 deletions

diff --git a/net/mac80211/tests/util.c b/net/mac80211/tests/util.c
new file mode 100644
index 000000000..0b01264af
--- /dev/null
+++ b/net/mac80211/tests/util.c
@@ -0,0 +1,309 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Utilities for mac80211 unit testing
+ *
+ * Copyright (C) 2024 Intel Corporation
+ */
+#include <linux/ieee80211.h>
+#include <net/mac80211.h>
+#include <kunit/test.h>
+#include <kunit/test-bug.h>
+#include "util.h"
+
+#define CHAN2G(_freq)  { \
+	.band = NL80211_BAND_2GHZ, \
+	.center_freq = (_freq), \
+	.hw_value = (_freq), \
+}
+
+static const struct ieee80211_channel channels_2ghz[] = {
+	CHAN2G(2412), /* Channel 1 */
+	CHAN2G(2417), /* Channel 2 */
+	CHAN2G(2422), /* Channel 3 */
+	CHAN2G(2427), /* Channel 4 */
+	CHAN2G(2432), /* Channel 5 */
+	CHAN2G(2437), /* Channel 6 */
+	CHAN2G(2442), /* Channel 7 */
+	CHAN2G(2447), /* Channel 8 */
+	CHAN2G(2452), /* Channel 9 */
+	CHAN2G(2457), /* Channel 10 */
+	CHAN2G(2462), /* Channel 11 */
+	CHAN2G(2467), /* Channel 12 */
+	CHAN2G(2472), /* Channel 13 */
+	CHAN2G(2484), /* Channel 14 */
+};
+
+#define CHAN5G(_freq) { \
+	.band = NL80211_BAND_5GHZ, \
+	.center_freq = (_freq), \
+	.hw_value = (_freq), \
+}
+
+static const struct ieee80211_channel channels_5ghz[] = {
+	CHAN5G(5180), /* Channel 36 */
+	CHAN5G(5200), /* Channel 40 */
+	CHAN5G(5220), /* Channel 44 */
+	CHAN5G(5240), /* Channel 48 */
+};
+
+static const struct ieee80211_rate bitrates[] = {
+	{ .bitrate = 10 },
+	{ .bitrate = 20, .flags = IEEE80211_RATE_SHORT_PREAMBLE },
+	{ .bitrate = 55, .flags = IEEE80211_RATE_SHORT_PREAMBLE },
+	{ .bitrate = 110, .flags = IEEE80211_RATE_SHORT_PREAMBLE },
+	{ .bitrate = 60 },
+	{ .bitrate = 90 },
+	{ .bitrate = 120 },
+	{ .bitrate = 180 },
+	{ .bitrate = 240 },
+	{ .bitrate = 360 },
+	{ .bitrate = 480 },
+	{ .bitrate = 540 }
+};
+
+/* Copied from hwsim except that it only supports 4 EHT streams and STA/P2P mode */
+static const struct ieee80211_sband_iftype_data sband_capa_5ghz[] = {
+	{
+		.types_mask = BIT(NL80211_IFTYPE_STATION) |
+			      BIT(NL80211_IFTYPE_P2P_CLIENT),
+		.he_cap = {
+			.has_he = true,
+			.he_cap_elem = {
+				.mac_cap_info[0] =
+					IEEE80211_HE_MAC_CAP0_HTC_HE,
+				.mac_cap_info[1] =
+					IEEE80211_HE_MAC_CAP1_TF_MAC_PAD_DUR_16US |
+					IEEE80211_HE_MAC_CAP1_MULTI_TID_AGG_RX_QOS_8,
+				.mac_cap_info[2] =
+					IEEE80211_HE_MAC_CAP2_BSR |
+					IEEE80211_HE_MAC_CAP2_MU_CASCADING |
+					IEEE80211_HE_MAC_CAP2_ACK_EN,
+				.mac_cap_info[3] =
+					IEEE80211_HE_MAC_CAP3_OMI_CONTROL |
+					IEEE80211_HE_MAC_CAP3_MAX_AMPDU_LEN_EXP_EXT_3,
+				.mac_cap_info[4] = IEEE80211_HE_MAC_CAP4_AMSDU_IN_AMPDU,
+				.phy_cap_info[0] =
+					IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_40MHZ_80MHZ_IN_5G |
+					IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_160MHZ_IN_5G |
+					IEEE80211_HE_PHY_CAP0_CHANNEL_WIDTH_SET_80PLUS80_MHZ_IN_5G,
+				.phy_cap_info[1] =
+					IEEE80211_HE_PHY_CAP1_PREAMBLE_PUNC_RX_MASK |
+					IEEE80211_HE_PHY_CAP1_DEVICE_CLASS_A |
+					IEEE80211_HE_PHY_CAP1_LDPC_CODING_IN_PAYLOAD |
+					IEEE80211_HE_PHY_CAP1_MIDAMBLE_RX_TX_MAX_NSTS,
+				.phy_cap_info[2] =
+					IEEE80211_HE_PHY_CAP2_NDP_4x_LTF_AND_3_2US |
+					IEEE80211_HE_PHY_CAP2_STBC_TX_UNDER_80MHZ |
+					IEEE80211_HE_PHY_CAP2_STBC_RX_UNDER_80MHZ |
+					IEEE80211_HE_PHY_CAP2_UL_MU_FULL_MU_MIMO |
+					IEEE80211_HE_PHY_CAP2_UL_MU_PARTIAL_MU_MIMO,
+
+				/* Leave all the other PHY capability bytes
+				 * unset, as DCM, beam forming, RU and PPE
+				 * threshold information are not supported
+				 */
+			},
+			.he_mcs_nss_supp = {
+				.rx_mcs_80 = cpu_to_le16(0xfffa),
+				.tx_mcs_80 = cpu_to_le16(0xfffa),
+				.rx_mcs_160 = cpu_to_le16(0xfffa),
+				.tx_mcs_160 = cpu_to_le16(0xfffa),
+				.rx_mcs_80p80 = cpu_to_le16(0xfffa),
+				.tx_mcs_80p80 = cpu_to_le16(0xfffa),
+			},
+		},
+		.eht_cap = {
+			.has_eht = true,
+			.eht_cap_elem = {
+				.mac_cap_info[0] =
+					IEEE80211_EHT_MAC_CAP0_EPCS_PRIO_ACCESS |
+					IEEE80211_EHT_MAC_CAP0_OM_CONTROL |
+					IEEE80211_EHT_MAC_CAP0_TRIG_TXOP_SHARING_MODE1,
+				.phy_cap_info[0] =
+					IEEE80211_EHT_PHY_CAP0_242_TONE_RU_GT20MHZ |
+					IEEE80211_EHT_PHY_CAP0_NDP_4_EHT_LFT_32_GI |
+					IEEE80211_EHT_PHY_CAP0_PARTIAL_BW_UL_MU_MIMO |
+					IEEE80211_EHT_PHY_CAP0_SU_BEAMFORMER |
+					IEEE80211_EHT_PHY_CAP0_SU_BEAMFORMEE |
+					IEEE80211_EHT_PHY_CAP0_BEAMFORMEE_SS_80MHZ_MASK,
+				.phy_cap_info[1] =
+					IEEE80211_EHT_PHY_CAP1_BEAMFORMEE_SS_80MHZ_MASK |
+					IEEE80211_EHT_PHY_CAP1_BEAMFORMEE_SS_160MHZ_MASK,
+				.phy_cap_info[2] =
+					IEEE80211_EHT_PHY_CAP2_SOUNDING_DIM_80MHZ_MASK |
+					IEEE80211_EHT_PHY_CAP2_SOUNDING_DIM_160MHZ_MASK,
+				.phy_cap_info[3] =
+					IEEE80211_EHT_PHY_CAP3_NG_16_SU_FEEDBACK |
+					IEEE80211_EHT_PHY_CAP3_NG_16_MU_FEEDBACK |
+					IEEE80211_EHT_PHY_CAP3_CODEBOOK_4_2_SU_FDBK |
+					IEEE80211_EHT_PHY_CAP3_CODEBOOK_7_5_MU_FDBK |
+					IEEE80211_EHT_PHY_CAP3_TRIG_SU_BF_FDBK |
+					IEEE80211_EHT_PHY_CAP3_TRIG_MU_BF_PART_BW_FDBK |
+					IEEE80211_EHT_PHY_CAP3_TRIG_CQI_FDBK,
+				.phy_cap_info[4] =
+					IEEE80211_EHT_PHY_CAP4_PART_BW_DL_MU_MIMO |
+					IEEE80211_EHT_PHY_CAP4_PSR_SR_SUPP |
+					IEEE80211_EHT_PHY_CAP4_POWER_BOOST_FACT_SUPP |
+					IEEE80211_EHT_PHY_CAP4_EHT_MU_PPDU_4_EHT_LTF_08_GI |
+					IEEE80211_EHT_PHY_CAP4_MAX_NC_MASK,
+				.phy_cap_info[5] =
+					IEEE80211_EHT_PHY_CAP5_NON_TRIG_CQI_FEEDBACK |
+					IEEE80211_EHT_PHY_CAP5_TX_LESS_242_TONE_RU_SUPP |
+					IEEE80211_EHT_PHY_CAP5_RX_LESS_242_TONE_RU_SUPP |
+					IEEE80211_EHT_PHY_CAP5_PPE_THRESHOLD_PRESENT |
+					IEEE80211_EHT_PHY_CAP5_COMMON_NOMINAL_PKT_PAD_MASK |
+					IEEE80211_EHT_PHY_CAP5_MAX_NUM_SUPP_EHT_LTF_MASK,
+				.phy_cap_info[6] =
+					IEEE80211_EHT_PHY_CAP6_MAX_NUM_SUPP_EHT_LTF_MASK |
+					IEEE80211_EHT_PHY_CAP6_MCS15_SUPP_MASK,
+				.phy_cap_info[7] =
+					IEEE80211_EHT_PHY_CAP7_20MHZ_STA_RX_NDP_WIDER_BW |
+					IEEE80211_EHT_PHY_CAP7_NON_OFDMA_UL_MU_MIMO_80MHZ |
+					IEEE80211_EHT_PHY_CAP7_NON_OFDMA_UL_MU_MIMO_160MHZ |
+					IEEE80211_EHT_PHY_CAP7_MU_BEAMFORMER_80MHZ |
+					IEEE80211_EHT_PHY_CAP7_MU_BEAMFORMER_160MHZ,
+			},
+
+			/* For all MCS and bandwidth, set 4 NSS for both Tx and
+			 * Rx
+			 */
+			.eht_mcs_nss_supp = {
+				/*
+				 * As B1 and B2 are set in the supported
+				 * channel width set field in the HE PHY
+				 * capabilities information field include all
+				 * the following MCS/NSS.
+				 */
+				.bw._80 = {
+					.rx_tx_mcs9_max_nss = 0x44,
+					.rx_tx_mcs11_max_nss = 0x44,
+					.rx_tx_mcs13_max_nss = 0x44,
+				},
+				.bw._160 = {
+					.rx_tx_mcs9_max_nss = 0x44,
+					.rx_tx_mcs11_max_nss = 0x44,
+					.rx_tx_mcs13_max_nss = 0x44,
+				},
+			},
+			/* PPE threshold information is not supported */
+		},
+	},
+};
+
+int t_sdata_init(struct kunit_resource *resource, void *ctx)
+{
+	struct kunit *test = kunit_get_current_test();
+	struct t_sdata *t_sdata;
+
+	t_sdata = kzalloc_obj(*t_sdata);
+	KUNIT_ASSERT_NOT_NULL(test, t_sdata);
+
+	resource->data = t_sdata;
+	resource->name = "sdata";
+
+	t_sdata->sdata = kzalloc_obj(*t_sdata->sdata);
+	KUNIT_ASSERT_NOT_NULL(test, t_sdata->sdata);
+
+	t_sdata->wiphy = kzalloc_obj(*t_sdata->wiphy);
+	KUNIT_ASSERT_NOT_NULL(test, t_sdata->wiphy);
+
+	strscpy(t_sdata->sdata->name, "kunit");
+
+	t_sdata->sdata->local = &t_sdata->local;
+	t_sdata->sdata->local->hw.wiphy = t_sdata->wiphy;
+	t_sdata->sdata->wdev.wiphy = t_sdata->wiphy;
+	t_sdata->sdata->vif.type = NL80211_IFTYPE_STATION;
+
+	t_sdata->sdata->deflink.sdata = t_sdata->sdata;
+	t_sdata->sdata->deflink.link_id = 0;
+
+	t_sdata->wiphy->bands[NL80211_BAND_2GHZ] = &t_sdata->band_2ghz;
+	t_sdata->wiphy->bands[NL80211_BAND_5GHZ] = &t_sdata->band_5ghz;
+
+	for (int band = NL80211_BAND_2GHZ; band <= NL80211_BAND_5GHZ; band++) {
+		struct ieee80211_supported_band *sband;
+
+		sband = t_sdata->wiphy->bands[band];
+		sband->band = band;
+
+		sband->bitrates =
+			kmemdup(bitrates, sizeof(bitrates), GFP_KERNEL);
+		sband->n_bitrates = ARRAY_SIZE(bitrates);
+
+		/* Initialize channels, feel free to add more channels/bands */
+		switch (band) {
+		case NL80211_BAND_2GHZ:
+			sband->channels = kmemdup(channels_2ghz,
+						  sizeof(channels_2ghz),
+						  GFP_KERNEL);
+			sband->n_channels = ARRAY_SIZE(channels_2ghz);
+			sband->bitrates = kmemdup(bitrates,
+						  sizeof(bitrates),
+						  GFP_KERNEL);
+			sband->n_bitrates = ARRAY_SIZE(bitrates);
+			break;
+		case NL80211_BAND_5GHZ:
+			sband->channels = kmemdup(channels_5ghz,
+						  sizeof(channels_5ghz),
+						  GFP_KERNEL);
+			sband->n_channels = ARRAY_SIZE(channels_5ghz);
+			sband->bitrates = kmemdup(bitrates,
+						  sizeof(bitrates),
+						  GFP_KERNEL);
+			sband->n_bitrates = ARRAY_SIZE(bitrates);
+
+			sband->vht_cap.vht_supported = true;
+			sband->vht_cap.cap =
+				IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_11454 |
+				IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ |
+				IEEE80211_VHT_CAP_RXLDPC |
+				IEEE80211_VHT_CAP_SHORT_GI_80 |
+				IEEE80211_VHT_CAP_SHORT_GI_160 |
+				IEEE80211_VHT_CAP_TXSTBC |
+				IEEE80211_VHT_CAP_RXSTBC_4 |
+				IEEE80211_VHT_CAP_MAX_A_MPDU_LENGTH_EXPONENT_MASK;
+			sband->vht_cap.vht_mcs.rx_mcs_map =
+				cpu_to_le16(IEEE80211_VHT_MCS_SUPPORT_0_9 << 0 |
+					    IEEE80211_VHT_MCS_SUPPORT_0_9 << 2 |
+					    IEEE80211_VHT_MCS_SUPPORT_0_9 << 4 |
+					    IEEE80211_VHT_MCS_SUPPORT_0_9 << 6);
+			sband->vht_cap.vht_mcs.tx_mcs_map =
+				sband->vht_cap.vht_mcs.rx_mcs_map;
+			break;
+		default:
+			continue;
+		}
+
+		sband->ht_cap.ht_supported = band != NL80211_BAND_6GHZ;
+		sband->ht_cap.cap = IEEE80211_HT_CAP_SUP_WIDTH_20_40 |
+					IEEE80211_HT_CAP_GRN_FLD |
+					IEEE80211_HT_CAP_SGI_20 |
+					IEEE80211_HT_CAP_SGI_40 |
+					IEEE80211_HT_CAP_DSSSCCK40;
+		sband->ht_cap.ampdu_factor = 0x3;
+		sband->ht_cap.ampdu_density = 0x6;
+		memset(&sband->ht_cap.mcs, 0, sizeof(sband->ht_cap.mcs));
+		sband->ht_cap.mcs.rx_mask[0] = 0xff;
+		sband->ht_cap.mcs.rx_mask[1] = 0xff;
+		sband->ht_cap.mcs.tx_params = IEEE80211_HT_MCS_TX_DEFINED;
+	}
+
+	ieee80211_set_sband_iftype_data(&t_sdata->band_5ghz, sband_capa_5ghz);
+
+	return 0;
+}
+
+void t_sdata_exit(struct kunit_resource *resource)
+{
+	struct t_sdata *t_sdata = resource->data;
+
+	kfree(t_sdata->band_2ghz.channels);
+	kfree(t_sdata->band_2ghz.bitrates);
+	kfree(t_sdata->band_5ghz.channels);
+	kfree(t_sdata->band_5ghz.bitrates);
+
+	kfree(t_sdata->sdata);
+	kfree(t_sdata->wiphy);
+
+	kfree(t_sdata);
+}