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, 94 insertions, 0 deletions

diff --git a/net/mac80211/wbrf.c b/net/mac80211/wbrf.c
new file mode 100644
index 000000000..478b34b81
--- /dev/null
+++ b/net/mac80211/wbrf.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Wifi Band Exclusion Interface for WLAN
+ * Copyright (C) 2023 Advanced Micro Devices
+ * Copyright (C) 2025 Intel Corporation
+ *
+ */
+
+#include <linux/acpi_amd_wbrf.h>
+#include <linux/units.h>
+#include <net/cfg80211.h>
+#include "ieee80211_i.h"
+
+void ieee80211_check_wbrf_support(struct ieee80211_local *local)
+{
+	struct wiphy *wiphy = local->hw.wiphy;
+	struct device *dev;
+
+	if (!wiphy)
+		return;
+
+	dev = wiphy->dev.parent;
+	if (!dev)
+		return;
+
+	local->wbrf_supported = acpi_amd_wbrf_supported_producer(dev);
+}
+
+static void get_chan_freq_boundary(u32 center_freq, u32 bandwidth, u64 *start, u64 *end)
+{
+	bandwidth *= KHZ_PER_MHZ;
+	center_freq *= KHZ_PER_MHZ;
+
+	*start = center_freq - bandwidth / 2;
+	*end = center_freq + bandwidth / 2;
+
+	/* Frequency in Hz is expected */
+	*start = *start * HZ_PER_KHZ;
+	*end = *end * HZ_PER_KHZ;
+}
+
+static void get_ranges_from_chandef(struct cfg80211_chan_def *chandef,
+				    struct wbrf_ranges_in_out *ranges_in)
+{
+	u64 start_freq1, end_freq1;
+	u64 start_freq2, end_freq2;
+	int bandwidth;
+
+	bandwidth = cfg80211_chandef_get_width(chandef);
+
+	get_chan_freq_boundary(chandef->center_freq1, bandwidth, &start_freq1, &end_freq1);
+
+	ranges_in->band_list[0].start = start_freq1;
+	ranges_in->band_list[0].end = end_freq1;
+	ranges_in->num_of_ranges = 1;
+
+	if (chandef->width == NL80211_CHAN_WIDTH_80P80) {
+		get_chan_freq_boundary(chandef->center_freq2, bandwidth, &start_freq2, &end_freq2);
+
+		ranges_in->band_list[1].start = start_freq2;
+		ranges_in->band_list[1].end = end_freq2;
+		ranges_in->num_of_ranges++;
+	}
+}
+
+void ieee80211_add_wbrf(struct ieee80211_local *local, struct cfg80211_chan_def *chandef)
+{
+	struct wbrf_ranges_in_out ranges_in = {0};
+	struct device *dev;
+
+	if (!local->wbrf_supported)
+		return;
+
+	dev = local->hw.wiphy->dev.parent;
+
+	get_ranges_from_chandef(chandef, &ranges_in);
+
+	acpi_amd_wbrf_add_remove(dev, WBRF_RECORD_ADD, &ranges_in);
+}
+
+void ieee80211_remove_wbrf(struct ieee80211_local *local, struct cfg80211_chan_def *chandef)
+{
+	struct wbrf_ranges_in_out ranges_in = {0};
+	struct device *dev;
+
+	if (!local->wbrf_supported)
+		return;
+
+	dev = local->hw.wiphy->dev.parent;
+
+	get_ranges_from_chandef(chandef, &ranges_in);
+
+	acpi_amd_wbrf_add_remove(dev, WBRF_RECORD_REMOVE, &ranges_in);
+}