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, 141 insertions, 0 deletions

diff --git a/net/wireless/wext-proc.c b/net/wireless/wext-proc.c
new file mode 100644
index 000000000..be6b2b695
--- /dev/null
+++ b/net/wireless/wext-proc.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file implement the Wireless Extensions proc API.
+ *
+ * Authors :	Jean Tourrilhes - HPL - <jt@hpl.hp.com>
+ * Copyright (c) 1997-2007 Jean Tourrilhes, All Rights Reserved.
+ */
+
+/*
+ * The /proc/net/wireless file is a human readable user-space interface
+ * exporting various wireless specific statistics from the wireless devices.
+ * This is the most popular part of the Wireless Extensions ;-)
+ *
+ * This interface is a pure clone of /proc/net/dev (in net/core/dev.c).
+ * The content of the file is basically the content of "struct iw_statistics".
+ */
+
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/wireless.h>
+#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
+#include <net/iw_handler.h>
+#include <net/wext.h>
+
+
+static void wireless_seq_printf_stats(struct seq_file *seq,
+				      struct net_device *dev)
+{
+	/* Get stats from the driver */
+	struct iw_statistics *stats = get_wireless_stats(dev);
+	static struct iw_statistics nullstats = {};
+
+	/* show device if it's wireless regardless of current stats */
+	if (!stats) {
+#ifdef CONFIG_WIRELESS_EXT
+		if (dev->wireless_handlers)
+			stats = &nullstats;
+#endif
+#ifdef CONFIG_CFG80211
+		if (dev->ieee80211_ptr)
+			stats = &nullstats;
+#endif
+	}
+
+	if (stats) {
+		seq_printf(seq, "%6s: %04x  %3d%c  %3d%c  %3d%c  %6d %6d %6d "
+				"%6d %6d   %6d\n",
+			   dev->name, stats->status, stats->qual.qual,
+			   stats->qual.updated & IW_QUAL_QUAL_UPDATED
+			   ? '.' : ' ',
+			   ((__s32) stats->qual.level) -
+			   ((stats->qual.updated & IW_QUAL_DBM) ? 0x100 : 0),
+			   stats->qual.updated & IW_QUAL_LEVEL_UPDATED
+			   ? '.' : ' ',
+			   ((__s32) stats->qual.noise) -
+			   ((stats->qual.updated & IW_QUAL_DBM) ? 0x100 : 0),
+			   stats->qual.updated & IW_QUAL_NOISE_UPDATED
+			   ? '.' : ' ',
+			   stats->discard.nwid, stats->discard.code,
+			   stats->discard.fragment, stats->discard.retries,
+			   stats->discard.misc, stats->miss.beacon);
+
+		if (stats != &nullstats)
+			stats->qual.updated &= ~IW_QUAL_ALL_UPDATED;
+	}
+}
+
+/* ---------------------------------------------------------------- */
+/*
+ * Print info for /proc/net/wireless (print all entries)
+ */
+static int wireless_dev_seq_show(struct seq_file *seq, void *v)
+{
+	might_sleep();
+
+	if (v == SEQ_START_TOKEN)
+		seq_printf(seq, "Inter-| sta-|   Quality        |   Discarded "
+				"packets               | Missed | WE\n"
+				" face | tus | link level noise |  nwid  "
+				"crypt   frag  retry   misc | beacon | %d\n",
+			   WIRELESS_EXT);
+	else
+		wireless_seq_printf_stats(seq, v);
+	return 0;
+}
+
+static void *wireless_dev_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct net *net = seq_file_net(seq);
+	loff_t off;
+	struct net_device *dev;
+
+	rtnl_lock();
+	if (!*pos)
+		return SEQ_START_TOKEN;
+
+	off = 1;
+	for_each_netdev(net, dev)
+		if (off++ == *pos)
+			return dev;
+	return NULL;
+}
+
+static void *wireless_dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct net *net = seq_file_net(seq);
+
+	++*pos;
+
+	return v == SEQ_START_TOKEN ?
+		first_net_device(net) : next_net_device(v);
+}
+
+static void wireless_dev_seq_stop(struct seq_file *seq, void *v)
+{
+	rtnl_unlock();
+}
+
+static const struct seq_operations wireless_seq_ops = {
+	.start = wireless_dev_seq_start,
+	.next  = wireless_dev_seq_next,
+	.stop  = wireless_dev_seq_stop,
+	.show  = wireless_dev_seq_show,
+};
+
+int __net_init wext_proc_init(struct net *net)
+{
+	/* Create /proc/net/wireless entry */
+	if (!proc_create_net("wireless", 0444, net->proc_net,
+			&wireless_seq_ops, sizeof(struct seq_net_private)))
+		return -ENOMEM;
+
+	return 0;
+}
+
+void __net_exit wext_proc_exit(struct net *net)
+{
+	remove_proc_entry("wireless", net->proc_net);
+}