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, 187 insertions, 0 deletions

diff --git a/net/wireless/sysfs.c b/net/wireless/sysfs.c
new file mode 100644
index 000000000..3ec25d3f0
--- /dev/null
+++ b/net/wireless/sysfs.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This file provides /sys/class/ieee80211/<wiphy name>/
+ * and some default attributes.
+ *
+ * Copyright 2005-2006	Jiri Benc <jbenc@suse.cz>
+ * Copyright 2006	Johannes Berg <johannes@sipsolutions.net>
+ * Copyright (C) 2020-2021, 2023-2024 Intel Corporation
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/nl80211.h>
+#include <linux/rtnetlink.h>
+#include <net/cfg80211.h>
+#include "sysfs.h"
+#include "core.h"
+#include "rdev-ops.h"
+
+static inline struct cfg80211_registered_device *dev_to_rdev(
+	struct device *dev)
+{
+	return container_of(dev, struct cfg80211_registered_device, wiphy.dev);
+}
+
+#define SHOW_FMT(name, fmt, member)					\
+static ssize_t name ## _show(struct device *dev,			\
+			      struct device_attribute *attr,		\
+			      char *buf)				\
+{									\
+	return sprintf(buf, fmt "\n", dev_to_rdev(dev)->member);	\
+}									\
+static DEVICE_ATTR_RO(name)
+
+SHOW_FMT(index, "%d", wiphy_idx);
+SHOW_FMT(macaddress, "%pM", wiphy.perm_addr);
+SHOW_FMT(address_mask, "%pM", wiphy.addr_mask);
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr,
+			 char *buf)
+{
+	struct wiphy *wiphy = &dev_to_rdev(dev)->wiphy;
+
+	return sprintf(buf, "%s\n", wiphy_name(wiphy));
+}
+static DEVICE_ATTR_RO(name);
+
+static ssize_t addresses_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	struct wiphy *wiphy = &dev_to_rdev(dev)->wiphy;
+	char *start = buf;
+	int i;
+
+	if (!wiphy->addresses)
+		return sprintf(buf, "%pM\n", wiphy->perm_addr);
+
+	for (i = 0; i < wiphy->n_addresses; i++)
+		buf += sprintf(buf, "%pM\n", wiphy->addresses[i].addr);
+
+	return buf - start;
+}
+static DEVICE_ATTR_RO(addresses);
+
+static struct attribute *ieee80211_attrs[] = {
+	&dev_attr_index.attr,
+	&dev_attr_macaddress.attr,
+	&dev_attr_address_mask.attr,
+	&dev_attr_addresses.attr,
+	&dev_attr_name.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(ieee80211);
+
+static void wiphy_dev_release(struct device *dev)
+{
+	struct cfg80211_registered_device *rdev = dev_to_rdev(dev);
+
+	cfg80211_dev_free(rdev);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static void cfg80211_leave_all(struct cfg80211_registered_device *rdev)
+{
+	struct wireless_dev *wdev;
+
+	list_for_each_entry(wdev, &rdev->wiphy.wdev_list, list)
+		cfg80211_leave(rdev, wdev, -1);
+}
+
+static int wiphy_suspend(struct device *dev)
+{
+	struct cfg80211_registered_device *rdev = dev_to_rdev(dev);
+	int ret = 0;
+
+	rdev->suspend_at = ktime_get_boottime_seconds();
+
+	rtnl_lock();
+	if (!rdev->wiphy.registered)
+		goto out_unlock_rtnl;
+
+	if (rdev->wiphy.wowlan_config) {
+		scoped_guard(wiphy, &rdev->wiphy) {
+			cfg80211_process_wiphy_works(rdev, NULL);
+			if (rdev->ops->suspend)
+				ret = rdev_suspend(rdev,
+						   rdev->wiphy.wowlan_config);
+			if (ret <= 0)
+				goto out_unlock_rtnl;
+		}
+	}
+
+	/* Driver refused to configure wowlan (ret = 1) or no wowlan */
+
+	cfg80211_leave_all(rdev);
+	scoped_guard(wiphy, &rdev->wiphy) {
+		cfg80211_process_rdev_events(rdev);
+		cfg80211_process_wiphy_works(rdev, NULL);
+		if (rdev->ops->suspend)
+			ret = rdev_suspend(rdev, NULL);
+	}
+out_unlock_rtnl:
+	if (ret == 0)
+		rdev->suspended = true;
+	rtnl_unlock();
+
+	return ret;
+}
+
+static int wiphy_resume(struct device *dev)
+{
+	struct cfg80211_registered_device *rdev = dev_to_rdev(dev);
+	int ret = 0;
+
+	/* Age scan results with time spent in suspend */
+	cfg80211_bss_age(rdev, ktime_get_boottime_seconds() - rdev->suspend_at);
+
+	rtnl_lock();
+	wiphy_lock(&rdev->wiphy);
+	if (rdev->wiphy.registered && rdev->ops->resume)
+		ret = rdev_resume(rdev);
+	rdev->suspended = false;
+	queue_work(system_dfl_wq, &rdev->wiphy_work);
+	wiphy_unlock(&rdev->wiphy);
+
+	if (ret)
+		cfg80211_shutdown_all_interfaces(&rdev->wiphy);
+
+	rtnl_unlock();
+
+	return ret;
+}
+
+static SIMPLE_DEV_PM_OPS(wiphy_pm_ops, wiphy_suspend, wiphy_resume);
+#define WIPHY_PM_OPS (&wiphy_pm_ops)
+#else
+#define WIPHY_PM_OPS NULL
+#endif
+
+static const struct ns_common *wiphy_namespace(const struct device *d)
+{
+	struct wiphy *wiphy = container_of(d, struct wiphy, dev);
+
+	return to_ns_common(wiphy_net(wiphy));
+}
+
+struct class ieee80211_class = {
+	.name = "ieee80211",
+	.dev_release = wiphy_dev_release,
+	.dev_groups = ieee80211_groups,
+	.pm = WIPHY_PM_OPS,
+	.ns_type = &net_ns_type_operations,
+	.namespace = wiphy_namespace,
+};
+
+int wiphy_sysfs_init(void)
+{
+	return class_register(&ieee80211_class);
+}
+
+void wiphy_sysfs_exit(void)
+{
+	class_unregister(&ieee80211_class);
+}