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, 121 insertions, 0 deletions

diff --git a/include/net/net_shaper.h b/include/net/net_shaper.h
new file mode 100644
index 000000000..3939b816b
--- /dev/null
+++ b/include/net/net_shaper.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _NET_SHAPER_H_
+#define _NET_SHAPER_H_
+
+#include <linux/types.h>
+
+#include <uapi/linux/net_shaper.h>
+
+struct net_device;
+struct devlink;
+struct netlink_ext_ack;
+
+enum net_shaper_binding_type {
+	NET_SHAPER_BINDING_TYPE_NETDEV,
+	/* NET_SHAPER_BINDING_TYPE_DEVLINK_PORT */
+};
+
+struct net_shaper_binding {
+	enum net_shaper_binding_type type;
+	union {
+		struct net_device *netdev;
+		struct devlink *devlink;
+	};
+};
+
+struct net_shaper_handle {
+	enum net_shaper_scope scope;
+	u32 id;
+};
+
+/**
+ * struct net_shaper - represents a shaping node on the NIC H/W
+ * zeroed field are considered not set.
+ * @parent: Unique identifier for the shaper parent, usually implied
+ * @handle: Unique identifier for this shaper
+ * @metric: Specify if the rate limits refers to PPS or BPS
+ * @bw_min: Minimum guaranteed rate for this shaper
+ * @bw_max: Maximum peak rate allowed for this shaper
+ * @burst: Maximum burst for the peek rate of this shaper
+ * @priority: Scheduling priority for this shaper
+ * @weight: Scheduling weight for this shaper
+ */
+struct net_shaper {
+	struct net_shaper_handle parent;
+	struct net_shaper_handle handle;
+	enum net_shaper_metric metric;
+	u64 bw_min;
+	u64 bw_max;
+	u64 burst;
+	u32 priority;
+	u32 weight;
+
+	/* private: */
+	u32 leaves; /* accounted only for NODE scope */
+	bool valid;
+	struct rcu_head rcu;
+};
+
+/**
+ * struct net_shaper_ops - Operations on device H/W shapers
+ *
+ * The operations applies to either net_device and devlink objects.
+ * The initial shaping configuration at device initialization is empty:
+ * does not constraint the rate in any way.
+ * The network core keeps track of the applied user-configuration in
+ * the net_device or devlink structure.
+ * The operations are serialized via a per device lock.
+ *
+ * Device not supporting any kind of nesting should not provide the
+ * group operation.
+ *
+ * Each shaper is uniquely identified within the device with a 'handle'
+ * comprising the shaper scope and a scope-specific id.
+ */
+struct net_shaper_ops {
+	/**
+	 * @group: create the specified shapers scheduling group
+	 *
+	 * Nest the @leaves shapers identified under the * @node shaper.
+	 * All the shapers belong to the device specified by @binding.
+	 * The @leaves arrays size is specified by @leaves_count.
+	 * Create either the @leaves and the @node shaper; or if they already
+	 * exists, links them together in the desired way.
+	 * @leaves scope must be NET_SHAPER_SCOPE_QUEUE.
+	 */
+	int (*group)(struct net_shaper_binding *binding, int leaves_count,
+		     const struct net_shaper *leaves,
+		     const struct net_shaper *node,
+		     struct netlink_ext_ack *extack);
+
+	/**
+	 * @set: Updates the specified shaper
+	 *
+	 * Updates or creates the @shaper on the device specified by @binding.
+	 */
+	int (*set)(struct net_shaper_binding *binding,
+		   const struct net_shaper *shaper,
+		   struct netlink_ext_ack *extack);
+
+	/**
+	 * @delete: Removes the specified shaper
+	 *
+	 * Removes the shaper configuration as identified by the given @handle
+	 * on the device specified by @binding, restoring the default behavior.
+	 */
+	int (*delete)(struct net_shaper_binding *binding,
+		      const struct net_shaper_handle *handle,
+		      struct netlink_ext_ack *extack);
+
+	/**
+	 * @capabilities: get the shaper features supported by the device
+	 *
+	 * Fills the bitmask @cap with the supported capabilities for the
+	 * specified @scope and device specified by @binding.
+	 */
+	void (*capabilities)(struct net_shaper_binding *binding,
+			     enum net_shaper_scope scope, unsigned long *cap);
+};
+
+#endif