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, 75 insertions, 0 deletions

diff --git a/net/ethtool/module_fw.h b/net/ethtool/module_fw.h
new file mode 100644
index 000000000..634543a12
--- /dev/null
+++ b/net/ethtool/module_fw.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <uapi/linux/ethtool.h>
+#include "netlink.h"
+
+/**
+ * struct ethnl_module_fw_flash_ntf_params - module firmware flashing
+ *						notifications parameters
+ * @portid: Netlink portid of sender.
+ * @seq: Sequence number of sender.
+ * @closed_sock: Indicates whether the socket was closed from user space.
+ */
+struct ethnl_module_fw_flash_ntf_params {
+	u32 portid;
+	u32 seq;
+	bool closed_sock;
+};
+
+/**
+ * struct ethtool_module_fw_flash_params - module firmware flashing parameters
+ * @password: Module password. Only valid when @pass_valid is set.
+ * @password_valid: Whether the module password is valid or not.
+ */
+struct ethtool_module_fw_flash_params {
+	__be32 password;
+	u8 password_valid:1;
+};
+
+/**
+ * struct ethtool_cmis_fw_update_params - CMIS firmware update specific
+ *						parameters
+ * @dev: Pointer to the net_device to be flashed.
+ * @params: Module firmware flashing parameters.
+ * @ntf_params: Module firmware flashing notification parameters.
+ * @fw: Firmware to flash.
+ */
+struct ethtool_cmis_fw_update_params {
+	struct net_device *dev;
+	struct ethtool_module_fw_flash_params params;
+	struct ethnl_module_fw_flash_ntf_params ntf_params;
+	const struct firmware *fw;
+};
+
+/**
+ * struct ethtool_module_fw_flash - module firmware flashing
+ * @list: List node for &module_fw_flash_work_list.
+ * @dev_tracker: Refcount tracker for @dev.
+ * @work: The flashing firmware work.
+ * @fw_update: CMIS firmware update specific parameters.
+ */
+struct ethtool_module_fw_flash {
+	struct list_head list;
+	netdevice_tracker dev_tracker;
+	struct work_struct work;
+	struct ethtool_cmis_fw_update_params fw_update;
+};
+
+void ethnl_module_fw_flash_sock_destroy(struct ethnl_sock_priv *sk_priv);
+
+void
+ethnl_module_fw_flash_ntf_err(struct net_device *dev,
+			      struct ethnl_module_fw_flash_ntf_params *params,
+			      char *err_msg, char *sub_err_msg);
+void
+ethnl_module_fw_flash_ntf_start(struct net_device *dev,
+				struct ethnl_module_fw_flash_ntf_params *params);
+void
+ethnl_module_fw_flash_ntf_complete(struct net_device *dev,
+				   struct ethnl_module_fw_flash_ntf_params *params);
+void
+ethnl_module_fw_flash_ntf_in_progress(struct net_device *dev,
+				      struct ethnl_module_fw_flash_ntf_params *params,
+				      u64 done, u64 total);
+
+void ethtool_cmis_fw_update(struct ethtool_cmis_fw_update_params *params);