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, 101 insertions, 0 deletions

diff --git a/net/netlabel/netlabel_user.c b/net/netlabel/netlabel_user.c
new file mode 100644
index 000000000..0da652844
--- /dev/null
+++ b/net/netlabel/netlabel_user.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * NetLabel NETLINK Interface
+ *
+ * This file defines the NETLINK interface for the NetLabel system.  The
+ * NetLabel system manages static and dynamic label mappings for network
+ * protocols such as CIPSO and RIPSO.
+ *
+ * Author: Paul Moore <paul@paul-moore.com>
+ */
+
+/*
+ * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
+ */
+
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/socket.h>
+#include <linux/audit.h>
+#include <linux/tty.h>
+#include <linux/security.h>
+#include <linux/gfp.h>
+#include <net/sock.h>
+#include <net/netlink.h>
+#include <net/genetlink.h>
+#include <net/netlabel.h>
+#include <asm/bug.h>
+
+#include "netlabel_mgmt.h"
+#include "netlabel_unlabeled.h"
+#include "netlabel_cipso_v4.h"
+#include "netlabel_calipso.h"
+#include "netlabel_user.h"
+
+/*
+ * NetLabel NETLINK Setup Functions
+ */
+
+/**
+ * netlbl_netlink_init - Initialize the NETLINK communication channel
+ *
+ * Description:
+ * Call out to the NetLabel components so they can register their families and
+ * commands with the Generic NETLINK mechanism.  Returns zero on success and
+ * non-zero on failure.
+ *
+ */
+int __init netlbl_netlink_init(void)
+{
+	int ret_val;
+
+	ret_val = netlbl_mgmt_genl_init();
+	if (ret_val != 0)
+		return ret_val;
+
+	ret_val = netlbl_cipsov4_genl_init();
+	if (ret_val != 0)
+		return ret_val;
+
+	ret_val = netlbl_calipso_genl_init();
+	if (ret_val != 0)
+		return ret_val;
+
+	return netlbl_unlabel_genl_init();
+}
+
+/*
+ * NetLabel Audit Functions
+ */
+
+/**
+ * netlbl_audit_start_common - Start an audit message
+ * @type: audit message type
+ * @audit_info: NetLabel audit information
+ *
+ * Description:
+ * Start an audit message using the type specified in @type and fill the audit
+ * message with some fields common to all NetLabel audit messages.  Returns
+ * a pointer to the audit buffer on success, NULL on failure.
+ *
+ */
+struct audit_buffer *netlbl_audit_start_common(int type,
+					       struct netlbl_audit *audit_info)
+{
+	struct audit_buffer *audit_buf;
+
+	if (audit_enabled == AUDIT_OFF)
+		return NULL;
+
+	audit_buf = audit_log_start(audit_context(), GFP_ATOMIC, type);
+	if (audit_buf == NULL)
+		return NULL;
+
+	audit_log_format(audit_buf, "netlabel: auid=%u ses=%u",
+			 from_kuid(&init_user_ns, audit_info->loginuid),
+			 audit_info->sessionid);
+	audit_log_subj_ctx(audit_buf, &audit_info->prop);
+
+	return audit_buf;
+}