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, 134 insertions, 0 deletions

diff --git a/fs/smb/server/proc.c b/fs/smb/server/proc.c
new file mode 100644
index 000000000..101a2cc45
--- /dev/null
+++ b/fs/smb/server/proc.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) 2025, LG Electronics.
+ *   Author(s): Hyunchul Lee <hyc.lee@gmail.com>
+ *   Copyright (C) 2025, Samsung Electronics.
+ *   Author(s): Vedansh Bhardwaj <v.bhardwaj@samsung.com>
+ */
+
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+
+#include "misc.h"
+#include "server.h"
+#include "stats.h"
+#include "smb_common.h"
+#include "smb2pdu.h"
+
+static struct proc_dir_entry *ksmbd_proc_fs;
+struct ksmbd_counters ksmbd_counters;
+
+struct proc_dir_entry *ksmbd_proc_create(const char *name,
+					 int (*show)(struct seq_file *m, void *v),
+						 void *v)
+{
+	return proc_create_single_data(name, 0400, ksmbd_proc_fs,
+			   show, v);
+}
+
+struct ksmbd_const_smb2_process_req {
+	unsigned int const_value;
+	const char *name;
+};
+
+static const struct ksmbd_const_smb2_process_req smb2_process_req[KSMBD_COUNTER_MAX_REQS] = {
+	{le16_to_cpu(SMB2_NEGOTIATE), "SMB2_NEGOTIATE"},
+	{le16_to_cpu(SMB2_SESSION_SETUP), "SMB2_SESSION_SETUP"},
+	{le16_to_cpu(SMB2_LOGOFF), "SMB2_LOGOFF"},
+	{le16_to_cpu(SMB2_TREE_CONNECT), "SMB2_TREE_CONNECT"},
+	{le16_to_cpu(SMB2_TREE_DISCONNECT), "SMB2_TREE_DISCONNECT"},
+	{le16_to_cpu(SMB2_CREATE), "SMB2_CREATE"},
+	{le16_to_cpu(SMB2_CLOSE), "SMB2_CLOSE"},
+	{le16_to_cpu(SMB2_FLUSH), "SMB2_FLUSH"},
+	{le16_to_cpu(SMB2_READ), "SMB2_READ"},
+	{le16_to_cpu(SMB2_WRITE), "SMB2_WRITE"},
+	{le16_to_cpu(SMB2_LOCK), "SMB2_LOCK"},
+	{le16_to_cpu(SMB2_IOCTL), "SMB2_IOCTL"},
+	{le16_to_cpu(SMB2_CANCEL), "SMB2_CANCEL"},
+	{le16_to_cpu(SMB2_ECHO), "SMB2_ECHO"},
+	{le16_to_cpu(SMB2_QUERY_DIRECTORY), "SMB2_QUERY_DIRECTORY"},
+	{le16_to_cpu(SMB2_CHANGE_NOTIFY), "SMB2_CHANGE_NOTIFY"},
+	{le16_to_cpu(SMB2_QUERY_INFO), "SMB2_QUERY_INFO"},
+	{le16_to_cpu(SMB2_SET_INFO), "SMB2_SET_INFO"},
+	{le16_to_cpu(SMB2_OPLOCK_BREAK), "SMB2_OPLOCK_BREAK"},
+};
+
+static int proc_show_ksmbd_stats(struct seq_file *m, void *v)
+{
+	int i;
+
+	seq_puts(m, "Server\n");
+	seq_printf(m, "name: %s\n", ksmbd_server_string());
+	seq_printf(m, "netbios: %s\n", ksmbd_netbios_name());
+	seq_printf(m, "work group: %s\n", ksmbd_work_group());
+	seq_printf(m, "min protocol: %s\n", ksmbd_get_protocol_string(server_conf.min_protocol));
+	seq_printf(m, "max protocol: %s\n", ksmbd_get_protocol_string(server_conf.max_protocol));
+	seq_printf(m, "flags: 0x%08x\n", server_conf.flags);
+	seq_printf(m, "share_fake_fscaps: 0x%08x\n",
+		   server_conf.share_fake_fscaps);
+	seq_printf(m, "sessions: %lld\n",
+		   ksmbd_counter_sum(KSMBD_COUNTER_SESSIONS));
+	seq_printf(m, "tree connects: %lld\n",
+		   ksmbd_counter_sum(KSMBD_COUNTER_TREE_CONNS));
+	seq_printf(m, "read bytes: %lld\n",
+		   ksmbd_counter_sum(KSMBD_COUNTER_READ_BYTES));
+	seq_printf(m, "written bytes: %lld\n",
+		   ksmbd_counter_sum(KSMBD_COUNTER_WRITE_BYTES));
+
+	seq_puts(m, "\nSMB2\n");
+	for (i = 0; i < KSMBD_COUNTER_MAX_REQS; i++)
+		seq_printf(m, "%-20s:\t%lld\n", smb2_process_req[i].name,
+			   ksmbd_counter_sum(KSMBD_COUNTER_FIRST_REQ + i));
+	return 0;
+}
+
+void ksmbd_proc_cleanup(void)
+{
+	int i;
+
+	if (!ksmbd_proc_fs)
+		return;
+
+	proc_remove(ksmbd_proc_fs);
+
+	for (i = 0; i < ARRAY_SIZE(ksmbd_counters.counters); i++)
+		percpu_counter_destroy(&ksmbd_counters.counters[i]);
+
+	ksmbd_proc_fs = NULL;
+}
+
+void ksmbd_proc_reset(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ksmbd_counters.counters); i++)
+		percpu_counter_set(&ksmbd_counters.counters[i], 0);
+}
+
+void ksmbd_proc_init(void)
+{
+	int i;
+	int retval;
+
+	ksmbd_proc_fs = proc_mkdir("fs/ksmbd", NULL);
+	if (!ksmbd_proc_fs)
+		return;
+
+	if (!proc_mkdir_mode("sessions", 0400, ksmbd_proc_fs))
+		goto err_out;
+
+	for (i = 0; i < ARRAY_SIZE(ksmbd_counters.counters); i++) {
+		retval = percpu_counter_init(&ksmbd_counters.counters[i], 0, GFP_KERNEL);
+		if (retval)
+			goto err_out;
+	}
+
+	if (!ksmbd_proc_create("server", proc_show_ksmbd_stats, NULL))
+		goto err_out;
+
+	ksmbd_proc_reset();
+	return;
+err_out:
+	ksmbd_proc_cleanup();
+}