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, 73 insertions, 0 deletions

diff --git a/fs/smb/server/stats.h b/fs/smb/server/stats.h
new file mode 100644
index 000000000..b60c30c69
--- /dev/null
+++ b/fs/smb/server/stats.h
@@ -0,0 +1,73 @@
+/* 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>
+ */
+
+#ifndef __KSMBD_STATS_H__
+#define __KSMBD_STATS_H__
+
+#define KSMBD_COUNTER_MAX_REQS	19
+
+enum {
+	KSMBD_COUNTER_SESSIONS = 0,
+	KSMBD_COUNTER_TREE_CONNS,
+	KSMBD_COUNTER_REQUESTS,
+	KSMBD_COUNTER_READ_BYTES,
+	KSMBD_COUNTER_WRITE_BYTES,
+	KSMBD_COUNTER_FIRST_REQ,
+	KSMBD_COUNTER_LAST_REQ = KSMBD_COUNTER_FIRST_REQ +
+				KSMBD_COUNTER_MAX_REQS - 1,
+	KSMBD_COUNTER_MAX,
+};
+
+#ifdef CONFIG_PROC_FS
+extern struct ksmbd_counters ksmbd_counters;
+
+struct ksmbd_counters {
+	struct percpu_counter	counters[KSMBD_COUNTER_MAX];
+};
+
+static inline void ksmbd_counter_inc(int type)
+{
+	percpu_counter_inc(&ksmbd_counters.counters[type]);
+}
+
+static inline void ksmbd_counter_dec(int type)
+{
+	percpu_counter_dec(&ksmbd_counters.counters[type]);
+}
+
+static inline void ksmbd_counter_add(int type, s64 value)
+{
+	percpu_counter_add(&ksmbd_counters.counters[type], value);
+}
+
+static inline void ksmbd_counter_sub(int type, s64 value)
+{
+	percpu_counter_sub(&ksmbd_counters.counters[type], value);
+}
+
+static inline void ksmbd_counter_inc_reqs(unsigned int cmd)
+{
+	if (cmd < KSMBD_COUNTER_MAX_REQS)
+		percpu_counter_inc(&ksmbd_counters.counters[KSMBD_COUNTER_FIRST_REQ + cmd]);
+}
+
+static inline s64 ksmbd_counter_sum(int type)
+{
+	return percpu_counter_sum_positive(&ksmbd_counters.counters[type]);
+}
+#else
+
+static inline void ksmbd_counter_inc(int type) {}
+static inline void ksmbd_counter_dec(int type) {}
+static inline void ksmbd_counter_add(int type, s64 value) {}
+static inline void ksmbd_counter_sub(int type, s64 value) {}
+static inline void ksmbd_counter_inc_reqs(unsigned int cmd) {}
+static inline s64 ksmbd_counter_sum(int type) { return 0; }
+#endif
+
+#endif