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, 229 insertions, 0 deletions

diff --git a/include/trace/events/nilfs2.h b/include/trace/events/nilfs2.h
new file mode 100644
index 000000000..49efbd209
--- /dev/null
+++ b/include/trace/events/nilfs2.h
@@ -0,0 +1,229 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM nilfs2
+
+#if !defined(_TRACE_NILFS2_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_NILFS2_H
+
+#include <linux/tracepoint.h>
+
+struct nilfs_sc_info;
+
+#define show_collection_stage(type)					\
+	__print_symbolic(type,						\
+	{ NILFS_ST_INIT, "ST_INIT" },					\
+	{ NILFS_ST_GC, "ST_GC" },					\
+	{ NILFS_ST_FILE, "ST_FILE" },					\
+	{ NILFS_ST_IFILE, "ST_IFILE" },					\
+	{ NILFS_ST_CPFILE, "ST_CPFILE" },				\
+	{ NILFS_ST_SUFILE, "ST_SUFILE" },				\
+	{ NILFS_ST_DAT, "ST_DAT" },					\
+	{ NILFS_ST_SR, "ST_SR" },					\
+	{ NILFS_ST_DSYNC, "ST_DSYNC" },					\
+	{ NILFS_ST_DONE, "ST_DONE"})
+
+TRACE_EVENT(nilfs2_collection_stage_transition,
+
+	    TP_PROTO(struct nilfs_sc_info *sci),
+
+	    TP_ARGS(sci),
+
+	    TP_STRUCT__entry(
+		    __field(void *, sci)
+		    __field(int, stage)
+	    ),
+
+	    TP_fast_assign(
+			__entry->sci = sci;
+			__entry->stage = sci->sc_stage.scnt;
+		    ),
+
+	    TP_printk("sci = %p stage = %s",
+		      __entry->sci,
+		      show_collection_stage(__entry->stage))
+);
+
+#ifndef TRACE_HEADER_MULTI_READ
+enum nilfs2_transaction_transition_state {
+	TRACE_NILFS2_TRANSACTION_BEGIN,
+	TRACE_NILFS2_TRANSACTION_COMMIT,
+	TRACE_NILFS2_TRANSACTION_ABORT,
+	TRACE_NILFS2_TRANSACTION_TRYLOCK,
+	TRACE_NILFS2_TRANSACTION_LOCK,
+	TRACE_NILFS2_TRANSACTION_UNLOCK,
+};
+#endif
+
+#define show_transaction_state(type)					\
+	__print_symbolic(type,						\
+			 { TRACE_NILFS2_TRANSACTION_BEGIN, "BEGIN" },	\
+			 { TRACE_NILFS2_TRANSACTION_COMMIT, "COMMIT" },	\
+			 { TRACE_NILFS2_TRANSACTION_ABORT, "ABORT" },	\
+			 { TRACE_NILFS2_TRANSACTION_TRYLOCK, "TRYLOCK" }, \
+			 { TRACE_NILFS2_TRANSACTION_LOCK, "LOCK" },	\
+			 { TRACE_NILFS2_TRANSACTION_UNLOCK, "UNLOCK" })
+
+TRACE_EVENT(nilfs2_transaction_transition,
+	    TP_PROTO(struct super_block *sb,
+		     struct nilfs_transaction_info *ti,
+		     int count,
+		     unsigned int flags,
+		     enum nilfs2_transaction_transition_state state),
+
+	    TP_ARGS(sb, ti, count, flags, state),
+
+	    TP_STRUCT__entry(
+		    __field(void *, sb)
+		    __field(void *, ti)
+		    __field(int, count)
+		    __field(unsigned int, flags)
+		    __field(int, state)
+	    ),
+
+	    TP_fast_assign(
+		    __entry->sb = sb;
+		    __entry->ti = ti;
+		    __entry->count = count;
+		    __entry->flags = flags;
+		    __entry->state = state;
+		    ),
+
+	    TP_printk("sb = %p ti = %p count = %d flags = %x state = %s",
+		      __entry->sb,
+		      __entry->ti,
+		      __entry->count,
+		      __entry->flags,
+		      show_transaction_state(__entry->state))
+);
+
+TRACE_EVENT(nilfs2_segment_usage_check,
+	    TP_PROTO(struct inode *sufile,
+		     __u64 segnum,
+		     unsigned long cnt),
+
+	    TP_ARGS(sufile, segnum, cnt),
+
+	    TP_STRUCT__entry(
+		    __field(struct inode *, sufile)
+		    __field(__u64, segnum)
+		    __field(unsigned long, cnt)
+	    ),
+
+	    TP_fast_assign(
+		    __entry->sufile = sufile;
+		    __entry->segnum = segnum;
+		    __entry->cnt = cnt;
+		    ),
+
+	    TP_printk("sufile = %p segnum = %llu cnt = %lu",
+		      __entry->sufile,
+		      __entry->segnum,
+		      __entry->cnt)
+);
+
+TRACE_EVENT(nilfs2_segment_usage_allocated,
+	    TP_PROTO(struct inode *sufile,
+		     __u64 segnum),
+
+	    TP_ARGS(sufile, segnum),
+
+	    TP_STRUCT__entry(
+		    __field(struct inode *, sufile)
+		    __field(__u64, segnum)
+	    ),
+
+	    TP_fast_assign(
+		    __entry->sufile = sufile;
+		    __entry->segnum = segnum;
+		    ),
+
+	    TP_printk("sufile = %p segnum = %llu",
+		      __entry->sufile,
+		      __entry->segnum)
+);
+
+TRACE_EVENT(nilfs2_segment_usage_freed,
+	    TP_PROTO(struct inode *sufile,
+		     __u64 segnum),
+
+	    TP_ARGS(sufile, segnum),
+
+	    TP_STRUCT__entry(
+		    __field(struct inode *, sufile)
+		    __field(__u64, segnum)
+	    ),
+
+	    TP_fast_assign(
+		    __entry->sufile = sufile;
+		    __entry->segnum = segnum;
+		    ),
+
+	    TP_printk("sufile = %p segnum = %llu",
+		      __entry->sufile,
+		      __entry->segnum)
+);
+
+TRACE_EVENT(nilfs2_mdt_insert_new_block,
+	    TP_PROTO(struct inode *inode,
+		     u64 ino,
+		     unsigned long block),
+
+	    TP_ARGS(inode, ino, block),
+
+	    TP_STRUCT__entry(
+		    __field(u64, ino)
+		    __field(struct inode *, inode)
+		    __field(unsigned long, block)
+	    ),
+
+	    TP_fast_assign(
+		    __entry->inode = inode;
+		    __entry->ino = ino;
+		    __entry->block = block;
+		    ),
+
+	    TP_printk("inode = %p ino = %llu block = %lu",
+		      __entry->inode,
+		      __entry->ino,
+		      __entry->block)
+);
+
+TRACE_EVENT(nilfs2_mdt_submit_block,
+	    TP_PROTO(struct inode *inode,
+		     u64 ino,
+		     unsigned long blkoff,
+		     enum req_op mode),
+
+	    TP_ARGS(inode, ino, blkoff, mode),
+
+	    TP_STRUCT__entry(
+		    __field(u64, ino)
+		    __field(struct inode *, inode)
+		    __field(unsigned long, blkoff)
+		    /*
+		     * Use field_struct() to avoid is_signed_type() on the
+		     * bitwise type enum req_op.
+		     */
+		    __field_struct(enum req_op, mode)
+	    ),
+
+	    TP_fast_assign(
+		    __entry->inode = inode;
+		    __entry->ino = ino;
+		    __entry->blkoff = blkoff;
+		    __entry->mode = mode;
+		    ),
+
+	    TP_printk("inode = %p ino = %llu blkoff = %lu mode = %x",
+		      __entry->inode,
+		      __entry->ino,
+		      __entry->blkoff,
+		      __entry->mode)
+);
+
+#endif /* _TRACE_NILFS2_H */
+
+/* This part must be outside protection */
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE nilfs2
+#include <trace/define_trace.h>