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, 281 insertions, 0 deletions

diff --git a/include/trace/events/filelock.h b/include/trace/events/filelock.h
new file mode 100644
index 000000000..f11284be0
--- /dev/null
+++ b/include/trace/events/filelock.h
@@ -0,0 +1,281 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Events for filesystem locks
+ *
+ * Copyright 2013 Jeff Layton <jlayton@poochiereds.net>
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM filelock
+
+#if !defined(_TRACE_FILELOCK_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_FILELOCK_H
+
+#include <linux/tracepoint.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/kdev_t.h>
+
+#define show_fl_flags(val)						\
+	__print_flags(val, "|", 					\
+		{ FL_POSIX,		"FL_POSIX" },			\
+		{ FL_FLOCK,		"FL_FLOCK" },			\
+		{ FL_DELEG,		"FL_DELEG" },			\
+		{ FL_ACCESS,		"FL_ACCESS" },			\
+		{ FL_EXISTS,		"FL_EXISTS" },			\
+		{ FL_LEASE,		"FL_LEASE" },			\
+		{ FL_CLOSE,		"FL_CLOSE" },			\
+		{ FL_SLEEP,		"FL_SLEEP" },			\
+		{ FL_DOWNGRADE_PENDING,	"FL_DOWNGRADE_PENDING" },	\
+		{ FL_UNLOCK_PENDING,	"FL_UNLOCK_PENDING" },		\
+		{ FL_OFDLCK,		"FL_OFDLCK" },			\
+		{ FL_RECLAIM,		"FL_RECLAIM" },			\
+		{ FL_IGN_DIR_CREATE,	"FL_IGN_DIR_CREATE" },		\
+		{ FL_IGN_DIR_DELETE,	"FL_IGN_DIR_DELETE" },		\
+		{ FL_IGN_DIR_RENAME,	"FL_IGN_DIR_RENAME" })
+
+#define show_fl_type(val)				\
+	__print_symbolic(val,				\
+			{ F_RDLCK, "F_RDLCK" },		\
+			{ F_WRLCK, "F_WRLCK" },		\
+			{ F_UNLCK, "F_UNLCK" })
+
+TRACE_EVENT(locks_get_lock_context,
+	TP_PROTO(struct inode *inode, int type, struct file_lock_context *ctx),
+
+	TP_ARGS(inode, type, ctx),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(struct file_lock_context *, ctx)
+		__field(dev_t, s_dev)
+		__field(unsigned char, type)
+	),
+
+	TP_fast_assign(
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->i_ino = inode->i_ino;
+		__entry->type = type;
+		__entry->ctx = ctx;
+	),
+
+	TP_printk("dev=0x%x:0x%x ino=0x%llx type=%s ctx=%p",
+		  MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+		  __entry->i_ino, show_fl_type(__entry->type), __entry->ctx)
+);
+
+DECLARE_EVENT_CLASS(filelock_lock,
+	TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
+
+	TP_ARGS(inode, fl, ret),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(loff_t, fl_start)
+		__field(loff_t, fl_end)
+		__field(struct file_lock *, fl)
+		__field(struct file_lock_core *, blocker)
+		__field(fl_owner_t, owner)
+		__field(dev_t, s_dev)
+		__field(unsigned int, pid)
+		__field(unsigned int, flags)
+		__field(unsigned char, type)
+		__field(int, ret)
+	),
+
+	TP_fast_assign(
+		__entry->fl = fl ? fl : NULL;
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->i_ino = inode->i_ino;
+		__entry->blocker = fl ? fl->c.flc_blocker : NULL;
+		__entry->owner = fl ? fl->c.flc_owner : NULL;
+		__entry->pid = fl ? fl->c.flc_pid : 0;
+		__entry->flags = fl ? fl->c.flc_flags : 0;
+		__entry->type = fl ? fl->c.flc_type : 0;
+		__entry->fl_start = fl ? fl->fl_start : 0;
+		__entry->fl_end = fl ? fl->fl_end : 0;
+		__entry->ret = ret;
+	),
+
+	TP_printk("fl=%p dev=0x%x:0x%x ino=0x%llx fl_blocker=%p fl_owner=%p fl_pid=%u fl_flags=%s fl_type=%s fl_start=%lld fl_end=%lld ret=%d",
+		__entry->fl, MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+		__entry->i_ino, __entry->blocker, __entry->owner,
+		__entry->pid, show_fl_flags(__entry->flags),
+		show_fl_type(__entry->type),
+		__entry->fl_start, __entry->fl_end, __entry->ret)
+);
+
+DEFINE_EVENT(filelock_lock, posix_lock_inode,
+		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
+		TP_ARGS(inode, fl, ret));
+
+DEFINE_EVENT(filelock_lock, fcntl_setlk,
+		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
+		TP_ARGS(inode, fl, ret));
+
+DEFINE_EVENT(filelock_lock, locks_remove_posix,
+		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
+		TP_ARGS(inode, fl, ret));
+
+DEFINE_EVENT(filelock_lock, flock_lock_inode,
+		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
+		TP_ARGS(inode, fl, ret));
+
+#define show_lease_break_flags(val)					\
+	__print_flags(val, "|",						\
+		{ LEASE_BREAK_LEASE,		"LEASE" },		\
+		{ LEASE_BREAK_DELEG,		"DELEG" },		\
+		{ LEASE_BREAK_LAYOUT,		"LAYOUT" },		\
+		{ LEASE_BREAK_NONBLOCK,		"NONBLOCK" },		\
+		{ LEASE_BREAK_OPEN_RDONLY,	"OPEN_RDONLY" },	\
+		{ LEASE_BREAK_DIR_CREATE,	"DIR_CREATE" },		\
+		{ LEASE_BREAK_DIR_DELETE,	"DIR_DELETE" },		\
+		{ LEASE_BREAK_DIR_RENAME,	"DIR_RENAME" })
+
+TRACE_EVENT(break_lease,
+	TP_PROTO(struct inode *inode, unsigned int flags),
+
+	TP_ARGS(inode, flags),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, i_ino)
+		__field(dev_t, s_dev)
+		__field(unsigned int, flags)
+	),
+
+	TP_fast_assign(
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->i_ino = inode->i_ino;
+		__entry->flags = flags;
+	),
+
+	TP_printk("dev=0x%x:0x%x ino=0x%lx flags=%s",
+		  MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+		  __entry->i_ino, show_lease_break_flags(__entry->flags))
+);
+
+DECLARE_EVENT_CLASS(filelock_lease,
+	TP_PROTO(struct inode *inode, struct file_lease *fl),
+
+	TP_ARGS(inode, fl),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(struct file_lease *, fl)
+		__field(struct file_lock_core *, blocker)
+		__field(fl_owner_t, owner)
+		__field(unsigned long, break_time)
+		__field(unsigned long, downgrade_time)
+		__field(dev_t, s_dev)
+		__field(unsigned int, flags)
+		__field(unsigned char, type)
+	),
+
+	TP_fast_assign(
+		__entry->fl = fl ? fl : NULL;
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->i_ino = inode->i_ino;
+		__entry->blocker = fl ? fl->c.flc_blocker : NULL;
+		__entry->owner = fl ? fl->c.flc_owner : NULL;
+		__entry->flags = fl ? fl->c.flc_flags : 0;
+		__entry->type = fl ? fl->c.flc_type : 0;
+		__entry->break_time = fl ? fl->fl_break_time : 0;
+		__entry->downgrade_time = fl ? fl->fl_downgrade_time : 0;
+	),
+
+	TP_printk("fl=%p dev=0x%x:0x%x ino=0x%llx fl_blocker=%p fl_owner=%p fl_flags=%s fl_type=%s fl_break_time=%lu fl_downgrade_time=%lu",
+		__entry->fl, MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+		__entry->i_ino, __entry->blocker, __entry->owner,
+		show_fl_flags(__entry->flags),
+		show_fl_type(__entry->type),
+		__entry->break_time, __entry->downgrade_time)
+);
+
+DEFINE_EVENT(filelock_lease, break_lease_noblock, TP_PROTO(struct inode *inode, struct file_lease *fl),
+		TP_ARGS(inode, fl));
+
+DEFINE_EVENT(filelock_lease, break_lease_block, TP_PROTO(struct inode *inode, struct file_lease *fl),
+		TP_ARGS(inode, fl));
+
+DEFINE_EVENT(filelock_lease, break_lease_unblock, TP_PROTO(struct inode *inode, struct file_lease *fl),
+		TP_ARGS(inode, fl));
+
+DEFINE_EVENT(filelock_lease, generic_delete_lease, TP_PROTO(struct inode *inode, struct file_lease *fl),
+		TP_ARGS(inode, fl));
+
+DEFINE_EVENT(filelock_lease, time_out_leases, TP_PROTO(struct inode *inode, struct file_lease *fl),
+		TP_ARGS(inode, fl));
+
+TRACE_EVENT(generic_add_lease,
+	TP_PROTO(struct inode *inode, struct file_lease *fl),
+
+	TP_ARGS(inode, fl),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(fl_owner_t, owner)
+		__field(dev_t, s_dev)
+		__field(int, wcount)
+		__field(int, rcount)
+		__field(int, icount)
+		__field(unsigned int, flags)
+		__field(unsigned char, type)
+	),
+
+	TP_fast_assign(
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->i_ino = inode->i_ino;
+		__entry->wcount = atomic_read(&inode->i_writecount);
+		__entry->rcount = atomic_read(&inode->i_readcount);
+		__entry->icount = icount_read_once(inode);
+		__entry->owner = fl->c.flc_owner;
+		__entry->flags = fl->c.flc_flags;
+		__entry->type = fl->c.flc_type;
+	),
+
+	TP_printk("dev=0x%x:0x%x ino=0x%llx wcount=%d rcount=%d icount=%d fl_owner=%p fl_flags=%s fl_type=%s",
+		MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+		__entry->i_ino, __entry->wcount, __entry->rcount,
+		__entry->icount, __entry->owner,
+		show_fl_flags(__entry->flags),
+		show_fl_type(__entry->type))
+);
+
+TRACE_EVENT(leases_conflict,
+	TP_PROTO(bool conflict, struct file_lease *lease, struct file_lease *breaker),
+
+	TP_ARGS(conflict, lease, breaker),
+
+	TP_STRUCT__entry(
+		__field(void *, lease)
+		__field(void *, breaker)
+		__field(unsigned int, l_fl_flags)
+		__field(unsigned int, b_fl_flags)
+		__field(unsigned char, l_fl_type)
+		__field(unsigned char, b_fl_type)
+		__field(bool, conflict)
+	),
+
+	TP_fast_assign(
+		__entry->lease = lease;
+		__entry->l_fl_flags = lease->c.flc_flags;
+		__entry->l_fl_type = lease->c.flc_type;
+		__entry->breaker = breaker;
+		__entry->b_fl_flags = breaker->c.flc_flags;
+		__entry->b_fl_type = breaker->c.flc_type;
+		__entry->conflict = conflict;
+	),
+
+	TP_printk("conflict %d: lease=%p fl_flags=%s fl_type=%s; breaker=%p fl_flags=%s fl_type=%s",
+		__entry->conflict,
+		__entry->lease,
+		show_fl_flags(__entry->l_fl_flags),
+		show_fl_type(__entry->l_fl_type),
+		__entry->breaker,
+		show_fl_flags(__entry->b_fl_flags),
+		show_fl_type(__entry->b_fl_type))
+);
+
+#endif /* _TRACE_FILELOCK_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>