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, 505 insertions, 0 deletions

diff --git a/include/trace/events/bcache.h b/include/trace/events/bcache.h
new file mode 100644
index 000000000..899fdacf5
--- /dev/null
+++ b/include/trace/events/bcache.h
@@ -0,0 +1,505 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM bcache
+
+#if !defined(_TRACE_BCACHE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_BCACHE_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(bcache_request,
+	TP_PROTO(struct bcache_device *d, struct bio *bio),
+	TP_ARGS(d, bio),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		dev			)
+		__field(unsigned int,	orig_major		)
+		__field(unsigned int,	orig_minor		)
+		__field(sector_t,	sector			)
+		__field(dev_t,		orig_sector		)
+		__field(unsigned int,	nr_sector		)
+		__array(char,		rwbs,	6		)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= bio_dev(bio);
+		__entry->orig_major	= d->disk->major;
+		__entry->orig_minor	= d->disk->first_minor;
+		__entry->sector		= bio->bi_iter.bi_sector;
+		__entry->orig_sector	= bio->bi_iter.bi_sector - 16;
+		__entry->nr_sector	= bio->bi_iter.bi_size >> 9;
+		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
+	),
+
+	TP_printk("%d,%d %s %llu + %u (from %d,%d @ %llu)",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->rwbs, (unsigned long long)__entry->sector,
+		  __entry->nr_sector, __entry->orig_major, __entry->orig_minor,
+		  (unsigned long long)__entry->orig_sector)
+);
+
+DECLARE_EVENT_CLASS(bkey,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k),
+
+	TP_STRUCT__entry(
+		__field(u32,	size				)
+		__field(u32,	inode				)
+		__field(u64,	offset				)
+		__field(bool,	dirty				)
+	),
+
+	TP_fast_assign(
+		__entry->inode	= KEY_INODE(k);
+		__entry->offset	= KEY_OFFSET(k);
+		__entry->size	= KEY_SIZE(k);
+		__entry->dirty	= KEY_DIRTY(k);
+	),
+
+	TP_printk("%u:%llu len %u dirty %u", __entry->inode,
+		  __entry->offset, __entry->size, __entry->dirty)
+);
+
+DECLARE_EVENT_CLASS(btree_node,
+	TP_PROTO(struct btree *b),
+	TP_ARGS(b),
+
+	TP_STRUCT__entry(
+		__field(size_t,		bucket			)
+	),
+
+	TP_fast_assign(
+		__entry->bucket	= PTR_BUCKET_NR(b->c, &b->key, 0);
+	),
+
+	TP_printk("bucket %zu", __entry->bucket)
+);
+
+/* request.c */
+
+DEFINE_EVENT(bcache_request, bcache_request_start,
+	TP_PROTO(struct bcache_device *d, struct bio *bio),
+	TP_ARGS(d, bio)
+);
+
+DEFINE_EVENT(bcache_request, bcache_request_end,
+	TP_PROTO(struct bcache_device *d, struct bio *bio),
+	TP_ARGS(d, bio)
+);
+
+DECLARE_EVENT_CLASS(bcache_bio,
+	TP_PROTO(struct bio *bio),
+	TP_ARGS(bio),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		dev			)
+		__field(sector_t,	sector			)
+		__field(unsigned int,	nr_sector		)
+		__array(char,		rwbs,	6		)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= bio_dev(bio);
+		__entry->sector		= bio->bi_iter.bi_sector;
+		__entry->nr_sector	= bio->bi_iter.bi_size >> 9;
+		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
+	),
+
+	TP_printk("%d,%d  %s %llu + %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->rwbs,
+		  (unsigned long long)__entry->sector, __entry->nr_sector)
+);
+
+DEFINE_EVENT(bcache_bio, bcache_bypass_sequential,
+	TP_PROTO(struct bio *bio),
+	TP_ARGS(bio)
+);
+
+DEFINE_EVENT(bcache_bio, bcache_bypass_congested,
+	TP_PROTO(struct bio *bio),
+	TP_ARGS(bio)
+);
+
+TRACE_EVENT(bcache_read,
+	TP_PROTO(struct bio *bio, bool hit, bool bypass),
+	TP_ARGS(bio, hit, bypass),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		dev			)
+		__field(sector_t,	sector			)
+		__field(unsigned int,	nr_sector		)
+		__array(char,		rwbs,	6		)
+		__field(bool,		cache_hit		)
+		__field(bool,		bypass			)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= bio_dev(bio);
+		__entry->sector		= bio->bi_iter.bi_sector;
+		__entry->nr_sector	= bio->bi_iter.bi_size >> 9;
+		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
+		__entry->cache_hit = hit;
+		__entry->bypass = bypass;
+	),
+
+	TP_printk("%d,%d  %s %llu + %u hit %u bypass %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->rwbs, (unsigned long long)__entry->sector,
+		  __entry->nr_sector, __entry->cache_hit, __entry->bypass)
+);
+
+TRACE_EVENT(bcache_write,
+	TP_PROTO(struct cache_set *c, u64 inode, struct bio *bio,
+		bool writeback, bool bypass),
+	TP_ARGS(c, inode, bio, writeback, bypass),
+
+	TP_STRUCT__entry(
+		__array(char,		uuid,	16		)
+		__field(u64,		inode			)
+		__field(sector_t,	sector			)
+		__field(unsigned int,	nr_sector		)
+		__array(char,		rwbs,	6		)
+		__field(bool,		writeback		)
+		__field(bool,		bypass			)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->uuid, c->set_uuid, 16);
+		__entry->inode		= inode;
+		__entry->sector		= bio->bi_iter.bi_sector;
+		__entry->nr_sector	= bio->bi_iter.bi_size >> 9;
+		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
+		__entry->writeback = writeback;
+		__entry->bypass = bypass;
+	),
+
+	TP_printk("%pU inode %llu  %s %llu + %u hit %u bypass %u",
+		  __entry->uuid, __entry->inode,
+		  __entry->rwbs, (unsigned long long)__entry->sector,
+		  __entry->nr_sector, __entry->writeback, __entry->bypass)
+);
+
+DEFINE_EVENT(bcache_bio, bcache_read_retry,
+	TP_PROTO(struct bio *bio),
+	TP_ARGS(bio)
+);
+
+DEFINE_EVENT(bkey, bcache_cache_insert,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k)
+);
+
+/* Journal */
+
+DECLARE_EVENT_CLASS(cache_set,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c),
+
+	TP_STRUCT__entry(
+		__array(char,		uuid,	16 )
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->uuid, c->set_uuid, 16);
+	),
+
+	TP_printk("%pU", __entry->uuid)
+);
+
+DEFINE_EVENT(bkey, bcache_journal_replay_key,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k)
+);
+
+DEFINE_EVENT(cache_set, bcache_journal_full,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c)
+);
+
+DEFINE_EVENT(cache_set, bcache_journal_entry_full,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c)
+);
+
+TRACE_EVENT(bcache_journal_write,
+	TP_PROTO(struct bio *bio, u32 keys),
+	TP_ARGS(bio, keys),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		dev			)
+		__field(sector_t,	sector			)
+		__field(unsigned int,	nr_sector		)
+		__array(char,		rwbs,	6		)
+		__field(u32,		nr_keys			)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= bio_dev(bio);
+		__entry->sector		= bio->bi_iter.bi_sector;
+		__entry->nr_sector	= bio->bi_iter.bi_size >> 9;
+		__entry->nr_keys	= keys;
+		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
+	),
+
+	TP_printk("%d,%d  %s %llu + %u keys %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->rwbs,
+		  (unsigned long long)__entry->sector, __entry->nr_sector,
+		  __entry->nr_keys)
+);
+
+/* Btree */
+
+DEFINE_EVENT(cache_set, bcache_btree_cache_cannibalize,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c)
+);
+
+DEFINE_EVENT(btree_node, bcache_btree_read,
+	TP_PROTO(struct btree *b),
+	TP_ARGS(b)
+);
+
+TRACE_EVENT(bcache_btree_write,
+	TP_PROTO(struct btree *b),
+	TP_ARGS(b),
+
+	TP_STRUCT__entry(
+		__field(size_t,		bucket			)
+		__field(unsigned,	block			)
+		__field(unsigned,	keys			)
+	),
+
+	TP_fast_assign(
+		__entry->bucket	= PTR_BUCKET_NR(b->c, &b->key, 0);
+		__entry->block	= b->written;
+		__entry->keys	= b->keys.set[b->keys.nsets].data->keys;
+	),
+
+	TP_printk("bucket %zu written block %u + %u",
+		__entry->bucket, __entry->block, __entry->keys)
+);
+
+DEFINE_EVENT(btree_node, bcache_btree_node_alloc,
+	TP_PROTO(struct btree *b),
+	TP_ARGS(b)
+);
+
+DEFINE_EVENT(cache_set, bcache_btree_node_alloc_fail,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c)
+);
+
+DEFINE_EVENT(btree_node, bcache_btree_node_free,
+	TP_PROTO(struct btree *b),
+	TP_ARGS(b)
+);
+
+TRACE_EVENT(bcache_btree_gc_coalesce,
+	TP_PROTO(unsigned nodes),
+	TP_ARGS(nodes),
+
+	TP_STRUCT__entry(
+		__field(unsigned,	nodes			)
+	),
+
+	TP_fast_assign(
+		__entry->nodes	= nodes;
+	),
+
+	TP_printk("coalesced %u nodes", __entry->nodes)
+);
+
+DEFINE_EVENT(cache_set, bcache_gc_start,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c)
+);
+
+DEFINE_EVENT(cache_set, bcache_gc_end,
+	TP_PROTO(struct cache_set *c),
+	TP_ARGS(c)
+);
+
+DEFINE_EVENT(bkey, bcache_gc_copy,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k)
+);
+
+DEFINE_EVENT(bkey, bcache_gc_copy_collision,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k)
+);
+
+TRACE_EVENT(bcache_btree_insert_key,
+	TP_PROTO(struct btree *b, struct bkey *k, unsigned op, unsigned status),
+	TP_ARGS(b, k, op, status),
+
+	TP_STRUCT__entry(
+		__field(u64,	btree_node			)
+		__field(u32,	btree_level			)
+		__field(u32,	inode				)
+		__field(u64,	offset				)
+		__field(u32,	size				)
+		__field(u8,	dirty				)
+		__field(u8,	op				)
+		__field(u8,	status				)
+	),
+
+	TP_fast_assign(
+		__entry->btree_node = PTR_BUCKET_NR(b->c, &b->key, 0);
+		__entry->btree_level = b->level;
+		__entry->inode	= KEY_INODE(k);
+		__entry->offset	= KEY_OFFSET(k);
+		__entry->size	= KEY_SIZE(k);
+		__entry->dirty	= KEY_DIRTY(k);
+		__entry->op = op;
+		__entry->status = status;
+	),
+
+	TP_printk("%u for %u at %llu(%u): %u:%llu len %u dirty %u",
+		  __entry->status, __entry->op,
+		  __entry->btree_node, __entry->btree_level,
+		  __entry->inode, __entry->offset,
+		  __entry->size, __entry->dirty)
+);
+
+DECLARE_EVENT_CLASS(btree_split,
+	TP_PROTO(struct btree *b, unsigned keys),
+	TP_ARGS(b, keys),
+
+	TP_STRUCT__entry(
+		__field(size_t,		bucket			)
+		__field(unsigned,	keys			)
+	),
+
+	TP_fast_assign(
+		__entry->bucket	= PTR_BUCKET_NR(b->c, &b->key, 0);
+		__entry->keys	= keys;
+	),
+
+	TP_printk("bucket %zu keys %u", __entry->bucket, __entry->keys)
+);
+
+DEFINE_EVENT(btree_split, bcache_btree_node_split,
+	TP_PROTO(struct btree *b, unsigned keys),
+	TP_ARGS(b, keys)
+);
+
+DEFINE_EVENT(btree_split, bcache_btree_node_compact,
+	TP_PROTO(struct btree *b, unsigned keys),
+	TP_ARGS(b, keys)
+);
+
+DEFINE_EVENT(btree_node, bcache_btree_set_root,
+	TP_PROTO(struct btree *b),
+	TP_ARGS(b)
+);
+
+TRACE_EVENT(bcache_keyscan,
+	TP_PROTO(unsigned nr_found,
+		 unsigned start_inode, uint64_t start_offset,
+		 unsigned end_inode, uint64_t end_offset),
+	TP_ARGS(nr_found,
+		start_inode, start_offset,
+		end_inode, end_offset),
+
+	TP_STRUCT__entry(
+		__field(__u32,	nr_found			)
+		__field(__u32,	start_inode			)
+		__field(__u64,	start_offset			)
+		__field(__u32,	end_inode			)
+		__field(__u64,	end_offset			)
+	),
+
+	TP_fast_assign(
+		__entry->nr_found	= nr_found;
+		__entry->start_inode	= start_inode;
+		__entry->start_offset	= start_offset;
+		__entry->end_inode	= end_inode;
+		__entry->end_offset	= end_offset;
+	),
+
+	TP_printk("found %u keys from %u:%llu to %u:%llu", __entry->nr_found,
+		  __entry->start_inode, __entry->start_offset,
+		  __entry->end_inode, __entry->end_offset)
+);
+
+/* Allocator */
+
+TRACE_EVENT(bcache_invalidate,
+	TP_PROTO(struct cache *ca, size_t bucket),
+	TP_ARGS(ca, bucket),
+
+	TP_STRUCT__entry(
+		__field(unsigned,	sectors			)
+		__field(dev_t,		dev			)
+		__field(__u64,		offset			)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= ca->bdev->bd_dev;
+		__entry->offset		= bucket << ca->set->bucket_bits;
+		__entry->sectors	= GC_SECTORS_USED(&ca->buckets[bucket]);
+	),
+
+	TP_printk("invalidated %u sectors at %d,%d sector=%llu",
+		  __entry->sectors, MAJOR(__entry->dev),
+		  MINOR(__entry->dev), __entry->offset)
+);
+
+TRACE_EVENT(bcache_alloc,
+	TP_PROTO(struct cache *ca, size_t bucket),
+	TP_ARGS(ca, bucket),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		dev			)
+		__field(__u64,		offset			)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= ca->bdev->bd_dev;
+		__entry->offset		= bucket << ca->set->bucket_bits;
+	),
+
+	TP_printk("allocated %d,%d sector=%llu", MAJOR(__entry->dev),
+		  MINOR(__entry->dev), __entry->offset)
+);
+
+TRACE_EVENT(bcache_alloc_fail,
+	TP_PROTO(struct cache *ca, unsigned reserve),
+	TP_ARGS(ca, reserve),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		dev			)
+		__field(unsigned,	free			)
+		__field(unsigned,	free_inc		)
+		__field(unsigned,	blocked			)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= ca->bdev->bd_dev;
+		__entry->free		= fifo_used(&ca->free[reserve]);
+		__entry->free_inc	= fifo_used(&ca->free_inc);
+		__entry->blocked	= atomic_read(&ca->set->prio_blocked);
+	),
+
+	TP_printk("alloc fail %d,%d free %u free_inc %u blocked %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->free,
+		  __entry->free_inc, __entry->blocked)
+);
+
+/* Background writeback */
+
+DEFINE_EVENT(bkey, bcache_writeback,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k)
+);
+
+DEFINE_EVENT(bkey, bcache_writeback_collision,
+	TP_PROTO(struct bkey *k),
+	TP_ARGS(k)
+);
+
+#endif /* _TRACE_BCACHE_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>