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, 343 insertions, 0 deletions

diff --git a/fs/hfsplus/bfind.c b/fs/hfsplus/bfind.c
new file mode 100644
index 000000000..ca9813f58
--- /dev/null
+++ b/fs/hfsplus/bfind.c
@@ -0,0 +1,343 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/hfsplus/bfind.c
+ *
+ * Copyright (C) 2001
+ * Brad Boyer (flar@allandria.com)
+ * (C) 2003 Ardis Technologies <roman@ardistech.com>
+ *
+ * Search routines for btrees
+ */
+
+#include <linux/slab.h>
+#include "hfsplus_fs.h"
+
+int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
+{
+	void *ptr;
+
+	fd->tree = tree;
+	fd->bnode = NULL;
+	hfs_find_result_init(fd);
+	ptr = kzalloc(tree->max_key_len * 2 + 4, GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+	fd->search_key = ptr;
+	fd->key = ptr + tree->max_key_len + 2;
+	hfs_dbg("cnid %d, caller %ps\n",
+		tree->cnid, __builtin_return_address(0));
+	mutex_lock_nested(&tree->tree_lock,
+			hfsplus_btree_lock_class(tree));
+	return 0;
+}
+
+void hfs_find_exit(struct hfs_find_data *fd)
+{
+	hfs_bnode_put(fd->bnode);
+	kfree(fd->search_key);
+	hfs_dbg("cnid %d, caller %ps\n",
+		fd->tree->cnid, __builtin_return_address(0));
+	mutex_unlock(&fd->tree->tree_lock);
+	fd->tree = NULL;
+}
+
+int hfs_find_1st_rec_by_cnid(struct hfs_bnode *bnode,
+				struct hfs_find_data *fd,
+				int *begin,
+				int *end,
+				int *cur_rec)
+{
+	__be32 cur_cnid;
+	__be32 search_cnid;
+
+	if (bnode->tree->cnid == HFSPLUS_EXT_CNID) {
+		cur_cnid = fd->key->ext.cnid;
+		search_cnid = fd->search_key->ext.cnid;
+	} else if (bnode->tree->cnid == HFSPLUS_CAT_CNID) {
+		cur_cnid = fd->key->cat.parent;
+		search_cnid = fd->search_key->cat.parent;
+	} else if (bnode->tree->cnid == HFSPLUS_ATTR_CNID) {
+		cur_cnid = fd->key->attr.cnid;
+		search_cnid = fd->search_key->attr.cnid;
+	} else {
+		cur_cnid = 0;	/* used-uninitialized warning */
+		search_cnid = 0;
+		BUG();
+	}
+
+	if (cur_cnid == search_cnid) {
+		(*end) = (*cur_rec);
+		if ((*begin) == (*end))
+			return 1;
+	} else {
+		if (be32_to_cpu(cur_cnid) < be32_to_cpu(search_cnid))
+			(*begin) = (*cur_rec) + 1;
+		else
+			(*end) = (*cur_rec) - 1;
+	}
+
+	return 0;
+}
+
+int hfs_find_rec_by_key(struct hfs_bnode *bnode,
+				struct hfs_find_data *fd,
+				int *begin,
+				int *end,
+				int *cur_rec)
+{
+	int cmpval;
+
+	cmpval = bnode->tree->keycmp(fd->key, fd->search_key);
+	if (!cmpval) {
+		(*end) = (*cur_rec);
+		return 1;
+	}
+	if (cmpval < 0)
+		(*begin) = (*cur_rec) + 1;
+	else
+		*(end) = (*cur_rec) - 1;
+
+	return 0;
+}
+
+/* Find the record in bnode that best matches key (not greater than...)*/
+int __hfs_brec_find(struct hfs_bnode *bnode, struct hfs_find_data *fd,
+					search_strategy_t rec_found)
+{
+	u16 off, len, keylen;
+	int rec;
+	int b, e;
+	int res = -ENOENT;
+
+	BUG_ON(!rec_found);
+	hfs_find_result_init(fd);
+	if (hfs_bnode_num_recs_invalid(bnode))
+		goto fail;
+
+	b = 0;
+	e = bnode->num_recs - 1;
+	do {
+		rec = (e + b) / 2;
+		len = hfs_brec_lenoff(bnode, rec, &off);
+		keylen = hfs_brec_keylen(bnode, rec);
+		if (hfs_brec_len_invalid(bnode, len) ||
+		    hfs_brec_len_invalid(bnode, keylen)) {
+			res = -EINVAL;
+			goto fail;
+		}
+		hfs_bnode_read(bnode, fd->key, off, keylen);
+		if (rec_found(bnode, fd, &b, &e, &rec)) {
+			res = 0;
+			goto done;
+		}
+	} while (b <= e);
+
+	if (rec != e && e >= 0) {
+		len = hfs_brec_lenoff(bnode, e, &off);
+		keylen = hfs_brec_keylen(bnode, e);
+		if (hfs_brec_len_invalid(bnode, keylen) ||
+		    hfs_brec_len_invalid(bnode, len)) {
+			res = -EINVAL;
+			goto fail;
+		}
+		hfs_bnode_read(bnode, fd->key, off, keylen);
+	}
+
+done:
+	fd->record = e;
+	fd->keyoffset = off;
+	fd->keylength = keylen;
+	fd->entryoffset = off + keylen;
+	fd->entrylength = len - keylen;
+
+fail:
+	return res;
+}
+
+/* Traverse a B*Tree from the root to a leaf finding best fit to key */
+/* Return allocated copy of node found, set recnum to best record */
+int hfs_brec_find(struct hfs_find_data *fd, search_strategy_t do_key_compare)
+{
+	struct hfs_btree *tree;
+	struct hfs_bnode *bnode;
+	u32 nidx, parent;
+	__be32 data;
+	int height, res;
+
+	hfs_find_result_init(fd);
+
+	tree = fd->tree;
+	if (fd->bnode)
+		hfs_bnode_put(fd->bnode);
+	fd->bnode = NULL;
+	nidx = tree->root;
+	if (!nidx)
+		return -ENOENT;
+	height = tree->depth;
+	res = 0;
+	parent = 0;
+	for (;;) {
+		bnode = hfs_bnode_find(tree, nidx);
+		if (IS_ERR(bnode)) {
+			res = PTR_ERR(bnode);
+			bnode = NULL;
+			break;
+		}
+		if (bnode->height != height)
+			goto invalid;
+		if (bnode->type != (--height ? HFS_NODE_INDEX : HFS_NODE_LEAF))
+			goto invalid;
+		bnode->parent = parent;
+
+		res = __hfs_brec_find(bnode, fd, do_key_compare);
+		if (!height)
+			break;
+		if (fd->record < 0)
+			goto release;
+
+		parent = nidx;
+		hfs_bnode_read(bnode, &data, fd->entryoffset, 4);
+		nidx = be32_to_cpu(data);
+		hfs_bnode_put(bnode);
+	}
+	fd->bnode = bnode;
+	return res;
+
+invalid:
+	pr_err("inconsistency in B*Tree (%d,%d,%d,%u,%u)\n",
+		height, bnode->height, bnode->type, nidx, parent);
+	res = -EIO;
+release:
+	hfs_bnode_put(bnode);
+	return res;
+}
+
+int hfs_brec_read(struct hfs_find_data *fd, void *rec, u32 rec_len)
+{
+	int res;
+
+	res = hfs_brec_find(fd, hfs_find_rec_by_key);
+	if (res)
+		return res;
+	if (fd->entrylength > rec_len)
+		return -EINVAL;
+	hfs_bnode_read(fd->bnode, rec, fd->entryoffset, fd->entrylength);
+	return 0;
+}
+
+int hfs_brec_goto(struct hfs_find_data *fd, int cnt)
+{
+	struct hfs_btree *tree;
+	struct hfs_bnode *bnode;
+	int idx, res = 0;
+	u16 off, len, keylen;
+
+	bnode = fd->bnode;
+	tree = bnode->tree;
+
+	if (cnt < 0) {
+		cnt = -cnt;
+		while (cnt > fd->record) {
+			cnt -= fd->record + 1;
+			fd->record = bnode->num_recs - 1;
+			idx = bnode->prev;
+			if (!idx) {
+				res = -ENOENT;
+				goto out;
+			}
+			hfs_bnode_put(bnode);
+			bnode = hfs_bnode_find(tree, idx);
+			if (IS_ERR(bnode)) {
+				res = PTR_ERR(bnode);
+				bnode = NULL;
+				goto out;
+			}
+		}
+		fd->record -= cnt;
+	} else {
+		while (cnt >= bnode->num_recs - fd->record) {
+			cnt -= bnode->num_recs - fd->record;
+			fd->record = 0;
+			idx = bnode->next;
+			if (!idx) {
+				res = -ENOENT;
+				goto out;
+			}
+			hfs_bnode_put(bnode);
+			bnode = hfs_bnode_find(tree, idx);
+			if (IS_ERR(bnode)) {
+				res = PTR_ERR(bnode);
+				bnode = NULL;
+				goto out;
+			}
+		}
+		fd->record += cnt;
+	}
+
+	len = hfs_brec_lenoff(bnode, fd->record, &off);
+	keylen = hfs_brec_keylen(bnode, fd->record);
+	if (hfs_brec_len_invalid(bnode, len) ||
+	    hfs_brec_len_invalid(bnode, keylen)) {
+		res = -EINVAL;
+		goto out;
+	}
+	fd->keyoffset = off;
+	fd->keylength = keylen;
+	fd->entryoffset = off + keylen;
+	fd->entrylength = len - keylen;
+	hfs_bnode_read(bnode, fd->key, off, keylen);
+out:
+	fd->bnode = bnode;
+	return res;
+}
+
+/**
+ * hfsplus_brec_read_cat - read and validate a catalog record
+ * @fd: find data structure
+ * @entry: pointer to catalog entry to read into
+ *
+ * Reads a catalog record and validates its size matches the expected
+ * size based on the record type.
+ *
+ * Returns 0 on success, or negative error code on failure.
+ */
+int hfsplus_brec_read_cat(struct hfs_find_data *fd, hfsplus_cat_entry *entry)
+{
+	int res;
+	u32 expected_size;
+
+	res = hfs_brec_read(fd, entry, sizeof(hfsplus_cat_entry));
+	if (res)
+		return res;
+
+	/* Validate catalog record size based on type */
+	switch (be16_to_cpu(entry->type)) {
+	case HFSPLUS_FOLDER:
+		expected_size = sizeof(struct hfsplus_cat_folder);
+		break;
+	case HFSPLUS_FILE:
+		expected_size = sizeof(struct hfsplus_cat_file);
+		break;
+	case HFSPLUS_FOLDER_THREAD:
+	case HFSPLUS_FILE_THREAD:
+		/* Ensure we have at least the fixed fields before reading nodeName.length */
+		if (fd->entrylength < HFSPLUS_MIN_THREAD_SZ) {
+			pr_err("thread record too short (got %u)\n", fd->entrylength);
+			return -EIO;
+		}
+		expected_size = hfsplus_cat_thread_size(&entry->thread);
+		break;
+	default:
+		pr_err("unknown catalog record type %d\n",
+		       be16_to_cpu(entry->type));
+		return -EIO;
+	}
+
+	if (fd->entrylength != expected_size) {
+		pr_err("catalog record size mismatch (type %d, got %u, expected %u)\n",
+		       be16_to_cpu(entry->type), fd->entrylength, expected_size);
+		return -EIO;
+	}
+
+	return 0;
+}