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, 340 insertions, 0 deletions

diff --git a/fs/udf/partition.c b/fs/udf/partition.c
new file mode 100644
index 000000000..2b85c9501
--- /dev/null
+++ b/fs/udf/partition.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * partition.c
+ *
+ * PURPOSE
+ *      Partition handling routines for the OSTA-UDF(tm) filesystem.
+ *
+ * COPYRIGHT
+ *  (C) 1998-2001 Ben Fennema
+ *
+ * HISTORY
+ *
+ * 12/06/98 blf  Created file.
+ *
+ */
+
+#include "udfdecl.h"
+#include "udf_sb.h"
+#include "udf_i.h"
+
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/mutex.h>
+
+uint32_t udf_get_pblock(struct super_block *sb, uint32_t block,
+			uint16_t partition, uint32_t offset)
+{
+	struct udf_sb_info *sbi = UDF_SB(sb);
+	struct udf_part_map *map;
+	if (partition >= sbi->s_partitions) {
+		udf_debug("block=%u, partition=%u, offset=%u: invalid partition\n",
+			  block, partition, offset);
+		return 0xFFFFFFFF;
+	}
+	map = &sbi->s_partmaps[partition];
+	if (map->s_partition_func)
+		return map->s_partition_func(sb, block, partition, offset);
+	else
+		return map->s_partition_root + block + offset;
+}
+
+uint32_t udf_get_pblock_virt15(struct super_block *sb, uint32_t block,
+			       uint16_t partition, uint32_t offset)
+{
+	struct buffer_head *bh = NULL;
+	uint32_t newblock;
+	uint32_t index;
+	uint32_t loc;
+	struct udf_sb_info *sbi = UDF_SB(sb);
+	struct udf_part_map *map;
+	struct udf_virtual_data *vdata;
+	struct udf_inode_info *iinfo = UDF_I(sbi->s_vat_inode);
+	int err;
+
+	map = &sbi->s_partmaps[partition];
+	vdata = &map->s_type_specific.s_virtual;
+
+	if (block > vdata->s_num_entries) {
+		udf_debug("Trying to access block beyond end of VAT (%u max %u)\n",
+			  block, vdata->s_num_entries);
+		return 0xFFFFFFFF;
+	}
+
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		loc = le32_to_cpu(((__le32 *)(iinfo->i_data +
+			vdata->s_start_offset))[block]);
+		goto translate;
+	}
+	index = (sb->s_blocksize - vdata->s_start_offset) / sizeof(uint32_t);
+	if (block >= index) {
+		block -= index;
+		newblock = 1 + (block / (sb->s_blocksize / sizeof(uint32_t)));
+		index = block % (sb->s_blocksize / sizeof(uint32_t));
+	} else {
+		newblock = 0;
+		index = vdata->s_start_offset / sizeof(uint32_t) + block;
+	}
+
+	bh = udf_bread(sbi->s_vat_inode, newblock, 0, &err);
+	if (!bh) {
+		udf_debug("get_pblock(UDF_VIRTUAL_MAP:%p,%u,%u)\n",
+			  sb, block, partition);
+		return 0xFFFFFFFF;
+	}
+
+	loc = le32_to_cpu(((__le32 *)bh->b_data)[index]);
+
+	brelse(bh);
+
+translate:
+	if (iinfo->i_location.partitionReferenceNum == partition) {
+		udf_debug("recursive call to udf_get_pblock!\n");
+		return 0xFFFFFFFF;
+	}
+
+	return udf_get_pblock(sb, loc,
+			      iinfo->i_location.partitionReferenceNum,
+			      offset);
+}
+
+inline uint32_t udf_get_pblock_virt20(struct super_block *sb, uint32_t block,
+				      uint16_t partition, uint32_t offset)
+{
+	return udf_get_pblock_virt15(sb, block, partition, offset);
+}
+
+uint32_t udf_get_pblock_spar15(struct super_block *sb, uint32_t block,
+			       uint16_t partition, uint32_t offset)
+{
+	int i;
+	struct sparingTable *st = NULL;
+	struct udf_sb_info *sbi = UDF_SB(sb);
+	struct udf_part_map *map;
+	uint32_t packet;
+	struct udf_sparing_data *sdata;
+
+	map = &sbi->s_partmaps[partition];
+	sdata = &map->s_type_specific.s_sparing;
+	packet = (block + offset) & ~(sdata->s_packet_len - 1);
+
+	for (i = 0; i < 4; i++) {
+		if (sdata->s_spar_map[i] != NULL) {
+			st = (struct sparingTable *)
+					sdata->s_spar_map[i]->b_data;
+			break;
+		}
+	}
+
+	if (st) {
+		for (i = 0; i < le16_to_cpu(st->reallocationTableLen); i++) {
+			struct sparingEntry *entry = &st->mapEntry[i];
+			u32 origLoc = le32_to_cpu(entry->origLocation);
+			if (origLoc >= 0xFFFFFFF0)
+				break;
+			else if (origLoc == packet)
+				return le32_to_cpu(entry->mappedLocation) +
+					((block + offset) &
+						(sdata->s_packet_len - 1));
+			else if (origLoc > packet)
+				break;
+		}
+	}
+
+	return map->s_partition_root + block + offset;
+}
+
+int udf_relocate_blocks(struct super_block *sb, long old_block, long *new_block)
+{
+	struct udf_sparing_data *sdata;
+	struct sparingTable *st = NULL;
+	struct sparingEntry mapEntry;
+	uint32_t packet;
+	int i, j, k, l;
+	struct udf_sb_info *sbi = UDF_SB(sb);
+	u16 reallocationTableLen;
+	struct buffer_head *bh;
+	int ret = 0;
+
+	mutex_lock(&sbi->s_alloc_mutex);
+	for (i = 0; i < sbi->s_partitions; i++) {
+		struct udf_part_map *map = &sbi->s_partmaps[i];
+		if (old_block > map->s_partition_root &&
+		    old_block < map->s_partition_root + map->s_partition_len) {
+			sdata = &map->s_type_specific.s_sparing;
+			packet = (old_block - map->s_partition_root) &
+						~(sdata->s_packet_len - 1);
+
+			for (j = 0; j < 4; j++)
+				if (sdata->s_spar_map[j] != NULL) {
+					st = (struct sparingTable *)
+						sdata->s_spar_map[j]->b_data;
+					break;
+				}
+
+			if (!st) {
+				ret = 1;
+				goto out;
+			}
+
+			reallocationTableLen =
+					le16_to_cpu(st->reallocationTableLen);
+			for (k = 0; k < reallocationTableLen; k++) {
+				struct sparingEntry *entry = &st->mapEntry[k];
+				u32 origLoc = le32_to_cpu(entry->origLocation);
+
+				if (origLoc == 0xFFFFFFFF) {
+					for (; j < 4; j++) {
+						int len;
+						bh = sdata->s_spar_map[j];
+						if (!bh)
+							continue;
+
+						st = (struct sparingTable *)
+								bh->b_data;
+						entry->origLocation =
+							cpu_to_le32(packet);
+						len =
+						  sizeof(struct sparingTable) +
+						  reallocationTableLen *
+						  sizeof(struct sparingEntry);
+						udf_update_tag((char *)st, len);
+						mark_buffer_dirty(bh);
+					}
+					*new_block = le32_to_cpu(
+							entry->mappedLocation) +
+						     ((old_block -
+							map->s_partition_root) &
+						     (sdata->s_packet_len - 1));
+					ret = 0;
+					goto out;
+				} else if (origLoc == packet) {
+					*new_block = le32_to_cpu(
+							entry->mappedLocation) +
+						     ((old_block -
+							map->s_partition_root) &
+						     (sdata->s_packet_len - 1));
+					ret = 0;
+					goto out;
+				} else if (origLoc > packet)
+					break;
+			}
+
+			for (l = k; l < reallocationTableLen; l++) {
+				struct sparingEntry *entry = &st->mapEntry[l];
+				u32 origLoc = le32_to_cpu(entry->origLocation);
+
+				if (origLoc != 0xFFFFFFFF)
+					continue;
+
+				for (; j < 4; j++) {
+					bh = sdata->s_spar_map[j];
+					if (!bh)
+						continue;
+
+					st = (struct sparingTable *)bh->b_data;
+					mapEntry = st->mapEntry[l];
+					mapEntry.origLocation =
+							cpu_to_le32(packet);
+					memmove(&st->mapEntry[k + 1],
+						&st->mapEntry[k],
+						(l - k) *
+						sizeof(struct sparingEntry));
+					st->mapEntry[k] = mapEntry;
+					udf_update_tag((char *)st,
+						sizeof(struct sparingTable) +
+						reallocationTableLen *
+						sizeof(struct sparingEntry));
+					mark_buffer_dirty(bh);
+				}
+				*new_block =
+					le32_to_cpu(
+					      st->mapEntry[k].mappedLocation) +
+					((old_block - map->s_partition_root) &
+					 (sdata->s_packet_len - 1));
+				ret = 0;
+				goto out;
+			}
+
+			ret = 1;
+			goto out;
+		} /* if old_block */
+	}
+
+	if (i == sbi->s_partitions) {
+		/* outside of partitions */
+		/* for now, fail =) */
+		ret = 1;
+	}
+
+out:
+	mutex_unlock(&sbi->s_alloc_mutex);
+	return ret;
+}
+
+static uint32_t udf_try_read_meta(struct inode *inode, uint32_t block,
+					uint16_t partition, uint32_t offset)
+{
+	struct super_block *sb = inode->i_sb;
+	struct udf_part_map *map;
+	struct kernel_lb_addr eloc;
+	uint32_t elen;
+	sector_t ext_offset;
+	struct extent_position epos = {};
+	uint32_t phyblock;
+	int8_t etype;
+	int err = 0;
+
+	err = inode_bmap(inode, block, &epos, &eloc, &elen, &ext_offset, &etype);
+	if (err <= 0 || etype != (EXT_RECORDED_ALLOCATED >> 30))
+		phyblock = 0xFFFFFFFF;
+	else {
+		map = &UDF_SB(sb)->s_partmaps[partition];
+		/* map to sparable/physical partition desc */
+		phyblock = udf_get_pblock(sb, eloc.logicalBlockNum,
+			map->s_type_specific.s_metadata.s_phys_partition_ref,
+			ext_offset + offset);
+	}
+
+	brelse(epos.bh);
+	return phyblock;
+}
+
+uint32_t udf_get_pblock_meta25(struct super_block *sb, uint32_t block,
+				uint16_t partition, uint32_t offset)
+{
+	struct udf_sb_info *sbi = UDF_SB(sb);
+	struct udf_part_map *map;
+	struct udf_meta_data *mdata;
+	uint32_t retblk;
+	struct inode *inode;
+
+	udf_debug("READING from METADATA\n");
+
+	map = &sbi->s_partmaps[partition];
+	mdata = &map->s_type_specific.s_metadata;
+	inode = mdata->s_metadata_fe ? : mdata->s_mirror_fe;
+
+	if (!inode)
+		return 0xFFFFFFFF;
+
+	retblk = udf_try_read_meta(inode, block, partition, offset);
+	if (retblk == 0xFFFFFFFF && mdata->s_metadata_fe) {
+		udf_warn(sb, "error reading from METADATA, trying to read from MIRROR\n");
+		if (!(mdata->s_flags & MF_MIRROR_FE_LOADED)) {
+			mdata->s_mirror_fe = udf_find_metadata_inode_efe(sb,
+				mdata->s_mirror_file_loc,
+				mdata->s_phys_partition_ref);
+			if (IS_ERR(mdata->s_mirror_fe))
+				mdata->s_mirror_fe = NULL;
+			mdata->s_flags |= MF_MIRROR_FE_LOADED;
+		}
+
+		inode = mdata->s_mirror_fe;
+		if (!inode)
+			return 0xFFFFFFFF;
+		retblk = udf_try_read_meta(inode, block, partition, offset);
+	}
+
+	return retblk;
+}