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, 417 insertions, 0 deletions

diff --git a/fs/affs/inode.c b/fs/affs/inode.c
new file mode 100644
index 000000000..d4a3f381c
--- /dev/null
+++ b/fs/affs/inode.c
@@ -0,0 +1,417 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/affs/inode.c
+ *
+ *  (c) 1996  Hans-Joachim Widmaier - Rewritten
+ *
+ *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
+ *
+ *  (C) 1992  Eric Youngdale Modified for ISO9660 filesystem.
+ *
+ *  (C) 1991  Linus Torvalds - minix filesystem
+ */
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/gfp.h>
+#include "affs.h"
+
+struct inode *affs_iget(struct super_block *sb, unsigned long ino)
+{
+	struct affs_sb_info	*sbi = AFFS_SB(sb);
+	struct buffer_head	*bh;
+	struct affs_tail	*tail;
+	struct inode		*inode;
+	u32			 block;
+	u32			 size;
+	u32			 prot;
+	u16			 id;
+
+	inode = iget_locked(sb, ino);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+	if (!(inode_state_read_once(inode) & I_NEW))
+		return inode;
+
+	pr_debug("affs_iget(%llu)\n", inode->i_ino);
+
+	block = inode->i_ino;
+	bh = affs_bread(sb, block);
+	if (!bh) {
+		affs_warning(sb, "read_inode", "Cannot read block %d", block);
+		goto bad_inode;
+	}
+	if (affs_checksum_block(sb, bh) || be32_to_cpu(AFFS_HEAD(bh)->ptype) != T_SHORT) {
+		affs_warning(sb,"read_inode",
+			   "Checksum or type (ptype=%d) error on inode %d",
+			   AFFS_HEAD(bh)->ptype, block);
+		goto bad_inode;
+	}
+
+	tail = AFFS_TAIL(sb, bh);
+	prot = be32_to_cpu(tail->protect);
+
+	inode->i_size = 0;
+	set_nlink(inode, 1);
+	inode->i_mode = 0;
+	AFFS_I(inode)->i_extcnt = 1;
+	AFFS_I(inode)->i_ext_last = ~1;
+	AFFS_I(inode)->i_protect = prot;
+	atomic_set(&AFFS_I(inode)->i_opencnt, 0);
+	AFFS_I(inode)->i_blkcnt = 0;
+	AFFS_I(inode)->i_lc = NULL;
+	AFFS_I(inode)->i_lc_size = 0;
+	AFFS_I(inode)->i_lc_shift = 0;
+	AFFS_I(inode)->i_lc_mask = 0;
+	AFFS_I(inode)->i_ac = NULL;
+	AFFS_I(inode)->i_ext_bh = NULL;
+	AFFS_I(inode)->mmu_private = 0;
+	AFFS_I(inode)->i_lastalloc = 0;
+	AFFS_I(inode)->i_pa_cnt = 0;
+
+	if (affs_test_opt(sbi->s_flags, SF_SETMODE))
+		inode->i_mode = sbi->s_mode;
+	else
+		inode->i_mode = affs_prot_to_mode(prot);
+
+	id = be16_to_cpu(tail->uid);
+	if (id == 0 || affs_test_opt(sbi->s_flags, SF_SETUID))
+		inode->i_uid = sbi->s_uid;
+	else if (id == 0xFFFF && affs_test_opt(sbi->s_flags, SF_MUFS))
+		i_uid_write(inode, 0);
+	else
+		i_uid_write(inode, id);
+
+	id = be16_to_cpu(tail->gid);
+	if (id == 0 || affs_test_opt(sbi->s_flags, SF_SETGID))
+		inode->i_gid = sbi->s_gid;
+	else if (id == 0xFFFF && affs_test_opt(sbi->s_flags, SF_MUFS))
+		i_gid_write(inode, 0);
+	else
+		i_gid_write(inode, id);
+
+	switch (be32_to_cpu(tail->stype)) {
+	case ST_ROOT:
+		inode->i_uid = sbi->s_uid;
+		inode->i_gid = sbi->s_gid;
+		fallthrough;
+	case ST_USERDIR:
+		if (be32_to_cpu(tail->stype) == ST_USERDIR ||
+		    affs_test_opt(sbi->s_flags, SF_SETMODE)) {
+			if (inode->i_mode & S_IRUSR)
+				inode->i_mode |= S_IXUSR;
+			if (inode->i_mode & S_IRGRP)
+				inode->i_mode |= S_IXGRP;
+			if (inode->i_mode & S_IROTH)
+				inode->i_mode |= S_IXOTH;
+			inode->i_mode |= S_IFDIR;
+		} else
+			inode->i_mode = S_IRUGO | S_IXUGO | S_IWUSR | S_IFDIR;
+		/* Maybe it should be controlled by mount parameter? */
+		//inode->i_mode |= S_ISVTX;
+		inode->i_op = &affs_dir_inode_operations;
+		inode->i_fop = &affs_dir_operations;
+		break;
+	case ST_LINKDIR:
+#if 0
+		affs_warning(sb, "read_inode", "inode is LINKDIR");
+		goto bad_inode;
+#else
+		inode->i_mode |= S_IFDIR;
+		/* ... and leave ->i_op and ->i_fop pointing to empty */
+		break;
+#endif
+	case ST_LINKFILE:
+		affs_warning(sb, "read_inode", "inode is LINKFILE");
+		goto bad_inode;
+	case ST_FILE:
+		size = be32_to_cpu(tail->size);
+		inode->i_mode |= S_IFREG;
+		AFFS_I(inode)->mmu_private = inode->i_size = size;
+		if (inode->i_size) {
+			AFFS_I(inode)->i_blkcnt = (size - 1) /
+					       sbi->s_data_blksize + 1;
+			AFFS_I(inode)->i_extcnt = (AFFS_I(inode)->i_blkcnt - 1) /
+					       sbi->s_hashsize + 1;
+		}
+		if (tail->link_chain)
+			set_nlink(inode, 2);
+		inode->i_mapping->a_ops = affs_test_opt(sbi->s_flags, SF_OFS) ?
+					  &affs_aops_ofs : &affs_aops;
+		inode->i_op = &affs_file_inode_operations;
+		inode->i_fop = &affs_file_operations;
+		break;
+	case ST_SOFTLINK:
+		inode->i_size = strlen((char *)AFFS_HEAD(bh)->table);
+		inode->i_mode |= S_IFLNK;
+		inode_nohighmem(inode);
+		inode->i_op = &affs_symlink_inode_operations;
+		inode->i_data.a_ops = &affs_symlink_aops;
+		break;
+	}
+
+	inode_set_mtime(inode,
+			inode_set_atime(inode, inode_set_ctime(inode, (be32_to_cpu(tail->change.days) * 86400LL + be32_to_cpu(tail->change.mins) * 60 + be32_to_cpu(tail->change.ticks) / 50 + AFFS_EPOCH_DELTA) + sys_tz.tz_minuteswest * 60, 0).tv_sec, 0).tv_sec,
+			0);
+	affs_brelse(bh);
+	unlock_new_inode(inode);
+	return inode;
+
+bad_inode:
+	affs_brelse(bh);
+	iget_failed(inode);
+	return ERR_PTR(-EIO);
+}
+
+int
+affs_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	struct super_block	*sb = inode->i_sb;
+	struct buffer_head	*bh;
+	struct affs_tail	*tail;
+	uid_t			 uid;
+	gid_t			 gid;
+
+	pr_debug("write_inode(%llu)\n", inode->i_ino);
+
+	if (!inode->i_nlink)
+		// possibly free block
+		return 0;
+	bh = affs_bread(sb, inode->i_ino);
+	if (!bh) {
+		affs_error(sb, "write_inode", "Cannot read block %llu", inode->i_ino);
+		return -EIO;
+	}
+	tail = AFFS_TAIL(sb, bh);
+	if (tail->stype == cpu_to_be32(ST_ROOT)) {
+		affs_secs_to_datestamp(inode_get_mtime_sec(inode),
+				       &AFFS_ROOT_TAIL(sb, bh)->root_change);
+	} else {
+		tail->protect = cpu_to_be32(AFFS_I(inode)->i_protect);
+		tail->size = cpu_to_be32(inode->i_size);
+		affs_secs_to_datestamp(inode_get_mtime_sec(inode),
+				       &tail->change);
+		if (!(inode->i_ino == AFFS_SB(sb)->s_root_block)) {
+			uid = i_uid_read(inode);
+			gid = i_gid_read(inode);
+			if (affs_test_opt(AFFS_SB(sb)->s_flags, SF_MUFS)) {
+				if (uid == 0 || uid == 0xFFFF)
+					uid = uid ^ ~0;
+				if (gid == 0 || gid == 0xFFFF)
+					gid = gid ^ ~0;
+			}
+			if (!affs_test_opt(AFFS_SB(sb)->s_flags, SF_SETUID))
+				tail->uid = cpu_to_be16(uid);
+			if (!affs_test_opt(AFFS_SB(sb)->s_flags, SF_SETGID))
+				tail->gid = cpu_to_be16(gid);
+		}
+	}
+	affs_fix_checksum(sb, bh);
+	mark_buffer_dirty(bh);
+	affs_brelse(bh);
+	affs_free_prealloc(inode);
+	return 0;
+}
+
+int
+affs_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	int error;
+
+	pr_debug("setattr(%llu,0x%x)\n", inode->i_ino, attr->ia_valid);
+
+	error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
+	if (error)
+		goto out;
+
+	if (((attr->ia_valid & ATTR_UID) &&
+	      affs_test_opt(AFFS_SB(inode->i_sb)->s_flags, SF_SETUID)) ||
+	    ((attr->ia_valid & ATTR_GID) &&
+	      affs_test_opt(AFFS_SB(inode->i_sb)->s_flags, SF_SETGID)) ||
+	    ((attr->ia_valid & ATTR_MODE) &&
+	     (AFFS_SB(inode->i_sb)->s_flags &
+	      (AFFS_MOUNT_SF_SETMODE | AFFS_MOUNT_SF_IMMUTABLE)))) {
+		if (!affs_test_opt(AFFS_SB(inode->i_sb)->s_flags, SF_QUIET))
+			error = -EPERM;
+		goto out;
+	}
+
+	if ((attr->ia_valid & ATTR_SIZE) &&
+	    attr->ia_size != i_size_read(inode)) {
+		error = inode_newsize_ok(inode, attr->ia_size);
+		if (error)
+			return error;
+
+		truncate_setsize(inode, attr->ia_size);
+		affs_truncate(inode);
+	}
+
+	setattr_copy(&nop_mnt_idmap, inode, attr);
+	mark_inode_dirty(inode);
+
+	if (attr->ia_valid & ATTR_MODE)
+		affs_mode_to_prot(inode);
+out:
+	return error;
+}
+
+void
+affs_evict_inode(struct inode *inode)
+{
+	unsigned long cache_page;
+	pr_debug("evict_inode(ino=%llu, nlink=%u)\n",
+		 inode->i_ino, inode->i_nlink);
+	truncate_inode_pages_final(&inode->i_data);
+
+	if (!inode->i_nlink) {
+		inode->i_size = 0;
+		affs_truncate(inode);
+	}
+
+	clear_inode(inode);
+	affs_free_prealloc(inode);
+	cache_page = (unsigned long)AFFS_I(inode)->i_lc;
+	if (cache_page) {
+		pr_debug("freeing ext cache\n");
+		AFFS_I(inode)->i_lc = NULL;
+		AFFS_I(inode)->i_ac = NULL;
+		free_page(cache_page);
+	}
+	affs_brelse(AFFS_I(inode)->i_ext_bh);
+	AFFS_I(inode)->i_ext_last = ~1;
+	AFFS_I(inode)->i_ext_bh = NULL;
+
+	if (!inode->i_nlink)
+		affs_free_block(inode->i_sb, inode->i_ino);
+}
+
+struct inode *
+affs_new_inode(struct inode *dir)
+{
+	struct super_block	*sb = dir->i_sb;
+	struct inode		*inode;
+	u32			 block;
+	struct buffer_head	*bh;
+
+	if (!(inode = new_inode(sb)))
+		goto err_inode;
+
+	if (!(block = affs_alloc_block(dir, dir->i_ino)))
+		goto err_block;
+
+	bh = affs_getzeroblk(sb, block);
+	if (!bh)
+		goto err_bh;
+	mark_buffer_dirty(bh);
+	affs_brelse(bh);
+
+	inode->i_uid     = current_fsuid();
+	inode->i_gid     = current_fsgid();
+	inode->i_ino     = block;
+	set_nlink(inode, 1);
+	simple_inode_init_ts(inode);
+	atomic_set(&AFFS_I(inode)->i_opencnt, 0);
+	AFFS_I(inode)->i_blkcnt = 0;
+	AFFS_I(inode)->i_lc = NULL;
+	AFFS_I(inode)->i_lc_size = 0;
+	AFFS_I(inode)->i_lc_shift = 0;
+	AFFS_I(inode)->i_lc_mask = 0;
+	AFFS_I(inode)->i_ac = NULL;
+	AFFS_I(inode)->i_ext_bh = NULL;
+	AFFS_I(inode)->mmu_private = 0;
+	AFFS_I(inode)->i_protect = 0;
+	AFFS_I(inode)->i_lastalloc = 0;
+	AFFS_I(inode)->i_pa_cnt = 0;
+	AFFS_I(inode)->i_extcnt = 1;
+	AFFS_I(inode)->i_ext_last = ~1;
+
+	insert_inode_hash(inode);
+
+	return inode;
+
+err_bh:
+	affs_free_block(sb, block);
+err_block:
+	iput(inode);
+err_inode:
+	return NULL;
+}
+
+/*
+ * Add an entry to a directory. Create the header block
+ * and insert it into the hash table.
+ */
+
+int
+affs_add_entry(struct inode *dir, struct inode *inode, struct dentry *dentry, s32 type)
+{
+	struct super_block *sb = dir->i_sb;
+	struct buffer_head *inode_bh = NULL;
+	struct buffer_head *bh;
+	u32 block = 0;
+	int retval;
+
+	pr_debug("%s(dir=%llu, inode=%llu, \"%pd\", type=%d)\n", __func__,
+		 dir->i_ino, inode->i_ino, dentry, type);
+
+	retval = -EIO;
+	bh = affs_bread(sb, inode->i_ino);
+	if (!bh)
+		goto done;
+
+	affs_lock_link(inode);
+	switch (type) {
+	case ST_LINKFILE:
+	case ST_LINKDIR:
+		retval = -ENOSPC;
+		block = affs_alloc_block(dir, dir->i_ino);
+		if (!block)
+			goto err;
+		retval = -EIO;
+		inode_bh = bh;
+		bh = affs_getzeroblk(sb, block);
+		if (!bh)
+			goto err;
+		break;
+	default:
+		break;
+	}
+
+	AFFS_HEAD(bh)->ptype = cpu_to_be32(T_SHORT);
+	AFFS_HEAD(bh)->key = cpu_to_be32(bh->b_blocknr);
+	affs_copy_name(AFFS_TAIL(sb, bh)->name, dentry);
+	AFFS_TAIL(sb, bh)->stype = cpu_to_be32(type);
+	AFFS_TAIL(sb, bh)->parent = cpu_to_be32(dir->i_ino);
+
+	if (inode_bh) {
+		__be32 chain;
+	       	chain = AFFS_TAIL(sb, inode_bh)->link_chain;
+		AFFS_TAIL(sb, bh)->original = cpu_to_be32(inode->i_ino);
+		AFFS_TAIL(sb, bh)->link_chain = chain;
+		AFFS_TAIL(sb, inode_bh)->link_chain = cpu_to_be32(block);
+		affs_adjust_checksum(inode_bh, block - be32_to_cpu(chain));
+		mark_buffer_dirty(inode_bh);
+		set_nlink(inode, 2);
+		ihold(inode);
+	}
+	affs_fix_checksum(sb, bh);
+	mark_buffer_dirty(bh);
+	dentry->d_fsdata = (void *)(long)bh->b_blocknr;
+
+	affs_lock_dir(dir);
+	retval = affs_insert_hash(dir, bh);
+	mark_buffer_dirty(bh);
+	affs_unlock_dir(dir);
+	affs_unlock_link(inode);
+
+	d_instantiate(dentry, inode);
+done:
+	affs_brelse(inode_bh);
+	affs_brelse(bh);
+	return retval;
+err:
+	if (block)
+		affs_free_block(sb, block);
+	affs_unlock_link(inode);
+	goto done;
+}