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, 318 insertions, 0 deletions

diff --git a/fs/hpfs/inode.c b/fs/hpfs/inode.c
new file mode 100644
index 000000000..1b4fcf760
--- /dev/null
+++ b/fs/hpfs/inode.c
@@ -0,0 +1,318 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/hpfs/inode.c
+ *
+ *  Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999
+ *
+ *  inode VFS functions
+ */
+
+#include <linux/slab.h>
+#include <linux/user_namespace.h>
+#include "hpfs_fn.h"
+
+void hpfs_init_inode(struct inode *i)
+{
+	struct super_block *sb = i->i_sb;
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
+
+	i->i_uid = hpfs_sb(sb)->sb_uid;
+	i->i_gid = hpfs_sb(sb)->sb_gid;
+	i->i_mode = hpfs_sb(sb)->sb_mode;
+	i->i_size = -1;
+	i->i_blocks = -1;
+	
+	hpfs_inode->i_dno = 0;
+	hpfs_inode->i_n_secs = 0;
+	hpfs_inode->i_file_sec = 0;
+	hpfs_inode->i_disk_sec = 0;
+	hpfs_inode->i_dpos = 0;
+	hpfs_inode->i_dsubdno = 0;
+	hpfs_inode->i_ea_mode = 0;
+	hpfs_inode->i_ea_uid = 0;
+	hpfs_inode->i_ea_gid = 0;
+	hpfs_inode->i_ea_size = 0;
+
+	hpfs_inode->i_rddir_off = NULL;
+	hpfs_inode->i_dirty = 0;
+
+	inode_set_ctime(i, 0, 0);
+	inode_set_mtime(i, 0, 0);
+	inode_set_atime(i, 0, 0);
+}
+
+void hpfs_read_inode(struct inode *i)
+{
+	struct buffer_head *bh;
+	struct fnode *fnode;
+	struct super_block *sb = i->i_sb;
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
+	void *ea;
+	int ea_size;
+
+	if (!(fnode = hpfs_map_fnode(sb, i->i_ino, &bh))) {
+		/*i->i_mode |= S_IFREG;
+		i->i_mode &= ~0111;
+		i->i_op = &hpfs_file_iops;
+		i->i_fop = &hpfs_file_ops;
+		clear_nlink(i);*/
+		make_bad_inode(i);
+		return;
+	}
+	if (hpfs_sb(i->i_sb)->sb_eas) {
+		if ((ea = hpfs_get_ea(i->i_sb, fnode, "UID", &ea_size))) {
+			if (ea_size == 2) {
+				i_uid_write(i, le16_to_cpu(*(__le16*)ea));
+				hpfs_inode->i_ea_uid = 1;
+			}
+			kfree(ea);
+		}
+		if ((ea = hpfs_get_ea(i->i_sb, fnode, "GID", &ea_size))) {
+			if (ea_size == 2) {
+				i_gid_write(i, le16_to_cpu(*(__le16*)ea));
+				hpfs_inode->i_ea_gid = 1;
+			}
+			kfree(ea);
+		}
+		if ((ea = hpfs_get_ea(i->i_sb, fnode, "SYMLINK", &ea_size))) {
+			kfree(ea);
+			i->i_mode = S_IFLNK | 0777;
+			i->i_op = &page_symlink_inode_operations;
+			inode_nohighmem(i);
+			i->i_data.a_ops = &hpfs_symlink_aops;
+			set_nlink(i, 1);
+			i->i_size = ea_size;
+			i->i_blocks = 1;
+			brelse(bh);
+			return;
+		}
+		if ((ea = hpfs_get_ea(i->i_sb, fnode, "MODE", &ea_size))) {
+			int rdev = 0;
+			umode_t mode = hpfs_sb(sb)->sb_mode;
+			if (ea_size == 2) {
+				mode = le16_to_cpu(*(__le16*)ea);
+				hpfs_inode->i_ea_mode = 1;
+			}
+			kfree(ea);
+			i->i_mode = mode;
+			if (S_ISBLK(mode) || S_ISCHR(mode)) {
+				if ((ea = hpfs_get_ea(i->i_sb, fnode, "DEV", &ea_size))) {
+					if (ea_size == 4)
+						rdev = le32_to_cpu(*(__le32*)ea);
+					kfree(ea);
+				}
+			}
+			if (S_ISBLK(mode) || S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode)) {
+				brelse(bh);
+				set_nlink(i, 1);
+				i->i_size = 0;
+				i->i_blocks = 1;
+				init_special_inode(i, mode,
+					new_decode_dev(rdev));
+				return;
+			}
+		}
+	}
+	if (fnode_is_dir(fnode)) {
+		int n_dnodes, n_subdirs;
+		i->i_mode |= S_IFDIR;
+		i->i_op = &hpfs_dir_iops;
+		i->i_fop = &hpfs_dir_ops;
+		hpfs_inode->i_parent_dir = le32_to_cpu(fnode->up);
+		hpfs_inode->i_dno = le32_to_cpu(fnode->u.external[0].disk_secno);
+		if (hpfs_sb(sb)->sb_chk >= 2) {
+			struct buffer_head *bh0;
+			if (hpfs_map_fnode(sb, hpfs_inode->i_parent_dir, &bh0)) brelse(bh0);
+		}
+		n_dnodes = 0; n_subdirs = 0;
+		hpfs_count_dnodes(i->i_sb, hpfs_inode->i_dno, &n_dnodes, &n_subdirs, NULL);
+		i->i_blocks = 4 * n_dnodes;
+		i->i_size = 2048 * n_dnodes;
+		set_nlink(i, 2 + n_subdirs);
+	} else {
+		i->i_mode |= S_IFREG;
+		if (!hpfs_inode->i_ea_mode) i->i_mode &= ~0111;
+		i->i_op = &hpfs_file_iops;
+		i->i_fop = &hpfs_file_ops;
+		set_nlink(i, 1);
+		i->i_size = le32_to_cpu(fnode->file_size);
+		i->i_blocks = ((i->i_size + 511) >> 9) + 1;
+		i->i_data.a_ops = &hpfs_aops;
+		hpfs_i(i)->mmu_private = i->i_size;
+	}
+	brelse(bh);
+}
+
+static void hpfs_write_inode_ea(struct inode *i, struct fnode *fnode)
+{
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
+	/*if (le32_to_cpu(fnode->acl_size_l) || le16_to_cpu(fnode->acl_size_s)) {
+		   Some unknown structures like ACL may be in fnode,
+		   we'd better not overwrite them
+		hpfs_error(i->i_sb, "fnode %08x has some unknown HPFS386 structures", i->i_ino);
+	} else*/ if (hpfs_sb(i->i_sb)->sb_eas >= 2) {
+		__le32 ea;
+		if (!uid_eq(i->i_uid, hpfs_sb(i->i_sb)->sb_uid) || hpfs_inode->i_ea_uid) {
+			ea = cpu_to_le32(i_uid_read(i));
+			hpfs_set_ea(i, fnode, "UID", (char*)&ea, 2);
+			hpfs_inode->i_ea_uid = 1;
+		}
+		if (!gid_eq(i->i_gid, hpfs_sb(i->i_sb)->sb_gid) || hpfs_inode->i_ea_gid) {
+			ea = cpu_to_le32(i_gid_read(i));
+			hpfs_set_ea(i, fnode, "GID", (char *)&ea, 2);
+			hpfs_inode->i_ea_gid = 1;
+		}
+		if (!S_ISLNK(i->i_mode))
+			if ((i->i_mode != ((hpfs_sb(i->i_sb)->sb_mode & ~(S_ISDIR(i->i_mode) ? 0 : 0111))
+			  | (S_ISDIR(i->i_mode) ? S_IFDIR : S_IFREG))
+			  && i->i_mode != ((hpfs_sb(i->i_sb)->sb_mode & ~(S_ISDIR(i->i_mode) ? 0222 : 0333))
+			  | (S_ISDIR(i->i_mode) ? S_IFDIR : S_IFREG))) || hpfs_inode->i_ea_mode) {
+				ea = cpu_to_le32(i->i_mode);
+				/* sick, but legal */
+				hpfs_set_ea(i, fnode, "MODE", (char *)&ea, 2);
+				hpfs_inode->i_ea_mode = 1;
+			}
+		if (S_ISBLK(i->i_mode) || S_ISCHR(i->i_mode)) {
+			ea = cpu_to_le32(new_encode_dev(i->i_rdev));
+			hpfs_set_ea(i, fnode, "DEV", (char *)&ea, 4);
+		}
+	}
+}
+
+void hpfs_write_inode(struct inode *i)
+{
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
+	struct inode *parent;
+	if (i->i_ino == hpfs_sb(i->i_sb)->sb_root) return;
+	if (hpfs_inode->i_rddir_off && !icount_read_once(i)) {
+		if (*hpfs_inode->i_rddir_off)
+			pr_err("write_inode: some position still there\n");
+		kfree(hpfs_inode->i_rddir_off);
+		hpfs_inode->i_rddir_off = NULL;
+	}
+	if (!i->i_nlink) {
+		return;
+	}
+	parent = iget_locked(i->i_sb, hpfs_inode->i_parent_dir);
+	if (parent) {
+		hpfs_inode->i_dirty = 0;
+		if (inode_state_read_once(parent) & I_NEW) {
+			hpfs_init_inode(parent);
+			hpfs_read_inode(parent);
+			unlock_new_inode(parent);
+		}
+		hpfs_write_inode_nolock(i);
+		iput(parent);
+	}
+}
+
+void hpfs_write_inode_nolock(struct inode *i)
+{
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
+	struct buffer_head *bh;
+	struct fnode *fnode;
+	struct quad_buffer_head qbh;
+	struct hpfs_dirent *de;
+	if (i->i_ino == hpfs_sb(i->i_sb)->sb_root) return;
+	if (!(fnode = hpfs_map_fnode(i->i_sb, i->i_ino, &bh))) return;
+	if (i->i_ino != hpfs_sb(i->i_sb)->sb_root && i->i_nlink) {
+		if (!(de = map_fnode_dirent(i->i_sb, i->i_ino, fnode, &qbh))) {
+			brelse(bh);
+			return;
+		}
+	} else de = NULL;
+	if (S_ISREG(i->i_mode)) {
+		fnode->file_size = cpu_to_le32(i->i_size);
+		if (de) de->file_size = cpu_to_le32(i->i_size);
+	} else if (S_ISDIR(i->i_mode)) {
+		fnode->file_size = cpu_to_le32(0);
+		if (de) de->file_size = cpu_to_le32(0);
+	}
+	hpfs_write_inode_ea(i, fnode);
+	if (de) {
+		de->write_date = cpu_to_le32(gmt_to_local(i->i_sb, inode_get_mtime_sec(i)));
+		de->read_date = cpu_to_le32(gmt_to_local(i->i_sb, inode_get_atime_sec(i)));
+		de->creation_date = cpu_to_le32(gmt_to_local(i->i_sb, inode_get_ctime_sec(i)));
+		de->read_only = !(i->i_mode & 0222);
+		de->ea_size = cpu_to_le32(hpfs_inode->i_ea_size);
+		hpfs_mark_4buffers_dirty(&qbh);
+		hpfs_brelse4(&qbh);
+	}
+	if (S_ISDIR(i->i_mode)) {
+		if ((de = map_dirent(i, hpfs_inode->i_dno, "\001\001", 2, NULL, &qbh))) {
+			de->write_date = cpu_to_le32(gmt_to_local(i->i_sb, inode_get_mtime_sec(i)));
+			de->read_date = cpu_to_le32(gmt_to_local(i->i_sb, inode_get_atime_sec(i)));
+			de->creation_date = cpu_to_le32(gmt_to_local(i->i_sb, inode_get_ctime_sec(i)));
+			de->read_only = !(i->i_mode & 0222);
+			de->ea_size = cpu_to_le32(/*hpfs_inode->i_ea_size*/0);
+			de->file_size = cpu_to_le32(0);
+			hpfs_mark_4buffers_dirty(&qbh);
+			hpfs_brelse4(&qbh);
+		} else
+			hpfs_error(i->i_sb,
+				"directory %08llx doesn't have '.' entry",
+				i->i_ino);
+	}
+	mark_buffer_dirty(bh);
+	brelse(bh);
+}
+
+int hpfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		 struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	int error = -EINVAL;
+
+	hpfs_lock(inode->i_sb);
+	if (inode->i_ino == hpfs_sb(inode->i_sb)->sb_root)
+		goto out_unlock;
+	if ((attr->ia_valid & ATTR_UID) &&
+	    from_kuid(&init_user_ns, attr->ia_uid) >= 0x10000)
+		goto out_unlock;
+	if ((attr->ia_valid & ATTR_GID) &&
+	    from_kgid(&init_user_ns, attr->ia_gid) >= 0x10000)
+		goto out_unlock;
+	if ((attr->ia_valid & ATTR_SIZE) && attr->ia_size > inode->i_size)
+		goto out_unlock;
+
+	error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
+	if (error)
+		goto out_unlock;
+
+	if ((attr->ia_valid & ATTR_SIZE) &&
+	    attr->ia_size != i_size_read(inode)) {
+		error = inode_newsize_ok(inode, attr->ia_size);
+		if (error)
+			goto out_unlock;
+
+		truncate_setsize(inode, attr->ia_size);
+		hpfs_truncate(inode);
+	}
+
+	setattr_copy(&nop_mnt_idmap, inode, attr);
+
+	hpfs_write_inode(inode);
+
+ out_unlock:
+	hpfs_unlock(inode->i_sb);
+	return error;
+}
+
+void hpfs_write_if_changed(struct inode *inode)
+{
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(inode);
+
+	if (hpfs_inode->i_dirty)
+		hpfs_write_inode(inode);
+}
+
+void hpfs_evict_inode(struct inode *inode)
+{
+	truncate_inode_pages_final(&inode->i_data);
+	clear_inode(inode);
+	if (!inode->i_nlink) {
+		hpfs_lock(inode->i_sb);
+		hpfs_remove_fnode(inode->i_sb, inode->i_ino);
+		hpfs_unlock(inode->i_sb);
+	}
+}