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, 331 insertions, 0 deletions

diff --git a/fs/hpfs/dir.c b/fs/hpfs/dir.c
new file mode 100644
index 000000000..3bf11202e
--- /dev/null
+++ b/fs/hpfs/dir.c
@@ -0,0 +1,331 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/hpfs/dir.c
+ *
+ *  Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999
+ *
+ *  directory VFS functions
+ */
+
+#include <linux/slab.h>
+#include "hpfs_fn.h"
+
+static int hpfs_dir_release(struct inode *inode, struct file *filp)
+{
+	hpfs_lock(inode->i_sb);
+	hpfs_del_pos(inode, &filp->f_pos);
+	/*hpfs_write_if_changed(inode);*/
+	hpfs_unlock(inode->i_sb);
+	return 0;
+}
+
+/* This is slow, but it's not used often */
+
+static loff_t hpfs_dir_lseek(struct file *filp, loff_t off, int whence)
+{
+	loff_t new_off = off + (whence == 1 ? filp->f_pos : 0);
+	loff_t pos;
+	struct quad_buffer_head qbh;
+	struct inode *i = file_inode(filp);
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
+	struct super_block *s = i->i_sb;
+
+	/* Somebody else will have to figure out what to do here */
+	if (whence == SEEK_DATA || whence == SEEK_HOLE)
+		return -EINVAL;
+
+	inode_lock(i);
+	hpfs_lock(s);
+
+	/*pr_info("dir lseek\n");*/
+	if (new_off == 0 || new_off == 1 || new_off == 11 || new_off == 12 || new_off == 13) goto ok;
+	pos = ((loff_t) hpfs_de_as_down_as_possible(s, hpfs_inode->i_dno) << 4) + 1;
+	while (pos != new_off) {
+		if (map_pos_dirent(i, &pos, &qbh)) hpfs_brelse4(&qbh);
+		else goto fail;
+		if (pos == 12) goto fail;
+	}
+	if (unlikely(hpfs_add_pos(i, &filp->f_pos) < 0)) {
+		hpfs_unlock(s);
+		inode_unlock(i);
+		return -ENOMEM;
+	}
+ok:
+	filp->f_pos = new_off;
+	hpfs_unlock(s);
+	inode_unlock(i);
+	return new_off;
+fail:
+	/*pr_warn("illegal lseek: %016llx\n", new_off);*/
+	hpfs_unlock(s);
+	inode_unlock(i);
+	return -ESPIPE;
+}
+
+static int hpfs_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct inode *inode = file_inode(file);
+	struct hpfs_inode_info *hpfs_inode = hpfs_i(inode);
+	struct quad_buffer_head qbh;
+	struct hpfs_dirent *de;
+	int lc;
+	loff_t next_pos;
+	unsigned char *tempname;
+	int c1, c2 = 0;
+	int ret = 0;
+
+	hpfs_lock(inode->i_sb);
+
+	if (hpfs_sb(inode->i_sb)->sb_chk) {
+		if (hpfs_chk_sectors(inode->i_sb, inode->i_ino, 1, "dir_fnode")) {
+			ret = -EFSERROR;
+			goto out;
+		}
+		if (hpfs_chk_sectors(inode->i_sb, hpfs_inode->i_dno, 4, "dir_dnode")) {
+			ret = -EFSERROR;
+			goto out;
+		}
+	}
+	if (hpfs_sb(inode->i_sb)->sb_chk >= 2) {
+		struct buffer_head *bh;
+		struct fnode *fno;
+		int e = 0;
+		if (!(fno = hpfs_map_fnode(inode->i_sb, inode->i_ino, &bh))) {
+			ret = -EIOERROR;
+			goto out;
+		}
+		if (!fnode_is_dir(fno)) {
+			e = 1;
+			hpfs_error(inode->i_sb, "not a directory, fnode %08llx",
+					inode->i_ino);
+		}
+		if (hpfs_inode->i_dno != le32_to_cpu(fno->u.external[0].disk_secno)) {
+			e = 1;
+			hpfs_error(inode->i_sb, "corrupted inode: i_dno == %08x, fnode -> dnode == %08x", hpfs_inode->i_dno, le32_to_cpu(fno->u.external[0].disk_secno));
+		}
+		brelse(bh);
+		if (e) {
+			ret = -EFSERROR;
+			goto out;
+		}
+	}
+	lc = hpfs_sb(inode->i_sb)->sb_lowercase;
+	if (ctx->pos == 12) { /* diff -r requires this (note, that diff -r */
+		ctx->pos = 13; /* also fails on msdos filesystem in 2.0) */
+		goto out;
+	}
+	if (ctx->pos == 13) {
+		ret = -ENOENT;
+		goto out;
+	}
+	
+	while (1) {
+		again:
+		/* This won't work when cycle is longer than number of dirents
+		   accepted by filldir, but what can I do?
+		   maybe killall -9 ls helps */
+		if (hpfs_sb(inode->i_sb)->sb_chk)
+			if (hpfs_stop_cycles(inode->i_sb, ctx->pos, &c1, &c2, "hpfs_readdir")) {
+				ret = -EFSERROR;
+				goto out;
+			}
+		if (ctx->pos == 12)
+			goto out;
+		if (ctx->pos == 3 || ctx->pos == 4 || ctx->pos == 5) {
+			pr_err("pos==%d\n", (int)ctx->pos);
+			goto out;
+		}
+		if (ctx->pos == 0) {
+			if (!dir_emit_dot(file, ctx))
+				goto out;
+			ctx->pos = 11;
+		}
+		if (ctx->pos == 11) {
+			if (!dir_emit(ctx, "..", 2, hpfs_inode->i_parent_dir, DT_DIR))
+				goto out;
+			ctx->pos = 1;
+		}
+		if (ctx->pos == 1) {
+			ret = hpfs_add_pos(inode, &file->f_pos);
+			if (unlikely(ret < 0))
+				goto out;
+			ctx->pos = ((loff_t) hpfs_de_as_down_as_possible(inode->i_sb, hpfs_inode->i_dno) << 4) + 1;
+		}
+		next_pos = ctx->pos;
+		if (!(de = map_pos_dirent(inode, &next_pos, &qbh))) {
+			ctx->pos = next_pos;
+			ret = -EIOERROR;
+			goto out;
+		}
+		if (de->first || de->last) {
+			if (hpfs_sb(inode->i_sb)->sb_chk) {
+				if (de->first && !de->last && (de->namelen != 2
+				    || de ->name[0] != 1 || de->name[1] != 1))
+					hpfs_error(inode->i_sb, "hpfs_readdir: bad ^A^A entry; pos = %08lx", (unsigned long)ctx->pos);
+				if (de->last && (de->namelen != 1 || de ->name[0] != 255))
+					hpfs_error(inode->i_sb, "hpfs_readdir: bad \\377 entry; pos = %08lx", (unsigned long)ctx->pos);
+			}
+			hpfs_brelse4(&qbh);
+			ctx->pos = next_pos;
+			goto again;
+		}
+		tempname = hpfs_translate_name(inode->i_sb, de->name, de->namelen, lc, de->not_8x3);
+		if (!dir_emit(ctx, tempname, de->namelen, le32_to_cpu(de->fnode), DT_UNKNOWN)) {
+			if (tempname != de->name) kfree(tempname);
+			hpfs_brelse4(&qbh);
+			goto out;
+		}
+		ctx->pos = next_pos;
+		if (tempname != de->name) kfree(tempname);
+		hpfs_brelse4(&qbh);
+	}
+out:
+	hpfs_unlock(inode->i_sb);
+	return ret;
+}
+
+/*
+ * lookup.  Search the specified directory for the specified name, set
+ * *result to the corresponding inode.
+ *
+ * lookup uses the inode number to tell read_inode whether it is reading
+ * the inode of a directory or a file -- file ino's are odd, directory
+ * ino's are even.  read_inode avoids i/o for file inodes; everything
+ * needed is up here in the directory.  (And file fnodes are out in
+ * the boondocks.)
+ *
+ *    - M.P.: this is over, sometimes we've got to read file's fnode for eas
+ *	      inode numbers are just fnode sector numbers; iget lock is used
+ *	      to tell read_inode to read fnode or not.
+ */
+
+struct dentry *hpfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	const unsigned char *name = dentry->d_name.name;
+	unsigned len = dentry->d_name.len;
+	struct quad_buffer_head qbh;
+	struct hpfs_dirent *de;
+	ino_t ino;
+	int err;
+	struct inode *result = NULL;
+	struct hpfs_inode_info *hpfs_result;
+
+	hpfs_lock(dir->i_sb);
+	if ((err = hpfs_chk_name(name, &len))) {
+		if (err == -ENAMETOOLONG) {
+			hpfs_unlock(dir->i_sb);
+			return ERR_PTR(-ENAMETOOLONG);
+		}
+		goto end_add;
+	}
+
+	/*
+	 * '.' and '..' will never be passed here.
+	 */
+
+	de = map_dirent(dir, hpfs_i(dir)->i_dno, name, len, NULL, &qbh);
+
+	/*
+	 * This is not really a bailout, just means file not found.
+	 */
+
+	if (!de) goto end;
+
+	/*
+	 * Get inode number, what we're after.
+	 */
+
+	ino = le32_to_cpu(de->fnode);
+
+	/*
+	 * Go find or make an inode.
+	 */
+
+	result = iget_locked(dir->i_sb, ino);
+	if (!result) {
+		hpfs_error(dir->i_sb, "hpfs_lookup: can't get inode");
+		result = ERR_PTR(-ENOMEM);
+		goto bail1;
+	}
+	if (inode_state_read_once(result) & I_NEW) {
+		hpfs_init_inode(result);
+		if (de->directory)
+			hpfs_read_inode(result);
+		else if (le32_to_cpu(de->ea_size) && hpfs_sb(dir->i_sb)->sb_eas)
+			hpfs_read_inode(result);
+		else {
+			result->i_mode |= S_IFREG;
+			result->i_mode &= ~0111;
+			result->i_op = &hpfs_file_iops;
+			result->i_fop = &hpfs_file_ops;
+			set_nlink(result, 1);
+		}
+		unlock_new_inode(result);
+	}
+	hpfs_result = hpfs_i(result);
+	if (!de->directory) hpfs_result->i_parent_dir = dir->i_ino;
+
+	if (de->has_acl || de->has_xtd_perm) if (!sb_rdonly(dir->i_sb)) {
+		hpfs_error(result->i_sb, "ACLs or XPERM found. This is probably HPFS386. This driver doesn't support it now. Send me some info on these structures");
+		iput(result);
+		result = ERR_PTR(-EINVAL);
+		goto bail1;
+	}
+
+	/*
+	 * Fill in the info from the directory if this is a newly created
+	 * inode.
+	 */
+
+	if (!inode_get_ctime_sec(result)) {
+		time64_t csec = local_to_gmt(dir->i_sb, le32_to_cpu(de->creation_date));
+
+		inode_set_ctime(result, csec ? csec : 1, 0);
+		inode_set_mtime(result,
+				local_to_gmt(dir->i_sb, le32_to_cpu(de->write_date)),
+				0);
+		inode_set_atime(result,
+				local_to_gmt(dir->i_sb, le32_to_cpu(de->read_date)),
+				0);
+		hpfs_result->i_ea_size = le32_to_cpu(de->ea_size);
+		if (!hpfs_result->i_ea_mode && de->read_only)
+			result->i_mode &= ~0222;
+		if (!de->directory) {
+			if (result->i_size == -1) {
+				result->i_size = le32_to_cpu(de->file_size);
+				result->i_data.a_ops = &hpfs_aops;
+				hpfs_i(result)->mmu_private = result->i_size;
+			/*
+			 * i_blocks should count the fnode and any anodes.
+			 * We count 1 for the fnode and don't bother about
+			 * anodes -- the disk heads are on the directory band
+			 * and we want them to stay there.
+			 */
+				result->i_blocks = 1 + ((result->i_size + 511) >> 9);
+			}
+		}
+	}
+
+bail1:
+	hpfs_brelse4(&qbh);
+
+	/*
+	 * Made it.
+	 */
+
+end:
+end_add:
+	hpfs_unlock(dir->i_sb);
+	return d_splice_alias(result, dentry);
+}
+
+const struct file_operations hpfs_dir_ops =
+{
+	.llseek		= hpfs_dir_lseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= hpfs_readdir,
+	.release	= hpfs_dir_release,
+	.fsync		= hpfs_file_fsync,
+	.unlocked_ioctl	= hpfs_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+};