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, 368 insertions, 0 deletions

diff --git a/fs/hpfs/ea.c b/fs/hpfs/ea.c
new file mode 100644
index 000000000..4664f9ab0
--- /dev/null
+++ b/fs/hpfs/ea.c
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/hpfs/ea.c
+ *
+ *  Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999
+ *
+ *  handling extended attributes
+ */
+
+#include "hpfs_fn.h"
+
+/* Remove external extended attributes. ano specifies whether a is a 
+   direct sector where eas starts or an anode */
+
+void hpfs_ea_ext_remove(struct super_block *s, secno a, int ano, unsigned len)
+{
+	unsigned pos = 0;
+	while (pos < len) {
+		char ex[4 + 255 + 1 + 8];
+		struct extended_attribute *ea = (struct extended_attribute *)ex;
+		if (pos + 4 > len) {
+			hpfs_error(s, "EAs don't end correctly, %s %08x, len %08x",
+				ano ? "anode" : "sectors", a, len);
+			return;
+		}
+		if (hpfs_ea_read(s, a, ano, pos, 4, ex)) return;
+		if (ea_indirect(ea)) {
+			if (ea_valuelen(ea) != 8) {
+				hpfs_error(s, "ea_indirect(ea) set while ea->valuelen!=8, %s %08x, pos %08x",
+					ano ? "anode" : "sectors", a, pos);
+				return;
+			}
+			if (hpfs_ea_read(s, a, ano, pos + 4, ea->namelen + 9, ex+4))
+				return;
+			hpfs_ea_remove(s, ea_sec(ea), ea_in_anode(ea), ea_len(ea));
+		}
+		pos += ea->namelen + ea_valuelen(ea) + 5;
+	}
+	if (!ano) hpfs_free_sectors(s, a, (len+511) >> 9);
+	else {
+		struct buffer_head *bh;
+		struct anode *anode;
+		if ((anode = hpfs_map_anode(s, a, &bh))) {
+			hpfs_remove_btree(s, GET_BTREE_PTR(&anode->btree));
+			brelse(bh);
+			hpfs_free_sectors(s, a, 1);
+		}
+	}
+}
+
+static char *get_indirect_ea(struct super_block *s, int ano, secno a, int size)
+{
+	char *ret;
+	if (!(ret = kmalloc(size + 1, GFP_NOFS))) {
+		pr_err("out of memory for EA\n");
+		return NULL;
+	}
+	if (hpfs_ea_read(s, a, ano, 0, size, ret)) {
+		kfree(ret);
+		return NULL;
+	}
+	ret[size] = 0;
+	return ret;
+}
+
+static void set_indirect_ea(struct super_block *s, int ano, secno a,
+			    const char *data, int size)
+{
+	hpfs_ea_write(s, a, ano, 0, size, data);
+}
+
+/* Read an extended attribute named 'key' into the provided buffer */
+
+int hpfs_read_ea(struct super_block *s, struct fnode *fnode, char *key,
+		char *buf, int size)
+{
+	unsigned pos;
+	int ano, len;
+	secno a;
+	char ex[4 + 255 + 1 + 8];
+	struct extended_attribute *ea;
+	struct extended_attribute *ea_end = fnode_end_ea(fnode);
+	for (ea = fnode_ea(fnode); ea < ea_end; ea = next_ea(ea))
+		if (!strcmp(ea->name, key)) {
+			if (ea_indirect(ea))
+				goto indirect;
+			if (ea_valuelen(ea) >= size)
+				return -EINVAL;
+			memcpy(buf, ea_data(ea), ea_valuelen(ea));
+			buf[ea_valuelen(ea)] = 0;
+			return 0;
+		}
+	a = le32_to_cpu(fnode->ea_secno);
+	len = le32_to_cpu(fnode->ea_size_l);
+	ano = fnode_in_anode(fnode);
+	pos = 0;
+	while (pos < len) {
+		ea = (struct extended_attribute *)ex;
+		if (pos + 4 > len) {
+			hpfs_error(s, "EAs don't end correctly, %s %08x, len %08x",
+				ano ? "anode" : "sectors", a, len);
+			return -EIO;
+		}
+		if (hpfs_ea_read(s, a, ano, pos, 4, ex)) return -EIO;
+		if (hpfs_ea_read(s, a, ano, pos + 4, ea->namelen + 1 + (ea_indirect(ea) ? 8 : 0), ex + 4))
+			return -EIO;
+		if (!strcmp(ea->name, key)) {
+			if (ea_indirect(ea))
+				goto indirect;
+			if (ea_valuelen(ea) >= size)
+				return -EINVAL;
+			if (hpfs_ea_read(s, a, ano, pos + 4 + ea->namelen + 1, ea_valuelen(ea), buf))
+				return -EIO;
+			buf[ea_valuelen(ea)] = 0;
+			return 0;
+		}
+		pos += ea->namelen + ea_valuelen(ea) + 5;
+	}
+	return -ENOENT;
+indirect:
+	if (ea_len(ea) >= size)
+		return -EINVAL;
+	if (hpfs_ea_read(s, ea_sec(ea), ea_in_anode(ea), 0, ea_len(ea), buf))
+		return -EIO;
+	buf[ea_len(ea)] = 0;
+	return 0;
+}
+
+/* Read an extended attribute named 'key' */
+char *hpfs_get_ea(struct super_block *s, struct fnode *fnode, char *key, int *size)
+{
+	char *ret;
+	unsigned pos;
+	int ano, len;
+	secno a;
+	struct extended_attribute *ea;
+	struct extended_attribute *ea_end = fnode_end_ea(fnode);
+	for (ea = fnode_ea(fnode); ea < ea_end; ea = next_ea(ea))
+		if (!strcmp(ea->name, key)) {
+			if (ea_indirect(ea))
+				return get_indirect_ea(s, ea_in_anode(ea), ea_sec(ea), *size = ea_len(ea));
+			if (!(ret = kmalloc((*size = ea_valuelen(ea)) + 1, GFP_NOFS))) {
+				pr_err("out of memory for EA\n");
+				return NULL;
+			}
+			memcpy(ret, ea_data(ea), ea_valuelen(ea));
+			ret[ea_valuelen(ea)] = 0;
+			return ret;
+		}
+	a = le32_to_cpu(fnode->ea_secno);
+	len = le32_to_cpu(fnode->ea_size_l);
+	ano = fnode_in_anode(fnode);
+	pos = 0;
+	while (pos < len) {
+		char ex[4 + 255 + 1 + 8];
+		ea = (struct extended_attribute *)ex;
+		if (pos + 4 > len) {
+			hpfs_error(s, "EAs don't end correctly, %s %08x, len %08x",
+				ano ? "anode" : "sectors", a, len);
+			return NULL;
+		}
+		if (hpfs_ea_read(s, a, ano, pos, 4, ex)) return NULL;
+		if (hpfs_ea_read(s, a, ano, pos + 4, ea->namelen + 1 + (ea_indirect(ea) ? 8 : 0), ex + 4))
+			return NULL;
+		if (!strcmp(ea->name, key)) {
+			if (ea_indirect(ea))
+				return get_indirect_ea(s, ea_in_anode(ea), ea_sec(ea), *size = ea_len(ea));
+			if (!(ret = kmalloc((*size = ea_valuelen(ea)) + 1, GFP_NOFS))) {
+				pr_err("out of memory for EA\n");
+				return NULL;
+			}
+			if (hpfs_ea_read(s, a, ano, pos + 4 + ea->namelen + 1, ea_valuelen(ea), ret)) {
+				kfree(ret);
+				return NULL;
+			}
+			ret[ea_valuelen(ea)] = 0;
+			return ret;
+		}
+		pos += ea->namelen + ea_valuelen(ea) + 5;
+	}
+	return NULL;
+}
+
+/* 
+ * Update or create extended attribute 'key' with value 'data'. Note that
+ * when this ea exists, it MUST have the same size as size of data.
+ * This driver can't change sizes of eas ('cause I just don't need it).
+ */
+
+void hpfs_set_ea(struct inode *inode, struct fnode *fnode, const char *key,
+		 const char *data, int size)
+{
+	fnode_secno fno = inode->i_ino;
+	struct super_block *s = inode->i_sb;
+	unsigned pos;
+	int ano, len;
+	secno a;
+	unsigned char h[4];
+	struct extended_attribute *ea;
+	struct extended_attribute *ea_end = fnode_end_ea(fnode);
+	for (ea = fnode_ea(fnode); ea < ea_end; ea = next_ea(ea))
+		if (!strcmp(ea->name, key)) {
+			if (ea_indirect(ea)) {
+				if (ea_len(ea) == size)
+					set_indirect_ea(s, ea_in_anode(ea), ea_sec(ea), data, size);
+			} else if (ea_valuelen(ea) == size) {
+				memcpy(ea_data(ea), data, size);
+			}
+			return;
+		}
+	a = le32_to_cpu(fnode->ea_secno);
+	len = le32_to_cpu(fnode->ea_size_l);
+	ano = fnode_in_anode(fnode);
+	pos = 0;
+	while (pos < len) {
+		char ex[4 + 255 + 1 + 8];
+		ea = (struct extended_attribute *)ex;
+		if (pos + 4 > len) {
+			hpfs_error(s, "EAs don't end correctly, %s %08x, len %08x",
+				ano ? "anode" : "sectors", a, len);
+			return;
+		}
+		if (hpfs_ea_read(s, a, ano, pos, 4, ex)) return;
+		if (hpfs_ea_read(s, a, ano, pos + 4, ea->namelen + 1 + (ea_indirect(ea) ? 8 : 0), ex + 4))
+			return;
+		if (!strcmp(ea->name, key)) {
+			if (ea_indirect(ea)) {
+				if (ea_len(ea) == size)
+					set_indirect_ea(s, ea_in_anode(ea), ea_sec(ea), data, size);
+			}
+			else {
+				if (ea_valuelen(ea) == size)
+					hpfs_ea_write(s, a, ano, pos + 4 + ea->namelen + 1, size, data);
+			}
+			return;
+		}
+		pos += ea->namelen + ea_valuelen(ea) + 5;
+	}
+	if (!le16_to_cpu(fnode->ea_offs)) {
+		/*if (le16_to_cpu(fnode->ea_size_s)) {
+			hpfs_error(s, "fnode %08x: ea_size_s == %03x, ea_offs == 0",
+				inode->i_ino, le16_to_cpu(fnode->ea_size_s));
+			return;
+		}*/
+		fnode->ea_offs = cpu_to_le16(0xc4);
+	}
+	if (le16_to_cpu(fnode->ea_offs) < 0xc4 || le16_to_cpu(fnode->ea_offs) + le16_to_cpu(fnode->acl_size_s) + le16_to_cpu(fnode->ea_size_s) > 0x200) {
+		hpfs_error(s, "fnode %08llx: ea_offs == %03x, ea_size_s == %03x",
+			inode->i_ino,
+			le16_to_cpu(fnode->ea_offs), le16_to_cpu(fnode->ea_size_s));
+		return;
+	}
+	if ((le16_to_cpu(fnode->ea_size_s) || !le32_to_cpu(fnode->ea_size_l)) &&
+	     le16_to_cpu(fnode->ea_offs) + le16_to_cpu(fnode->acl_size_s) + le16_to_cpu(fnode->ea_size_s) + strlen(key) + size + 5 <= 0x200) {
+		ea = fnode_end_ea(fnode);
+		*(char *)ea = 0;
+		ea->namelen = strlen(key);
+		ea->valuelen_lo = size;
+		ea->valuelen_hi = size >> 8;
+		strcpy(ea->name, key);
+		memcpy(ea_data(ea), data, size);
+		fnode->ea_size_s = cpu_to_le16(le16_to_cpu(fnode->ea_size_s) + strlen(key) + size + 5);
+		goto ret;
+	}
+	/* Most the code here is 99.9993422% unused. I hope there are no bugs.
+	   But what .. HPFS.IFS has also bugs in ea management. */
+	if (le16_to_cpu(fnode->ea_size_s) && !le32_to_cpu(fnode->ea_size_l)) {
+		secno n;
+		struct buffer_head *bh;
+		char *data;
+		if (!(n = hpfs_alloc_sector(s, fno, 1, 0))) return;
+		if (!(data = hpfs_get_sector(s, n, &bh))) {
+			hpfs_free_sectors(s, n, 1);
+			return;
+		}
+		memcpy(data, fnode_ea(fnode), le16_to_cpu(fnode->ea_size_s));
+		fnode->ea_size_l = cpu_to_le32(le16_to_cpu(fnode->ea_size_s));
+		fnode->ea_size_s = cpu_to_le16(0);
+		fnode->ea_secno = cpu_to_le32(n);
+		fnode->flags &= ~FNODE_anode;
+		mark_buffer_dirty(bh);
+		brelse(bh);
+	}
+	pos = le32_to_cpu(fnode->ea_size_l) + 5 + strlen(key) + size;
+	len = (le32_to_cpu(fnode->ea_size_l) + 511) >> 9;
+	if (pos >= 30000) goto bail;
+	while (((pos + 511) >> 9) > len) {
+		if (!len) {
+			secno q = hpfs_alloc_sector(s, fno, 1, 0);
+			if (!q) goto bail;
+			fnode->ea_secno = cpu_to_le32(q);
+			fnode->flags &= ~FNODE_anode;
+			len++;
+		} else if (!fnode_in_anode(fnode)) {
+			if (hpfs_alloc_if_possible(s, le32_to_cpu(fnode->ea_secno) + len)) {
+				len++;
+			} else {
+				/* Aargh... don't know how to create ea anodes :-( */
+				/*struct buffer_head *bh;
+				struct anode *anode;
+				anode_secno a_s;
+				if (!(anode = hpfs_alloc_anode(s, fno, &a_s, &bh)))
+					goto bail;
+				anode->up = cpu_to_le32(fno);
+				anode->btree.fnode_parent = 1;
+				anode->btree.n_free_nodes--;
+				anode->btree.n_used_nodes++;
+				anode->btree.first_free = cpu_to_le16(le16_to_cpu(anode->btree.first_free) + 12);
+				anode->u.external[0].disk_secno = cpu_to_le32(le32_to_cpu(fnode->ea_secno));
+				anode->u.external[0].file_secno = cpu_to_le32(0);
+				anode->u.external[0].length = cpu_to_le32(len);
+				mark_buffer_dirty(bh);
+				brelse(bh);
+				fnode->flags |= FNODE_anode;
+				fnode->ea_secno = cpu_to_le32(a_s);*/
+				secno new_sec;
+				int i;
+				if (!(new_sec = hpfs_alloc_sector(s, fno, 1, 1 - ((pos + 511) >> 9))))
+					goto bail;
+				for (i = 0; i < len; i++) {
+					struct buffer_head *bh1, *bh2;
+					void *b1, *b2;
+					if (!(b1 = hpfs_map_sector(s, le32_to_cpu(fnode->ea_secno) + i, &bh1, len - i - 1))) {
+						hpfs_free_sectors(s, new_sec, (pos + 511) >> 9);
+						goto bail;
+					}
+					if (!(b2 = hpfs_get_sector(s, new_sec + i, &bh2))) {
+						brelse(bh1);
+						hpfs_free_sectors(s, new_sec, (pos + 511) >> 9);
+						goto bail;
+					}
+					memcpy(b2, b1, 512);
+					brelse(bh1);
+					mark_buffer_dirty(bh2);
+					brelse(bh2);
+				}
+				hpfs_free_sectors(s, le32_to_cpu(fnode->ea_secno), len);
+				fnode->ea_secno = cpu_to_le32(new_sec);
+				len = (pos + 511) >> 9;
+			}
+		}
+		if (fnode_in_anode(fnode)) {
+			if (hpfs_add_sector_to_btree(s, le32_to_cpu(fnode->ea_secno),
+						     0, len) != -1) {
+				len++;
+			} else {
+				goto bail;
+			}
+		}
+	}
+	h[0] = 0;
+	h[1] = strlen(key);
+	h[2] = size & 0xff;
+	h[3] = size >> 8;
+	if (hpfs_ea_write(s, le32_to_cpu(fnode->ea_secno), fnode_in_anode(fnode), le32_to_cpu(fnode->ea_size_l), 4, h)) goto bail;
+	if (hpfs_ea_write(s, le32_to_cpu(fnode->ea_secno), fnode_in_anode(fnode), le32_to_cpu(fnode->ea_size_l) + 4, h[1] + 1, key)) goto bail;
+	if (hpfs_ea_write(s, le32_to_cpu(fnode->ea_secno), fnode_in_anode(fnode), le32_to_cpu(fnode->ea_size_l) + 5 + h[1], size, data)) goto bail;
+	fnode->ea_size_l = cpu_to_le32(pos);
+	ret:
+	hpfs_i(inode)->i_ea_size += 5 + strlen(key) + size;
+	return;
+	bail:
+	if (le32_to_cpu(fnode->ea_secno))
+		if (fnode_in_anode(fnode)) hpfs_truncate_btree(s, le32_to_cpu(fnode->ea_secno), 1, (le32_to_cpu(fnode->ea_size_l) + 511) >> 9);
+		else hpfs_free_sectors(s, le32_to_cpu(fnode->ea_secno) + ((le32_to_cpu(fnode->ea_size_l) + 511) >> 9), len - ((le32_to_cpu(fnode->ea_size_l) + 511) >> 9));
+	else fnode->ea_secno = fnode->ea_size_l = cpu_to_le32(0);
+}
+