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, 259 insertions, 0 deletions

diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
new file mode 100644
index 000000000..85d3dd48b
--- /dev/null
+++ b/fs/ceph/acl.c
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/fs/ceph/acl.c
+ *
+ * Copyright (C) 2013 Guangliang Zhao, <lucienchao@gmail.com>
+ */
+
+#include <linux/ceph/ceph_debug.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/posix_acl.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "super.h"
+#include "mds_client.h"
+
+static inline void ceph_set_cached_acl(struct inode *inode,
+					int type, struct posix_acl *acl)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+
+	spin_lock(&ci->i_ceph_lock);
+	if (__ceph_caps_issued_mask_metric(ci, CEPH_CAP_XATTR_SHARED, 0))
+		set_cached_acl(inode, type, acl);
+	else
+		forget_cached_acl(inode, type);
+	spin_unlock(&ci->i_ceph_lock);
+}
+
+struct posix_acl *ceph_get_acl(struct inode *inode, int type, bool rcu)
+{
+	struct ceph_client *cl = ceph_inode_to_client(inode);
+	int size;
+	unsigned int retry_cnt = 0;
+	const char *name;
+	char *value = NULL;
+	struct posix_acl *acl;
+
+	if (rcu)
+		return ERR_PTR(-ECHILD);
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		name = XATTR_NAME_POSIX_ACL_ACCESS;
+		break;
+	case ACL_TYPE_DEFAULT:
+		name = XATTR_NAME_POSIX_ACL_DEFAULT;
+		break;
+	default:
+		BUG();
+	}
+
+retry:
+	size = __ceph_getxattr(inode, name, "", 0);
+	if (size > 0) {
+		value = kzalloc(size, GFP_NOFS);
+		if (!value)
+			return ERR_PTR(-ENOMEM);
+		size = __ceph_getxattr(inode, name, value, size);
+	}
+
+	if (size == -ERANGE && retry_cnt < 10) {
+		retry_cnt++;
+		kfree(value);
+		value = NULL;
+		goto retry;
+	}
+
+	if (size > 0) {
+		acl = posix_acl_from_xattr(&init_user_ns, value, size);
+	} else if (size == -ENODATA || size == 0) {
+		acl = NULL;
+	} else {
+		pr_err_ratelimited_client(cl, "%llx.%llx failed, err=%d\n",
+					  ceph_vinop(inode), size);
+		acl = ERR_PTR(-EIO);
+	}
+
+	kfree(value);
+
+	if (!IS_ERR(acl))
+		ceph_set_cached_acl(inode, type, acl);
+
+	return acl;
+}
+
+int ceph_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+		 struct posix_acl *acl, int type)
+{
+	int ret = 0;
+	size_t size = 0;
+	const char *name = NULL;
+	char *value = NULL;
+	struct iattr newattrs;
+	struct inode *inode = d_inode(dentry);
+	struct timespec64 old_ctime = inode_get_ctime(inode);
+	umode_t new_mode = inode->i_mode, old_mode = inode->i_mode;
+
+	if (ceph_snap(inode) != CEPH_NOSNAP) {
+		ret = -EROFS;
+		goto out;
+	}
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		name = XATTR_NAME_POSIX_ACL_ACCESS;
+		if (acl) {
+			ret = posix_acl_update_mode(idmap, inode,
+						    &new_mode, &acl);
+			if (ret)
+				goto out;
+		}
+		break;
+	case ACL_TYPE_DEFAULT:
+		if (!S_ISDIR(inode->i_mode)) {
+			ret = acl ? -EINVAL : 0;
+			goto out;
+		}
+		name = XATTR_NAME_POSIX_ACL_DEFAULT;
+		break;
+	default:
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (acl) {
+		value = posix_acl_to_xattr(&init_user_ns, acl, &size, GFP_NOFS);
+		if (!value) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	if (new_mode != old_mode) {
+		newattrs.ia_ctime = current_time(inode);
+		newattrs.ia_mode = new_mode;
+		newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
+		ret = __ceph_setattr(idmap, inode, &newattrs, NULL);
+		if (ret)
+			goto out_free;
+	}
+
+	ret = __ceph_setxattr(inode, name, value, size, 0);
+	if (ret) {
+		if (new_mode != old_mode) {
+			newattrs.ia_ctime = old_ctime;
+			newattrs.ia_mode = old_mode;
+			newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
+			__ceph_setattr(idmap, inode, &newattrs, NULL);
+		}
+		goto out_free;
+	}
+
+	ceph_set_cached_acl(inode, type, acl);
+
+out_free:
+	kfree(value);
+out:
+	return ret;
+}
+
+int ceph_pre_init_acls(struct inode *dir, umode_t *mode,
+		       struct ceph_acl_sec_ctx *as_ctx)
+{
+	struct posix_acl *acl, *default_acl;
+	size_t val_size1 = 0, val_size2 = 0;
+	struct ceph_pagelist *pagelist = NULL;
+	void *tmp_buf1 = NULL, *tmp_buf2 = NULL;
+	int err;
+
+	err = posix_acl_create(dir, mode, &default_acl, &acl);
+	if (err)
+		return err;
+
+	if (acl) {
+		err = posix_acl_equiv_mode(acl, mode);
+		if (err < 0)
+			goto out_err;
+		if (err == 0) {
+			posix_acl_release(acl);
+			acl = NULL;
+		}
+	}
+
+	if (!default_acl && !acl)
+		return 0;
+
+	err = -ENOMEM;
+	pagelist = ceph_pagelist_alloc(GFP_KERNEL);
+	if (!pagelist)
+		goto out_err;
+
+	err = ceph_pagelist_reserve(pagelist, PAGE_SIZE);
+	if (err)
+		goto out_err;
+
+	ceph_pagelist_encode_32(pagelist, acl && default_acl ? 2 : 1);
+
+	if (acl) {
+		size_t len = strlen(XATTR_NAME_POSIX_ACL_ACCESS);
+
+		err = -ENOMEM;
+		tmp_buf1 = posix_acl_to_xattr(&init_user_ns, acl,
+					      &val_size1, GFP_KERNEL);
+		if (!tmp_buf1)
+			goto out_err;
+		err = ceph_pagelist_reserve(pagelist, len + val_size1 + 8);
+		if (err)
+			goto out_err;
+		ceph_pagelist_encode_string(pagelist, XATTR_NAME_POSIX_ACL_ACCESS,
+					    len);
+		ceph_pagelist_encode_32(pagelist, val_size1);
+		ceph_pagelist_append(pagelist, tmp_buf1, val_size1);
+	}
+	if (default_acl) {
+		size_t len = strlen(XATTR_NAME_POSIX_ACL_DEFAULT);
+
+		err = -ENOMEM;
+		tmp_buf2 = posix_acl_to_xattr(&init_user_ns, default_acl,
+					      &val_size2, GFP_KERNEL);
+		if (!tmp_buf2)
+			goto out_err;
+		err = ceph_pagelist_reserve(pagelist, len + val_size2 + 8);
+		if (err)
+			goto out_err;
+		ceph_pagelist_encode_string(pagelist,
+					  XATTR_NAME_POSIX_ACL_DEFAULT, len);
+		ceph_pagelist_encode_32(pagelist, val_size2);
+		ceph_pagelist_append(pagelist, tmp_buf2, val_size2);
+	}
+
+	kfree(tmp_buf1);
+	kfree(tmp_buf2);
+
+	as_ctx->acl = acl;
+	as_ctx->default_acl = default_acl;
+	as_ctx->pagelist = pagelist;
+	return 0;
+
+out_err:
+	posix_acl_release(acl);
+	posix_acl_release(default_acl);
+	kfree(tmp_buf1);
+	kfree(tmp_buf2);
+	if (pagelist)
+		ceph_pagelist_release(pagelist);
+	return err;
+}
+
+void ceph_init_inode_acls(struct inode *inode, struct ceph_acl_sec_ctx *as_ctx)
+{
+	if (!inode)
+		return;
+	ceph_set_cached_acl(inode, ACL_TYPE_ACCESS, as_ctx->acl);
+	ceph_set_cached_acl(inode, ACL_TYPE_DEFAULT, as_ctx->default_acl);
+}