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, 271 insertions, 0 deletions

diff --git a/security/tomoyo/securityfs_if.c b/security/tomoyo/securityfs_if.c
new file mode 100644
index 000000000..33933645f
--- /dev/null
+++ b/security/tomoyo/securityfs_if.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * security/tomoyo/securityfs_if.c
+ *
+ * Copyright (C) 2005-2011  NTT DATA CORPORATION
+ */
+
+#include <linux/security.h>
+#include "common.h"
+
+/**
+ * tomoyo_check_task_acl - Check permission for task operation.
+ *
+ * @r:   Pointer to "struct tomoyo_request_info".
+ * @ptr: Pointer to "struct tomoyo_acl_info".
+ *
+ * Returns true if granted, false otherwise.
+ */
+static bool tomoyo_check_task_acl(struct tomoyo_request_info *r,
+				  const struct tomoyo_acl_info *ptr)
+{
+	const struct tomoyo_task_acl *acl = container_of(ptr, typeof(*acl),
+							 head);
+
+	return !tomoyo_pathcmp(r->param.task.domainname, acl->domainname);
+}
+
+/**
+ * tomoyo_write_self - write() for /sys/kernel/security/tomoyo/self_domain interface.
+ *
+ * @file:  Pointer to "struct file".
+ * @buf:   Domainname to transit to.
+ * @count: Size of @buf.
+ * @ppos:  Unused.
+ *
+ * Returns @count on success, negative value otherwise.
+ *
+ * If domain transition was permitted but the domain transition failed, this
+ * function returns error rather than terminating current thread with SIGKILL.
+ */
+static ssize_t tomoyo_write_self(struct file *file, const char __user *buf,
+			      size_t count, loff_t *ppos)
+{
+	char *data;
+	int error;
+
+	if (!count || count >= TOMOYO_EXEC_TMPSIZE - 10)
+		return -ENOMEM;
+	data = memdup_user_nul(buf, count);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+	tomoyo_normalize_line(data);
+	if (tomoyo_correct_domain(data)) {
+		const int idx = tomoyo_read_lock();
+		struct tomoyo_path_info name;
+		struct tomoyo_request_info r;
+
+		name.name = data;
+		tomoyo_fill_path_info(&name);
+		/* Check "task manual_domain_transition" permission. */
+		tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_EXECUTE);
+		r.param_type = TOMOYO_TYPE_MANUAL_TASK_ACL;
+		r.param.task.domainname = &name;
+		tomoyo_check_acl(&r, tomoyo_check_task_acl);
+		if (!r.granted)
+			error = -EPERM;
+		else {
+			struct tomoyo_domain_info *new_domain =
+				tomoyo_assign_domain(data, true);
+			if (!new_domain) {
+				error = -ENOENT;
+			} else {
+				struct tomoyo_task *s = tomoyo_task(current);
+				struct tomoyo_domain_info *old_domain =
+					s->domain_info;
+
+				s->domain_info = new_domain;
+				atomic_inc(&new_domain->users);
+				atomic_dec(&old_domain->users);
+				error = 0;
+			}
+		}
+		tomoyo_read_unlock(idx);
+	} else
+		error = -EINVAL;
+	kfree(data);
+	return error ? error : count;
+}
+
+/**
+ * tomoyo_read_self - read() for /sys/kernel/security/tomoyo/self_domain interface.
+ *
+ * @file:  Pointer to "struct file".
+ * @buf:   Domainname which current thread belongs to.
+ * @count: Size of @buf.
+ * @ppos:  Bytes read by now.
+ *
+ * Returns read size on success, negative value otherwise.
+ */
+static ssize_t tomoyo_read_self(struct file *file, char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	const char *domain = tomoyo_domain()->domainname->name;
+	loff_t len = strlen(domain);
+	loff_t pos = *ppos;
+
+	if (pos >= len || !count)
+		return 0;
+	len -= pos;
+	if (count < len)
+		len = count;
+	if (copy_to_user(buf, domain + pos, len))
+		return -EFAULT;
+	*ppos += len;
+	return len;
+}
+
+/* Operations for /sys/kernel/security/tomoyo/self_domain interface. */
+static const struct file_operations tomoyo_self_operations = {
+	.write = tomoyo_write_self,
+	.read  = tomoyo_read_self,
+};
+
+/**
+ * tomoyo_open - open() for /sys/kernel/security/tomoyo/ interface.
+ *
+ * @inode: Pointer to "struct inode".
+ * @file:  Pointer to "struct file".
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+static int tomoyo_open(struct inode *inode, struct file *file)
+{
+	const u8 key = (uintptr_t) file_inode(file)->i_private;
+
+	return tomoyo_open_control(key, file);
+}
+
+/**
+ * tomoyo_release - close() for /sys/kernel/security/tomoyo/ interface.
+ *
+ * @inode: Pointer to "struct inode".
+ * @file:  Pointer to "struct file".
+ *
+ */
+static int tomoyo_release(struct inode *inode, struct file *file)
+{
+	tomoyo_close_control(file->private_data);
+	return 0;
+}
+
+/**
+ * tomoyo_poll - poll() for /sys/kernel/security/tomoyo/ interface.
+ *
+ * @file: Pointer to "struct file".
+ * @wait: Pointer to "poll_table". Maybe NULL.
+ *
+ * Returns EPOLLIN | EPOLLRDNORM | EPOLLOUT | EPOLLWRNORM if ready to read/write,
+ * EPOLLOUT | EPOLLWRNORM otherwise.
+ */
+static __poll_t tomoyo_poll(struct file *file, poll_table *wait)
+{
+	return tomoyo_poll_control(file, wait);
+}
+
+/**
+ * tomoyo_read - read() for /sys/kernel/security/tomoyo/ interface.
+ *
+ * @file:  Pointer to "struct file".
+ * @buf:   Pointer to buffer.
+ * @count: Size of @buf.
+ * @ppos:  Unused.
+ *
+ * Returns bytes read on success, negative value otherwise.
+ */
+static ssize_t tomoyo_read(struct file *file, char __user *buf, size_t count,
+			   loff_t *ppos)
+{
+	return tomoyo_read_control(file->private_data, buf, count);
+}
+
+/**
+ * tomoyo_write - write() for /sys/kernel/security/tomoyo/ interface.
+ *
+ * @file:  Pointer to "struct file".
+ * @buf:   Pointer to buffer.
+ * @count: Size of @buf.
+ * @ppos:  Unused.
+ *
+ * Returns @count on success, negative value otherwise.
+ */
+static ssize_t tomoyo_write(struct file *file, const char __user *buf,
+			    size_t count, loff_t *ppos)
+{
+	return tomoyo_write_control(file->private_data, buf, count);
+}
+
+/*
+ * tomoyo_operations is a "struct file_operations" which is used for handling
+ * /sys/kernel/security/tomoyo/ interface.
+ *
+ * Some files under /sys/kernel/security/tomoyo/ directory accept open(O_RDWR).
+ * See tomoyo_io_buffer for internals.
+ */
+static const struct file_operations tomoyo_operations = {
+	.open    = tomoyo_open,
+	.release = tomoyo_release,
+	.poll    = tomoyo_poll,
+	.read    = tomoyo_read,
+	.write   = tomoyo_write,
+	.llseek  = noop_llseek,
+};
+
+/**
+ * tomoyo_create_entry - Create interface files under /sys/kernel/security/tomoyo/ directory.
+ *
+ * @name:   The name of the interface file.
+ * @mode:   The permission of the interface file.
+ * @parent: The parent directory.
+ * @key:    Type of interface.
+ *
+ * Returns nothing.
+ */
+static void __init tomoyo_create_entry(const char *name, const umode_t mode,
+				       struct dentry *parent, const u8 key)
+{
+	securityfs_create_file(name, mode, parent, (void *) (uintptr_t) key,
+			       &tomoyo_operations);
+}
+
+/**
+ * tomoyo_interface_init - Initialize /sys/kernel/security/tomoyo/ interface.
+ *
+ * Returns 0.
+ */
+int __init tomoyo_interface_init(void)
+{
+	struct tomoyo_domain_info *domain;
+	struct dentry *tomoyo_dir;
+
+	if (!tomoyo_enabled)
+		return 0;
+	domain = tomoyo_domain();
+	/* Don't create securityfs entries unless registered. */
+	if (domain != &tomoyo_kernel_domain)
+		return 0;
+
+	tomoyo_dir = securityfs_create_dir("tomoyo", NULL);
+	tomoyo_create_entry("query",            0600, tomoyo_dir,
+			    TOMOYO_QUERY);
+	tomoyo_create_entry("domain_policy",    0600, tomoyo_dir,
+			    TOMOYO_DOMAINPOLICY);
+	tomoyo_create_entry("exception_policy", 0600, tomoyo_dir,
+			    TOMOYO_EXCEPTIONPOLICY);
+	tomoyo_create_entry("audit",            0400, tomoyo_dir,
+			    TOMOYO_AUDIT);
+	tomoyo_create_entry(".process_status",  0600, tomoyo_dir,
+			    TOMOYO_PROCESS_STATUS);
+	tomoyo_create_entry("stat",             0644, tomoyo_dir,
+			    TOMOYO_STAT);
+	tomoyo_create_entry("profile",          0600, tomoyo_dir,
+			    TOMOYO_PROFILE);
+	tomoyo_create_entry("manager",          0600, tomoyo_dir,
+			    TOMOYO_MANAGER);
+	tomoyo_create_entry("version",          0400, tomoyo_dir,
+			    TOMOYO_VERSION);
+	securityfs_create_file("self_domain", 0666, tomoyo_dir, NULL,
+			       &tomoyo_self_operations);
+	tomoyo_load_builtin_policy();
+	return 0;
+}