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>

5 files changed, 676 insertions, 0 deletions

diff --git a/fs/ramfs/Makefile b/fs/ramfs/Makefile
new file mode 100644
index 000000000..d1198adb5
--- /dev/null
+++ b/fs/ramfs/Makefile
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the linux ramfs routines.
+#
+
+obj-y += ramfs.o
+
+file-mmu-y := file-nommu.o
+file-mmu-$(CONFIG_MMU) := file-mmu.o
+ramfs-objs += inode.o $(file-mmu-y)
diff --git a/fs/ramfs/file-mmu.c b/fs/ramfs/file-mmu.c
new file mode 100644
index 000000000..c3ed1c511
--- /dev/null
+++ b/fs/ramfs/file-mmu.c
@@ -0,0 +1,55 @@
+/* file-mmu.c: ramfs MMU-based file operations
+ *
+ * Resizable simple ram filesystem for Linux.
+ *
+ * Copyright (C) 2000 Linus Torvalds.
+ *               2000 Transmeta Corp.
+ *
+ * Usage limits added by David Gibson, Linuxcare Australia.
+ * This file is released under the GPL.
+ */
+
+/*
+ * NOTE! This filesystem is probably most useful
+ * not as a real filesystem, but as an example of
+ * how virtual filesystems can be written.
+ *
+ * It doesn't get much simpler than this. Consider
+ * that this file implements the full semantics of
+ * a POSIX-compliant read-write filesystem.
+ *
+ * Note in particular how the filesystem does not
+ * need to implement any data structures of its own
+ * to keep track of the virtual data: using the VFS
+ * caches is sufficient.
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/ramfs.h>
+#include <linux/sched.h>
+
+#include "internal.h"
+
+static unsigned long ramfs_mmu_get_unmapped_area(struct file *file,
+		unsigned long addr, unsigned long len, unsigned long pgoff,
+		unsigned long flags)
+{
+	return mm_get_unmapped_area(file, addr, len, pgoff, flags);
+}
+
+const struct file_operations ramfs_file_operations = {
+	.read_iter	= generic_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.mmap_prepare	= generic_file_mmap_prepare,
+	.fsync		= noop_fsync,
+	.splice_read	= filemap_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.llseek		= generic_file_llseek,
+	.get_unmapped_area	= ramfs_mmu_get_unmapped_area,
+};
+
+const struct inode_operations ramfs_file_inode_operations = {
+	.setattr	= simple_setattr,
+	.getattr	= simple_getattr,
+};
diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
new file mode 100644
index 000000000..2f79bcb89
--- /dev/null
+++ b/fs/ramfs/file-nommu.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* file-nommu.c: no-MMU version of ramfs
+ *
+ * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/backing-dev.h>
+#include <linux/ramfs.h>
+#include <linux/folio_batch.h>
+#include <linux/mman.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include <linux/uaccess.h>
+#include "internal.h"
+
+static int ramfs_nommu_setattr(struct mnt_idmap *, struct dentry *, struct iattr *);
+static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
+						   unsigned long addr,
+						   unsigned long len,
+						   unsigned long pgoff,
+						   unsigned long flags);
+static int ramfs_nommu_mmap_prepare(struct vm_area_desc *desc);
+
+static unsigned ramfs_mmap_capabilities(struct file *file)
+{
+	return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ |
+		NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
+}
+
+const struct file_operations ramfs_file_operations = {
+	.mmap_capabilities	= ramfs_mmap_capabilities,
+	.mmap_prepare		= ramfs_nommu_mmap_prepare,
+	.get_unmapped_area	= ramfs_nommu_get_unmapped_area,
+	.read_iter		= generic_file_read_iter,
+	.write_iter		= generic_file_write_iter,
+	.fsync			= noop_fsync,
+	.splice_read		= filemap_splice_read,
+	.splice_write		= iter_file_splice_write,
+	.llseek			= generic_file_llseek,
+};
+
+const struct inode_operations ramfs_file_inode_operations = {
+	.setattr		= ramfs_nommu_setattr,
+	.getattr		= simple_getattr,
+};
+
+/*****************************************************************************/
+/*
+ * add a contiguous set of pages into a ramfs inode when it's truncated from
+ * size 0 on the assumption that it's going to be used for an mmap of shared
+ * memory
+ */
+int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
+{
+	unsigned long npages, xpages, loop;
+	struct page *pages;
+	unsigned order;
+	void *data;
+	int ret;
+	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
+
+	/* make various checks */
+	order = get_order(newsize);
+	if (unlikely(order > MAX_PAGE_ORDER))
+		return -EFBIG;
+
+	ret = inode_newsize_ok(inode, newsize);
+	if (ret)
+		return ret;
+
+	i_size_write(inode, newsize);
+
+	/* allocate enough contiguous pages to be able to satisfy the
+	 * request */
+	pages = alloc_pages(gfp, order);
+	if (!pages)
+		return -ENOMEM;
+
+	/* split the high-order page into an array of single pages */
+	xpages = 1UL << order;
+	npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+	split_page(pages, order);
+
+	/* trim off any pages we don't actually require */
+	for (loop = npages; loop < xpages; loop++)
+		__free_page(pages + loop);
+
+	/* clear the memory we allocated */
+	newsize = PAGE_SIZE * npages;
+	data = page_address(pages);
+	memset(data, 0, newsize);
+
+	/* attach all the pages to the inode's address space */
+	for (loop = 0; loop < npages; loop++) {
+		struct page *page = pages + loop;
+
+		ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
+					gfp);
+		if (ret < 0)
+			goto add_error;
+
+		/* prevent the page from being discarded on memory pressure */
+		SetPageDirty(page);
+		SetPageUptodate(page);
+
+		unlock_page(page);
+		put_page(page);
+	}
+
+	return 0;
+
+add_error:
+	while (loop < npages)
+		__free_page(pages + loop++);
+	return ret;
+}
+
+/*****************************************************************************/
+/*
+ *
+ */
+static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
+{
+	int ret;
+
+	/* assume a truncate from zero size is going to be for the purposes of
+	 * shared mmap */
+	if (size == 0) {
+		if (unlikely(newsize >> 32))
+			return -EFBIG;
+
+		return ramfs_nommu_expand_for_mapping(inode, newsize);
+	}
+
+	/* check that a decrease in size doesn't cut off any shared mappings */
+	if (newsize < size) {
+		ret = nommu_shrink_inode_mappings(inode, size, newsize);
+		if (ret < 0)
+			return ret;
+	}
+
+	truncate_setsize(inode, newsize);
+	return 0;
+}
+
+/*****************************************************************************/
+/*
+ * handle a change of attributes
+ * - we're specifically interested in a change of size
+ */
+static int ramfs_nommu_setattr(struct mnt_idmap *idmap,
+			       struct dentry *dentry, struct iattr *ia)
+{
+	struct inode *inode = d_inode(dentry);
+	unsigned int old_ia_valid = ia->ia_valid;
+	int ret = 0;
+
+	/* POSIX UID/GID verification for setting inode attributes */
+	ret = setattr_prepare(&nop_mnt_idmap, dentry, ia);
+	if (ret)
+		return ret;
+
+	/* pick out size-changing events */
+	if (ia->ia_valid & ATTR_SIZE) {
+		loff_t size = inode->i_size;
+
+		if (ia->ia_size != size) {
+			ret = ramfs_nommu_resize(inode, ia->ia_size, size);
+			if (ret < 0 || ia->ia_valid == ATTR_SIZE)
+				goto out;
+		} else {
+			/* we skipped the truncate but must still update
+			 * timestamps
+			 */
+			ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
+		}
+	}
+
+	setattr_copy(&nop_mnt_idmap, inode, ia);
+ out:
+	ia->ia_valid = old_ia_valid;
+	return ret;
+}
+
+/*****************************************************************************/
+/*
+ * try to determine where a shared mapping can be made
+ * - we require that:
+ *   - the pages to be mapped must exist
+ *   - the pages be physically contiguous in sequence
+ */
+static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
+					    unsigned long addr, unsigned long len,
+					    unsigned long pgoff, unsigned long flags)
+{
+	unsigned long maxpages, lpages, nr_folios, loop, ret, nr_pages, pfn;
+	struct inode *inode = file_inode(file);
+	struct folio_batch fbatch;
+	loff_t isize;
+
+	/* the mapping mustn't extend beyond the EOF */
+	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	isize = i_size_read(inode);
+
+	ret = -ENOSYS;
+	maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if (pgoff >= maxpages)
+		goto out;
+
+	if (maxpages - pgoff < lpages)
+		goto out;
+
+	/* gang-find the pages */
+	folio_batch_init(&fbatch);
+	nr_pages = 0;
+repeat:
+	nr_folios = filemap_get_folios_contig(inode->i_mapping, &pgoff,
+			ULONG_MAX, &fbatch);
+	if (!nr_folios) {
+		ret = -ENOSYS;
+		return ret;
+	}
+
+	if (ret == -ENOSYS) {
+		ret = (unsigned long) folio_address(fbatch.folios[0]);
+		pfn = folio_pfn(fbatch.folios[0]);
+	}
+	/* check the pages for physical adjacency */
+	for (loop = 0; loop < nr_folios; loop++) {
+		if (pfn + nr_pages != folio_pfn(fbatch.folios[loop])) {
+			ret = -ENOSYS;
+			goto out_free; /* leave if not physical adjacent */
+		}
+		nr_pages += folio_nr_pages(fbatch.folios[loop]);
+		if (nr_pages >= lpages)
+			goto out_free; /* successfully found desired pages*/
+	}
+
+	if (nr_pages < lpages) {
+		folio_batch_release(&fbatch);
+		goto repeat; /* loop if pages are missing */
+	}
+	/* okay - all conditions fulfilled */
+
+out_free:
+	folio_batch_release(&fbatch);
+out:
+	return ret;
+}
+
+/*****************************************************************************/
+/*
+ * set up a mapping for shared memory segments
+ */
+static int ramfs_nommu_mmap_prepare(struct vm_area_desc *desc)
+{
+	if (!is_nommu_shared_vma_flags(&desc->vma_flags))
+		return -ENOSYS;
+
+	file_accessed(desc->file);
+	desc->vm_ops = &generic_file_vm_ops;
+	return 0;
+}
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
new file mode 100644
index 000000000..0a88ede48
--- /dev/null
+++ b/fs/ramfs/inode.c
@@ -0,0 +1,329 @@
+/*
+ * Resizable simple ram filesystem for Linux.
+ *
+ * Copyright (C) 2000 Linus Torvalds.
+ *               2000 Transmeta Corp.
+ *
+ * Usage limits added by David Gibson, Linuxcare Australia.
+ * This file is released under the GPL.
+ */
+
+/*
+ * NOTE! This filesystem is probably most useful
+ * not as a real filesystem, but as an example of
+ * how virtual filesystems can be written.
+ *
+ * It doesn't get much simpler than this. Consider
+ * that this file implements the full semantics of
+ * a POSIX-compliant read-write filesystem.
+ *
+ * Note in particular how the filesystem does not
+ * need to implement any data structures of its own
+ * to keep track of the virtual data: using the VFS
+ * caches is sufficient.
+ */
+
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/time.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/backing-dev.h>
+#include <linux/ramfs.h>
+#include <linux/sched.h>
+#include <linux/parser.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+struct ramfs_mount_opts {
+	umode_t mode;
+};
+
+struct ramfs_fs_info {
+	struct ramfs_mount_opts mount_opts;
+};
+
+#define RAMFS_DEFAULT_MODE	0755
+
+static const struct super_operations ramfs_ops;
+static const struct inode_operations ramfs_dir_inode_operations;
+
+struct inode *ramfs_get_inode(struct super_block *sb,
+				const struct inode *dir, umode_t mode, dev_t dev)
+{
+	struct inode * inode = new_inode(sb);
+
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
+		inode->i_mapping->a_ops = &ram_aops;
+		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+		mapping_set_unevictable(inode->i_mapping);
+		simple_inode_init_ts(inode);
+		switch (mode & S_IFMT) {
+		default:
+			init_special_inode(inode, mode, dev);
+			break;
+		case S_IFREG:
+			inode->i_op = &ramfs_file_inode_operations;
+			inode->i_fop = &ramfs_file_operations;
+			break;
+		case S_IFDIR:
+			inode->i_op = &ramfs_dir_inode_operations;
+			inode->i_fop = &simple_dir_operations;
+
+			/* directory inodes start off with i_nlink == 2 (for "." entry) */
+			inc_nlink(inode);
+			break;
+		case S_IFLNK:
+			inode->i_op = &page_symlink_inode_operations;
+			inode_nohighmem(inode);
+			break;
+		}
+	}
+	return inode;
+}
+
+/*
+ * File creation. Allocate an inode, and we're done..
+ */
+/* SMP-safe */
+static int
+ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
+	    struct dentry *dentry, umode_t mode, dev_t dev)
+{
+	struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
+	int error = -ENOSPC;
+
+	if (inode) {
+		error = security_inode_init_security(inode, dir,
+						     &dentry->d_name, NULL,
+						     NULL);
+		if (error) {
+			iput(inode);
+			goto out;
+		}
+
+		d_make_persistent(dentry, inode);
+		error = 0;
+		inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
+	}
+out:
+	return error;
+}
+
+static struct dentry *ramfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+				 struct dentry *dentry, umode_t mode)
+{
+	int retval = ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode, 0);
+	if (!retval)
+		inc_nlink(dir);
+	return ERR_PTR(retval);
+}
+
+static int ramfs_create(struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry, umode_t mode)
+{
+	return ramfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
+}
+
+static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
+			 struct dentry *dentry, const char *symname)
+{
+	struct inode *inode;
+	int error = -ENOSPC;
+
+	inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
+	if (inode) {
+		int l = strlen(symname)+1;
+
+		error = security_inode_init_security(inode, dir,
+						     &dentry->d_name, NULL,
+						     NULL);
+		if (error) {
+			iput(inode);
+			goto out;
+		}
+
+		error = page_symlink(inode, symname, l);
+		if (!error) {
+			d_make_persistent(dentry, inode);
+			inode_set_mtime_to_ts(dir,
+					      inode_set_ctime_current(dir));
+		} else
+			iput(inode);
+	}
+out:
+	return error;
+}
+
+static int ramfs_tmpfile(struct mnt_idmap *idmap,
+			 struct inode *dir, struct file *file, umode_t mode)
+{
+	struct inode *inode;
+	int error;
+
+	inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
+	if (!inode)
+		return -ENOSPC;
+
+	error = security_inode_init_security(inode, dir,
+					     &file_dentry(file)->d_name, NULL,
+					     NULL);
+	if (error) {
+		iput(inode);
+		goto out;
+	}
+
+	d_tmpfile(file, inode);
+out:
+	return finish_open_simple(file, error);
+}
+
+static const struct inode_operations ramfs_dir_inode_operations = {
+	.create		= ramfs_create,
+	.lookup		= simple_lookup,
+	.link		= simple_link,
+	.unlink		= simple_unlink,
+	.symlink	= ramfs_symlink,
+	.mkdir		= ramfs_mkdir,
+	.rmdir		= simple_rmdir,
+	.mknod		= ramfs_mknod,
+	.rename		= simple_rename,
+	.tmpfile	= ramfs_tmpfile,
+};
+
+/*
+ * Display the mount options in /proc/mounts.
+ */
+static int ramfs_show_options(struct seq_file *m, struct dentry *root)
+{
+	struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
+
+	if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
+		seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
+	return 0;
+}
+
+static const struct super_operations ramfs_ops = {
+	.statfs		= simple_statfs,
+	.drop_inode	= inode_just_drop,
+	.show_options	= ramfs_show_options,
+};
+
+enum ramfs_param {
+	Opt_mode,
+};
+
+const struct fs_parameter_spec ramfs_fs_parameters[] = {
+	fsparam_u32oct("mode",	Opt_mode),
+	{}
+};
+
+static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct fs_parse_result result;
+	struct ramfs_fs_info *fsi = fc->s_fs_info;
+	int opt;
+
+	opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
+	if (opt == -ENOPARAM) {
+		opt = vfs_parse_fs_param_source(fc, param);
+		if (opt != -ENOPARAM)
+			return opt;
+		/*
+		 * We might like to report bad mount options here;
+		 * but traditionally ramfs has ignored all mount options,
+		 * and as it is used as a !CONFIG_SHMEM simple substitute
+		 * for tmpfs, better continue to ignore other mount options.
+		 */
+		return 0;
+	}
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case Opt_mode:
+		fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
+		break;
+	}
+
+	return 0;
+}
+
+static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct ramfs_fs_info *fsi = sb->s_fs_info;
+	struct inode *inode;
+
+	sb->s_maxbytes		= MAX_LFS_FILESIZE;
+	sb->s_blocksize		= PAGE_SIZE;
+	sb->s_blocksize_bits	= PAGE_SHIFT;
+	sb->s_magic		= RAMFS_MAGIC;
+	sb->s_op		= &ramfs_ops;
+	sb->s_d_flags		= DCACHE_DONTCACHE;
+	sb->s_time_gran		= 1;
+
+	inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
+	sb->s_root = d_make_root(inode);
+	if (!sb->s_root)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int ramfs_get_tree(struct fs_context *fc)
+{
+	return get_tree_nodev(fc, ramfs_fill_super);
+}
+
+static void ramfs_free_fc(struct fs_context *fc)
+{
+	kfree(fc->s_fs_info);
+}
+
+static const struct fs_context_operations ramfs_context_ops = {
+	.free		= ramfs_free_fc,
+	.parse_param	= ramfs_parse_param,
+	.get_tree	= ramfs_get_tree,
+};
+
+int ramfs_init_fs_context(struct fs_context *fc)
+{
+	struct ramfs_fs_info *fsi;
+
+	fsi = kzalloc_obj(*fsi);
+	if (!fsi)
+		return -ENOMEM;
+
+	fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
+	fc->s_fs_info = fsi;
+	fc->ops = &ramfs_context_ops;
+	return 0;
+}
+
+void ramfs_kill_sb(struct super_block *sb)
+{
+	kfree(sb->s_fs_info);
+	kill_anon_super(sb);
+}
+
+static struct file_system_type ramfs_fs_type = {
+	.name		= "ramfs",
+	.init_fs_context = ramfs_init_fs_context,
+	.parameters	= ramfs_fs_parameters,
+	.kill_sb	= ramfs_kill_sb,
+	.fs_flags	= FS_USERNS_MOUNT,
+};
+
+static int __init init_ramfs_fs(void)
+{
+	return register_filesystem(&ramfs_fs_type);
+}
+fs_initcall(init_ramfs_fs);
diff --git a/fs/ramfs/internal.h b/fs/ramfs/internal.h
new file mode 100644
index 000000000..3257fc180
--- /dev/null
+++ b/fs/ramfs/internal.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* internal.h: ramfs internal definitions
+ *
+ * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+
+extern const struct inode_operations ramfs_file_inode_operations;