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, 856 insertions, 0 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
new file mode 100644
index 000000000..26086a283
--- /dev/null
+++ b/fs/proc/generic.c
@@ -0,0 +1,856 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * proc/fs/generic.c --- generic routines for the proc-fs
+ *
+ * This file contains generic proc-fs routines for handling
+ * directories and files.
+ * 
+ * Copyright (C) 1991, 1992 Linus Torvalds.
+ * Copyright (C) 1997 Theodore Ts'o
+ */
+
+#include <linux/cache.h>
+#include <linux/errno.h>
+#include <linux/time.h>
+#include <linux/proc_fs.h>
+#include <linux/stat.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/namei.h>
+#include <linux/slab.h>
+#include <linux/printk.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/idr.h>
+#include <linux/bitops.h>
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/uaccess.h>
+#include <linux/seq_file.h>
+
+#include "internal.h"
+
+static DEFINE_RWLOCK(proc_subdir_lock);
+
+struct kmem_cache *proc_dir_entry_cache __ro_after_init;
+
+void pde_free(struct proc_dir_entry *pde)
+{
+	if (S_ISLNK(pde->mode))
+		kfree(pde->data);
+	if (pde->name != pde->inline_name)
+		kfree(pde->name);
+	kmem_cache_free(proc_dir_entry_cache, pde);
+}
+
+static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)
+{
+	if (len < de->namelen)
+		return -1;
+	if (len > de->namelen)
+		return 1;
+
+	return memcmp(name, de->name, len);
+}
+
+static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
+{
+	return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
+			     subdir_node);
+}
+
+static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
+{
+	return rb_entry_safe(rb_next(&dir->subdir_node), struct proc_dir_entry,
+			     subdir_node);
+}
+
+static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
+					      const char *name,
+					      unsigned int len)
+{
+	struct rb_node *node = dir->subdir.rb_node;
+
+	while (node) {
+		struct proc_dir_entry *de = rb_entry(node,
+						     struct proc_dir_entry,
+						     subdir_node);
+		int result = proc_match(name, de, len);
+
+		if (result < 0)
+			node = node->rb_left;
+		else if (result > 0)
+			node = node->rb_right;
+		else
+			return de;
+	}
+	return NULL;
+}
+
+static bool pde_subdir_insert(struct proc_dir_entry *dir,
+			      struct proc_dir_entry *de)
+{
+	struct rb_root *root = &dir->subdir;
+	struct rb_node **new = &root->rb_node, *parent = NULL;
+
+	/* Figure out where to put new node */
+	while (*new) {
+		struct proc_dir_entry *this = rb_entry(*new,
+						       struct proc_dir_entry,
+						       subdir_node);
+		int result = proc_match(de->name, this, de->namelen);
+
+		parent = *new;
+		if (result < 0)
+			new = &(*new)->rb_left;
+		else if (result > 0)
+			new = &(*new)->rb_right;
+		else
+			return false;
+	}
+
+	/* Add new node and rebalance tree. */
+	rb_link_node(&de->subdir_node, parent, new);
+	rb_insert_color(&de->subdir_node, root);
+	if (S_ISDIR(de->mode))
+		dir->nlink++;
+	return true;
+}
+
+static int proc_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		struct iattr *iattr)
+{
+	struct inode *inode = d_inode(dentry);
+	struct proc_dir_entry *de = PDE(inode);
+	int error;
+
+	error = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
+	if (error)
+		return error;
+
+	setattr_copy(&nop_mnt_idmap, inode, iattr);
+
+	proc_set_user(de, inode->i_uid, inode->i_gid);
+	de->mode = inode->i_mode;
+	return 0;
+}
+
+static int proc_getattr(struct mnt_idmap *idmap,
+			const struct path *path, struct kstat *stat,
+			u32 request_mask, unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct proc_dir_entry *de = PDE(inode);
+	if (de) {
+		nlink_t nlink = READ_ONCE(de->nlink);
+		if (nlink > 0) {
+			set_nlink(inode, nlink);
+		}
+	}
+
+	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
+	return 0;
+}
+
+static const struct inode_operations proc_file_inode_operations = {
+	.setattr	= proc_setattr,
+};
+
+/*
+ * This function parses a name such as "tty/driver/serial", and
+ * returns the struct proc_dir_entry for "/proc/tty/driver", and
+ * returns "serial" in residual.
+ */
+static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
+			     const char **residual)
+{
+	const char     		*cp = name, *next;
+	struct proc_dir_entry	*de;
+
+	de = *ret ?: &proc_root;
+	while ((next = strchr(cp, '/')) != NULL) {
+		de = pde_subdir_find(de, cp, next - cp);
+		if (!de) {
+			WARN(1, "name '%s'\n", name);
+			return -ENOENT;
+		}
+		cp = next + 1;
+	}
+	*residual = cp;
+	*ret = de;
+	return 0;
+}
+
+static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
+			   const char **residual)
+{
+	int rv;
+
+	read_lock(&proc_subdir_lock);
+	rv = __xlate_proc_name(name, ret, residual);
+	read_unlock(&proc_subdir_lock);
+	return rv;
+}
+
+static DEFINE_IDA(proc_inum_ida);
+
+#define PROC_DYNAMIC_FIRST 0xF0000000U
+
+/*
+ * Return an inode number between PROC_DYNAMIC_FIRST and
+ * 0xffffffff, or zero on failure.
+ */
+int proc_alloc_inum(unsigned int *inum)
+{
+	int i;
+
+	i = ida_alloc_max(&proc_inum_ida, UINT_MAX - PROC_DYNAMIC_FIRST,
+			  GFP_KERNEL);
+	if (i < 0)
+		return i;
+
+	*inum = PROC_DYNAMIC_FIRST + (unsigned int)i;
+	return 0;
+}
+
+void proc_free_inum(unsigned int inum)
+{
+	ida_free(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
+}
+
+static int proc_misc_d_revalidate(struct inode *dir, const struct qstr *name,
+				  struct dentry *dentry, unsigned int flags)
+{
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0)
+		return 0; /* revalidate */
+	return 1;
+}
+
+static int proc_misc_d_delete(const struct dentry *dentry)
+{
+	return atomic_read(&PDE(d_inode(dentry))->in_use) < 0;
+}
+
+static const struct dentry_operations proc_misc_dentry_ops = {
+	.d_revalidate	= proc_misc_d_revalidate,
+	.d_delete	= proc_misc_d_delete,
+};
+
+/*
+ * Don't create negative dentries here, return -ENOENT by hand
+ * instead.
+ */
+struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
+			      struct proc_dir_entry *de)
+{
+	struct inode *inode;
+
+	read_lock(&proc_subdir_lock);
+	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
+	if (de) {
+		pde_get(de);
+		read_unlock(&proc_subdir_lock);
+		inode = proc_get_inode(dir->i_sb, de);
+		if (!inode)
+			return ERR_PTR(-ENOMEM);
+		if (de->flags & PROC_ENTRY_FORCE_LOOKUP)
+			return d_splice_alias_ops(inode, dentry,
+						  &proc_net_dentry_ops);
+		return d_splice_alias_ops(inode, dentry,
+					  &proc_misc_dentry_ops);
+	}
+	read_unlock(&proc_subdir_lock);
+	return ERR_PTR(-ENOENT);
+}
+
+struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
+		unsigned int flags)
+{
+	struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);
+
+	if (fs_info->pidonly == PROC_PIDONLY_ON)
+		return ERR_PTR(-ENOENT);
+
+	return proc_lookup_de(dir, dentry, PDE(dir));
+}
+
+/*
+ * This returns non-zero if at EOF, so that the /proc
+ * root directory can use this and check if it should
+ * continue with the <pid> entries..
+ *
+ * Note that the VFS-layer doesn't care about the return
+ * value of the readdir() call, as long as it's non-negative
+ * for success..
+ */
+int proc_readdir_de(struct file *file, struct dir_context *ctx,
+		    struct proc_dir_entry *de)
+{
+	int i;
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+
+	i = ctx->pos - 2;
+	read_lock(&proc_subdir_lock);
+	de = pde_subdir_first(de);
+	for (;;) {
+		if (!de) {
+			read_unlock(&proc_subdir_lock);
+			return 0;
+		}
+		if (!i)
+			break;
+		de = pde_subdir_next(de);
+		i--;
+	}
+
+	do {
+		struct proc_dir_entry *next;
+		pde_get(de);
+		read_unlock(&proc_subdir_lock);
+		if (!dir_emit(ctx, de->name, de->namelen,
+			    de->low_ino, de->mode >> 12)) {
+			pde_put(de);
+			return 0;
+		}
+		ctx->pos++;
+		read_lock(&proc_subdir_lock);
+		next = pde_subdir_next(de);
+		pde_put(de);
+		de = next;
+	} while (de);
+	read_unlock(&proc_subdir_lock);
+	return 1;
+}
+
+int proc_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct inode *inode = file_inode(file);
+	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
+
+	if (fs_info->pidonly == PROC_PIDONLY_ON)
+		return 1;
+
+	return proc_readdir_de(file, ctx, PDE(inode));
+}
+
+/*
+ * These are the generic /proc directory operations. They
+ * use the in-memory "struct proc_dir_entry" tree to parse
+ * the /proc directory.
+ */
+static const struct file_operations proc_dir_operations = {
+	.llseek			= generic_file_llseek,
+	.read			= generic_read_dir,
+	.iterate_shared		= proc_readdir,
+};
+
+static int proc_net_d_revalidate(struct inode *dir, const struct qstr *name,
+				 struct dentry *dentry, unsigned int flags)
+{
+	return 0;
+}
+
+const struct dentry_operations proc_net_dentry_ops = {
+	.d_revalidate	= proc_net_d_revalidate,
+	.d_delete	= always_delete_dentry,
+};
+
+/*
+ * proc directories can do almost nothing..
+ */
+static const struct inode_operations proc_dir_inode_operations = {
+	.lookup		= proc_lookup,
+	.getattr	= proc_getattr,
+	.setattr	= proc_setattr,
+};
+
+static void pde_set_flags(struct proc_dir_entry *pde)
+{
+	const struct proc_ops *proc_ops = pde->proc_ops;
+
+	if (!proc_ops)
+		return;
+
+	if (proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
+		pde->flags |= PROC_ENTRY_PERMANENT;
+	if (proc_ops->proc_read_iter)
+		pde->flags |= PROC_ENTRY_proc_read_iter;
+#ifdef CONFIG_COMPAT
+	if (proc_ops->proc_compat_ioctl)
+		pde->flags |= PROC_ENTRY_proc_compat_ioctl;
+#endif
+	if (proc_ops->proc_lseek)
+		pde->flags |= PROC_ENTRY_proc_lseek;
+}
+
+/* returns the registered entry, or frees dp and returns NULL on failure */
+struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
+		struct proc_dir_entry *dp)
+{
+	if (proc_alloc_inum(&dp->low_ino))
+		goto out_free_entry;
+
+	if (!S_ISDIR(dp->mode))
+		pde_set_flags(dp);
+
+	write_lock(&proc_subdir_lock);
+	dp->parent = dir;
+	if (pde_subdir_insert(dir, dp) == false) {
+		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
+		     dir->name, dp->name);
+		write_unlock(&proc_subdir_lock);
+		goto out_free_inum;
+	}
+	write_unlock(&proc_subdir_lock);
+
+	return dp;
+out_free_inum:
+	proc_free_inum(dp->low_ino);
+out_free_entry:
+	pde_free(dp);
+	return NULL;
+}
+
+static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
+					  const char *name,
+					  umode_t mode,
+					  nlink_t nlink)
+{
+	struct proc_dir_entry *ent = NULL;
+	const char *fn;
+	struct qstr qstr;
+
+	if (xlate_proc_name(name, parent, &fn) != 0)
+		goto out;
+	qstr.name = fn;
+	qstr.len = strnlen(fn, NAME_MAX + 1);
+	if (qstr.len == 0) {
+		WARN(1, "empty name\n");
+		return NULL;
+	}
+	if (qstr.len > NAME_MAX) {
+		WARN(1, "name too long\n");
+		return NULL;
+	}
+	if (qstr.len == 1 && fn[0] == '.') {
+		WARN(1, "name '.'\n");
+		return NULL;
+	}
+	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
+		WARN(1, "name '..'\n");
+		return NULL;
+	}
+	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
+		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
+		return NULL;
+	}
+	if (is_empty_pde(*parent)) {
+		WARN(1, "attempt to add to permanently empty directory");
+		return NULL;
+	}
+
+	ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
+	if (!ent)
+		goto out;
+
+	if (qstr.len + 1 <= SIZEOF_PDE_INLINE_NAME) {
+		ent->name = ent->inline_name;
+	} else {
+		ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
+		if (!ent->name) {
+			pde_free(ent);
+			return NULL;
+		}
+	}
+
+	memcpy(ent->name, fn, qstr.len + 1);
+	ent->namelen = qstr.len;
+	ent->mode = mode;
+	ent->nlink = nlink;
+	ent->subdir = RB_ROOT;
+	refcount_set(&ent->refcnt, 1);
+	spin_lock_init(&ent->pde_unload_lock);
+	INIT_LIST_HEAD(&ent->pde_openers);
+	proc_set_user(ent, (*parent)->uid, (*parent)->gid);
+
+	/* Revalidate everything under /proc/${pid}/net */
+	if ((*parent)->flags & PROC_ENTRY_FORCE_LOOKUP)
+		pde_force_lookup(ent);
+
+out:
+	return ent;
+}
+
+struct proc_dir_entry *proc_symlink(const char *name,
+		struct proc_dir_entry *parent, const char *dest)
+{
+	struct proc_dir_entry *ent;
+
+	ent = __proc_create(&parent, name,
+			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
+
+	if (ent) {
+		ent->size = strlen(dest);
+		ent->data = kmemdup(dest, ent->size + 1, GFP_KERNEL);
+		if (ent->data) {
+			ent->proc_iops = &proc_link_inode_operations;
+			ent = proc_register(parent, ent);
+		} else {
+			pde_free(ent);
+			ent = NULL;
+		}
+	}
+	return ent;
+}
+EXPORT_SYMBOL(proc_symlink);
+
+struct proc_dir_entry *_proc_mkdir(const char *name, umode_t mode,
+		struct proc_dir_entry *parent, void *data, bool force_lookup)
+{
+	struct proc_dir_entry *ent;
+
+	if (mode == 0)
+		mode = S_IRUGO | S_IXUGO;
+
+	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
+	if (ent) {
+		ent->data = data;
+		ent->proc_dir_ops = &proc_dir_operations;
+		ent->proc_iops = &proc_dir_inode_operations;
+		if (force_lookup) {
+			pde_force_lookup(ent);
+		}
+		ent = proc_register(parent, ent);
+	}
+	return ent;
+}
+EXPORT_SYMBOL_GPL(_proc_mkdir);
+
+struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
+		struct proc_dir_entry *parent, void *data)
+{
+	return _proc_mkdir(name, mode, parent, data, false);
+}
+EXPORT_SYMBOL_GPL(proc_mkdir_data);
+
+struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
+				       struct proc_dir_entry *parent)
+{
+	return proc_mkdir_data(name, mode, parent, NULL);
+}
+EXPORT_SYMBOL(proc_mkdir_mode);
+
+struct proc_dir_entry *proc_mkdir(const char *name,
+		struct proc_dir_entry *parent)
+{
+	return proc_mkdir_data(name, 0, parent, NULL);
+}
+EXPORT_SYMBOL(proc_mkdir);
+
+struct proc_dir_entry *proc_create_mount_point(const char *name)
+{
+	umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
+	struct proc_dir_entry *ent, *parent = NULL;
+
+	ent = __proc_create(&parent, name, mode, 2);
+	if (ent) {
+		ent->data = NULL;
+		ent->proc_dir_ops = NULL;
+		ent->proc_iops = NULL;
+		ent = proc_register(parent, ent);
+	}
+	return ent;
+}
+EXPORT_SYMBOL(proc_create_mount_point);
+
+struct proc_dir_entry *proc_create_reg(const char *name, umode_t mode,
+		struct proc_dir_entry **parent, void *data)
+{
+	struct proc_dir_entry *p;
+
+	if ((mode & S_IFMT) == 0)
+		mode |= S_IFREG;
+	if ((mode & S_IALLUGO) == 0)
+		mode |= S_IRUGO;
+	if (WARN_ON_ONCE(!S_ISREG(mode)))
+		return NULL;
+
+	p = __proc_create(parent, name, mode, 1);
+	if (p) {
+		p->proc_iops = &proc_file_inode_operations;
+		p->data = data;
+	}
+	return p;
+}
+
+struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
+		struct proc_dir_entry *parent,
+		const struct proc_ops *proc_ops, void *data)
+{
+	struct proc_dir_entry *p;
+
+	p = proc_create_reg(name, mode, &parent, data);
+	if (!p)
+		return NULL;
+	p->proc_ops = proc_ops;
+	return proc_register(parent, p);
+}
+EXPORT_SYMBOL(proc_create_data);
+ 
+struct proc_dir_entry *proc_create(const char *name, umode_t mode,
+				   struct proc_dir_entry *parent,
+				   const struct proc_ops *proc_ops)
+{
+	return proc_create_data(name, mode, parent, proc_ops, NULL);
+}
+EXPORT_SYMBOL(proc_create);
+
+static int proc_seq_open(struct inode *inode, struct file *file)
+{
+	struct proc_dir_entry *de = PDE(inode);
+
+	if (de->state_size)
+		return seq_open_private(file, de->seq_ops, de->state_size);
+	return seq_open(file, de->seq_ops);
+}
+
+static int proc_seq_release(struct inode *inode, struct file *file)
+{
+	struct proc_dir_entry *de = PDE(inode);
+
+	if (de->state_size)
+		return seq_release_private(inode, file);
+	return seq_release(inode, file);
+}
+
+static const struct proc_ops proc_seq_ops = {
+	/* not permanent -- can call into arbitrary seq_operations */
+	.proc_open	= proc_seq_open,
+	.proc_read_iter	= seq_read_iter,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= proc_seq_release,
+};
+
+struct proc_dir_entry *proc_create_seq_private(const char *name, umode_t mode,
+		struct proc_dir_entry *parent, const struct seq_operations *ops,
+		unsigned int state_size, void *data)
+{
+	struct proc_dir_entry *p;
+
+	p = proc_create_reg(name, mode, &parent, data);
+	if (!p)
+		return NULL;
+	p->proc_ops = &proc_seq_ops;
+	p->seq_ops = ops;
+	p->state_size = state_size;
+	return proc_register(parent, p);
+}
+EXPORT_SYMBOL(proc_create_seq_private);
+
+static int proc_single_open(struct inode *inode, struct file *file)
+{
+	struct proc_dir_entry *de = PDE(inode);
+
+	return single_open(file, de->single_show, de->data);
+}
+
+static const struct proc_ops proc_single_ops = {
+	/* not permanent -- can call into arbitrary ->single_show */
+	.proc_open	= proc_single_open,
+	.proc_read_iter = seq_read_iter,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+};
+
+struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
+		struct proc_dir_entry *parent,
+		int (*show)(struct seq_file *, void *), void *data)
+{
+	struct proc_dir_entry *p;
+
+	p = proc_create_reg(name, mode, &parent, data);
+	if (!p)
+		return NULL;
+	p->proc_ops = &proc_single_ops;
+	p->single_show = show;
+	return proc_register(parent, p);
+}
+EXPORT_SYMBOL(proc_create_single_data);
+
+void proc_set_size(struct proc_dir_entry *de, loff_t size)
+{
+	de->size = size;
+}
+EXPORT_SYMBOL(proc_set_size);
+
+void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
+{
+	de->uid = uid;
+	de->gid = gid;
+}
+EXPORT_SYMBOL(proc_set_user);
+
+void pde_put(struct proc_dir_entry *pde)
+{
+	if (refcount_dec_and_test(&pde->refcnt)) {
+		proc_free_inum(pde->low_ino);
+		pde_free(pde);
+	}
+}
+
+static void pde_erase(struct proc_dir_entry *pde, struct proc_dir_entry *parent)
+{
+	rb_erase(&pde->subdir_node, &parent->subdir);
+	RB_CLEAR_NODE(&pde->subdir_node);
+	if (S_ISDIR(pde->mode))
+		parent->nlink--;
+}
+
+/*
+ * Remove a /proc entry and free it if it's not currently in use.
+ */
+void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
+{
+	struct proc_dir_entry *de = NULL;
+	const char *fn = name;
+	unsigned int len;
+
+	write_lock(&proc_subdir_lock);
+	if (__xlate_proc_name(name, &parent, &fn) != 0) {
+		write_unlock(&proc_subdir_lock);
+		return;
+	}
+	len = strlen(fn);
+
+	de = pde_subdir_find(parent, fn, len);
+	if (de) {
+		if (unlikely(pde_is_permanent(de))) {
+			WARN(1, "removing permanent /proc entry '%s'", de->name);
+			de = NULL;
+		} else {
+			pde_erase(de, parent);
+		}
+	}
+	write_unlock(&proc_subdir_lock);
+	if (!de) {
+		WARN(1, "name '%s'\n", name);
+		return;
+	}
+
+	proc_entry_rundown(de);
+
+	WARN(pde_subdir_first(de),
+	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
+	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
+	pde_put(de);
+}
+EXPORT_SYMBOL(remove_proc_entry);
+
+int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
+{
+	struct proc_dir_entry *root = NULL, *de, *next;
+	const char *fn = name;
+	unsigned int len;
+
+	write_lock(&proc_subdir_lock);
+	if (__xlate_proc_name(name, &parent, &fn) != 0) {
+		write_unlock(&proc_subdir_lock);
+		return -ENOENT;
+	}
+	len = strlen(fn);
+
+	root = pde_subdir_find(parent, fn, len);
+	if (!root) {
+		write_unlock(&proc_subdir_lock);
+		return -ENOENT;
+	}
+	if (unlikely(pde_is_permanent(root))) {
+		write_unlock(&proc_subdir_lock);
+		WARN(1, "removing permanent /proc entry '%s/%s'",
+			root->parent->name, root->name);
+		return -EINVAL;
+	}
+	pde_erase(root, parent);
+
+	de = root;
+	while (1) {
+		next = pde_subdir_first(de);
+		if (next) {
+			if (unlikely(pde_is_permanent(next))) {
+				write_unlock(&proc_subdir_lock);
+				WARN(1, "removing permanent /proc entry '%s/%s'",
+					next->parent->name, next->name);
+				return -EINVAL;
+			}
+			pde_erase(next, de);
+			de = next;
+			continue;
+		}
+		next = de->parent;
+		write_unlock(&proc_subdir_lock);
+
+		proc_entry_rundown(de);
+		if (de == root)
+			break;
+		pde_put(de);
+
+		write_lock(&proc_subdir_lock);
+		de = next;
+	}
+	pde_put(root);
+	return 0;
+}
+EXPORT_SYMBOL(remove_proc_subtree);
+
+void *proc_get_parent_data(const struct inode *inode)
+{
+	struct proc_dir_entry *de = PDE(inode);
+	return de->parent->data;
+}
+EXPORT_SYMBOL_GPL(proc_get_parent_data);
+
+void proc_remove(struct proc_dir_entry *de)
+{
+	if (de)
+		remove_proc_subtree(de->name, de->parent);
+}
+EXPORT_SYMBOL(proc_remove);
+
+/*
+ * Pull a user buffer into memory and pass it to the file's write handler if
+ * one is supplied.  The ->write() method is permitted to modify the
+ * kernel-side buffer.
+ */
+ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,
+			  loff_t *_pos)
+{
+	struct proc_dir_entry *pde = PDE(file_inode(f));
+	char *buf;
+	int ret;
+
+	if (!pde->write)
+		return -EACCES;
+	if (size == 0 || size > PAGE_SIZE - 1)
+		return -EINVAL;
+	buf = memdup_user_nul(ubuf, size);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+	ret = pde->write(f, buf, size);
+	kfree(buf);
+	return ret == 0 ? size : ret;
+}
+
+/*
+ * Not exported to modules:
+ * modules' /proc files aren't permanent because modules aren't permanent.
+ */
+void impl_proc_make_permanent(struct proc_dir_entry *pde)
+{
+	if (pde)
+		pde_make_permanent(pde);
+}