+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * dcookies.c
- *
- * Copyright 2002 John Levon <levon@movementarian.org>
- *
- * Persistent cookie-path mappings. These are used by
- * profilers to convert a per-task EIP value into something
- * non-transitory that can be processed at a later date.
- * This is done by locking the dentry/vfsmnt pair in the
- * kernel until released by the tasks needing the persistent
- * objects. The tag is simply an unsigned long that refers
- * to the pair and can be looked up from userspace.
- */
-
-#include <linux/syscalls.h>
-#include <linux/export.h>
-#include <linux/slab.h>
-#include <linux/list.h>
-#include <linux/mount.h>
-#include <linux/capability.h>
-#include <linux/dcache.h>
-#include <linux/mm.h>
-#include <linux/err.h>
-#include <linux/errno.h>
-#include <linux/dcookies.h>
-#include <linux/mutex.h>
-#include <linux/path.h>
-#include <linux/compat.h>
-#include <linux/uaccess.h>
-
-/* The dcookies are allocated from a kmem_cache and
- * hashed onto a small number of lists. None of the
- * code here is particularly performance critical
- */
-struct dcookie_struct {
- struct path path;
- struct list_head hash_list;
-};
-
-static LIST_HEAD(dcookie_users);
-static DEFINE_MUTEX(dcookie_mutex);
-static struct kmem_cache *dcookie_cache __read_mostly;
-static struct list_head *dcookie_hashtable __read_mostly;
-static size_t hash_size __read_mostly;
-
-static inline int is_live(void)
-{
- return !(list_empty(&dcookie_users));
-}
-
-
-/* The dentry is locked, its address will do for the cookie */
-static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
-{
- return (unsigned long)dcs->path.dentry;
-}
-
-
-static size_t dcookie_hash(unsigned long dcookie)
-{
- return (dcookie >> L1_CACHE_SHIFT) & (hash_size - 1);
-}
-
-
-static struct dcookie_struct * find_dcookie(unsigned long dcookie)
-{
- struct dcookie_struct *found = NULL;
- struct dcookie_struct * dcs;
- struct list_head * pos;
- struct list_head * list;
-
- list = dcookie_hashtable + dcookie_hash(dcookie);
-
- list_for_each(pos, list) {
- dcs = list_entry(pos, struct dcookie_struct, hash_list);
- if (dcookie_value(dcs) == dcookie) {
- found = dcs;
- break;
- }
- }
-
- return found;
-}
-
-
-static void hash_dcookie(struct dcookie_struct * dcs)
-{
- struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
- list_add(&dcs->hash_list, list);
-}
-
-
-static struct dcookie_struct *alloc_dcookie(const struct path *path)
-{
- struct dcookie_struct *dcs = kmem_cache_alloc(dcookie_cache,
- GFP_KERNEL);
- struct dentry *d;
- if (!dcs)
- return NULL;
-
- d = path->dentry;
- spin_lock(&d->d_lock);
- d->d_flags |= DCACHE_COOKIE;
- spin_unlock(&d->d_lock);
-
- dcs->path = *path;
- path_get(path);
- hash_dcookie(dcs);
- return dcs;
-}
-
-
-/* This is the main kernel-side routine that retrieves the cookie
- * value for a dentry/vfsmnt pair.
- */
-int get_dcookie(const struct path *path, unsigned long *cookie)
-{
- int err = 0;
- struct dcookie_struct * dcs;
-
- mutex_lock(&dcookie_mutex);
-
- if (!is_live()) {
- err = -EINVAL;
- goto out;
- }
-
- if (path->dentry->d_flags & DCACHE_COOKIE) {
- dcs = find_dcookie((unsigned long)path->dentry);
- } else {
- dcs = alloc_dcookie(path);
- if (!dcs) {
- err = -ENOMEM;
- goto out;
- }
- }
-
- *cookie = dcookie_value(dcs);
-
-out:
- mutex_unlock(&dcookie_mutex);
- return err;
-}
-
-
-/* And here is where the userspace process can look up the cookie value
- * to retrieve the path.
- */
-static int do_lookup_dcookie(u64 cookie64, char __user *buf, size_t len)
-{
- unsigned long cookie = (unsigned long)cookie64;
- int err = -EINVAL;
- char * kbuf;
- char * path;
- size_t pathlen;
- struct dcookie_struct * dcs;
-
- /* we could leak path information to users
- * without dir read permission without this
- */
- if (!capable(CAP_SYS_ADMIN))
- return -EPERM;
-
- mutex_lock(&dcookie_mutex);
-
- if (!is_live()) {
- err = -EINVAL;
- goto out;
- }
-
- if (!(dcs = find_dcookie(cookie)))
- goto out;
-
- err = -ENOMEM;
- kbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
- if (!kbuf)
- goto out;
-
- /* FIXME: (deleted) ? */
- path = d_path(&dcs->path, kbuf, PAGE_SIZE);
-
- mutex_unlock(&dcookie_mutex);
-
- if (IS_ERR(path)) {
- err = PTR_ERR(path);
- goto out_free;
- }
-
- err = -ERANGE;
-
- pathlen = kbuf + PAGE_SIZE - path;
- if (pathlen <= len) {
- err = pathlen;
- if (copy_to_user(buf, path, pathlen))
- err = -EFAULT;
- }
-
-out_free:
- kfree(kbuf);
- return err;
-out:
- mutex_unlock(&dcookie_mutex);
- return err;
-}
-
-SYSCALL_DEFINE3(lookup_dcookie, u64, cookie64, char __user *, buf, size_t, len)
-{
- return do_lookup_dcookie(cookie64, buf, len);
-}
-
-#ifdef CONFIG_COMPAT
-COMPAT_SYSCALL_DEFINE4(lookup_dcookie, u32, w0, u32, w1, char __user *, buf, compat_size_t, len)
-{
-#ifdef __BIG_ENDIAN
- return do_lookup_dcookie(((u64)w0 << 32) | w1, buf, len);
-#else
- return do_lookup_dcookie(((u64)w1 << 32) | w0, buf, len);
-#endif
-}
-#endif
-
-static int dcookie_init(void)
-{
- struct list_head * d;
- unsigned int i, hash_bits;
- int err = -ENOMEM;
-
- dcookie_cache = kmem_cache_create("dcookie_cache",
- sizeof(struct dcookie_struct),
- 0, 0, NULL);
-
- if (!dcookie_cache)
- goto out;
-
- dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
- if (!dcookie_hashtable)
- goto out_kmem;
-
- err = 0;
-
- /*
- * Find the power-of-two list-heads that can fit into the allocation..
- * We don't guarantee that "sizeof(struct list_head)" is necessarily
- * a power-of-two.
- */
- hash_size = PAGE_SIZE / sizeof(struct list_head);
- hash_bits = 0;
- do {
- hash_bits++;
- } while ((hash_size >> hash_bits) != 0);
- hash_bits--;
-
- /*
- * Re-calculate the actual number of entries and the mask
- * from the number of bits we can fit.
- */
- hash_size = 1UL << hash_bits;
-
- /* And initialize the newly allocated array */
- d = dcookie_hashtable;
- i = hash_size;
- do {
- INIT_LIST_HEAD(d);
- d++;
- i--;
- } while (i);
-
-out:
- return err;
-out_kmem:
- kmem_cache_destroy(dcookie_cache);
- goto out;
-}
-
-
-static void free_dcookie(struct dcookie_struct * dcs)
-{
- struct dentry *d = dcs->path.dentry;
-
- spin_lock(&d->d_lock);
- d->d_flags &= ~DCACHE_COOKIE;
- spin_unlock(&d->d_lock);
-
- path_put(&dcs->path);
- kmem_cache_free(dcookie_cache, dcs);
-}
-
-
-static void dcookie_exit(void)
-{
- struct list_head * list;
- struct list_head * pos;
- struct list_head * pos2;
- struct dcookie_struct * dcs;
- size_t i;
-
- for (i = 0; i < hash_size; ++i) {
- list = dcookie_hashtable + i;
- list_for_each_safe(pos, pos2, list) {
- dcs = list_entry(pos, struct dcookie_struct, hash_list);
- list_del(&dcs->hash_list);
- free_dcookie(dcs);
- }
- }
-
- kfree(dcookie_hashtable);
- kmem_cache_destroy(dcookie_cache);
-}
-
-
-struct dcookie_user {
- struct list_head next;
-};
-
-struct dcookie_user * dcookie_register(void)
-{
- struct dcookie_user * user;
-
- mutex_lock(&dcookie_mutex);
-
- user = kmalloc(sizeof(struct dcookie_user), GFP_KERNEL);
- if (!user)
- goto out;
-
- if (!is_live() && dcookie_init())
- goto out_free;
-
- list_add(&user->next, &dcookie_users);
-
-out:
- mutex_unlock(&dcookie_mutex);
- return user;
-out_free:
- kfree(user);
- user = NULL;
- goto out;
-}
-
-
-void dcookie_unregister(struct dcookie_user * user)
-{
- mutex_lock(&dcookie_mutex);
-
- list_del(&user->next);
- kfree(user);
-
- if (!is_live())
- dcookie_exit();
-
- mutex_unlock(&dcookie_mutex);
-}
-
-EXPORT_SYMBOL_GPL(dcookie_register);
-EXPORT_SYMBOL_GPL(dcookie_unregister);
-EXPORT_SYMBOL_GPL(get_dcookie);
projects / linux-2.6-block.git / blobdiff