diff options
author | Linus Torvalds | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /fs/dcookies.c |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'fs/dcookies.c')
-rw-r--r-- | fs/dcookies.c | 330 |
1 files changed, 330 insertions, 0 deletions
diff --git a/fs/dcookies.c b/fs/dcookies.c new file mode 100644 index 000000000000..581aac959cd3 --- /dev/null +++ b/fs/dcookies.c @@ -0,0 +1,330 @@ +/* + * 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/config.h> +#include <linux/syscalls.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/list.h> +#include <linux/mount.h> +#include <linux/dcache.h> +#include <linux/mm.h> +#include <linux/errno.h> +#include <linux/dcookies.h> +#include <asm/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 dentry * dentry; + struct vfsmount * vfsmnt; + struct list_head hash_list; +}; + +static LIST_HEAD(dcookie_users); +static DECLARE_MUTEX(dcookie_sem); +static kmem_cache_t * dcookie_cache; +static struct list_head * dcookie_hashtable; +static size_t hash_size; + +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->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(struct dentry * dentry, + struct vfsmount * vfsmnt) +{ + struct dcookie_struct * dcs = kmem_cache_alloc(dcookie_cache, GFP_KERNEL); + if (!dcs) + return NULL; + + atomic_inc(&dentry->d_count); + atomic_inc(&vfsmnt->mnt_count); + dentry->d_cookie = dcs; + + dcs->dentry = dentry; + dcs->vfsmnt = vfsmnt; + 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(struct dentry * dentry, struct vfsmount * vfsmnt, + unsigned long * cookie) +{ + int err = 0; + struct dcookie_struct * dcs; + + down(&dcookie_sem); + + if (!is_live()) { + err = -EINVAL; + goto out; + } + + dcs = dentry->d_cookie; + + if (!dcs) + dcs = alloc_dcookie(dentry, vfsmnt); + + if (!dcs) { + err = -ENOMEM; + goto out; + } + + *cookie = dcookie_value(dcs); + +out: + up(&dcookie_sem); + return err; +} + + +/* And here is where the userspace process can look up the cookie value + * to retrieve the path. + */ +asmlinkage long sys_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; + + down(&dcookie_sem); + + 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->dentry, dcs->vfsmnt, kbuf, PAGE_SIZE); + + 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); +out: + up(&dcookie_sem); + return err; +} + + +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, 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) +{ + dcs->dentry->d_cookie = NULL; + dput(dcs->dentry); + mntput(dcs->vfsmnt); + 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; + + down(&dcookie_sem); + + 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: + up(&dcookie_sem); + return user; +out_free: + kfree(user); + user = NULL; + goto out; +} + + +void dcookie_unregister(struct dcookie_user * user) +{ + down(&dcookie_sem); + + list_del(&user->next); + kfree(user); + + if (!is_live()) + dcookie_exit(); + + up(&dcookie_sem); +} + +EXPORT_SYMBOL_GPL(dcookie_register); +EXPORT_SYMBOL_GPL(dcookie_unregister); +EXPORT_SYMBOL_GPL(get_dcookie); |