From 77b14db502cb85a031fe8fde6c85d52f3e0acb63 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 14 Feb 2007 00:34:12 -0800 Subject: [PATCH] sysctl: reimplement the sysctl proc support With this change the sysctl inodes can be cached and nothing needs to be done when removing a sysctl table. For a cost of 2K code we will save about 4K of static tables (when we remove de from ctl_table) and 70K in proc_dir_entries that we will not allocate, or about half that on a 32bit arch. The speed feels about the same, even though we can now cache the sysctl dentries :( We get the core advantage that we don't need to have a 1 to 1 mapping between ctl table entries and proc files. Making it possible to have /proc/sys vary depending on the namespace you are in. The currently merged namespaces don't have an issue here but the network namespace under /proc/sys/net needs to have different directories depending on which network adapters are visible. By simply being a cache different directories being visible depending on who you are is trivial to implement. [akpm@osdl.org: fix uninitialised var] [akpm@osdl.org: fix ARM build] [bunk@stusta.de: make things static] Signed-off-by: Eric W. Biederman Cc: Russell King Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/proc_sysctl.c | 478 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 478 insertions(+) create mode 100644 fs/proc/proc_sysctl.c (limited to 'fs/proc/proc_sysctl.c') diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c new file mode 100644 index 00000000000..bb16a1e7882 --- /dev/null +++ b/fs/proc/proc_sysctl.c @@ -0,0 +1,478 @@ +/* + * /proc/sys support + */ + +#include +#include +#include +#include "internal.h" + +static struct dentry_operations proc_sys_dentry_operations; +static const struct file_operations proc_sys_file_operations; +static struct inode_operations proc_sys_inode_operations; + +static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table) +{ + /* Refresh the cached information bits in the inode */ + if (table) { + inode->i_uid = 0; + inode->i_gid = 0; + inode->i_mode = table->mode; + if (table->proc_handler) { + inode->i_mode |= S_IFREG; + inode->i_nlink = 1; + } else { + inode->i_mode |= S_IFDIR; + inode->i_nlink = 0; /* It is too hard to figure out */ + } + } +} + +static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table) +{ + struct inode *inode; + struct proc_inode *dir_ei, *ei; + int depth; + + inode = new_inode(dir->i_sb); + if (!inode) + goto out; + + /* A directory is always one deeper than it's parent */ + dir_ei = PROC_I(dir); + depth = dir_ei->fd + 1; + + ei = PROC_I(inode); + ei->fd = depth; + inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; + inode->i_op = &proc_sys_inode_operations; + inode->i_fop = &proc_sys_file_operations; + proc_sys_refresh_inode(inode, table); +out: + return inode; +} + +static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth) +{ + for (;;) { + struct proc_inode *ei; + + ei = PROC_I(dentry->d_inode); + if (ei->fd == depth) + break; /* found */ + + dentry = dentry->d_parent; + } + return dentry; +} + +static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table, + struct qstr *name) +{ + int len; + for ( ; table->ctl_name || table->procname; table++) { + + if (!table->procname) + continue; + + len = strlen(table->procname); + if (len != name->len) + continue; + + if (memcmp(table->procname, name->name, len) != 0) + continue; + + /* I have a match */ + return table; + } + return NULL; +} + +static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry, + struct ctl_table *table) +{ + struct dentry *ancestor; + struct proc_inode *ei; + int depth, i; + + ei = PROC_I(dentry->d_inode); + depth = ei->fd; + + if (depth == 0) + return table; + + for (i = 1; table && (i <= depth); i++) { + ancestor = proc_sys_ancestor(dentry, i); + table = proc_sys_lookup_table_one(table, &ancestor->d_name); + if (table) + table = table->child; + } + return table; + +} +static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent, + struct qstr *name, + struct ctl_table *table) +{ + table = proc_sys_lookup_table(dparent, table); + if (table) + table = proc_sys_lookup_table_one(table, name); + return table; +} + +static struct ctl_table *do_proc_sys_lookup(struct dentry *parent, + struct qstr *name, + struct ctl_table_header **ptr) +{ + struct ctl_table_header *head; + struct ctl_table *table = NULL; + + for (head = sysctl_head_next(NULL); head; + head = sysctl_head_next(head)) { + table = proc_sys_lookup_entry(parent, name, head->ctl_table); + if (table) + break; + } + *ptr = head; + return table; +} + +static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, + struct nameidata *nd) +{ + struct ctl_table_header *head; + struct inode *inode; + struct dentry *err; + struct ctl_table *table; + + err = ERR_PTR(-ENOENT); + table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); + if (!table) + goto out; + + err = ERR_PTR(-ENOMEM); + inode = proc_sys_make_inode(dir, table); + if (!inode) + goto out; + + err = NULL; + dentry->d_op = &proc_sys_dentry_operations; + d_add(dentry, inode); + +out: + sysctl_head_finish(head); + return err; +} + +static ssize_t proc_sys_read(struct file *filp, char __user *buf, + size_t count, loff_t *ppos) +{ + struct dentry *dentry = filp->f_dentry; + struct ctl_table_header *head; + struct ctl_table *table; + ssize_t error, res; + + table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); + /* Has the sysctl entry disappeared on us? */ + error = -ENOENT; + if (!table) + goto out; + + /* Has the sysctl entry been replaced by a directory? */ + error = -EISDIR; + if (!table->proc_handler) + goto out; + + /* + * At this point we know that the sysctl was not unregistered + * and won't be until we finish. + */ + error = -EPERM; + if (sysctl_perm(table, MAY_READ)) + goto out; + + /* careful: calling conventions are nasty here */ + res = count; + error = table->proc_handler(table, 0, filp, buf, &res, ppos); + if (!error) + error = res; +out: + sysctl_head_finish(head); + + return error; +} + +static ssize_t proc_sys_write(struct file *filp, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct dentry *dentry = filp->f_dentry; + struct ctl_table_header *head; + struct ctl_table *table; + ssize_t error, res; + + table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); + /* Has the sysctl entry disappeared on us? */ + error = -ENOENT; + if (!table) + goto out; + + /* Has the sysctl entry been replaced by a directory? */ + error = -EISDIR; + if (!table->proc_handler) + goto out; + + /* + * At this point we know that the sysctl was not unregistered + * and won't be until we finish. + */ + error = -EPERM; + if (sysctl_perm(table, MAY_WRITE)) + goto out; + + /* careful: calling conventions are nasty here */ + res = count; + error = table->proc_handler(table, 1, filp, (char __user *)buf, + &res, ppos); + if (!error) + error = res; +out: + sysctl_head_finish(head); + + return error; +} + + +static int proc_sys_fill_cache(struct file *filp, void *dirent, + filldir_t filldir, struct ctl_table *table) +{ + struct ctl_table_header *head; + struct ctl_table *child_table = NULL; + struct dentry *child, *dir = filp->f_path.dentry; + struct inode *inode; + struct qstr qname; + ino_t ino = 0; + unsigned type = DT_UNKNOWN; + int ret; + + qname.name = table->procname; + qname.len = strlen(table->procname); + qname.hash = full_name_hash(qname.name, qname.len); + + /* Suppress duplicates. + * Only fill a directory entry if it is the value that + * an ordinary lookup of that name returns. Hide all + * others. + * + * If we ever cache this translation in the dcache + * I should do a dcache lookup first. But for now + * it is just simpler not to. + */ + ret = 0; + child_table = do_proc_sys_lookup(dir, &qname, &head); + sysctl_head_finish(head); + if (child_table != table) + return 0; + + child = d_lookup(dir, &qname); + if (!child) { + struct dentry *new; + new = d_alloc(dir, &qname); + if (new) { + inode = proc_sys_make_inode(dir->d_inode, table); + if (!inode) + child = ERR_PTR(-ENOMEM); + else { + new->d_op = &proc_sys_dentry_operations; + d_add(new, inode); + } + if (child) + dput(new); + else + child = new; + } + } + if (!child || IS_ERR(child) || !child->d_inode) + goto end_instantiate; + inode = child->d_inode; + if (inode) { + ino = inode->i_ino; + type = inode->i_mode >> 12; + } + dput(child); +end_instantiate: + if (!ino) + ino= find_inode_number(dir, &qname); + if (!ino) + ino = 1; + return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type); +} + +static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) +{ + struct dentry *dentry = filp->f_dentry; + struct inode *inode = dentry->d_inode; + struct ctl_table_header *head = NULL; + struct ctl_table *table; + unsigned long pos; + int ret; + + ret = -ENOTDIR; + if (!S_ISDIR(inode->i_mode)) + goto out; + + ret = 0; + /* Avoid a switch here: arm builds fail with missing __cmpdi2 */ + if (filp->f_pos == 0) { + if (filldir(dirent, ".", 1, filp->f_pos, + inode->i_ino, DT_DIR) < 0) + goto out; + filp->f_pos++; + } + if (filp->f_pos == 1) { + if (filldir(dirent, "..", 2, filp->f_pos, + parent_ino(dentry), DT_DIR) < 0) + goto out; + filp->f_pos++; + } + pos = 2; + + /* - Find each instance of the directory + * - Read all entries in each instance + * - Before returning an entry to user space lookup the entry + * by name and if I find a different entry don't return + * this one because it means it is a buried dup. + * For sysctl this should only happen for directory entries. + */ + for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) { + table = proc_sys_lookup_table(dentry, head->ctl_table); + + if (!table) + continue; + + for (; table->ctl_name || table->procname; table++, pos++) { + /* Can't do anything without a proc name */ + if (!table->procname) + continue; + + if (pos < filp->f_pos) + continue; + + if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0) + goto out; + filp->f_pos = pos + 1; + } + } + ret = 1; +out: + sysctl_head_finish(head); + return ret; +} + +static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd) +{ + /* + * sysctl entries that are not writeable, + * are _NOT_ writeable, capabilities or not. + */ + struct ctl_table_header *head; + struct ctl_table *table; + struct dentry *dentry; + int mode; + int depth; + int error; + + head = NULL; + depth = PROC_I(inode)->fd; + + /* First check the cached permissions, in case we don't have + * enough information to lookup the sysctl table entry. + */ + error = -EACCES; + mode = inode->i_mode; + + if (current->euid == 0) + mode >>= 6; + else if (in_group_p(0)) + mode >>= 3; + + if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask) + error = 0; + + /* If we can't get a sysctl table entry the permission + * checks on the cached mode will have to be enough. + */ + if (!nd || !depth) + goto out; + + dentry = nd->dentry; + table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); + + /* If the entry does not exist deny permission */ + error = -EACCES; + if (!table) + goto out; + + /* Use the permissions on the sysctl table entry */ + error = sysctl_perm(table, mask); +out: + sysctl_head_finish(head); + return error; +} + +static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr) +{ + struct inode *inode = dentry->d_inode; + int error; + + if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) + return -EPERM; + + error = inode_change_ok(inode, attr); + if (!error) { + error = security_inode_setattr(dentry, attr); + if (!error) + error = inode_setattr(inode, attr); + } + + return error; +} + +/* I'm lazy and don't distinguish between files and directories, + * until access time. + */ +static const struct file_operations proc_sys_file_operations = { + .read = proc_sys_read, + .write = proc_sys_write, + .readdir = proc_sys_readdir, +}; + +static struct inode_operations proc_sys_inode_operations = { + .lookup = proc_sys_lookup, + .permission = proc_sys_permission, + .setattr = proc_sys_setattr, +}; + +static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd) +{ + struct ctl_table_header *head; + struct ctl_table *table; + table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); + proc_sys_refresh_inode(dentry->d_inode, table); + sysctl_head_finish(head); + return !!table; +} + +static struct dentry_operations proc_sys_dentry_operations = { + .d_revalidate = proc_sys_revalidate, +}; + +static struct proc_dir_entry *proc_sys_root; + +int proc_sys_init(void) +{ + proc_sys_root = proc_mkdir("sys", NULL); + proc_sys_root->proc_iops = &proc_sys_inode_operations; + proc_sys_root->proc_fops = &proc_sys_file_operations; + proc_sys_root->nlink = 0; + return 0; +} -- cgit v1.2.3