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552 lines
14 KiB
552 lines
14 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* inode.c - part of tracefs, a pseudo file system for activating tracing |
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* |
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* Based on debugfs by: Greg Kroah-Hartman <[email protected]> |
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* |
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* Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <[email protected]> |
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* |
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* tracefs is the file system that is used by the tracing infrastructure. |
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*/ |
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|
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#include <linux/module.h> |
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#include <linux/fs.h> |
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#include <linux/mount.h> |
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#include <linux/kobject.h> |
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#include <linux/namei.h> |
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#include <linux/tracefs.h> |
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#include <linux/fsnotify.h> |
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#include <linux/security.h> |
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#include <linux/seq_file.h> |
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#include <linux/parser.h> |
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#include <linux/magic.h> |
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#include <linux/slab.h> |
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#define TRACEFS_DEFAULT_MODE 0700 |
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static struct vfsmount *tracefs_mount; |
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static int tracefs_mount_count; |
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static bool tracefs_registered; |
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static ssize_t default_read_file(struct file *file, char __user *buf, |
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size_t count, loff_t *ppos) |
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{ |
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return 0; |
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} |
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static ssize_t default_write_file(struct file *file, const char __user *buf, |
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size_t count, loff_t *ppos) |
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{ |
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return count; |
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} |
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static const struct file_operations tracefs_file_operations = { |
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.read = default_read_file, |
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.write = default_write_file, |
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.open = simple_open, |
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.llseek = noop_llseek, |
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}; |
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static struct tracefs_dir_ops { |
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int (*mkdir)(const char *name); |
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int (*rmdir)(const char *name); |
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} tracefs_ops __ro_after_init; |
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static char *get_dname(struct dentry *dentry) |
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{ |
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const char *dname; |
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char *name; |
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int len = dentry->d_name.len; |
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dname = dentry->d_name.name; |
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name = kmalloc(len + 1, GFP_KERNEL); |
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if (!name) |
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return NULL; |
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memcpy(name, dname, len); |
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name[len] = 0; |
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return name; |
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} |
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static int tracefs_syscall_mkdir(struct user_namespace *mnt_userns, |
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struct inode *inode, struct dentry *dentry, |
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umode_t mode) |
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{ |
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char *name; |
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int ret; |
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name = get_dname(dentry); |
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if (!name) |
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return -ENOMEM; |
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/* |
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* The mkdir call can call the generic functions that create |
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* the files within the tracefs system. It is up to the individual |
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* mkdir routine to handle races. |
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*/ |
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inode_unlock(inode); |
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ret = tracefs_ops.mkdir(name); |
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inode_lock(inode); |
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kfree(name); |
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return ret; |
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} |
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static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry) |
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{ |
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char *name; |
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int ret; |
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name = get_dname(dentry); |
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if (!name) |
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return -ENOMEM; |
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/* |
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* The rmdir call can call the generic functions that create |
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* the files within the tracefs system. It is up to the individual |
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* rmdir routine to handle races. |
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* This time we need to unlock not only the parent (inode) but |
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* also the directory that is being deleted. |
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*/ |
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inode_unlock(inode); |
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inode_unlock(dentry->d_inode); |
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ret = tracefs_ops.rmdir(name); |
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inode_lock_nested(inode, I_MUTEX_PARENT); |
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inode_lock(dentry->d_inode); |
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kfree(name); |
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return ret; |
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} |
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static const struct inode_operations tracefs_dir_inode_operations = { |
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.lookup = simple_lookup, |
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.mkdir = tracefs_syscall_mkdir, |
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.rmdir = tracefs_syscall_rmdir, |
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}; |
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static struct inode *tracefs_get_inode(struct super_block *sb) |
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{ |
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struct inode *inode = new_inode(sb); |
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if (inode) { |
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inode->i_ino = get_next_ino(); |
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inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); |
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} |
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return inode; |
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} |
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struct tracefs_mount_opts { |
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kuid_t uid; |
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kgid_t gid; |
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umode_t mode; |
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}; |
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enum { |
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Opt_uid, |
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Opt_gid, |
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Opt_mode, |
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Opt_err |
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}; |
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static const match_table_t tokens = { |
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{Opt_uid, "uid=%u"}, |
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{Opt_gid, "gid=%u"}, |
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{Opt_mode, "mode=%o"}, |
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{Opt_err, NULL} |
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}; |
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struct tracefs_fs_info { |
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struct tracefs_mount_opts mount_opts; |
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}; |
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static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts) |
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{ |
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substring_t args[MAX_OPT_ARGS]; |
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int option; |
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int token; |
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kuid_t uid; |
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kgid_t gid; |
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char *p; |
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opts->mode = TRACEFS_DEFAULT_MODE; |
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while ((p = strsep(&data, ",")) != NULL) { |
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if (!*p) |
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continue; |
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token = match_token(p, tokens, args); |
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switch (token) { |
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case Opt_uid: |
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if (match_int(&args[0], &option)) |
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return -EINVAL; |
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uid = make_kuid(current_user_ns(), option); |
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if (!uid_valid(uid)) |
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return -EINVAL; |
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opts->uid = uid; |
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break; |
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case Opt_gid: |
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if (match_int(&args[0], &option)) |
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return -EINVAL; |
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gid = make_kgid(current_user_ns(), option); |
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if (!gid_valid(gid)) |
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return -EINVAL; |
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opts->gid = gid; |
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break; |
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case Opt_mode: |
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if (match_octal(&args[0], &option)) |
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return -EINVAL; |
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opts->mode = option & S_IALLUGO; |
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break; |
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/* |
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* We might like to report bad mount options here; |
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* but traditionally tracefs has ignored all mount options |
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*/ |
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} |
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} |
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return 0; |
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} |
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static int tracefs_apply_options(struct super_block *sb) |
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{ |
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struct tracefs_fs_info *fsi = sb->s_fs_info; |
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struct inode *inode = sb->s_root->d_inode; |
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struct tracefs_mount_opts *opts = &fsi->mount_opts; |
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inode->i_mode &= ~S_IALLUGO; |
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inode->i_mode |= opts->mode; |
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inode->i_uid = opts->uid; |
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inode->i_gid = opts->gid; |
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return 0; |
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} |
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static int tracefs_remount(struct super_block *sb, int *flags, char *data) |
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{ |
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int err; |
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struct tracefs_fs_info *fsi = sb->s_fs_info; |
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sync_filesystem(sb); |
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err = tracefs_parse_options(data, &fsi->mount_opts); |
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if (err) |
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goto fail; |
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tracefs_apply_options(sb); |
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fail: |
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return err; |
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} |
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static int tracefs_show_options(struct seq_file *m, struct dentry *root) |
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{ |
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struct tracefs_fs_info *fsi = root->d_sb->s_fs_info; |
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struct tracefs_mount_opts *opts = &fsi->mount_opts; |
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if (!uid_eq(opts->uid, GLOBAL_ROOT_UID)) |
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seq_printf(m, ",uid=%u", |
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from_kuid_munged(&init_user_ns, opts->uid)); |
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if (!gid_eq(opts->gid, GLOBAL_ROOT_GID)) |
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seq_printf(m, ",gid=%u", |
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from_kgid_munged(&init_user_ns, opts->gid)); |
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if (opts->mode != TRACEFS_DEFAULT_MODE) |
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seq_printf(m, ",mode=%o", opts->mode); |
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return 0; |
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} |
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static const struct super_operations tracefs_super_operations = { |
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.statfs = simple_statfs, |
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.remount_fs = tracefs_remount, |
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.show_options = tracefs_show_options, |
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}; |
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static int trace_fill_super(struct super_block *sb, void *data, int silent) |
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{ |
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static const struct tree_descr trace_files[] = {{""}}; |
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struct tracefs_fs_info *fsi; |
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int err; |
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fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL); |
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sb->s_fs_info = fsi; |
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if (!fsi) { |
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err = -ENOMEM; |
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goto fail; |
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} |
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err = tracefs_parse_options(data, &fsi->mount_opts); |
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if (err) |
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goto fail; |
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err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files); |
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if (err) |
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goto fail; |
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sb->s_op = &tracefs_super_operations; |
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tracefs_apply_options(sb); |
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return 0; |
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fail: |
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kfree(fsi); |
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sb->s_fs_info = NULL; |
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return err; |
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} |
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static struct dentry *trace_mount(struct file_system_type *fs_type, |
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int flags, const char *dev_name, |
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void *data) |
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{ |
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return mount_single(fs_type, flags, data, trace_fill_super); |
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} |
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static struct file_system_type trace_fs_type = { |
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.owner = THIS_MODULE, |
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.name = "tracefs", |
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.mount = trace_mount, |
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.kill_sb = kill_litter_super, |
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}; |
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MODULE_ALIAS_FS("tracefs"); |
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static struct dentry *start_creating(const char *name, struct dentry *parent) |
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{ |
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struct dentry *dentry; |
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int error; |
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pr_debug("tracefs: creating file '%s'\n",name); |
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error = simple_pin_fs(&trace_fs_type, &tracefs_mount, |
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&tracefs_mount_count); |
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if (error) |
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return ERR_PTR(error); |
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/* If the parent is not specified, we create it in the root. |
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* We need the root dentry to do this, which is in the super |
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* block. A pointer to that is in the struct vfsmount that we |
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* have around. |
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*/ |
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if (!parent) |
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parent = tracefs_mount->mnt_root; |
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inode_lock(parent->d_inode); |
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if (unlikely(IS_DEADDIR(parent->d_inode))) |
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dentry = ERR_PTR(-ENOENT); |
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else |
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dentry = lookup_one_len(name, parent, strlen(name)); |
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if (!IS_ERR(dentry) && dentry->d_inode) { |
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dput(dentry); |
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dentry = ERR_PTR(-EEXIST); |
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} |
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if (IS_ERR(dentry)) { |
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inode_unlock(parent->d_inode); |
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simple_release_fs(&tracefs_mount, &tracefs_mount_count); |
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} |
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return dentry; |
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} |
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static struct dentry *failed_creating(struct dentry *dentry) |
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{ |
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inode_unlock(dentry->d_parent->d_inode); |
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dput(dentry); |
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simple_release_fs(&tracefs_mount, &tracefs_mount_count); |
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return NULL; |
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} |
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static struct dentry *end_creating(struct dentry *dentry) |
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{ |
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inode_unlock(dentry->d_parent->d_inode); |
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return dentry; |
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} |
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/** |
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* tracefs_create_file - create a file in the tracefs filesystem |
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* @name: a pointer to a string containing the name of the file to create. |
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* @mode: the permission that the file should have. |
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* @parent: a pointer to the parent dentry for this file. This should be a |
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* directory dentry if set. If this parameter is NULL, then the |
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* file will be created in the root of the tracefs filesystem. |
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* @data: a pointer to something that the caller will want to get to later |
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* on. The inode.i_private pointer will point to this value on |
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* the open() call. |
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* @fops: a pointer to a struct file_operations that should be used for |
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* this file. |
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* |
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* This is the basic "create a file" function for tracefs. It allows for a |
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* wide range of flexibility in creating a file, or a directory (if you want |
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* to create a directory, the tracefs_create_dir() function is |
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* recommended to be used instead.) |
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* |
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* This function will return a pointer to a dentry if it succeeds. This |
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* pointer must be passed to the tracefs_remove() function when the file is |
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* to be removed (no automatic cleanup happens if your module is unloaded, |
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* you are responsible here.) If an error occurs, %NULL will be returned. |
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* |
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* If tracefs is not enabled in the kernel, the value -%ENODEV will be |
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* returned. |
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*/ |
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struct dentry *tracefs_create_file(const char *name, umode_t mode, |
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struct dentry *parent, void *data, |
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const struct file_operations *fops) |
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{ |
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struct dentry *dentry; |
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struct inode *inode; |
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if (security_locked_down(LOCKDOWN_TRACEFS)) |
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return NULL; |
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if (!(mode & S_IFMT)) |
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mode |= S_IFREG; |
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BUG_ON(!S_ISREG(mode)); |
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dentry = start_creating(name, parent); |
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if (IS_ERR(dentry)) |
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return NULL; |
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inode = tracefs_get_inode(dentry->d_sb); |
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if (unlikely(!inode)) |
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return failed_creating(dentry); |
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inode->i_mode = mode; |
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inode->i_fop = fops ? fops : &tracefs_file_operations; |
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inode->i_private = data; |
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d_instantiate(dentry, inode); |
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fsnotify_create(dentry->d_parent->d_inode, dentry); |
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return end_creating(dentry); |
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} |
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static struct dentry *__create_dir(const char *name, struct dentry *parent, |
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const struct inode_operations *ops) |
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{ |
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struct dentry *dentry = start_creating(name, parent); |
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struct inode *inode; |
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if (IS_ERR(dentry)) |
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return NULL; |
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inode = tracefs_get_inode(dentry->d_sb); |
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if (unlikely(!inode)) |
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return failed_creating(dentry); |
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inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; |
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inode->i_op = ops; |
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inode->i_fop = &simple_dir_operations; |
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/* directory inodes start off with i_nlink == 2 (for "." entry) */ |
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inc_nlink(inode); |
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d_instantiate(dentry, inode); |
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inc_nlink(dentry->d_parent->d_inode); |
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fsnotify_mkdir(dentry->d_parent->d_inode, dentry); |
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return end_creating(dentry); |
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} |
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/** |
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* tracefs_create_dir - create a directory in the tracefs filesystem |
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* @name: a pointer to a string containing the name of the directory to |
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* create. |
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* @parent: a pointer to the parent dentry for this file. This should be a |
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* directory dentry if set. If this parameter is NULL, then the |
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* directory will be created in the root of the tracefs filesystem. |
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* |
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* This function creates a directory in tracefs with the given name. |
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* |
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* This function will return a pointer to a dentry if it succeeds. This |
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* pointer must be passed to the tracefs_remove() function when the file is |
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* to be removed. If an error occurs, %NULL will be returned. |
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* |
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* If tracing is not enabled in the kernel, the value -%ENODEV will be |
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* returned. |
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*/ |
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struct dentry *tracefs_create_dir(const char *name, struct dentry *parent) |
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{ |
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return __create_dir(name, parent, &simple_dir_inode_operations); |
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} |
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/** |
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* tracefs_create_instance_dir - create the tracing instances directory |
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* @name: The name of the instances directory to create |
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* @parent: The parent directory that the instances directory will exist |
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* @mkdir: The function to call when a mkdir is performed. |
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* @rmdir: The function to call when a rmdir is performed. |
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* |
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* Only one instances directory is allowed. |
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* |
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* The instances directory is special as it allows for mkdir and rmdir to |
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* to be done by userspace. When a mkdir or rmdir is performed, the inode |
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* locks are released and the methods passed in (@mkdir and @rmdir) are |
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* called without locks and with the name of the directory being created |
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* within the instances directory. |
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* |
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* Returns the dentry of the instances directory. |
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*/ |
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__init struct dentry *tracefs_create_instance_dir(const char *name, |
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struct dentry *parent, |
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int (*mkdir)(const char *name), |
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int (*rmdir)(const char *name)) |
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{ |
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struct dentry *dentry; |
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/* Only allow one instance of the instances directory. */ |
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if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir)) |
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return NULL; |
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dentry = __create_dir(name, parent, &tracefs_dir_inode_operations); |
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if (!dentry) |
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return NULL; |
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tracefs_ops.mkdir = mkdir; |
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tracefs_ops.rmdir = rmdir; |
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return dentry; |
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} |
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static void remove_one(struct dentry *victim) |
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{ |
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simple_release_fs(&tracefs_mount, &tracefs_mount_count); |
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} |
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/** |
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* tracefs_remove - recursively removes a directory |
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* @dentry: a pointer to a the dentry of the directory to be removed. |
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* |
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* This function recursively removes a directory tree in tracefs that |
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* was previously created with a call to another tracefs function |
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* (like tracefs_create_file() or variants thereof.) |
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*/ |
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void tracefs_remove(struct dentry *dentry) |
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{ |
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if (IS_ERR_OR_NULL(dentry)) |
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return; |
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simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count); |
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simple_recursive_removal(dentry, remove_one); |
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simple_release_fs(&tracefs_mount, &tracefs_mount_count); |
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} |
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/** |
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* tracefs_initialized - Tells whether tracefs has been registered |
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*/ |
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bool tracefs_initialized(void) |
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{ |
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return tracefs_registered; |
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} |
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static int __init tracefs_init(void) |
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{ |
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int retval; |
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retval = sysfs_create_mount_point(kernel_kobj, "tracing"); |
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if (retval) |
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return -EINVAL; |
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retval = register_filesystem(&trace_fs_type); |
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if (!retval) |
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tracefs_registered = true; |
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return retval; |
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} |
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core_initcall(tracefs_init);
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