From 0097875bd41528922fb3bb5f348c53f17e00e2fd Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 31 Jul 2014 03:10:50 -0700 Subject: proc: Implement /proc/thread-self to point at the directory of the current thread /proc/thread-self is derived from /proc/self. /proc/thread-self points to the directory in proc containing information about the current thread. This funtionality has been missing for a long time, and is tricky to implement in userspace as gettid() is not exported by glibc. More importantly this allows fixing defects in /proc/mounts and /proc/net where in a threaded application today they wind up being empty files when only the initial pthread has exited, causing problems for other threads. Signed-off-by: "Eric W. Biederman" --- fs/proc/thread_self.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 fs/proc/thread_self.c (limited to 'fs/proc/thread_self.c') diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c new file mode 100644 index 00000000000..59075b509df --- /dev/null +++ b/fs/proc/thread_self.c @@ -0,0 +1,85 @@ +#include +#include +#include +#include +#include "internal.h" + +/* + * /proc/thread_self: + */ +static int proc_thread_self_readlink(struct dentry *dentry, char __user *buffer, + int buflen) +{ + struct pid_namespace *ns = dentry->d_sb->s_fs_info; + pid_t tgid = task_tgid_nr_ns(current, ns); + pid_t pid = task_pid_nr_ns(current, ns); + char tmp[PROC_NUMBUF + 6 + PROC_NUMBUF]; + if (!pid) + return -ENOENT; + sprintf(tmp, "%d/task/%d", tgid, pid); + return readlink_copy(buffer, buflen, tmp); +} + +static void *proc_thread_self_follow_link(struct dentry *dentry, struct nameidata *nd) +{ + struct pid_namespace *ns = dentry->d_sb->s_fs_info; + pid_t tgid = task_tgid_nr_ns(current, ns); + pid_t pid = task_pid_nr_ns(current, ns); + char *name = ERR_PTR(-ENOENT); + if (pid) { + name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF, GFP_KERNEL); + if (!name) + name = ERR_PTR(-ENOMEM); + else + sprintf(name, "%d/task/%d", tgid, pid); + } + nd_set_link(nd, name); + return NULL; +} + +static const struct inode_operations proc_thread_self_inode_operations = { + .readlink = proc_thread_self_readlink, + .follow_link = proc_thread_self_follow_link, + .put_link = kfree_put_link, +}; + +static unsigned thread_self_inum; + +int proc_setup_thread_self(struct super_block *s) +{ + struct inode *root_inode = s->s_root->d_inode; + struct pid_namespace *ns = s->s_fs_info; + struct dentry *thread_self; + + mutex_lock(&root_inode->i_mutex); + thread_self = d_alloc_name(s->s_root, "thread-self"); + if (thread_self) { + struct inode *inode = new_inode_pseudo(s); + if (inode) { + inode->i_ino = thread_self_inum; + inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; + inode->i_mode = S_IFLNK | S_IRWXUGO; + inode->i_uid = GLOBAL_ROOT_UID; + inode->i_gid = GLOBAL_ROOT_GID; + inode->i_op = &proc_thread_self_inode_operations; + d_add(thread_self, inode); + } else { + dput(thread_self); + thread_self = ERR_PTR(-ENOMEM); + } + } else { + thread_self = ERR_PTR(-ENOMEM); + } + mutex_unlock(&root_inode->i_mutex); + if (IS_ERR(thread_self)) { + pr_err("proc_fill_super: can't allocate /proc/thread_self\n"); + return PTR_ERR(thread_self); + } + ns->proc_thread_self = thread_self; + return 0; +} + +void __init proc_thread_self_init(void) +{ + proc_alloc_inum(&thread_self_inum); +} -- cgit v1.2.3-70-g09d2