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authorEric W. Biederman <ebiederm@xmission.com>2014-07-31 03:10:50 -0700
committerEric W. Biederman <ebiederm@xmission.com>2014-08-04 10:07:11 -0700
commit0097875bd41528922fb3bb5f348c53f17e00e2fd (patch)
tree414cffac820d04e4542dc7654e7ef188f00ba0b2 /fs/proc/thread_self.c
parent6ba8ed79a3cce14bd5597218fd46408b8376f8f3 (diff)
downloadlinux-0097875bd41528922fb3bb5f348c53f17e00e2fd.tar.bz2
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" <ebiederm@xmission.com>
Diffstat (limited to 'fs/proc/thread_self.c')
-rw-r--r--fs/proc/thread_self.c85
1 files changed, 85 insertions, 0 deletions
diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
new file mode 100644
index 000000000000..59075b509df3
--- /dev/null
+++ b/fs/proc/thread_self.c
@@ -0,0 +1,85 @@
+#include <linux/sched.h>
+#include <linux/namei.h>
+#include <linux/slab.h>
+#include <linux/pid_namespace.h>
+#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);
+}