v4.19.13 snapshot.
diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
new file mode 100644
index 0000000..b905010
--- /dev/null
+++ b/fs/proc/thread_self.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/cache.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/pid_namespace.h>
+#include "internal.h"
+
+/*
+ * /proc/thread_self:
+ */
+static const char *proc_thread_self_get_link(struct dentry *dentry,
+ struct inode *inode,
+ struct delayed_call *done)
+{
+ struct pid_namespace *ns = proc_pid_ns(inode);
+ pid_t tgid = task_tgid_nr_ns(current, ns);
+ pid_t pid = task_pid_nr_ns(current, ns);
+ char *name;
+
+ if (!pid)
+ return ERR_PTR(-ENOENT);
+ name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
+ if (unlikely(!name))
+ return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
+ sprintf(name, "%u/task/%u", tgid, pid);
+ set_delayed_call(done, kfree_link, name);
+ return name;
+}
+
+static const struct inode_operations proc_thread_self_inode_operations = {
+ .get_link = proc_thread_self_get_link,
+};
+
+static unsigned thread_self_inum __ro_after_init;
+
+int proc_setup_thread_self(struct super_block *s)
+{
+ struct inode *root_inode = d_inode(s->s_root);
+ struct pid_namespace *ns = proc_pid_ns(root_inode);
+ struct dentry *thread_self;
+
+ inode_lock(root_inode);
+ 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);
+ 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);
+ }
+ inode_unlock(root_inode);
+ 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);
+}