linux/fs/proc/thread_self.c
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   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/cache.h>
   3#include <linux/sched.h>
   4#include <linux/slab.h>
   5#include <linux/pid_namespace.h>
   6#include "internal.h"
   7
   8/*
   9 * /proc/thread_self:
  10 */
  11static const char *proc_thread_self_get_link(struct dentry *dentry,
  12                                             struct inode *inode,
  13                                             struct delayed_call *done)
  14{
  15        struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
  16        pid_t tgid = task_tgid_nr_ns(current, ns);
  17        pid_t pid = task_pid_nr_ns(current, ns);
  18        char *name;
  19
  20        if (!pid)
  21                return ERR_PTR(-ENOENT);
  22        name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
  23        if (unlikely(!name))
  24                return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
  25        sprintf(name, "%u/task/%u", tgid, pid);
  26        set_delayed_call(done, kfree_link, name);
  27        return name;
  28}
  29
  30static const struct inode_operations proc_thread_self_inode_operations = {
  31        .get_link       = proc_thread_self_get_link,
  32};
  33
  34static unsigned thread_self_inum __ro_after_init;
  35
  36int proc_setup_thread_self(struct super_block *s)
  37{
  38        struct inode *root_inode = d_inode(s->s_root);
  39        struct proc_fs_info *fs_info = proc_sb_info(s);
  40        struct dentry *thread_self;
  41        int ret = -ENOMEM;
  42
  43        inode_lock(root_inode);
  44        thread_self = d_alloc_name(s->s_root, "thread-self");
  45        if (thread_self) {
  46                struct inode *inode = new_inode(s);
  47                if (inode) {
  48                        inode->i_ino = thread_self_inum;
  49                        inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
  50                        inode->i_mode = S_IFLNK | S_IRWXUGO;
  51                        inode->i_uid = GLOBAL_ROOT_UID;
  52                        inode->i_gid = GLOBAL_ROOT_GID;
  53                        inode->i_op = &proc_thread_self_inode_operations;
  54                        d_add(thread_self, inode);
  55                        ret = 0;
  56                } else {
  57                        dput(thread_self);
  58                }
  59        }
  60        inode_unlock(root_inode);
  61
  62        if (ret)
  63                pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
  64        else
  65                fs_info->proc_thread_self = thread_self;
  66
  67        return ret;
  68}
  69
  70void __init proc_thread_self_init(void)
  71{
  72        proc_alloc_inum(&thread_self_inum);
  73}
  74
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