fs/proc/self.c

   1 #include <linux/proc_fs.h>
   2 #include <linux/sched.h>
   3 #include <linux/namei.h>
   4
   5 /*
   6  * /proc/self:
   7  */
   8 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
   9                               int buflen)
  10 {
  11         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  12         pid_t tgid = task_tgid_nr_ns(current, ns);
  13         char tmp[PROC_NUMBUF];
  14         if (!tgid)
  15                 return -ENOENT;
  16         sprintf(tmp, "%d", tgid);
  17         return vfs_readlink(dentry,buffer,buflen,tmp);
  18 }
  19
  20 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
  21 {
  22         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  23         pid_t tgid = task_tgid_nr_ns(current, ns);
  24         char *name = ERR_PTR(-ENOENT);
  25         if (tgid) {
  26                 /* 11 for max length of signed int in decimal + NULL term */
  27                 name = kmalloc(12, GFP_KERNEL);
  28                 if (!name)
  29                         name = ERR_PTR(-ENOMEM);
  30                 else
  31                         sprintf(name, "%d", tgid);
  32         }
  33         nd_set_link(nd, name);
  34         return NULL;
  35 }
  36
  37 static void proc_self_put_link(struct dentry *dentry, struct nameidata *nd,
  38                                 void *cookie)
  39 {
  40         char *s = nd_get_link(nd);
  41         if (!IS_ERR(s))
  42                 kfree(s);
  43 }
  44
  45 static const struct inode_operations proc_self_inode_operations = {
  46         .readlink       = proc_self_readlink,
  47         .follow_link    = proc_self_follow_link,
  48         .put_link       = proc_self_put_link,
  49 };
  50
  51 void __init proc_self_init(void)
  52 {
  53         struct proc_dir_entry *proc_self_symlink;
  54         mode_t mode;
  55
  56         mode = S_IFLNK | S_IRWXUGO;
  57         proc_self_symlink = proc_create("self", mode, NULL, NULL );
  58         proc_self_symlink->proc_iops = &proc_self_inode_operations;
  59 }