procfs: Use the proc generic infrastructure for proc/self.

[firefly-linux-kernel-4.4.55.git] / fs / proc / self.c

diff --git a/fs/proc/self.c b/fs/proc/self.c
new file mode 100644 (file)
index 0000000..aa5cc3b
--- /dev/null
+++ b/fs/proc/self.c
@@ -0,0 +1,59 @@
+#include <linux/proc_fs.h>
+#include <linux/sched.h>
+#include <linux/namei.h>
+
+/*
+ * /proc/self:
+ */
+static int proc_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);
+       char tmp[PROC_NUMBUF];
+       if (!tgid)
+               return -ENOENT;
+       sprintf(tmp, "%d", tgid);
+       return vfs_readlink(dentry,buffer,buflen,tmp);
+}
+
+static void *proc_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);
+       char *name = ERR_PTR(-ENOENT);
+       if (tgid) {
+               /* 11 for max length of signed int in decimal + NULL term */
+               name = kmalloc(12, GFP_KERNEL);
+               if (!name)
+                       name = ERR_PTR(-ENOMEM);
+               else
+                       sprintf(name, "%d", tgid);
+       }
+       nd_set_link(nd, name);
+       return NULL;
+}
+
+static void proc_self_put_link(struct dentry *dentry, struct nameidata *nd,
+                               void *cookie)
+{
+       char *s = nd_get_link(nd);
+       if (!IS_ERR(s))
+               kfree(s);
+}
+
+static const struct inode_operations proc_self_inode_operations = {
+       .readlink       = proc_self_readlink,
+       .follow_link    = proc_self_follow_link,
+       .put_link       = proc_self_put_link,
+};
+
+void __init proc_self_init(void)
+{
+       struct proc_dir_entry *proc_self_symlink;
+       mode_t mode;
+
+       mode = S_IFLNK | S_IRWXUGO;
+       proc_self_symlink = proc_create("self", mode, NULL, NULL );
+       proc_self_symlink->proc_iops = &proc_self_inode_operations;
+}