procfs: Use the proc generic infrastructure for proc/self.
I had visions at one point of splitting proc into two filesystems. If
that had happened proc/self being the the part of proc that actually deals
with pids would have been a nice cleanup. As it is proc/self requires
a lot of unnecessary infrastructure for a single file.
The only user visible change is that a mounted /proc for a pid namespace
that is dead now shows a broken proc symlink, instead of being completely
invisible. I don't think anyone will notice or care.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/fs/proc/self.c b/fs/proc/self.c
new file mode 100644
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;
+}