x86/mm/dump_pagetables: Add page table directory to the debugfs VFS hierarchy

The upcoming support for dumping the kernel and the user space page tables
of the current process would create more random files in the top level
debugfs directory.

Add a page table directory and move the existing file to it.
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/debug_pagetables.c

@@ -22,21 +22,26 @@ static const struct file_operations ptdump_fops = {
 	.release	= single_release,
 };
 
-static struct dentry *pe;
+static struct dentry *dir, *pe;
 
 static int __init pt_dump_debug_init(void)
 {
-	pe = debugfs_create_file("kernel_page_tables", S_IRUSR, NULL, NULL,
-				 &ptdump_fops);
-	if (!pe)
+	dir = debugfs_create_dir("page_tables", NULL);
+	if (!dir)
 		return -ENOMEM;
 
+	pe = debugfs_create_file("kernel", 0400, dir, NULL, &ptdump_fops);
+	if (!pe)
+		goto err;
 	return 0;
+err:
+	debugfs_remove_recursive(dir);
+	return -ENOMEM;
 }
 
 static void __exit pt_dump_debug_exit(void)
 {
-	debugfs_remove_recursive(pe);
+	debugfs_remove_recursive(dir);
 }
 
 module_init(pt_dump_debug_init);