x86/mm/pti: Share entry text PMD

Share the entry text PMD of the kernel mapping with the user space
mapping. If large pages are enabled this is a single PMD entry and at the
point where it is copied into the user page table the RW bit has not been
cleared yet. Clear it right away so the user space visible map becomes RX.

Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: KAGA-KOKO

arch/x86/mm/pti.c

@@ -287,6 +287,15 @@ static void __init pti_clone_user_shared(void)
 	pti_clone_p4d(CPU_ENTRY_AREA_BASE);
 }
 
+/*
+ * Clone the populated PMDs of the entry and irqentry text and force it RO.
+ */
+static void __init pti_clone_entry_text(void)
+{
+	pti_clone_pmds((unsigned long) __entry_text_start,
+			(unsigned long) __irqentry_text_end, _PAGE_RW);
+}
+
 /*
  * Initialize kernel page table isolation
  */
@@ -298,4 +307,5 @@ void __init pti_init(void)
 	pr_info("enabled\n");
 
 	pti_clone_user_shared();
+	pti_clone_entry_text();
 }