x86/exceptions: Enable IST guard pages

All usage sites which expected that the exception stacks in the CPU entry
area are mapped linearly are fixed up. Enable guard pages between the
IST stacks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190414160145.349862042@linutronix.de

diff --git a/arch/x86/include/asm/cpu_entry_area.h b/arch/x86/include/asm/cpu_entry_area.h
index 310eeb62d4184a83ebe606bf909501a10661aa69..9c96406e6d2b877845c6607b4d93c9113640cad2 100644 (file)
--- a/arch/x86/include/asm/cpu_entry_area.h
+++ b/arch/x86/include/asm/cpu_entry_area.h
@@ -26,13 +26,9 @@ struct exception_stacks {
        ESTACKS_MEMBERS(0)
 };
 
-/*
- * The effective cpu entry area mapping with guard pages. Guard size is
- * zero until the code which makes assumptions about linear mappings is
- * cleaned up.
- */
+/* The effective cpu entry area mapping with guard pages. */
 struct cea_exception_stacks {
-       ESTACKS_MEMBERS(0)
+       ESTACKS_MEMBERS(PAGE_SIZE)
 };
 
 /*