From f7cfbee91559ca7e3e961a00ffac921208a115ad Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 4 Dec 2017 15:07:45 +0100 Subject: [PATCH] x86/mm/pti: Share cpu_entry_area with user space page tables Share the cpu entry area so the user space and kernel space page tables have the same P4D page. Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Signed-off-by: Ingo Molnar --- arch/x86/mm/pti.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index d58bcee..5929035 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -265,6 +265,29 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear) } /* + * Clone a single p4d (i.e. a top-level entry on 4-level systems and a + * next-level entry on 5-level systems. + */ +static void __init pti_clone_p4d(unsigned long addr) +{ + p4d_t *kernel_p4d, *user_p4d; + pgd_t *kernel_pgd; + + user_p4d = pti_user_pagetable_walk_p4d(addr); + kernel_pgd = pgd_offset_k(addr); + kernel_p4d = p4d_offset(kernel_pgd, addr); + *user_p4d = *kernel_p4d; +} + +/* + * Clone the CPU_ENTRY_AREA into the user space visible page table. + */ +static void __init pti_clone_user_shared(void) +{ + pti_clone_p4d(CPU_ENTRY_AREA_BASE); +} + +/* * Initialize kernel page table isolation */ void __init pti_init(void) @@ -273,4 +296,6 @@ void __init pti_init(void) return; pr_info("enabled\n"); + + pti_clone_user_shared(); } -- 2.7.4