linux-kernel - [PATCH 19/24] x86/mm/kaiser: Respect disabled CPU features

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Date:   Mon, 27 Nov 2017 11:49:18 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 19/24] x86/mm/kaiser: Respect disabled CPU features

From: Thomas Gleixner <tglx@...utronix.de>

PAGE_NX and PAGE_GLOBAL might not be supported, or migth be disabled
on the command line, but Kaiser sets them unconditionally.

Add proper protection against that.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: daniel.gruss@...k.tugraz.at
Cc: hughd@...gle.com
Cc: keescook@...gle.com
Cc: linux-mm@...ck.org
Cc: michael.schwarz@...k.tugraz.at
Cc: moritz.lipp@...k.tugraz.at
Cc: richard.fellner@...dent.tugraz.at
Link: http://lkml.kernel.org/r/20171126232414.313869499@linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/pgtable_64.h |  3 ++-
 arch/x86/mm/kaiser.c              | 12 +++++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 0c6e14f1e274..1c9f1f803ad8 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -222,7 +222,8 @@ static inline pgd_t kaiser_set_shadow_pgd(pgd_t *pgdp, pgd_t pgd)
 			 * wrong CR3 value, userspace will crash
 			 * instead of running.
 			 */
-			pgd.pgd |= _PAGE_NX;
+			if (__supported_pte_mask & _PAGE_NX)
+				pgd.pgd |= _PAGE_NX;
 		}
 	} else if (pgd_userspace_access(*pgdp)) {
 		/*
diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 10c0e9e6bf6b..6e3c5da5f7e8 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -42,6 +42,8 @@
 
 #define KAISER_WALK_ATOMIC  0x1
 
+static pteval_t kaiser_pte_mask __ro_after_init = ~(_PAGE_NX | _PAGE_GLOBAL);
+
 /*
  * At runtime, the only things we map are some things for CPU
  * hotplug, and stacks for new processes.  No two CPUs will ever
@@ -244,11 +246,14 @@ static pte_t *kaiser_shadow_pagetable_walk(unsigned long address,
 int kaiser_add_user_map(const void *__start_addr, unsigned long size,
 			unsigned long flags)
 {
-	pte_t *pte;
 	unsigned long start_addr = (unsigned long)__start_addr;
 	unsigned long address = start_addr & PAGE_MASK;
 	unsigned long end_addr = PAGE_ALIGN(start_addr + size);
 	unsigned long target_address;
+	pte_t *pte;
+
+	/* Clear not supported bits */
+	flags &= kaiser_pte_mask;
 
 	for (; address < end_addr; address += PAGE_SIZE) {
 		target_address = get_pa_from_kernel_map(address);
@@ -308,6 +313,11 @@ static void __init kaiser_init_all_pgds(void)
 	pgd_t *pgd;
 	int i;
 
+	if (__supported_pte_mask & _PAGE_NX)
+		kaiser_pte_mask |= _PAGE_NX;
+	if (boot_cpu_has(X86_FEATURE_PGE))
+		kaiser_pte_mask |= _PAGE_GLOBAL;
+
 	pgd = kernel_to_shadow_pgdp(pgd_offset_k(0UL));
 	for (i = PTRS_PER_PGD / 2; i < PTRS_PER_PGD; i++) {
 		/*
-- 
2.14.1