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

Ingo Molnar
2017-11-27T10:53:50Z

From: Thomas Gleixner <tglx@linutronix.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@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Cc: michael.schwarz@iaik.tugraz.at
Cc: moritz.lipp@iaik.tugraz.at
Cc: richard.fellner@student.tugraz.at
Link: http://lkml.kernel.org/r/20171126232414.313869499@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.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