[PATCH v6 10/18] khwasan, arm64: enable top byte ignore for the kernel

From: Andrey Konovalov
Date: Wed Aug 29 2018 - 07:36:39 EST


KHWASAN uses the Top Byte Ignore feature of arm64 CPUs to store a pointer
tag in the top byte of each pointer. This commit enables the TCR_TBI1 bit,
which enables Top Byte Ignore for the kernel, when KHWASAN is used.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
arch/arm64/include/asm/pgtable-hwdef.h | 1 +
arch/arm64/mm/proc.S | 8 +++++++-
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index fd208eac9f2a..483aceedad76 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -289,6 +289,7 @@
#define TCR_A1 (UL(1) << 22)
#define TCR_ASID16 (UL(1) << 36)
#define TCR_TBI0 (UL(1) << 37)
+#define TCR_TBI1 (UL(1) << 38)
#define TCR_HA (UL(1) << 39)
#define TCR_HD (UL(1) << 40)
#define TCR_NFD1 (UL(1) << 54)
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 03646e6a2ef4..c5175e098d02 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -47,6 +47,12 @@
/* PTWs cacheable, inner/outer WBWA */
#define TCR_CACHE_FLAGS TCR_IRGN_WBWA | TCR_ORGN_WBWA

+#ifdef CONFIG_KASAN_HW
+#define TCR_KASAN_FLAGS TCR_TBI1
+#else
+#define TCR_KASAN_FLAGS 0
+#endif
+
#define MAIR(attr, mt) ((attr) << ((mt) * 8))

/*
@@ -440,7 +446,7 @@ ENTRY(__cpu_setup)
*/
ldr x10, =TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
- TCR_TBI0 | TCR_A1
+ TCR_TBI0 | TCR_A1 | TCR_KASAN_FLAGS
tcr_set_idmap_t0sz x10, x9

/*
--
2.19.0.rc0.228.g281dcd1b4d0-goog