[PATCH v4 09/17] khwasan, arm64: enable top byte ignore for the kernel

[Andrey Konovalov]

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
 
 	/*
-- 
2.18.0.rc2.346.g013aa6912e-goog