Set TCR_EL1.EPD1 bit to 1

In the S-EL1&0 translation regime we aren't using the higher VA range,
whose translation table base address is held in TTBR1_EL1. The bit
TCR_EL1.EPD1 can be used to disable translations using TTBR1_EL1, but
the code wasn't setting it to 1. Additionally, other fields in TCR1_EL1
associated with the higher VA range (TBI1, TG1, SH1, ORGN1, IRGN1 and
A1) weren't set correctly as they were left as 0. In particular, 0 is a
reserved value for TG1. Also, TBBR1_EL1 was not explicitly set and its
reset value is UNKNOWN.

Therefore memory accesses to the higher VA range would result in
unpredictable behaviour as a translation table walk would be attempted
using an UNKNOWN value in TTBR1_EL1.

On the FVP and Juno platforms accessing the higher VA range resulted in
a translation fault, but this may not always be the case on all
platforms.

This patch sets the bit TCR_EL1.EPD1 to 1 so that any kind of
unpredictable behaviour is prevented.

This bug only affects the AArch64 version of the code, the AArch32
version sets this bit to 1 as expected.

Change-Id: I481c000deda5bc33a475631301767b9e0474a303
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

include/lib/aarch64/arch.h

@@ -348,6 +348,8 @@
 #define TCR_SH_OUTER_SHAREABLE	(U(0x2) << 12)
 #define TCR_SH_INNER_SHAREABLE	(U(0x3) << 12)
 
+#define TCR_EPD1_BIT		(U(1) << 23)
+
 #define MODE_SP_SHIFT		U(0x0)
 #define MODE_SP_MASK		U(0x1)
 #define MODE_SP_EL0		U(0x0)

lib/xlat_tables/aarch64/xlat_tables.c

@@ -182,7 +182,11 @@ void init_xlat_tables(void)
 
 /* Define EL1 and EL3 variants of the function enabling the MMU */
 DEFINE_ENABLE_MMU_EL(1,
-		(tcr_ps_bits << TCR_EL1_IPS_SHIFT),
+		/*
+		 * TCR_EL1.EPD1: Disable translation table walk for addresses
+		 * that are translated using TTBR1_EL1.
+		 */
+		TCR_EPD1_BIT | (tcr_ps_bits << TCR_EL1_IPS_SHIFT),
 		tlbivmalle1)
 DEFINE_ENABLE_MMU_EL(3,
 		TCR_EL3_RES1 | (tcr_ps_bits << TCR_EL3_PS_SHIFT),

lib/xlat_tables_v2/aarch64/xlat_tables_arch.c

@@ -256,7 +256,11 @@ void enable_mmu_arch(unsigned int flags,
 
 #if IMAGE_EL == 1
 	assert(IS_IN_EL(1));
-	tcr |= tcr_ps_bits << TCR_EL1_IPS_SHIFT;
+	/*
+	 * TCR_EL1.EPD1: Disable translation table walk for addresses that are
+	 * translated using TTBR1_EL1.
+	 */
+	tcr |= TCR_EPD1_BIT | (tcr_ps_bits << TCR_EL1_IPS_SHIFT);
 	enable_mmu_internal_el1(flags, mair, tcr, ttbr);
 #elif IMAGE_EL == 3
 	assert(IS_IN_EL(3));