Cortex A9:errata 794073 workaround

On Cortex A9 an errata can cause the processor to violate the rules for
speculative fetches when the MMU is off but branch prediction has not
been disabled. The workaround for this is to execute an Invalidate
Entire Branch Prediction Array (BPIALL) followed by a DSB.

see:http://arminfo.emea.arm.com/help/topic/com.arm.doc.uan0009d/UAN0009_cortex_a9_errata_r4.pdf


for more details.

Change-Id: I9146c1fa7563a79f4e15b6251617b9620a587c93
Signed-off-by: Joel Hutton <Joel.Hutton@arm.com>

docs/cpu-specific-build-macros.rst

@@ -71,6 +71,11 @@ for it to specify which errata workarounds should be enabled or not.
 The value of the build flags is 0 by default, that is, disabled. A value of 1
 will enable it.
 
+For Cortex-A9, the following errata build flags are defined :
+
+-  ``ERRATA_A9_794073``: This applies errata 794073 workaround to Cortex-A15
+   CPU. This needs to be enabled for all revisions of the CPU.
+
 For Cortex-A15, the following errata build flags are defined :
 
 -  ``ERRATA_A15_816470``: This applies errata 816470 workaround to Cortex-A15
@@ -260,7 +265,7 @@ architecture that can be enabled by the platform as desired.
 
 --------------
 
-*Copyright (c) 2014-2018, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2014-2019, Arm Limited and Contributors. All rights reserved.*
 
 .. _CVE-2017-5715: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715
 .. _CVE-2018-3639: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3639

lib/aarch32/misc_helpers.S

 /*
- * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -171,6 +171,10 @@ endfunc memcpy4
 func disable_mmu_secure
 	mov	r1, #(SCTLR_M_BIT | SCTLR_C_BIT)
 do_disable_mmu:
+#if ERRATA_A9_794073
+	stcopr	r0, BPIALL
+	dsb
+#endif
 	ldcopr	r0, SCTLR
 	bic	r0, r0, r1
 	stcopr	r0, SCTLR

lib/cpus/aarch32/cortex_a9.S

@@ -35,6 +35,15 @@ func cortex_a9_enable_smp
 	bx	lr
 endfunc cortex_a9_enable_smp
 
+func check_errata_a9_794073
+#if ERRATA_A9_794073
+	mov	r0, #ERRATA_APPLIES
+#else
+	mov	r0, #ERRATA_MISSING
+#endif
+	bx	lr
+endfunc check_errata_cve_2017_5715
+
 func check_errata_cve_2017_5715
 #if WORKAROUND_CVE_2017_5715
 	mov	r0, #ERRATA_APPLIES
@@ -59,6 +68,7 @@ func cortex_a9_errata_report
 	 * checking functions of each errata.
 	 */
 	report_errata WORKAROUND_CVE_2017_5715, cortex_a9, cve_2017_5715
+	report_errata ERRATA_A9_794073, cortex_a9, a9_79407
 
 	pop	{r12, lr}
 	bx	lr

lib/cpus/cpu-ops.mk

@@ -53,6 +53,9 @@ endif
 # These should be enabled by the platform if the erratum workaround needs to be
 # applied.
 
+# Flag to apply erratum 794073 workaround when disabling mmu.
+ERRATA_A9_794073	?=0
+
 # Flag to apply erratum 816470 workaround during power down. This erratum
 # applies only to revision >= r3p0 of the Cortex A15 cpu.
 ERRATA_A15_816470	?=0
@@ -212,6 +215,10 @@ ERRATA_N1_1043202	?=1
 # higher DSU power consumption on idle.
 ERRATA_DSU_936184	?=0
 
+# Process ERRATA_A9_794073 flag
+$(eval $(call assert_boolean,ERRATA_A9_794073))
+$(eval $(call add_define,ERRATA_A9_794073))
+
 # Process ERRATA_A15_816470 flag
 $(eval $(call assert_boolean,ERRATA_A15_816470))
 $(eval $(call add_define,ERRATA_A15_816470))