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Update macro to check need for CVE-2017-5715 mitigation

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Armv8.5 introduces the field CSV2 to register ID_AA64PFR0_EL1. It can
have the following 3 values:

- 0: Branch targets trained in one hardware described context may affect
     speculative execution in a different hardware described context. In
     some CPUs it may be needed to apply mitigations.

- 1: Branch targets trained in one hardware described context can only
     affect speculative execution in a different hardware described
     context in a hard-to-determine way. No mitigation required.

- 2: Same as 1, but the device is also aware of SCXTNUM_ELx register
     contexts. The TF doesn't use the registers, so there is no
     difference with 1.

The field CSV2 was originally introduced in the TRM of the Cortex-A76
before the release of the Armv8.5 architecture. That TRM only mentions
the meaning of values 0 and 1. Because of this, the code only checks if
the field has value 1 to know whether to enable or disable the
mitigations.

This patch makes it aware of value 2 as well. Both values 1 and 2
disable the mitigation, and 0 enables it.

Change-Id: I5af33de25a0197c98173f52c6c8c77b51a51429f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
This commit is contained in:
Antonio Nino Diaz 2019-02-12 11:25:02 +00:00
parent 3e310f30f2
commit ff6f62e105
1 changed files with 17 additions and 5 deletions
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22
include/lib/cpus/aarch64/cpu_macros.S
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
* Copyright (c) 2014-2019, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@ -7,6 +7,7 @@
#define CPU_MACROS_S
#include <arch.h>
#include <assert_macros.S>
#include <lib/cpus/errata_report.h>
#define CPU_IMPL_PN_MASK (MIDR_IMPL_MASK << MIDR_IMPL_SHIFT) | \
@ -263,11 +264,22 @@
mrs \_reg, id_aa64pfr0_el1
ubfx \_reg, \_reg, #ID_AA64PFR0_CSV2_SHIFT, #ID_AA64PFR0_CSV2_LENGTH
/*
* If the field equals to 1 then branch targets trained in one
* context cannot affect speculative execution in a different context.
* If the field equals 1, branch targets trained in one context cannot
* affect speculative execution in a different context.
*
* If the field equals 2, it means that the system is also aware of
* SCXTNUM_ELx register contexts. We aren't using them in the TF, so we
* expect users of the registers to do the right thing.
*
* Only apply mitigations if the value of this field is 0.
*/
cmp \_reg, #1
beq \_label
#if ENABLE_ASSERTIONS
cmp \_reg, #3 /* Only values 0 to 2 are expected */
ASM_ASSERT(lo)
#endif
cmp \_reg, #0
bne \_label
.endm
/*