From 8035edbe12f0f2a58e8fa9b06d05c8ee1c69ffae Mon Sep 17 00:00:00 2001 From: Vijayenthiran Subramaniam Date: Thu, 4 Jun 2020 18:42:09 +0530 Subject: [PATCH] ArmPkg/ArmSvcLib: prevent speculative execution beyond svc Supervisor Call instruction (SVC) is used by the Arm Standalone MM environment to request services from the privileged software (such as ARM Trusted Firmware running in EL3) and also return back to the non-secure caller via EL3. Some Arm CPUs speculatively executes the instructions after the SVC instruction without crossing the privilege level (S-EL0). Although the results of this execution are architecturally discarded, adversary running on the non-secure side can manipulate the contents of the general purpose registers to leak the secure work memory through spectre like micro-architectural side channel attacks. This behavior is demonstrated by the SafeSide project [1] and [2]. Add barrier instructions after SVC to prevent speculative execution to mitigate such attacks. [1]: https://github.com/google/safeside/blob/master/demos/eret_hvc_smc_wrapper.cc [2]: https://github.com/google/safeside/blob/master/kernel_modules/kmod_eret_hvc_smc/eret_hvc_smc_module.c Signed-off-by: Vijayenthiran Subramaniam Reviewed-by: Ard Biesheuvel --- ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S | 5 ++++- ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.S | 5 ++++- ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.asm | 5 ++++- 3 files changed, 12 insertions(+), 3 deletions(-) diff --git a/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S b/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S index 7c94db3451..ee265f94b9 100644 --- a/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S +++ b/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S @@ -1,5 +1,5 @@ // -// Copyright (c) 2012 - 2017, ARM Limited. All rights reserved. +// Copyright (c) 2012 - 2020, ARM Limited. All rights reserved. // // SPDX-License-Identifier: BSD-2-Clause-Patent // @@ -25,6 +25,9 @@ ASM_PFX(ArmCallSvc): ldp x0, x1, [x0, #0] svc #0 + // Prevent speculative execution beyond svc instruction + dsb nsh + isb // Pop the ARM_SVC_ARGS structure address from the stack into x9 ldr x9, [sp, #16] diff --git a/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.S b/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.S index fc2886b6b5..e81eb88f2e 100644 --- a/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.S +++ b/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.S @@ -1,5 +1,5 @@ // -// Copyright (c) 2016 - 2017, ARM Limited. All rights reserved. +// Copyright (c) 2016 - 2020, ARM Limited. All rights reserved. // // SPDX-License-Identifier: BSD-2-Clause-Patent // @@ -18,6 +18,9 @@ ASM_PFX(ArmCallSvc): ldm r0, {r0-r7} svc #0 + // Prevent speculative execution beyond svc instruction + dsb nsh + isb // Load the ARM_SVC_ARGS structure address from the stack into r8 ldr r8, [sp] diff --git a/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.asm b/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.asm index 82d10c023a..d1751488b2 100644 --- a/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.asm +++ b/ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.asm @@ -1,5 +1,5 @@ // -// Copyright (c) 2016 - 2017, ARM Limited. All rights reserved. +// Copyright (c) 2016 - 2020, ARM Limited. All rights reserved. // // SPDX-License-Identifier: BSD-2-Clause-Patent // @@ -16,6 +16,9 @@ ldm r0, {r0-r7} svc #0 + // Prevent speculative execution beyond svc instruction + dsb nsh + isb // Load the ARM_SVC_ARGS structure address from the stack into r8 ldr r8, [sp] -- 2.39.2