From: Will Deacon <will.dea...@arm.com>
commit 679db70801da9fda91d26caf13bf5b5ccc74e8e8 upstream
Some CPUs can speculate past an ERET instruction and potentially perform
speculative accesses to memory before processing the exception return.
Since the register state is often controlled by a lower privilege level
at the point of an ERET, this could potentially be used as part of a
side-channel attack.
This patch emits an SB sequence after each ERET so that speculation is
held up on exception return.
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Florian Fainelli <f.faine...@gmail.com>
---
arch/arm64/kernel/entry.S | 2 ++
arch/arm64/kvm/hyp/entry.S | 1 +
arch/arm64/kvm/hyp/hyp-entry.S | 4 ++++
3 files changed, 7 insertions(+)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 5f800384cb9a..49f80b5627fa 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -363,6 +363,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
.else
eret
.endif
+ sb
.endm
.macro irq_stack_entry
@@ -994,6 +995,7 @@ alternative_insn isb, nop,
ARM64_WORKAROUND_QCOM_FALKOR_E1003
mrs x30, far_el1
.endif
eret
+ sb
.endm
.align 11
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index fad1e164fe48..675fdc186e3b 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -83,6 +83,7 @@ ENTRY(__guest_enter)
// Do not touch any register after this!
eret
+ sb
ENDPROC(__guest_enter)
ENTRY(__guest_exit)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 24b4fbafe3e4..e35abf84eb96 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -96,6 +96,7 @@ el1_sync: // Guest trapped into
EL2
do_el2_call
eret
+ sb
el1_hvc_guest:
/*
@@ -146,6 +147,7 @@ wa_epilogue:
mov x0, xzr
add sp, sp, #16
eret
+ sb
el1_trap:
get_vcpu_ptr x1, x0
@@ -185,6 +187,7 @@ el2_error:
b.ne __hyp_panic
mov x0, #(1 << ARM_EXIT_WITH_SERROR_BIT)
eret
+ sb
ENTRY(__hyp_do_panic)
mov lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
@@ -193,6 +196,7 @@ ENTRY(__hyp_do_panic)
ldr lr, =panic
msr elr_el2, lr
eret
+ sb
ENDPROC(__hyp_do_panic)
ENTRY(__hyp_panic)
--
2.17.1
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