From: Will Deacon will.deacon@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.deacon@arm.com [florian: update arch/arm64/kvm/entry.S::__fpsimd_guest_restore] Signed-off-by: Florian Fainelli f.fainelli@gmail.com --- arch/arm64/kernel/entry.S | 2 ++ arch/arm64/kvm/hyp/entry.S | 2 ++ arch/arm64/kvm/hyp/hyp-entry.S | 4 ++++ 3 files changed, 8 insertions(+)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index c1ffa95c0ad2..f70e0893ba51 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -367,6 +367,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 .else eret .endif + sb .endm
.macro irq_stack_entry @@ -1046,6 +1047,7 @@ 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 a360ac6e89e9..93704e6894d2 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) @@ -195,4 +196,5 @@ alternative_endif ldp x0, x1, [sp], #16
eret + sb ENDPROC(__fpsimd_guest_restore) diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S index 3c283fd8c8f5..b4d6a6c6c6ce 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 @@ -204,6 +206,7 @@ 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 |\ @@ -212,6 +215,7 @@ ENTRY(__hyp_do_panic) ldr lr, =panic msr elr_el2, lr eret + sb ENDPROC(__hyp_do_panic)
ENTRY(__hyp_panic)