[PATCH v4 01/28] arm64: hyp-stub: Stop pointlessly clobbering lr

Marc Zyngier
2017-03-21T19:20:31Z

When entering the kernel hyp stub, we check whether or not we've
made it here through an HVC instruction, clobbering lr (aka x30)
in the process.

This is completely pointless, as HVC is the only way to get here
(all traps to EL2 are disabled, no interrupt override is applied).

So let's remove this bit of code whose only point is to corrupt
a valuable register.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/kernel/hyp-stub.S | 6 ------
1 file changed, 6 deletions(-)

diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index d3b5f75e652e..e4215ad06930 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -55,12 +55,6 @@ ENDPROC(__hyp_stub_vectors)
.align 11

el1_sync:
- mrs x30, esr_el2
- lsr x30, x30, #ESR_ELx_EC_SHIFT
-
- cmp x30, #ESR_ELx_EC_HVC64
- b.ne 9f // Not an HVC trap
-
cmp x0, #HVC_GET_VECTORS
b.ne 1f
mrs x0, vbar_el2
--
2.11.0