Emit speculation barriers after ERETs
According to Linux commit 679db70801da9fda91d26caf13bf5b5ccc74e8e8
some ARM64 CPUs may speculate past an ERET. This could be used as part
of a side-channel attack.
To mitigate the issue, emit DSB/ISB barriers after every ERET.
Add a build step which dumps the generated ELF and check that this holds
for every ERET in the binary to prevent regressing.
Bug: 146490856
Change-Id: Ie5ceeabb10d27b19c6f5ea334a643eede89c82c0
diff --git a/src/arch/aarch64/hypervisor/exceptions.S b/src/arch/aarch64/hypervisor/exceptions.S
index 2f47c00..a4c12af 100644
--- a/src/arch/aarch64/hypervisor/exceptions.S
+++ b/src/arch/aarch64/hypervisor/exceptions.S
@@ -518,7 +518,7 @@
/* Restore x0..x3, which we have used as scratch before. */
ldp x2, x3, [x0, #VCPU_REGS + 8 * 2]
ldp x0, x1, [x0, #VCPU_REGS + 8 * 0]
- eret
+ eret_with_sb
.balign 0x40
/**
@@ -526,4 +526,4 @@
*/
restore_from_stack_and_return:
restore_volatile_from_stack el2
- eret
+ eret_with_sb