switcher: avoid reload of mtdc in cross-call
Having spilled s0 already, we're free to use it rather than clobber t2.
We'll zero t2 on the error path here, so there is no concern of it
leaking.
diff --git a/sdk/core/switcher/entry.S b/sdk/core/switcher/entry.S
index 3fe407e..d780e1a 100644
--- a/sdk/core/switcher/entry.S
+++ b/sdk/core/switcher/entry.S
@@ -205,10 +205,9 @@
// make sure the trusted stack is still in bounds
clhu tp, TrustedStack_offset_frameoffset(ct2)
- cgetlen t2, ct2
- bgeu tp, t2, .Lout_of_trusted_stack
- // we are past the stacks checks. Reload ct2; tp is still as it was
- cspecialr ct2, mtdc
+ cgetlen s0, ct2
+ bgeu tp, s0, .Lout_of_trusted_stack
+ // we are past the stacks checks.
// ctp points to the current available trusted stack frame.
cincoffset ctp, ct2, tp
csc csp, TrustedStackFrame_offset_csp(ctp)
