fix[sgx]: Document xchg usage in uarch.rs
Closes:
@@ -137,6 +137,11 @@ impl TargetInfo {
// will be initialized by the CPU as the next step.
let mut report = core::mem::MaybeUninit::<Report>::uninit();
+ // In Rust inline assembly rbx is not preserved by the compiler, even
+ // when part of the input list. It is one of the callee saved registers
+ // dictated by:
+ //
+ // https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf
unsafe {
asm!(
"xchg {RBX}, rbx",
