Merge #336

336: Avoiding use of LLVM reserved register `rbx` r=jethrogb a=raoulstrackx

LLVM reserves register `rbx` in inline assembly (issue: #335). This PR avoids the use of this register until [rust-lang issue 85056](rust-lang/rust#85056) is merged

Co-authored-by: Raoul Strackx <raoul.strackx@fortanix.com>

Author: bors[bot]

enclave-runner/src/tcs.rs

@@ -184,10 +184,12 @@ pub(crate) fn coenter<T: Tcs>(
         } else {
             asm!("
                     lea 1f(%rip), %rcx // set SGX AEP
+                    xchg {0}, %rbx
 1:                  enclu
+                    xchg %rbx, {0}
                 ",
+                inout(reg) tcs.address() => _, // rbx is used internally by LLVM and cannot be used as an operand for inline asm (#84658)
                 inout("eax") Enclu::EEnter as u32 => sgx_result,
-                inout("rbx") tcs.address() => _,
                 out("rcx") _,
                 inout("rdx") p3,
                 inout("rdi") p1,

enclave-runner/src/usercalls/mod.rs

@@ -1226,7 +1226,14 @@ async fn trap_attached_debugger(tcs: usize, debug_buf: *const u8) {
     // Synchronized
     unsafe {
         let old = signal::sigaction(signal::SIGTRAP, &sig_action).unwrap();
-        asm!("int3", in("rbx") tcs, in("r10") debug_buf, options(nomem, nostack, att_syntax));
+        asm!("
+            xchg %rbx, {0}
+            int3
+            xchg {0}, %rbx
+            ",
+            in(reg) tcs, // rbx is used internally by LLVM and cannot be used as an operand for inline asm (#84658)
+            in("r10") debug_buf,
+            options(nomem, nostack, att_syntax));
         signal::sigaction(signal::SIGTRAP, &old).unwrap();
     }
 }