feat: add Rust userspace support; fix TLS layout for p_align < 16; kill whole process on sibling-thread faults

programs/include/montauk/statuscodes.h

@@ -32,6 +32,9 @@ typedef enum {
     WouldBlock = 16
 } StatusCode;
 
+// Highest defined StatusCode; update when adding a code above.
+enum { MaxStatusCode = WouldBlock };
+
 inline const char* GetStatusText(StatusCode statusCode) {
     const char* statusText[] = {
         "Success", // 0
@@ -53,7 +56,7 @@ inline const char* GetStatusText(StatusCode statusCode) {
         "Operation would block", // 16
     };
 
-    if (statusCode > 0 && statusCode <= 16) {
+    if (statusCode > 0 && statusCode <= MaxStatusCode) {
         return statusText[statusCode];
     } else {
         return "Unknown error";
@@ -63,7 +66,7 @@ inline const char* GetStatusText(StatusCode statusCode) {
 // Map a raw syscall result to a StatusCode.
 inline StatusCode StatusFromResult(long long rc) {
     if (rc >= 0) return Success;
-    if (rc < -(long long)WouldBlock) return GenericFailure;
+    if (rc < -(long long)MaxStatusCode) return GenericFailure;
     return (StatusCode)(-rc);
 }
 
@@ -89,7 +92,7 @@ inline const char* GetStatusExplanationText(StatusCode statusCode) {
         0, // 16
     };
 
-    if (statusCode > 0 && statusCode <= 16) {
+    if (statusCode > 0 && statusCode <= MaxStatusCode) {
         if (explanationText[statusCode] != 0) {
             return explanationText[statusCode];
         }