IOS LLE: StarOS's panic words must not alias

LoadBootstrapELF accepted __panic_state and __panic_code at the same
address, or as two words sharing bytes: the code's store would then also
set the guard, and nothing could tell the two apart. They must now be two
non-overlapping words of the data segment, like the other checks, before
any byte is written. BootstrapELFTest.PanicWordsMustNotAlias: the same
word and three partial overlaps, all inside the data segment, are
rejected; adjacent words are accepted. With the rule disabled, the test
fails. (StarOS MMU-001 review of F1.)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

Source/Core/Core/IOS/Starlet/BootstrapELF.cpp

@@ -216,9 +216,14 @@ bool LoadBootstrapELF(std::span<const u8> image, ARMBus& bus, BootstrapELFInfo*
   {
     return Fail(error, "bootstrap ELF is missing the trace or fault symbols");
   }
-  // The panic words are optional, but both or neither, as words of the data segment.
+  // The panic words are optional, but both or neither, as two distinct words of the data segment:
+  // aliased, the code's store would also set the guard, and a probe could not tell them apart.
+  const bool panic_words_overlap =
+      static_cast<u64>(parsed.panic_state) < static_cast<u64>(parsed.panic_code) + 4 &&
+      static_cast<u64>(parsed.panic_code) < static_cast<u64>(parsed.panic_state) + 4;
   if ((parsed.panic_state != 0) != (parsed.panic_code != 0) ||
-      (parsed.panic_state != 0 && (!in_data(parsed.panic_state, 4) || !in_data(parsed.panic_code, 4))))
+      (parsed.panic_state != 0 && (!in_data(parsed.panic_state, 4) ||
+                                   !in_data(parsed.panic_code, 4) || panic_words_overlap)))
   {
     return Fail(error, "bootstrap ELF has an invalid panic symbol");
   }