[llvm] [hwasan] Add hwasan-all-globals option (PR #149621)

[Peter Collingbourne via llvm-commits]

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@@ -1780,11 +1790,21 @@ void HWAddressSanitizer::instrumentGlobals() {
     if (GV.hasCommonLinkage())
       continue;
 
-    // Globals with custom sections may be used in __start_/__stop_ enumeration,
-    // which would be broken both by adding tags and potentially by the extra
-    // padding/alignment that we insert.
-    if (GV.hasSection())
-      continue;
+    if (ClAllGlobals) {
+      // Avoid adding metadata emitted for the hwasan instrumentation itself.
+      // Code which makes assumptions about memory layout of globals between
+      // __start_<section>/__end_<section> linker-generated symbols may need
+      // manual adaptation.
+      auto Section = GV.getSection();
+      if (Section == "hwasan_globals" || Section == ".note.hwasan.globals")
----------------
pcc wrote:

No, the sanitizer passes are only run once (it's a bug otherwise). `instrumentGlobals` produces the list of globals to be instrumented before calling `instrumentGlobal` so I don't think the new globals should matter.

I was discussing this change with @fmayer and we think it needs to exclude globals in the `llvm.metadata` section, i.e. synthetic globals created for global constructors, destructors and globals with `__attribute__((used))`, among other things.

https://github.com/llvm/llvm-project/pull/149621