[asan] Implement address sanitizer on AIX: address descriptions

[jakeegan]

Adapt address description logic for AIX.

Issue: #138916

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Jake Egan (jakeegan)

Changes

Adapt address description logic for AIX.

---

Full diff: https://github.com/llvm/llvm-project/pull/138891.diff

1 Files Affected:

• (modified) compiler-rt/lib/asan/asan_descriptions.cpp (+13-8)

diff --git a/compiler-rt/lib/asan/asan_descriptions.cpp b/compiler-rt/lib/asan/asan_descriptions.cpp
index c9f3e4d682d95..1cbf0e6b193f6 100644
--- a/compiler-rt/lib/asan/asan_descriptions.cpp
+++ b/compiler-rt/lib/asan/asan_descriptions.cpp
@@ -211,10 +211,10 @@ bool GetStackAddressInformation(uptr addr, uptr access_size,
   descr->frame_pc = access.frame_pc;
   descr->frame_descr = access.frame_descr;
 
-#if SANITIZER_PPC64V1
-  // On PowerPC64 ELFv1, the address of a function actually points to a
-  // three-doubleword data structure with the first field containing
-  // the address of the function's code.
+#if SANITIZER_PPC64V1 || SANITIZER_AIX
+  // On PowerPC64 ELFv1 or AIX, the address of a function actually points to a
+  // three-doubleword (or three-word for 32-bit AIX) data structure with
+  // the first field containing the address of the function's code.
   descr->frame_pc = *reinterpret_cast<uptr *>(descr->frame_pc);
 #endif
   descr->frame_pc += 16;
@@ -444,6 +444,15 @@ AddressDescription::AddressDescription(uptr addr, uptr access_size,
     data.kind = kAddressKindShadow;
     return;
   }
+
+  // Check global first. On AIX, some global data defined in shared libraries
+  // are put to the STACK region for unknown reasons. Check global first can
+  // workaround this issue.
+  if (GetGlobalAddressInformation(addr, access_size, &data.global)) {
+    data.kind = kAddressKindGlobal;
+    return;
+  }
+
   if (GetHeapAddressInformation(addr, access_size, &data.heap)) {
     data.kind = kAddressKindHeap;
     return;
@@ -461,10 +470,6 @@ AddressDescription::AddressDescription(uptr addr, uptr access_size,
     return;
   }
 
-  if (GetGlobalAddressInformation(addr, access_size, &data.global)) {
-    data.kind = kAddressKindGlobal;
-    return;
-  }
   data.kind = kAddressKindWild;
   data.wild.addr = addr;
   data.wild.access_size = access_size;

[hubert-reinterpretcast]

@jakeegan, the comment makes it sound like the problem being solved is not well-understood.
For further analysis, can we verify what fails when this change is not present?
I think we may want to leave a TODO comment here in case there is a different solution.