[compiler-rt] Re-exec TSan with no ASLR if memory layout is incompatible (PR #78351)

[Thurston Dang via llvm-commits]

================
@@ -294,52 +380,22 @@ void InitializePlatform() {
   // is not compiled with -pie.
 #if !SANITIZER_GO
   {
-    bool reexec = false;
-    // TSan doesn't play well with unlimited stack size (as stack
-    // overlaps with shadow memory). If we detect unlimited stack size,
-    // we re-exec the program with limited stack size as a best effort.
-    if (StackSizeIsUnlimited()) {
-      const uptr kMaxStackSize = 32 * 1024 * 1024;
-      VReport(1, "Program is run with unlimited stack size, which wouldn't "
-                 "work with ThreadSanitizer.\n"
-                 "Re-execing with stack size limited to %zd bytes.\n",
-              kMaxStackSize);
-      SetStackSizeLimitInBytes(kMaxStackSize);
-      reexec = true;
-    }
-
-    if (!AddressSpaceIsUnlimited()) {
-      Report("WARNING: Program is run with limited virtual address space,"
-             " which wouldn't work with ThreadSanitizer.\n");
-      Report("Re-execing with unlimited virtual address space.\n");
-      SetAddressSpaceUnlimited();
-      reexec = true;
-    }
-#if SANITIZER_ANDROID && (defined(__aarch64__) || defined(__x86_64__))
-    // After patch "arm64: mm: support ARCH_MMAP_RND_BITS." is introduced in
-    // linux kernel, the random gap between stack and mapped area is increased
-    // from 128M to 36G on 39-bit aarch64. As it is almost impossible to cover
-    // this big range, we should disable randomized virtual space on aarch64.
-    // ASLR personality check.
-    int old_personality = personality(0xffffffff);
-    if (old_personality != -1 && (old_personality & ADDR_NO_RANDOMIZE) == 0) {
-      VReport(1, "WARNING: Program is run with randomized virtual address "
-              "space, which wouldn't work with ThreadSanitizer.\n"
-              "Re-execing with fixed virtual address space.\n");
-      CHECK_NE(personality(old_personality | ADDR_NO_RANDOMIZE), -1);
-      reexec = true;
-    }
-
-#endif
-#if SANITIZER_LINUX && (defined(__aarch64__) || defined(__loongarch_lp64))
+#    if SANITIZER_LINUX && (defined(__aarch64__) || defined(__loongarch_lp64))
     // Initialize the xor key used in {sig}{set,long}jump.
     InitializeLongjmpXorKey();
-#endif
-    if (reexec)
-      ReExec();
+#    endif
+  }
+
+  // Earlier initialization steps already re-exec'ed until we got a compatible
+  // memory layout, so we don't expect any more issues here.
+  if (!CheckAndProtect(true, true, true)) {
----------------
thurstond wrote:

Good point! I've made the function call compatible on Mac, though I haven't added the re-exec functionality (I don't have a Mac to even test that it compiles, let alone works).

https://github.com/llvm/llvm-project/pull/78351