[llvm] r368101 - [WebAssembly] Lower ASan constructor priority on Emscripten

[Guanzhong Chen via llvm-commits]

Author: quantum
Date: Tue Aug  6 14:52:58 2019
New Revision: 368101

URL: http://llvm.org/viewvc/llvm-project?rev=368101&view=rev
Log:
[WebAssembly] Lower ASan constructor priority on Emscripten

Summary:
This change gives Emscripten the ability to use more than one constructor
priorities that runs before ASan. By convention, constructor priorites 0-100
are reserved for use by the system. ASan on Emscripten now uses priority 50,
leaving plenty of room for use by Emscripten before and after ASan.

This change is done in response to:
https://github.com/emscripten-core/emscripten/pull/9076#discussion_r310323723

Reviewers: kripken, tlively, aheejin

Reviewed By: tlively

Subscribers: cfe-commits, dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D65684

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp

Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=368101&r1=368100&r2=368101&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Tue Aug  6 14:52:58 2019
@@ -129,6 +129,8 @@ static const uintptr_t kRetiredStackFram
 static const char *const kAsanModuleCtorName = "asan.module_ctor";
 static const char *const kAsanModuleDtorName = "asan.module_dtor";
 static const uint64_t kAsanCtorAndDtorPriority = 1;
+// On Emscripten, the system needs more than one priorities for constructors.
+static const uint64_t kAsanEmscriptenCtorAndDtorPriority = 50;
 static const char *const kAsanReportErrorTemplate = "__asan_report_";
 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
 static const char *const kAsanUnregisterGlobalsName =
@@ -530,6 +532,14 @@ static size_t RedzoneSizeForScale(int Ma
   return std::max(32U, 1U << MappingScale);
 }
 
+static uint64_t GetCtorAndDtorPriority(Triple &TargetTriple) {
+  if (TargetTriple.isOSEmscripten()) {
+    return kAsanEmscriptenCtorAndDtorPriority;
+  } else {
+    return kAsanCtorAndDtorPriority;
+  }
+}
+
 namespace {
 
 /// Module analysis for getting various metadata about the module.
@@ -1777,7 +1787,8 @@ void ModuleAddressSanitizer::createIniti
       if (F->getName() == kAsanModuleCtorName) continue;
       ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
       // Don't instrument CTORs that will run before asan.module_ctor.
-      if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue;
+      if (Priority->getLimitedValue() <= GetCtorAndDtorPriority(TargetTriple))
+        continue;
       poisonOneInitializer(*F, ModuleName);
     }
   }
@@ -2429,22 +2440,22 @@ bool ModuleAddressSanitizer::instrumentM
     Changed |= InstrumentGlobals(IRB, M, &CtorComdat);
   }
 
+  const uint64_t Priority = GetCtorAndDtorPriority(TargetTriple);
+
   // Put the constructor and destructor in comdat if both
   // (1) global instrumentation is not TU-specific
   // (2) target is ELF.
   if (UseCtorComdat && TargetTriple.isOSBinFormatELF() && CtorComdat) {
     AsanCtorFunction->setComdat(M.getOrInsertComdat(kAsanModuleCtorName));
-    appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority,
-                        AsanCtorFunction);
+    appendToGlobalCtors(M, AsanCtorFunction, Priority, AsanCtorFunction);
     if (AsanDtorFunction) {
       AsanDtorFunction->setComdat(M.getOrInsertComdat(kAsanModuleDtorName));
-      appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority,
-                          AsanDtorFunction);
+      appendToGlobalDtors(M, AsanDtorFunction, Priority, AsanDtorFunction);
     }
   } else {
-    appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
+    appendToGlobalCtors(M, AsanCtorFunction, Priority);
     if (AsanDtorFunction)
-      appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
+      appendToGlobalDtors(M, AsanDtorFunction, Priority);
   }
 
   return Changed;