[compiler-rt] r287780 - [asan/win] Fix incremental linking vs. global registration

[Reid Kleckner via llvm-commits]

Author: rnk
Date: Wed Nov 23 11:37:00 2016
New Revision: 287780

URL: http://llvm.org/viewvc/llvm-project?rev=287780&view=rev
Log:
[asan/win] Fix incremental linking vs. global registration

The MSVC incremental linker pads every global out to 256 bytes in case
it changes size after an incremental link. So, skip over null entries in
the DSO-wide asan globals array. This only works if the global padding
size is divisible by the size of the asan global object, so add some
defensive CHECKs.

Modified:
    compiler-rt/trunk/lib/asan/CMakeLists.txt
    compiler-rt/trunk/lib/asan/asan_globals.cc
    compiler-rt/trunk/lib/asan/asan_globals_win.cc
    compiler-rt/trunk/lib/asan/tests/CMakeLists.txt

Modified: compiler-rt/trunk/lib/asan/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/CMakeLists.txt?rev=287780&r1=287779&r2=287780&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/CMakeLists.txt (original)
+++ compiler-rt/trunk/lib/asan/CMakeLists.txt Wed Nov 23 11:37:00 2016
@@ -64,7 +64,6 @@ set(ASAN_DYNAMIC_CFLAGS ${ASAN_CFLAGS})
 append_list_if(COMPILER_RT_HAS_FTLS_MODEL_INITIAL_EXEC
   -ftls-model=initial-exec ASAN_DYNAMIC_CFLAGS)
 append_list_if(MSVC /DEBUG ASAN_DYNAMIC_LINK_FLAGS)
-append_list_if(MSVC /INCREMENTAL:NO ASAN_DYNAMIC_LINK_FLAGS)
 
 append_list_if(COMPILER_RT_HAS_LIBC c ASAN_DYNAMIC_LIBS)
 append_list_if(COMPILER_RT_HAS_LIBDL dl ASAN_DYNAMIC_LIBS)

Modified: compiler-rt/trunk/lib/asan/asan_globals.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_globals.cc?rev=287780&r1=287779&r2=287780&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_globals.cc (original)
+++ compiler-rt/trunk/lib/asan/asan_globals.cc Wed Nov 23 11:37:00 2016
@@ -192,7 +192,6 @@ static inline bool UseODRIndicator(const
 // This function may be called more than once for every global
 // so we store the globals in a map.
 static void RegisterGlobal(const Global *g) {
-  CHECK(g->beg);
   CHECK(asan_inited);
   if (flags()->report_globals >= 2)
     ReportGlobal(*g, "Added");
@@ -349,6 +348,20 @@ void __asan_register_globals(__asan_glob
     Printf("=== ID %d; %p %p\n", stack_id, &globals[0], &globals[n - 1]);
   }
   for (uptr i = 0; i < n; i++) {
+    if (SANITIZER_WINDOWS && globals[i].beg == 0) {
+      // The MSVC incremental linker may pad globals out to 256 bytes. As long
+      // as __asan_global is less than 256 bytes large and its size is a power
+      // of two, we can skip over the padding.
+      static_assert(
+          sizeof(__asan_global) < 256 &&
+              (sizeof(__asan_global) & (sizeof(__asan_global) - 1)) == 0,
+          "sizeof(__asan_global) incompatible with incremental linker padding");
+      // If these are padding bytes, the rest of the global should be zero.
+      CHECK(globals[i].size == 0 && globals[i].size_with_redzone == 0 &&
+            globals[i].name == nullptr && globals[i].module_name == nullptr &&
+            globals[i].odr_indicator == 0);
+      continue;
+    }
     RegisterGlobal(&globals[i]);
   }
 }

Modified: compiler-rt/trunk/lib/asan/asan_globals_win.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_globals_win.cc?rev=287780&r1=287779&r2=287780&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_globals_win.cc (original)
+++ compiler-rt/trunk/lib/asan/asan_globals_win.cc Wed Nov 23 11:37:00 2016
@@ -19,13 +19,13 @@ namespace __asan {
 #pragma section(".ASAN$GA", read, write)  // NOLINT
 #pragma section(".ASAN$GZ", read, write)  // NOLINT
 extern "C" __declspec(allocate(".ASAN$GA"))
-uptr __asan_globals_start = 0;
+__asan_global __asan_globals_start = {};
 extern "C" __declspec(allocate(".ASAN$GZ"))
-uptr __asan_globals_end = 0;
+__asan_global __asan_globals_end = {};
 #pragma comment(linker, "/merge:.ASAN=.data")
 
 static void call_on_globals(void (*hook)(__asan_global *, uptr)) {
-  __asan_global *start = (__asan_global *)(&__asan_globals_start + 1);
+  __asan_global *start = &__asan_globals_start + 1;
   __asan_global *end = (__asan_global *)&__asan_globals_end;
   // We know end >= start because the linker sorts the portion after the dollar
   // sign alphabetically.

Modified: compiler-rt/trunk/lib/asan/tests/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/tests/CMakeLists.txt?rev=287780&r1=287779&r2=287780&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/tests/CMakeLists.txt (original)
+++ compiler-rt/trunk/lib/asan/tests/CMakeLists.txt Wed Nov 23 11:37:00 2016
@@ -47,8 +47,6 @@ else()
 endif()
 if(MSVC)
   list(APPEND ASAN_UNITTEST_COMMON_CFLAGS -gcodeview)
-  # Incremental linking appears to break our global registration mechanism.
-  list(APPEND ASAN_UNITTEST_COMMON_LINKFLAGS -Wl,-incremental:no)
 endif()
 list(APPEND ASAN_UNITTEST_COMMON_LINKFLAGS -g)