[asan] Create a .ASAN$G(A-Z) section for global registration

[rnk]

Summary

The expectation is that new instrumented code will add global variable
metadata to the .ASAN$GL section, and we will use this new code to
iterate over it.

This technique seems to break when using incremental linking, which
seems to align every global to a 256 byte boundary. Presumably this is
so that it can incrementally cope with global changing size. Clang
already passes -incremental:no as a linker flag when you invoke it to do
the link step.

[kcc]

Vitaly, FYI.
Reid, could you please also add a test with a DSO?

lib/asan/asan_globals_win.cc

28

will this work in the presence of multiple DSOs?
I.e. if asan rt is on one DSO and the callback comes from the other.
(Just asking, I don't remember how this is done on Windows)

[rnk]

• Add DLL test

lib/asan/asan_globals_win.cc

28

Yes, this file is special because we link it into every DSO. I added a test that shows we report globals from DSOs when stripping is enabled.

[kcc]

LGTM (but not a windows expert)
Thanks!

lib/asan/CMakeLists.txt

 # Build for the AddressSanitizer runtime support library.
 
 set(ASAN_SOURCES
   asan_allocator.cc
   asan_activation.cc
   asan_debugging.cc
   asan_descriptions.cc
   asan_errors.cc
   asan_fake_stack.cc
   asan_flags.cc
   asan_globals.cc
+  asan_globals_win.cc
   asan_interceptors.cc
   asan_linux.cc
   asan_mac.cc
   asan_malloc_linux.cc
   asan_malloc_mac.cc
   asan_malloc_win.cc
   asan_memory_profile.cc
   asan_poisoning.cc
if (UNIX AND NOT ${arch} MATCHES "i386|i686")
       add_dependencies(asan clang_rt.asan-${arch}-symbols)
     endif()
 
     if (WIN32)
       add_compiler_rt_runtime(clang_rt.asan_dll_thunk
         STATIC
         ARCHS ${arch}
         SOURCES asan_win_dll_thunk.cc
+                asan_globals_win.cc
                 $<TARGET_OBJECTS:RTInterception.${arch}>
         CFLAGS ${ASAN_CFLAGS} -DASAN_DLL_THUNK
         DEFS ${ASAN_COMMON_DEFINITIONS}
         PARENT_TARGET asan)
 
       set(DYNAMIC_RUNTIME_THUNK_CFLAGS "-DASAN_DYNAMIC_RUNTIME_THUNK")
       if(MSVC)
         list(APPEND DYNAMIC_RUNTIME_THUNK_CFLAGS "-Zl")
       elseif(CMAKE_C_COMPILER_ID MATCHES Clang)
         list(APPEND DYNAMIC_RUNTIME_THUNK_CFLAGS "-nodefaultlibs")
       endif()
 
       add_compiler_rt_runtime(clang_rt.asan_dynamic_runtime_thunk
         STATIC
         ARCHS ${arch}
         SOURCES asan_win_dynamic_runtime_thunk.cc
+                asan_globals_win.cc
         CFLAGS ${ASAN_CFLAGS} ${DYNAMIC_RUNTIME_THUNK_CFLAGS}
         DEFS ${ASAN_COMMON_DEFINITIONS}
         PARENT_TARGET asan)
     endif()
   endforeach()
 endif()
 
 add_compiler_rt_resource_file(asan_blacklist asan_blacklist.txt asan)
 
 add_subdirectory(scripts)
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(tests)
 endif()

lib/asan/asan_globals.cc

static inline bool UseODRIndicator(const Global *g) {
   // indicator symbol address is not 0.
   return flags()->use_odr_indicator && g->odr_indicator > 0;
 }
 
 // Register a global variable.
 // 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");
   CHECK(flags()->report_globals);
   CHECK(AddrIsInMem(g->beg));
   if (!AddrIsAlignedByGranularity(g->beg)) {
     Report("The following global variable is not properly aligned.\n");
     Report("This may happen if another global with the same name\n");

lib/asan/asan_globals_win.h

+//===-- asan_globals_win.h --------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Interface to the Windows-specific global management code. Separated into a
+// standalone header to allow inclusion from asan_win_dynamic_runtime_thunk,
+// which defines symbols that clash with other sanitizer headers.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef ASAN_GLOBALS_WIN_H
+#define ASAN_GLOBALS_WIN_H
+
+#if !defined(_MSC_VER)
+#error "this file is Windows-only, and uses MSVC pragmas"
+#endif
+
+#if defined(_WIN64)
+#define SANITIZER_SYM_PREFIX
+#else
+#define SANITIZER_SYM_PREFIX "_"
+#endif
+
+// Use this macro to force linking asan_globals_win.cc into the DSO.
+#define ASAN_LINK_GLOBALS_WIN() \
+  __pragma(                     \
+      comment(linker, "/include:" SANITIZER_SYM_PREFIX "__asan_dso_reg_hook"))
+
+#endif // ASAN_GLOBALS_WIN_H

lib/asan/asan_globals_win.cc

+//===-- asan_globals_win.cc -----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Global registration code that is linked into every Windows DLL and EXE.
+//
+//===----------------------------------------------------------------------===//
+
+#include "asan_interface_internal.h"
+#if SANITIZER_WINDOWS
+
+namespace __asan {
+
+#pragma section(".ASAN$GA", read, write)  // NOLINT
+#pragma section(".ASAN$GZ", read, write)  // NOLINT
+extern "C" __declspec(allocate(".ASAN$GA"))
+uptr __asan_globals_start = 0;
+extern "C" __declspec(allocate(".ASAN$GZ"))
+uptr __asan_globals_end = 0;
+#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 *end = (__asan_global *)&__asan_globals_end;
+  // We know end >= start because the linker sorts the portion after the dollar
+  // sign alphabetically.
+  uptr n = end - start;
+  hook(start, n);
+}
+
+static void register_dso_globals() {
+  call_on_globals(&__asan_register_globals);
+}
+
+static void unregister_dso_globals() {
+  call_on_globals(&__asan_unregister_globals);
+}
+
+// Register globals
+#pragma section(".CRT$XCU", long, read)  // NOLINT
+#pragma section(".CRT$XTX", long, read)  // NOLINT
+extern "C" __declspec(allocate(".CRT$XCU"))
+void (*const __asan_dso_reg_hook)() = &register_dso_globals;
+extern "C" __declspec(allocate(".CRT$XTX"))
+void (*const __asan_dso_unreg_hook)() = &unregister_dso_globals;
+
+} // namespace __asan
+
+#endif  // SANITIZER_WINDOWS

lib/asan/asan_win.cc

 
 #include "sanitizer_common/sanitizer_platform.h"
 #if SANITIZER_WINDOWS
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
 #include <stdlib.h>
 
+#include "asan_globals_win.h"
 #include "asan_interceptors.h"
 #include "asan_internal.h"
 #include "asan_report.h"
 #include "asan_stack.h"
 #include "asan_thread.h"
 #include "asan_mapping.h"
 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_mutex.h"
static void NTAPI asan_thread_init(void *module, DWORD reason, void *reserved) {
   if (reason == DLL_PROCESS_ATTACH) __asan_init();
 }
 
 #pragma section(".CRT$XLAB", long, read)  // NOLINT
 __declspec(allocate(".CRT$XLAB")) void (NTAPI *__asan_tls_init)(void *,
     unsigned long, void *) = asan_thread_init;
 #endif
 
+ASAN_LINK_GLOBALS_WIN()
 
 // }}}
 }  // namespace __asan
 
-#endif  // _WIN32
+#endif  // SANITIZER_WINDOWS

lib/asan/asan_win_dll_thunk.cc

 // See https://github.com/google/sanitizers/issues/209 for the details.
 //===----------------------------------------------------------------------===//
 
 // Only compile this code when building asan_dll_thunk.lib
 // Using #ifdef rather than relying on Makefiles etc.
 // simplifies the build procedure.
 #ifdef ASAN_DLL_THUNK
 #include "asan_init_version.h"
+#include "asan_globals_win.h"
 #include "interception/interception.h"
 #include "sanitizer_common/sanitizer_platform_interceptors.h"
 
 #ifdef _M_IX86
 #define WINAPI __stdcall
 #else
 #define WINAPI
 #endif
static void WINAPI asan_thread_init(void *mod, unsigned long reason,
                                    void *reserved) {
   if (reason == /*DLL_PROCESS_ATTACH=*/1) __asan_init();
 }
 
 #pragma section(".CRT$XLAB", long, read)  // NOLINT
 __declspec(allocate(".CRT$XLAB")) void (WINAPI *__asan_tls_init)(void *,
     unsigned long, void *) = asan_thread_init;
 
+ASAN_LINK_GLOBALS_WIN()
+
 #endif // ASAN_DLL_THUNK

lib/asan/asan_win_dynamic_runtime_thunk.cc

 //  - installing a custom SEH handler
 //
 //===----------------------------------------------------------------------===//
 
 // Only compile this code when building asan_dynamic_runtime_thunk.lib
 // Using #ifdef rather than relying on Makefiles etc.
 // simplifies the build procedure.
 #ifdef ASAN_DYNAMIC_RUNTIME_THUNK
+#include "asan_globals_win.h"
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
 // First, declare CRT sections we'll be using in this file
 #pragma section(".CRT$XIB", long, read)  // NOLINT
 #pragma section(".CRT$XID", long, read)  // NOLINT
 #pragma section(".CRT$XCAB", long, read)  // NOLINT
 #pragma section(".CRT$XTW", long, read)  // NOLINT

 static int SetSEHFilter() { return __asan_set_seh_filter(); }
 
 // Unfortunately, putting a pointer to __asan_set_seh_filter into
 // __asan_intercept_seh gets optimized out, so we have to use an extra function.
 __declspec(allocate(".CRT$XCAB")) int (*__asan_seh_interceptor)() =
     SetSEHFilter;
 }
 
+ASAN_LINK_GLOBALS_WIN()
+
 #endif // ASAN_DYNAMIC_RUNTIME_THUNK

lib/asan/tests/CMakeLists.txt

 # -gline-tables-only must be enough for ASan, so use it if possible.
 if(COMPILER_RT_TEST_COMPILER_ID MATCHES "Clang")
   list(APPEND ASAN_UNITTEST_COMMON_CFLAGS -gline-tables-only)
 else()
   list(APPEND ASAN_UNITTEST_COMMON_CFLAGS -g)
 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)
 
 # Use -D instead of definitions to please custom compile command.
 list(APPEND ASAN_UNITTEST_COMMON_CFLAGS
   -DASAN_HAS_BLACKLIST=1
   -DASAN_HAS_EXCEPTIONS=1
   -DASAN_UAR=0)

test/asan/TestCases/Windows/global-dead-strip.c

+// RUN: %clang_cl_asan /O0 %s /Fe%t.exe
+// RUN: %env_asan_opts=report_globals=2 %t.exe 2>&1 | FileCheck %s --check-prefix=NOSTRIP
+// RUN: %clang_cl_asan /O2 %s /Fe%t.exe
+// RUN: %env_asan_opts=report_globals=2 %t.exe 2>&1 | FileCheck %s --check-prefix=STRIP
+
+#include <stdio.h>
+int dead_global = 42;
+int main() { puts("main"); }
+
+// Check that our global registration scheme works with MSVC's linker dead
+// stripping (/OPT:REF).
+
+// NOSTRIP: Added Global{{.*}}name=dead_global
+// NOSTRIP: main
+
+// STRIP-NOT: Added Global{{.*}}name=dead_global
+// STRIP: main