[compiler-rt] Provide access to the default implementation of weak functions for MD on Windows.

[mpividori]

Summary

When considering MD, asan is implemented as an external dll: clang-rt_asan_dynamic-arch.dll

Also, a static library clang-rt_asan_dynamic_runtime_thunk-arch.lib, which provides some functionalities, is statically linked with both, instrumented dlls and executables,

As I mentioned in the previous revision: https://reviews.llvm.org/D28596 , for asan dll on windows, we are exposing weak functions with WIN_WEAK_EXPORT_DEF(), which export the default implementation with __dll suffix. For example: for __sanitizer_cov_trace_cmp , its default implementation is exported as: __sanitizer_cov_trace_cmp__dll.

So, in this diff I update clang-rt_asan_dynamic_runtime_thunk-arch.lib to include weak aliases to the imported implementation from asan dll, using the macro WIN_WEAK_IMPORT_DEF() like:

WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp);
WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp1);
....

Which will be expanded to "weak aliases":

  __sanitizer_cov_trace_cmp = __sanitizer_cov_trace_cmp__dll
  __sanitizer_cov_trace_cmp1 = __sanitizer_cov_trace_cmp1__dll 
.....

So, by default, all users's programs that include calls to weak functions like __sanitizer_cov_trace_cmp, will be redirected to the implementation in asan dll, when linking to clang-rt_asan_dynamic_runtime_thunk-arch.lib.

After this diff, we are able to compile code with MD and sanitizer coverage instrumentation. When the instrumented object files are linked with clang-rt_asan_dynamic_runtime_thunk-arch.lib all the symbols will be resolved to the implementation imported from asan dll.

Also, I need to remove SANITIZER_INTERFACE_ATTRIBUTE from __asan_shadow_memory_dynamic_address and __asan_option_detect_stack_use_after_return, because we are not exporting that symbols, since we redefine them in asan_win_dynamic_runtime_thunk.cc. Otherwise, the compiler fails because the declaration included from the header includes SANITIZER_INTERFACE_ATTRIBUTE (which expands to dllimport), and the definition in asan_win_dynamic_runtime_thunk.cc doesn't include SANITIZER_INTERFACE_ATTRIBUTE.

[rnk]

I don't like the way that including a .h file has side effects. I'd like to find another way to do this.

[mpividori]

@rnk I updated the code according to changes in revision: https://reviews.llvm.org/D28596
Let me know if you agree now.

[mpividori]

Abandon revision, because this was redesigned in: https://reviews.llvm.org/D29158

lib/asan/asan_interface_internal.h

extern "C" {
   void __asan_set_error_report_callback(void (*callback)(const char*));
 
   WEAK_DECL(void, __asan_on_error, void);
 
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_print_accumulated_stats();
 
   WEAK_DECL(const char*, __asan_default_options, void);
 
-  SANITIZER_INTERFACE_ATTRIBUTE
   extern uptr __asan_shadow_memory_dynamic_address;
 
   // Global flag, copy of ASAN_OPTIONS=detect_stack_use_after_return
-  SANITIZER_INTERFACE_ATTRIBUTE
   extern int __asan_option_detect_stack_use_after_return;
 
   SANITIZER_INTERFACE_ATTRIBUTE
   extern uptr *__asan_test_only_reported_buggy_pointer;
 
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_load1(uptr p);
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_load2(uptr p);
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_load4(uptr p);

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
+#define SANITIZER_IMPORT_INTERFACE 1
+#include "asan_interface_internal.h"
+#include "sanitizer_common/sanitizer_allocator_interface.h"
+#include "sanitizer_common/sanitizer_interface_internal.h"
 #include "sanitizer_common/sanitizer_win_defs.h"
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
+// Define weak alias for all weak functions imported from asan dll.
+WIN_WEAK_IMPORT_DEF(__sanitizer_malloc_hook)
+WIN_WEAK_IMPORT_DEF(__sanitizer_free_hook)
+WIN_WEAK_IMPORT_DEF(__sanitizer_print_memory_profile)
+WIN_WEAK_IMPORT_DEF(__sanitizer_sandbox_on_notify)
+WIN_WEAK_IMPORT_DEF(__sanitizer_report_error_summary)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp1)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp2)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp4)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_cmp8)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_switch)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_div4)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_div8)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_gep)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_pc_indir)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_pc_guard)
+WIN_WEAK_IMPORT_DEF(__sanitizer_cov_trace_pc_guard_init)
+WIN_WEAK_IMPORT_DEF(__asan_on_error)
+WIN_WEAK_IMPORT_DEF(__asan_default_options)
+
 // 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
 #pragma section(".CRT$XTY", long, read)  // NOLINT
 #pragma section(".CRT$XLAB", long, read)  // NOLINT
 
 ////////////////////////////////////////////////////////////////////////////////
 // Define a copy of __asan_option_detect_stack_use_after_return that should be
 // used when linking an MD runtime with a set of object files on Windows.
 //
 // The ASan MD runtime dllexports '__asan_option_detect_stack_use_after_return',
 // so normally we would just dllimport it.  Unfortunately, the dllimport
 // attribute adds __imp_ prefix to the symbol name of a variable.
 // Since in general we don't know if a given TU is going to be used
 // with a MT or MD runtime and we don't want to use ugly __imp_ names on Windows
 // just to work around this issue, let's clone the variable that is constant
 // after initialization anyways.
 extern "C" {
 __declspec(dllimport) int __asan_should_detect_stack_use_after_return();
 int __asan_option_detect_stack_use_after_return;
 
-__declspec(dllimport) void* __asan_get_shadow_memory_dynamic_address();
-void* __asan_shadow_memory_dynamic_address;
+__declspec(dllimport) uptr __asan_get_shadow_memory_dynamic_address();
+uptr __asan_shadow_memory_dynamic_address;
 }
 
 static int InitializeClonedVariables() {
   __asan_option_detect_stack_use_after_return =
     __asan_should_detect_stack_use_after_return();
   __asan_shadow_memory_dynamic_address =
     __asan_get_shadow_memory_dynamic_address();
   return 0;