[hwasan] Remove system allocator fallback.

[eugenis]

Summary

This has been an experiment with late malloc interposition, made
possible by a non-standard feature of the Android dynamic loader.

[pcc]

LGTM

[mmalcomson]

If late interposition is no longer a supported use-case, does that apply to the pthread use case as well?
https://reviews.llvm.org/D56038

I would be quite keen to remove the lazy thread-initialisation check from every function prologue.

[eugenis]

Indeed, it looks like all that complexity is no longer needed.
@pcc to confirm that there are no hidden dependencies.

It should be fine to remove the late-init instrumentation and reinstate the pthread_create interceptor.

compiler-rt/lib/hwasan/hwasan_allocator.h

 //===-- hwasan_allocator.h --------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of HWAddressSanitizer.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef HWASAN_ALLOCATOR_H
 #define HWASAN_ALLOCATOR_H
 
-#include "interception/interception.h"
 #include "sanitizer_common/sanitizer_allocator.h"
 #include "sanitizer_common/sanitizer_allocator_checks.h"
 #include "sanitizer_common/sanitizer_allocator_interface.h"
 #include "sanitizer_common/sanitizer_allocator_report.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_ring_buffer.h"
 #include "hwasan_poisoning.h"
 
 #if !defined(__aarch64__) && !defined(__x86_64__)
 #error Unsupported platform
 #endif
 
-#if HWASAN_WITH_INTERCEPTORS
-DECLARE_REAL(void *, realloc, void *ptr, uptr size)
-DECLARE_REAL(void, free, void *ptr)
-#endif
-
 namespace __hwasan {
 
 struct Metadata {
   u32 requested_size : 31;  // sizes are < 2G.
   u32 right_aligned  : 1;
   u32 alloc_context_id;
 };
 

compiler-rt/lib/hwasan/hwasan_allocator.cpp

 #include "hwasan.h"
 #include "hwasan_allocator.h"
 #include "hwasan_checks.h"
 #include "hwasan_mapping.h"
 #include "hwasan_malloc_bisect.h"
 #include "hwasan_thread.h"
 #include "hwasan_report.h"
 
-#if HWASAN_WITH_INTERCEPTORS
-DEFINE_REAL(void *, realloc, void *ptr, uptr size)
-DEFINE_REAL(void, free, void *ptr)
-#endif
-
 namespace __hwasan {
 
 static Allocator allocator;
 static AllocatorCache fallback_allocator_cache;
 static SpinMutex fallback_mutex;
 static atomic_uint8_t hwasan_allocator_tagging_enabled;
 
 static const tag_t kFallbackAllocTag = 0xBB;

 
 void *hwasan_calloc(uptr nmemb, uptr size, StackTrace *stack) {
   return SetErrnoOnNull(HwasanCalloc(stack, nmemb, size));
 }
 
 void *hwasan_realloc(void *ptr, uptr size, StackTrace *stack) {
   if (!ptr)
     return SetErrnoOnNull(HwasanAllocate(stack, size, sizeof(u64), false));
-
-#if HWASAN_WITH_INTERCEPTORS
-  // A tag of 0 means that this is a system allocator allocation, so we must use
-  // the system allocator to realloc it.
-  if (!flags()->disable_allocator_tagging && GetTagFromPointer((uptr)ptr) == 0)
-    return REAL(realloc)(ptr, size);
-#endif
-
   if (size == 0) {
     HwasanDeallocate(stack, ptr);
     return nullptr;
   }
   return SetErrnoOnNull(HwasanReallocate(stack, ptr, size, sizeof(u64)));
 }
 
 void *hwasan_reallocarray(void *ptr, uptr nmemb, uptr size, StackTrace *stack) {
if (UNLIKELY(!ptr))
     // OOM error is already taken care of by HwasanAllocate.
     return errno_ENOMEM;
   CHECK(IsAligned((uptr)ptr, alignment));
   *memptr = ptr;
   return 0;
 }
 
 void hwasan_free(void *ptr, StackTrace *stack) {
-#if HWASAN_WITH_INTERCEPTORS
-  // A tag of 0 means that this is a system allocator allocation, so we must use
-  // the system allocator to free it.
-  if (!flags()->disable_allocator_tagging && GetTagFromPointer((uptr)ptr) == 0)
-    return REAL(free)(ptr);
-#endif
-
   return HwasanDeallocate(stack, ptr);
 }
 
 }  // namespace __hwasan
 
 using namespace __hwasan;
 
 void __hwasan_enable_allocator_tagging() {
   atomic_store_relaxed(&hwasan_allocator_tagging_enabled, 1);
 }
 
 void __hwasan_disable_allocator_tagging() {
-#if HWASAN_WITH_INTERCEPTORS
-  // Allocator tagging must be enabled for the system allocator fallback to work
-  // correctly. This means that we can't disable it at runtime if it was enabled
-  // at startup since that might result in our deallocations going to the system
-  // allocator. If tagging was disabled at startup we avoid this problem by
-  // disabling the fallback altogether.
-  CHECK(flags()->disable_allocator_tagging);
-#endif
-
   atomic_store_relaxed(&hwasan_allocator_tagging_enabled, 0);
 }
 
 uptr __sanitizer_get_current_allocated_bytes() {
   uptr stats[AllocatorStatCount];
   allocator.GetStats(stats);
   return stats[AllocatorStatAllocated];
 }

compiler-rt/lib/hwasan/hwasan_interceptors.cpp

 
 #if HWASAN_WITH_INTERCEPTORS
 #if defined(__linux__)
   INTERCEPT_FUNCTION(vfork);
 #endif  // __linux__
 #if !defined(__aarch64__)
   INTERCEPT_FUNCTION(pthread_create);
 #endif  // __aarch64__
-  INTERCEPT_FUNCTION(realloc);
-  INTERCEPT_FUNCTION(free);
 #endif
 
   inited = 1;
 }
 } // namespace __hwasan

compiler-rt/test/hwasan/TestCases/Posix/system-allocator-fallback.cpp

-// RUN: %clangxx %s -o %t -ldl
-// RUN: %clangxx_hwasan -shared %s -o %t.so -DSHARED_LIB -shared-libsan -Wl,-rpath,%compiler_rt_libdir
-// RUN: %env_hwasan_opts=disable_allocator_tagging=0 %run %t
-
-// The dynamic loader on Android O appears to have a bug where it crashes when
-// dlopening DF_1_GLOBAL libraries.
-// REQUIRES: android-28
-
-#include <stddef.h>
-
-// Test that allocations made by the system allocator can be realloc'd and freed
-// by the hwasan allocator.
-
-typedef void run_test_fn(void *(*system_malloc)(size_t size));
-
-#ifdef SHARED_LIB
-
-// Call the __sanitizer_ versions of these functions so that the test
-// doesn't require the Android dynamic loader.
-extern "C" void *__sanitizer_realloc(void *ptr, size_t size);
-extern "C" void __sanitizer_free(void *ptr);
-
-extern "C" run_test_fn run_test;
-void run_test(void *(*system_malloc)(size_t size)) {
-  void *mem = system_malloc(64);
-  mem = __sanitizer_realloc(mem, 128);
-  __sanitizer_free(mem);
-}
-
-#else
-
-#include <dlfcn.h>
-#include <stdlib.h>
-#include <string>
-
-int main(int argc, char **argv) {
-  std::string path = argv[0];
-  path += ".so";
-  void *lib = dlopen(path.c_str(), RTLD_NOW);
-  if (!lib) {
-    printf("error in dlopen(): %s\n", dlerror());
-    return 1;
-  }
-
-  auto run_test = reinterpret_cast<run_test_fn *>(dlsym(lib, "run_test"));
-  if (!run_test) {
-    printf("failed dlsym\n");
-    return 1;
-  }
-
-  run_test(malloc);
-}
-
-#endif