xref: /aosp_15_r20/external/scudo/standalone/tests/wrappers_c_test.cpp (revision 76559068c068bd27e82aff38fac3bfc865233bca)

//===-- wrappers_c_test.cpp -------------------------------------*- 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
//
//===----------------------------------------------------------------------===//

#include "common.h"
#include "memtag.h"
#include "scudo/interface.h"
#include "tests/scudo_unit_test.h"

#include <errno.h>
#include <limits.h>
#include <malloc.h>
#include <stdlib.h>
#include <unistd.h>
#include <vector>

#ifndef __GLIBC_PREREQ
#define __GLIBC_PREREQ(x, y) 0
#endif

#if SCUDO_FUCHSIA
// Fuchsia only has valloc
#define HAVE_VALLOC 1
#elif SCUDO_ANDROID
// Android only has pvalloc/valloc on 32 bit
#if !defined(__LP64__)
#define HAVE_PVALLOC 1
#define HAVE_VALLOC 1
#endif // !defined(__LP64__)
#else
// All others assumed to support both functions.
#define HAVE_PVALLOC 1
#define HAVE_VALLOC 1
#endif

extern "C" {
void malloc_enable(void);
void malloc_disable(void);
int malloc_iterate(uintptr_t base, size_t size,
                   void (*callback)(uintptr_t base, size_t size, void *arg),
                   void *arg);
void *valloc(size_t size);
void *pvalloc(size_t size);

#ifndef SCUDO_ENABLE_HOOKS_TESTS
#define SCUDO_ENABLE_HOOKS_TESTS 0
#endif

#if (SCUDO_ENABLE_HOOKS_TESTS == 1) && (SCUDO_ENABLE_HOOKS == 0)
#error "Hooks tests should have hooks enabled as well!"
#endif

struct AllocContext {
  void *Ptr;
  size_t Size;
};
struct DeallocContext {
  void *Ptr;
};
struct ReallocContext {
  void *AllocPtr;
  void *DeallocPtr;
  size_t Size;
};
static AllocContext AC;
static DeallocContext DC;
static ReallocContext RC;

#if (SCUDO_ENABLE_HOOKS_TESTS == 1)
__attribute__((visibility("default"))) void __scudo_allocate_hook(void *Ptr,
                                                                  size_t Size) {
  AC.Ptr = Ptr;
  AC.Size = Size;
}
__attribute__((visibility("default"))) void __scudo_deallocate_hook(void *Ptr) {
  DC.Ptr = Ptr;
}
__attribute__((visibility("default"))) void
__scudo_realloc_allocate_hook(void *OldPtr, void *NewPtr, size_t Size) {
  // Verify that __scudo_realloc_deallocate_hook is called first and set the
  // right pointer.
  EXPECT_EQ(OldPtr, RC.DeallocPtr);
  RC.AllocPtr = NewPtr;
  RC.Size = Size;

  // Note that this is only used for testing. In general, only one pair of hooks
  // will be invoked in `realloc`. if __scudo_realloc_*_hook are not defined,
  // it'll call the general hooks only. To make the test easier, we call the
  // general one here so that either case (whether __scudo_realloc_*_hook are
  // defined) will be verified without separating them into different tests.
  __scudo_allocate_hook(NewPtr, Size);
}
__attribute__((visibility("default"))) void
__scudo_realloc_deallocate_hook(void *Ptr) {
  RC.DeallocPtr = Ptr;

  // See the comment in the __scudo_realloc_allocate_hook above.
  __scudo_deallocate_hook(Ptr);
}
#endif // (SCUDO_ENABLE_HOOKS_TESTS == 1)
}

class ScudoWrappersCTest : public Test {
protected:
  void SetUp() override {
    if (SCUDO_ENABLE_HOOKS && !SCUDO_ENABLE_HOOKS_TESTS)
      printf("Hooks are enabled but hooks tests are disabled.\n");
  }

  void invalidateHookPtrs() {
    if (SCUDO_ENABLE_HOOKS_TESTS) {
      void *InvalidPtr = reinterpret_cast<void *>(0xdeadbeef);
      AC.Ptr = InvalidPtr;
      DC.Ptr = InvalidPtr;
      RC.AllocPtr = RC.DeallocPtr = InvalidPtr;
    }
  }
  void verifyAllocHookPtr(UNUSED void *Ptr) {
    if (SCUDO_ENABLE_HOOKS_TESTS)
      EXPECT_EQ(Ptr, AC.Ptr);
  }
  void verifyAllocHookSize(UNUSED size_t Size) {
    if (SCUDO_ENABLE_HOOKS_TESTS)
      EXPECT_EQ(Size, AC.Size);
  }
  void verifyDeallocHookPtr(UNUSED void *Ptr) {
    if (SCUDO_ENABLE_HOOKS_TESTS)
      EXPECT_EQ(Ptr, DC.Ptr);
  }
  void verifyReallocHookPtrs(UNUSED void *OldPtr, void *NewPtr, size_t Size) {
    if (SCUDO_ENABLE_HOOKS_TESTS) {
      EXPECT_EQ(OldPtr, RC.DeallocPtr);
      EXPECT_EQ(NewPtr, RC.AllocPtr);
      EXPECT_EQ(Size, RC.Size);
    }
  }
};
using ScudoWrappersCDeathTest = ScudoWrappersCTest;

// Note that every C allocation function in the test binary will be fulfilled
// by Scudo (this includes the gtest APIs, etc.), which is a test by itself.
// But this might also lead to unexpected side-effects, since the allocation and
// deallocation operations in the TEST functions will coexist with others (see
// the EXPECT_DEATH comment below).

// We have to use a small quarantine to make sure that our double-free tests
// trigger. Otherwise EXPECT_DEATH ends up reallocating the chunk that was just
// freed (this depends on the size obviously) and the following free succeeds.

static const size_t Size = 100U;

TEST_F(ScudoWrappersCDeathTest, Malloc) {
  void *P = malloc(Size);
  EXPECT_NE(P, nullptr);
  EXPECT_LE(Size, malloc_usable_size(P));
  EXPECT_EQ(reinterpret_cast<uintptr_t>(P) % FIRST_32_SECOND_64(8U, 16U), 0U);
  verifyAllocHookPtr(P);
  verifyAllocHookSize(Size);

  // An update to this warning in Clang now triggers in this line, but it's ok
  // because the check is expecting a bad pointer and should fail.
#if defined(__has_warning) && __has_warning("-Wfree-nonheap-object")
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
#endif
  EXPECT_DEATH(
      free(reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(P) | 1U)), "");
#if defined(__has_warning) && __has_warning("-Wfree-nonheap-object")
#pragma GCC diagnostic pop
#endif

  free(P);
  verifyDeallocHookPtr(P);
  EXPECT_DEATH(free(P), "");

  P = malloc(0U);
  EXPECT_NE(P, nullptr);
  free(P);

  errno = 0;
  EXPECT_EQ(malloc(SIZE_MAX), nullptr);
  EXPECT_EQ(errno, ENOMEM);
}

TEST_F(ScudoWrappersCTest, Calloc) {
  void *P = calloc(1U, Size);
  EXPECT_NE(P, nullptr);
  EXPECT_LE(Size, malloc_usable_size(P));
  verifyAllocHookPtr(P);
  verifyAllocHookSize(Size);
  for (size_t I = 0; I < Size; I++)
    EXPECT_EQ((reinterpret_cast<uint8_t *>(P))[I], 0U);
  free(P);
  verifyDeallocHookPtr(P);

  P = calloc(1U, 0U);
  EXPECT_NE(P, nullptr);
  free(P);
  P = calloc(0U, 1U);
  EXPECT_NE(P, nullptr);
  free(P);

  errno = 0;
  EXPECT_EQ(calloc(SIZE_MAX, 1U), nullptr);
  EXPECT_EQ(errno, ENOMEM);
  errno = 0;
  EXPECT_EQ(calloc(static_cast<size_t>(LONG_MAX) + 1U, 2U), nullptr);
  if (SCUDO_ANDROID)
    EXPECT_EQ(errno, ENOMEM);
  errno = 0;
  EXPECT_EQ(calloc(SIZE_MAX, SIZE_MAX), nullptr);
  EXPECT_EQ(errno, ENOMEM);
}

TEST_F(ScudoWrappersCTest, SmallAlign) {
  // Allocating pointers by the powers of 2 from 1 to 0x10000
  // Using powers of 2 due to memalign using powers of 2 and test more sizes
  constexpr size_t MaxSize = 0x10000;
  std::vector<void *> ptrs;
  // Reserving space to prevent further allocation during the test
  ptrs.reserve((scudo::getLeastSignificantSetBitIndex(MaxSize) + 1) *
               (scudo::getLeastSignificantSetBitIndex(MaxSize) + 1) * 3);
  for (size_t Size = 1; Size <= MaxSize; Size <<= 1) {
    for (size_t Align = 1; Align <= MaxSize; Align <<= 1) {
      for (size_t Count = 0; Count < 3; ++Count) {
        void *P = memalign(Align, Size);
        EXPECT_TRUE(reinterpret_cast<uintptr_t>(P) % Align == 0);
        ptrs.push_back(P);
      }
    }
  }
  for (void *ptr : ptrs)
    free(ptr);
}

TEST_F(ScudoWrappersCTest, Memalign) {
  void *P;
  for (size_t I = FIRST_32_SECOND_64(2U, 3U); I <= 18U; I++) {
    const size_t Alignment = 1U << I;

    P = memalign(Alignment, Size);
    EXPECT_NE(P, nullptr);
    EXPECT_LE(Size, malloc_usable_size(P));
    EXPECT_EQ(reinterpret_cast<uintptr_t>(P) % Alignment, 0U);
    verifyAllocHookPtr(P);
    verifyAllocHookSize(Size);
    free(P);
    verifyDeallocHookPtr(P);

    P = nullptr;
    EXPECT_EQ(posix_memalign(&P, Alignment, Size), 0);
    EXPECT_NE(P, nullptr);
    EXPECT_LE(Size, malloc_usable_size(P));
    EXPECT_EQ(reinterpret_cast<uintptr_t>(P) % Alignment, 0U);
    verifyAllocHookPtr(P);
    verifyAllocHookSize(Size);
    free(P);
    verifyDeallocHookPtr(P);
  }

  EXPECT_EQ(memalign(4096U, SIZE_MAX), nullptr);
  EXPECT_EQ(posix_memalign(&P, 15U, Size), EINVAL);
  EXPECT_EQ(posix_memalign(&P, 4096U, SIZE_MAX), ENOMEM);

  // Android's memalign accepts non power-of-2 alignments, and 0.
  if (SCUDO_ANDROID) {
    for (size_t Alignment = 0U; Alignment <= 128U; Alignment++) {
      P = memalign(Alignment, 1024U);
      EXPECT_NE(P, nullptr);
      verifyAllocHookPtr(P);
      verifyAllocHookSize(Size);
      free(P);
      verifyDeallocHookPtr(P);
    }
  }
}

TEST_F(ScudoWrappersCTest, AlignedAlloc) {
  const size_t Alignment = 4096U;
  void *P = aligned_alloc(Alignment, Alignment * 4U);
  EXPECT_NE(P, nullptr);
  EXPECT_LE(Alignment * 4U, malloc_usable_size(P));
  EXPECT_EQ(reinterpret_cast<uintptr_t>(P) % Alignment, 0U);
  verifyAllocHookPtr(P);
  verifyAllocHookSize(Alignment * 4U);
  free(P);
  verifyDeallocHookPtr(P);

  errno = 0;
  P = aligned_alloc(Alignment, Size);
  EXPECT_EQ(P, nullptr);
  EXPECT_EQ(errno, EINVAL);
}

TEST_F(ScudoWrappersCDeathTest, Realloc) {
  invalidateHookPtrs();
  // realloc(nullptr, N) is malloc(N)
  void *P = realloc(nullptr, Size);
  EXPECT_NE(P, nullptr);
  verifyAllocHookPtr(P);
  verifyAllocHookSize(Size);
  free(P);
  verifyDeallocHookPtr(P);

  invalidateHookPtrs();
  P = malloc(Size);
  EXPECT_NE(P, nullptr);
  // realloc(P, 0U) is free(P) and returns nullptr
  EXPECT_EQ(realloc(P, 0U), nullptr);
  verifyDeallocHookPtr(P);

  P = malloc(Size);
  EXPECT_NE(P, nullptr);
  EXPECT_LE(Size, malloc_usable_size(P));
  memset(P, 0x42, Size);

  invalidateHookPtrs();
  void *OldP = P;
  P = realloc(P, Size * 2U);
  EXPECT_NE(P, nullptr);
  EXPECT_LE(Size * 2U, malloc_usable_size(P));
  for (size_t I = 0; I < Size; I++)
    EXPECT_EQ(0x42, (reinterpret_cast<uint8_t *>(P))[I]);
  if (OldP == P) {
    verifyDeallocHookPtr(OldP);
    verifyAllocHookPtr(OldP);
  } else {
    verifyAllocHookPtr(P);
    verifyAllocHookSize(Size * 2U);
    verifyDeallocHookPtr(OldP);
  }
  verifyReallocHookPtrs(OldP, P, Size * 2U);

  invalidateHookPtrs();
  OldP = P;
  P = realloc(P, Size / 2U);
  EXPECT_NE(P, nullptr);
  EXPECT_LE(Size / 2U, malloc_usable_size(P));
  for (size_t I = 0; I < Size / 2U; I++)
    EXPECT_EQ(0x42, (reinterpret_cast<uint8_t *>(P))[I]);
  if (OldP == P) {
    verifyDeallocHookPtr(OldP);
    verifyAllocHookPtr(OldP);
  } else {
    verifyAllocHookPtr(P);
    verifyAllocHookSize(Size / 2U);
  }
  verifyReallocHookPtrs(OldP, P, Size / 2U);
  free(P);

  EXPECT_DEATH(P = realloc(P, Size), "");

  errno = 0;
  EXPECT_EQ(realloc(nullptr, SIZE_MAX), nullptr);
  EXPECT_EQ(errno, ENOMEM);
  P = malloc(Size);
  EXPECT_NE(P, nullptr);
  errno = 0;
  EXPECT_EQ(realloc(P, SIZE_MAX), nullptr);
  EXPECT_EQ(errno, ENOMEM);
  free(P);

  // Android allows realloc of memalign pointers.
  if (SCUDO_ANDROID) {
    const size_t Alignment = 1024U;
    P = memalign(Alignment, Size);
    EXPECT_NE(P, nullptr);
    EXPECT_LE(Size, malloc_usable_size(P));
    EXPECT_EQ(reinterpret_cast<uintptr_t>(P) % Alignment, 0U);
    memset(P, 0x42, Size);

    P = realloc(P, Size * 2U);
    EXPECT_NE(P, nullptr);
    EXPECT_LE(Size * 2U, malloc_usable_size(P));
    for (size_t I = 0; I < Size; I++)
      EXPECT_EQ(0x42, (reinterpret_cast<uint8_t *>(P))[I]);
    free(P);
  }
}

#if !SCUDO_FUCHSIA
TEST_F(ScudoWrappersCTest, MallOpt) {
  errno = 0;
  EXPECT_EQ(mallopt(-1000, 1), 0);
  // mallopt doesn't set errno.
  EXPECT_EQ(errno, 0);

  EXPECT_EQ(mallopt(M_PURGE, 0), 1);

  EXPECT_EQ(mallopt(M_DECAY_TIME, 1), 1);
  EXPECT_EQ(mallopt(M_DECAY_TIME, 0), 1);
  EXPECT_EQ(mallopt(M_DECAY_TIME, 1), 1);
  EXPECT_EQ(mallopt(M_DECAY_TIME, 0), 1);

  if (SCUDO_ANDROID) {
    EXPECT_EQ(mallopt(M_CACHE_COUNT_MAX, 100), 1);
    EXPECT_EQ(mallopt(M_CACHE_SIZE_MAX, 1024 * 1024 * 2), 1);
    EXPECT_EQ(mallopt(M_TSDS_COUNT_MAX, 10), 1);
  }
}
#endif

TEST_F(ScudoWrappersCTest, OtherAlloc) {
#if HAVE_PVALLOC
  const size_t PageSize = static_cast<size_t>(sysconf(_SC_PAGESIZE));

  void *P = pvalloc(Size);
  EXPECT_NE(P, nullptr);
  EXPECT_EQ(reinterpret_cast<uintptr_t>(P) & (PageSize - 1), 0U);
  EXPECT_LE(PageSize, malloc_usable_size(P));
  verifyAllocHookPtr(P);
  // Size will be rounded up to PageSize.
  verifyAllocHookSize(PageSize);
  free(P);
  verifyDeallocHookPtr(P);

  EXPECT_EQ(pvalloc(SIZE_MAX), nullptr);

  P = pvalloc(Size);
  EXPECT_NE(P, nullptr);
  EXPECT_EQ(reinterpret_cast<uintptr_t>(P) & (PageSize - 1), 0U);
  free(P);
#endif

#if HAVE_VALLOC
  EXPECT_EQ(valloc(SIZE_MAX), nullptr);
#endif
}

template<typename FieldType>
void MallInfoTest() {
  // mallinfo is deprecated.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
  const FieldType BypassQuarantineSize = 1024U;
  struct mallinfo MI = mallinfo();
  FieldType Allocated = MI.uordblks;
  void *P = malloc(BypassQuarantineSize);
  EXPECT_NE(P, nullptr);
  MI = mallinfo();
  EXPECT_GE(MI.uordblks, Allocated + BypassQuarantineSize);
  EXPECT_GT(MI.hblkhd, static_cast<FieldType>(0));
  FieldType Free = MI.fordblks;
  free(P);
  MI = mallinfo();
  EXPECT_GE(MI.fordblks, Free + BypassQuarantineSize);
#pragma clang diagnostic pop
}

#if !SCUDO_FUCHSIA
TEST_F(ScudoWrappersCTest, MallInfo) {
#if SCUDO_ANDROID
  // Android accidentally set the fields to size_t instead of int.
  MallInfoTest<size_t>();
#else
  MallInfoTest<int>();
#endif
}
#endif

#if __GLIBC_PREREQ(2, 33) || SCUDO_ANDROID
TEST_F(ScudoWrappersCTest, MallInfo2) {
  const size_t BypassQuarantineSize = 1024U;
  struct mallinfo2 MI = mallinfo2();
  size_t Allocated = MI.uordblks;
  void *P = malloc(BypassQuarantineSize);
  EXPECT_NE(P, nullptr);
  MI = mallinfo2();
  EXPECT_GE(MI.uordblks, Allocated + BypassQuarantineSize);
  EXPECT_GT(MI.hblkhd, 0U);
  size_t Free = MI.fordblks;
  free(P);
  MI = mallinfo2();
  EXPECT_GE(MI.fordblks, Free + BypassQuarantineSize);
}
#endif

static uintptr_t BoundaryP;
static size_t Count;

static void callback(uintptr_t Base, UNUSED size_t Size, UNUSED void *Arg) {
  if (scudo::archSupportsMemoryTagging()) {
    Base = scudo::untagPointer(Base);
    BoundaryP = scudo::untagPointer(BoundaryP);
  }
  if (Base == BoundaryP)
    Count++;
}

// Verify that a block located on an iteration boundary is not mis-accounted.
// To achieve this, we allocate a chunk for which the backing block will be
// aligned on a page, then run the malloc_iterate on both the pages that the
// block is a boundary for. It must only be seen once by the callback function.
TEST_F(ScudoWrappersCTest, MallocIterateBoundary) {
  const size_t PageSize = static_cast<size_t>(sysconf(_SC_PAGESIZE));
#if SCUDO_ANDROID
  // Android uses a 16 byte alignment for both 32 bit and 64 bit.
  const size_t BlockDelta = 16U;
#else
  const size_t BlockDelta = FIRST_32_SECOND_64(8U, 16U);
#endif
  const size_t SpecialSize = PageSize - BlockDelta;

  // We aren't guaranteed that any size class is exactly a page wide. So we need
  // to keep making allocations until we get an allocation that starts exactly
  // on a page boundary. The BlockDelta value is expected to be the number of
  // bytes to subtract from a returned pointer to get to the actual start of
  // the pointer in the size class. In practice, this means BlockDelta should
  // be set to the minimum alignment in bytes for the allocation.
  //
  // With a 16-byte block alignment and 4096-byte page size, each allocation has
  // a probability of (1 - (16/4096)) of failing to meet the alignment
  // requirements, and the probability of failing 65536 times is
  // (1 - (16/4096))^65536 < 10^-112. So if we still haven't succeeded after
  // 65536 tries, give up.
  uintptr_t Block;
  void *P = nullptr;
  for (unsigned I = 0; I != 65536; ++I) {
    void *PrevP = P;
    P = malloc(SpecialSize);
    EXPECT_NE(P, nullptr);
    *reinterpret_cast<void **>(P) = PrevP;
    BoundaryP = reinterpret_cast<uintptr_t>(P);
    Block = BoundaryP - BlockDelta;
    if ((Block & (PageSize - 1)) == 0U)
      break;
  }
  EXPECT_EQ((Block & (PageSize - 1)), 0U);

  Count = 0U;
  malloc_disable();
  malloc_iterate(Block - PageSize, PageSize, callback, nullptr);
  malloc_iterate(Block, PageSize, callback, nullptr);
  malloc_enable();
  EXPECT_EQ(Count, 1U);

  while (P) {
    void *NextP = *reinterpret_cast<void **>(P);
    free(P);
    P = NextP;
  }
}

// Fuchsia doesn't have alarm, fork or malloc_info.
#if !SCUDO_FUCHSIA
TEST_F(ScudoWrappersCDeathTest, MallocDisableDeadlock) {
  // We expect heap operations within a disable/enable scope to deadlock.
  EXPECT_DEATH(
      {
        void *P = malloc(Size);
        EXPECT_NE(P, nullptr);
        free(P);
        malloc_disable();
        alarm(1);
        P = malloc(Size);
        malloc_enable();
      },
      "");
}

TEST_F(ScudoWrappersCTest, MallocInfo) {
  // Use volatile so that the allocations don't get optimized away.
  void *volatile P1 = malloc(1234);
  void *volatile P2 = malloc(4321);

  char Buffer[16384];
  FILE *F = fmemopen(Buffer, sizeof(Buffer), "w+");
  EXPECT_NE(F, nullptr);
  errno = 0;
  EXPECT_EQ(malloc_info(0, F), 0);
  EXPECT_EQ(errno, 0);
  fclose(F);
  EXPECT_EQ(strncmp(Buffer, "<malloc version=\"scudo-", 23), 0);
  EXPECT_NE(nullptr, strstr(Buffer, "<alloc size=\"1234\" count=\""));
  EXPECT_NE(nullptr, strstr(Buffer, "<alloc size=\"4321\" count=\""));

  free(P1);
  free(P2);
}

TEST_F(ScudoWrappersCDeathTest, Fork) {
  void *P;
  pid_t Pid = fork();
  EXPECT_GE(Pid, 0) << strerror(errno);
  if (Pid == 0) {
    P = malloc(Size);
    EXPECT_NE(P, nullptr);
    memset(P, 0x42, Size);
    free(P);
    _exit(0);
  }
  waitpid(Pid, nullptr, 0);
  P = malloc(Size);
  EXPECT_NE(P, nullptr);
  memset(P, 0x42, Size);
  free(P);

  // fork should stall if the allocator has been disabled.
  EXPECT_DEATH(
      {
        malloc_disable();
        alarm(1);
        Pid = fork();
        EXPECT_GE(Pid, 0);
      },
      "");
}

static pthread_mutex_t Mutex;
static pthread_cond_t Conditional = PTHREAD_COND_INITIALIZER;
static bool Ready;

static void *enableMalloc(UNUSED void *Unused) {
  // Initialize the allocator for this thread.
  void *P = malloc(Size);
  EXPECT_NE(P, nullptr);
  memset(P, 0x42, Size);
  free(P);

  // Signal the main thread we are ready.
  pthread_mutex_lock(&Mutex);
  Ready = true;
  pthread_cond_signal(&Conditional);
  pthread_mutex_unlock(&Mutex);

  // Wait for the malloc_disable & fork, then enable the allocator again.
  sleep(1);
  malloc_enable();

  return nullptr;
}

TEST_F(ScudoWrappersCTest, DisableForkEnable) {
  pthread_t ThreadId;
  Ready = false;
  EXPECT_EQ(pthread_create(&ThreadId, nullptr, &enableMalloc, nullptr), 0);

  // Wait for the thread to be warmed up.
  pthread_mutex_lock(&Mutex);
  while (!Ready)
    pthread_cond_wait(&Conditional, &Mutex);
  pthread_mutex_unlock(&Mutex);

  // Disable the allocator and fork. fork should succeed after malloc_enable.
  malloc_disable();
  pid_t Pid = fork();
  EXPECT_GE(Pid, 0);
  if (Pid == 0) {
    void *P = malloc(Size);
    EXPECT_NE(P, nullptr);
    memset(P, 0x42, Size);
    free(P);
    _exit(0);
  }
  waitpid(Pid, nullptr, 0);
  EXPECT_EQ(pthread_join(ThreadId, 0), 0);
}

#endif // SCUDO_FUCHSIA