1 files changed, 354 insertions, 0 deletions
diff --git a/js/src/jsapi-tests/testGCAllocator.cpp b/js/src/jsapi-tests/testGCAllocator.cpp
new file mode 100644
index 0000000000..c740a3b10b
--- /dev/null
+++ b/js/src/jsapi-tests/testGCAllocator.cpp
@@ -0,0 +1,354 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <cstdlib>
+
+#include "gc/Memory.h"
+#include "jsapi-tests/tests.h"
+
+#if defined(XP_WIN)
+#  include "util/WindowsWrapper.h"
+#  include <psapi.h>
+#elif defined(__wasi__)
+// Nothing.
+#else
+#  include <algorithm>
+#  include <errno.h>
+#  include <sys/mman.h>
+#  include <sys/resource.h>
+#  include <sys/stat.h>
+#  include <sys/types.h>
+#  include <unistd.h>
+#endif
+
+BEGIN_TEST(testGCAllocator) {
+#ifdef JS_64BIT
+  // If we're using the scattershot allocator, this test does not apply.
+  if (js::gc::UsingScattershotAllocator()) {
+    return true;
+  }
+#endif
+
+  size_t PageSize = js::gc::SystemPageSize();
+
+  /* Finish any ongoing background free activity. */
+  js::gc::FinishGC(cx);
+
+  bool growUp = false;
+  CHECK(addressesGrowUp(&growUp));
+
+  if (growUp) {
+    return testGCAllocatorUp(PageSize);
+  } else {
+    return testGCAllocatorDown(PageSize);
+  }
+}
+
+static const size_t Chunk = 512 * 1024;
+static const size_t Alignment = 2 * Chunk;
+static const int MaxTempChunks = 4096;
+static const size_t StagingSize = 16 * Chunk;
+
+bool addressesGrowUp(bool* resultOut) {
+  /*
+   * Try to detect whether the OS allocates memory in increasing or decreasing
+   * address order by making several allocations and comparing the addresses.
+   */
+
+  static const unsigned ChunksToTest = 20;
+  static const int ThresholdCount = 15;
+
+  void* chunks[ChunksToTest];
+  for (unsigned i = 0; i < ChunksToTest; i++) {
+    chunks[i] = mapMemory(2 * Chunk);
+    CHECK(chunks[i]);
+  }
+
+  int upCount = 0;
+  int downCount = 0;
+
+  for (unsigned i = 0; i < ChunksToTest - 1; i++) {
+    if (chunks[i] < chunks[i + 1]) {
+      upCount++;
+    } else {
+      downCount++;
+    }
+  }
+
+  for (unsigned i = 0; i < ChunksToTest; i++) {
+    unmapPages(chunks[i], 2 * Chunk);
+  }
+
+  /* Check results were mostly consistent. */
+  CHECK(abs(upCount - downCount) >= ThresholdCount);
+
+  *resultOut = upCount > downCount;
+
+  return true;
+}
+
+size_t offsetFromAligned(void* p) { return uintptr_t(p) % Alignment; }
+
+enum AllocType { UseNormalAllocator, UseLastDitchAllocator };
+
+bool testGCAllocatorUp(const size_t PageSize) {
+  const size_t UnalignedSize = StagingSize + Alignment - PageSize;
+  void* chunkPool[MaxTempChunks];
+  // Allocate a contiguous chunk that we can partition for testing.
+  void* stagingArea = mapMemory(UnalignedSize);
+  if (!stagingArea) {
+    return false;
+  }
+  // Ensure that the staging area is aligned.
+  unmapPages(stagingArea, UnalignedSize);
+  if (offsetFromAligned(stagingArea)) {
+    const size_t Offset = offsetFromAligned(stagingArea);
+    // Place the area at the lowest aligned address.
+    stagingArea = (void*)(uintptr_t(stagingArea) + (Alignment - Offset));
+  }
+  mapMemoryAt(stagingArea, StagingSize);
+  // Make sure there are no available chunks below the staging area.
+  int tempChunks;
+  if (!fillSpaceBeforeStagingArea(tempChunks, stagingArea, chunkPool, false)) {
+    return false;
+  }
+  // Unmap the staging area so we can set it up for testing.
+  unmapPages(stagingArea, StagingSize);
+  // Check that the first chunk is used if it is aligned.
+  CHECK(positionIsCorrect("xxooxxx---------", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that the first chunk is used if it can be aligned.
+  CHECK(positionIsCorrect("x-ooxxx---------", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that an aligned chunk after a single unalignable chunk is used.
+  CHECK(positionIsCorrect("x--xooxxx-------", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that we fall back to the slow path after two unalignable chunks.
+  CHECK(positionIsCorrect("x--xx--xoo--xxx-", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that we also fall back after an unalignable and an alignable chunk.
+  CHECK(positionIsCorrect("x--xx---x-oo--x-", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that the last ditch allocator works as expected.
+  CHECK(positionIsCorrect("x--xx--xx-oox---", stagingArea, chunkPool,
+                          tempChunks, UseLastDitchAllocator));
+  // Check that the last ditch allocator can deal with naturally aligned chunks.
+  CHECK(positionIsCorrect("x--xx--xoo------", stagingArea, chunkPool,
+                          tempChunks, UseLastDitchAllocator));
+
+  // Clean up.
+  while (--tempChunks >= 0) {
+    unmapPages(chunkPool[tempChunks], 2 * Chunk);
+  }
+  return true;
+}
+
+bool testGCAllocatorDown(const size_t PageSize) {
+  const size_t UnalignedSize = StagingSize + Alignment - PageSize;
+  void* chunkPool[MaxTempChunks];
+  // Allocate a contiguous chunk that we can partition for testing.
+  void* stagingArea = mapMemory(UnalignedSize);
+  if (!stagingArea) {
+    return false;
+  }
+  // Ensure that the staging area is aligned.
+  unmapPages(stagingArea, UnalignedSize);
+  if (offsetFromAligned(stagingArea)) {
+    void* stagingEnd = (void*)(uintptr_t(stagingArea) + UnalignedSize);
+    const size_t Offset = offsetFromAligned(stagingEnd);
+    // Place the area at the highest aligned address.
+    stagingArea = (void*)(uintptr_t(stagingEnd) - Offset - StagingSize);
+  }
+  mapMemoryAt(stagingArea, StagingSize);
+  // Make sure there are no available chunks above the staging area.
+  int tempChunks;
+  if (!fillSpaceBeforeStagingArea(tempChunks, stagingArea, chunkPool, true)) {
+    return false;
+  }
+  // Unmap the staging area so we can set it up for testing.
+  unmapPages(stagingArea, StagingSize);
+  // Check that the first chunk is used if it is aligned.
+  CHECK(positionIsCorrect("---------xxxooxx", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that the first chunk is used if it can be aligned.
+  CHECK(positionIsCorrect("---------xxxoo-x", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that an aligned chunk after a single unalignable chunk is used.
+  CHECK(positionIsCorrect("-------xxxoox--x", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that we fall back to the slow path after two unalignable chunks.
+  CHECK(positionIsCorrect("-xxx--oox--xx--x", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that we also fall back after an unalignable and an alignable chunk.
+  CHECK(positionIsCorrect("-x--oo-x---xx--x", stagingArea, chunkPool,
+                          tempChunks));
+  // Check that the last ditch allocator works as expected.
+  CHECK(positionIsCorrect("---xoo-xx--xx--x", stagingArea, chunkPool,
+                          tempChunks, UseLastDitchAllocator));
+  // Check that the last ditch allocator can deal with naturally aligned chunks.
+  CHECK(positionIsCorrect("------oox--xx--x", stagingArea, chunkPool,
+                          tempChunks, UseLastDitchAllocator));
+
+  // Clean up.
+  while (--tempChunks >= 0) {
+    unmapPages(chunkPool[tempChunks], 2 * Chunk);
+  }
+  return true;
+}
+
+bool fillSpaceBeforeStagingArea(int& tempChunks, void* stagingArea,
+                                void** chunkPool, bool addressesGrowDown) {
+  // Make sure there are no available chunks before the staging area.
+  tempChunks = 0;
+  chunkPool[tempChunks++] = mapMemory(2 * Chunk);
+  while (tempChunks < MaxTempChunks && chunkPool[tempChunks - 1] &&
+         (chunkPool[tempChunks - 1] < stagingArea) ^ addressesGrowDown) {
+    chunkPool[tempChunks++] = mapMemory(2 * Chunk);
+    if (!chunkPool[tempChunks - 1]) {
+      break;  // We already have our staging area, so OOM here is okay.
+    }
+    if ((chunkPool[tempChunks - 1] < chunkPool[tempChunks - 2]) ^
+        addressesGrowDown) {
+      break;  // The address growth direction is inconsistent!
+    }
+  }
+  // OOM also means success in this case.
+  if (!chunkPool[tempChunks - 1]) {
+    --tempChunks;
+    return true;
+  }
+  // Bail if we can't guarantee the right address space layout.
+  if ((chunkPool[tempChunks - 1] < stagingArea) ^ addressesGrowDown ||
+      (tempChunks > 1 &&
+       (chunkPool[tempChunks - 1] < chunkPool[tempChunks - 2]) ^
+           addressesGrowDown)) {
+    while (--tempChunks >= 0) {
+      unmapPages(chunkPool[tempChunks], 2 * Chunk);
+    }
+    unmapPages(stagingArea, StagingSize);
+    return false;
+  }
+  return true;
+}
+
+bool positionIsCorrect(const char* str, void* base, void** chunkPool,
+                       int tempChunks,
+                       AllocType allocator = UseNormalAllocator) {
+  // str represents a region of memory, with each character representing a
+  // region of Chunk bytes. str should contain only x, o and -, where
+  // x = mapped by the test to set up the initial conditions,
+  // o = mapped by the GC allocator, and
+  // - = unmapped.
+  // base should point to a region of contiguous free memory
+  // large enough to hold strlen(str) chunks of Chunk bytes.
+  int len = strlen(str);
+  int i;
+  // Find the index of the desired address.
+  for (i = 0; i < len && str[i] != 'o'; ++i)
+    ;
+  void* desired = (void*)(uintptr_t(base) + i * Chunk);
+  // Map the regions indicated by str.
+  for (i = 0; i < len; ++i) {
+    if (str[i] == 'x') {
+      mapMemoryAt((void*)(uintptr_t(base) + i * Chunk), Chunk);
+    }
+  }
+  // Allocate using the GC's allocator.
+  void* result;
+  if (allocator == UseNormalAllocator) {
+    result = js::gc::MapAlignedPages(2 * Chunk, Alignment);
+  } else {
+    result = js::gc::TestMapAlignedPagesLastDitch(2 * Chunk, Alignment);
+  }
+  // Clean up the mapped regions.
+  if (result) {
+    js::gc::UnmapPages(result, 2 * Chunk);
+  }
+  for (--i; i >= 0; --i) {
+    if (str[i] == 'x') {
+      js::gc::UnmapPages((void*)(uintptr_t(base) + i * Chunk), Chunk);
+    }
+  }
+  // CHECK returns, so clean up on failure.
+  if (result != desired) {
+    while (--tempChunks >= 0) {
+      js::gc::UnmapPages(chunkPool[tempChunks], 2 * Chunk);
+    }
+  }
+  return result == desired;
+}
+
+#if defined(XP_WIN)
+
+void* mapMemoryAt(void* desired, size_t length) {
+  return VirtualAlloc(desired, length, MEM_COMMIT | MEM_RESERVE,
+                      PAGE_READWRITE);
+}
+
+void* mapMemory(size_t length) {
+  return VirtualAlloc(nullptr, length, MEM_COMMIT | MEM_RESERVE,
+                      PAGE_READWRITE);
+}
+
+void unmapPages(void* p, size_t size) {
+  MOZ_ALWAYS_TRUE(VirtualFree(p, 0, MEM_RELEASE));
+}
+
+#elif defined(__wasi__)
+
+void* mapMemoryAt(void* desired, size_t length) { return nullptr; }
+
+void* mapMemory(size_t length) {
+  void* addr = nullptr;
+  if (int err = posix_memalign(&addr, js::gc::SystemPageSize(), length)) {
+    MOZ_ASSERT(err == ENOMEM);
+  }
+  MOZ_ASSERT(addr);
+  memset(addr, 0, length);
+  return addr;
+}
+
+void unmapPages(void* p, size_t size) { free(p); }
+
+#else
+
+void* mapMemoryAt(void* desired, size_t length) {
+  void* region = mmap(desired, length, PROT_READ | PROT_WRITE,
+                      MAP_PRIVATE | MAP_ANON, -1, 0);
+  if (region == MAP_FAILED) {
+    return nullptr;
+  }
+  if (region != desired) {
+    if (munmap(region, length)) {
+      MOZ_RELEASE_ASSERT(errno == ENOMEM);
+    }
+    return nullptr;
+  }
+  return region;
+}
+
+void* mapMemory(size_t length) {
+  int prot = PROT_READ | PROT_WRITE;
+  int flags = MAP_PRIVATE | MAP_ANON;
+  int fd = -1;
+  off_t offset = 0;
+  void* region = mmap(nullptr, length, prot, flags, fd, offset);
+  if (region == MAP_FAILED) {
+    return nullptr;
+  }
+  return region;
+}
+
+void unmapPages(void* p, size_t size) {
+  if (munmap(p, size)) {
+    MOZ_RELEASE_ASSERT(errno == ENOMEM);
+  }
+}
+
+#endif
+
+END_TEST(testGCAllocator)