zircon/kernel/lib/fbl/gparena_tests.cc

// Copyright 2019 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <lib/unittest/unittest.h>
#include <platform.h>

#include <fbl/alloc_checker.h>
#include <fbl/gparena.h>

using fbl::GPArena;

static bool can_declare_small_objectsize() {
  BEGIN_TEST;

  // This is just exercising the static_assert in GPArena that ensures we can have fairly small
  // objectsize even in the presence of preservation.
  GPArena<0, 8> smallest;
  GPArena<4, 16> smallest_with_preserve;

  END_TEST;
}

static bool basic_lifo() {
  BEGIN_TEST;

  GPArena<0, 8> arena;
  ASSERT_EQ(arena.Init("test", 4), ZX_OK);

  void* first = arena.Alloc();
  ASSERT_NONNULL(first);

  void* second = arena.Alloc();
  ASSERT_NONNULL(second);

  // Alloc should always return the last Free.
  arena.Free(second);
  EXPECT_EQ(second, arena.Alloc());

  // If we Free multiple we should get them back in last-in-first-out order.
  arena.Free(second);
  arena.Free(first);
  EXPECT_EQ(first, arena.Alloc());
  EXPECT_EQ(second, arena.Alloc());

  // Cleanup.
  arena.Free(second);
  arena.Free(first);

  END_TEST;
}

static bool out_of_memory() {
  BEGIN_TEST;

  // Use large objects so we can store all the allocations in a stack array.
  GPArena<0, 512> arena;
  constexpr int count = PAGE_SIZE / 512;
  ASSERT_EQ(arena.Init("test", count), ZX_OK);
  void* allocs[count];

  // Allocate all objects from the arena.
  for (int i = 0; i < count; i++) {
    allocs[i] = arena.Alloc();
    ASSERT_NONNULL(allocs[i]);
  }

  // Unless we calculated wrong, allocations should now fail.
  EXPECT_NULL(arena.Alloc());
  EXPECT_NULL(arena.Alloc());

  // Should be able to put objects back and then successfully re-allocate them.
  arena.Free(allocs[count - 1]);
  arena.Free(allocs[count - 2]);
  EXPECT_EQ(allocs[count - 2], arena.Alloc());
  EXPECT_EQ(allocs[count - 1], arena.Alloc());

  // Once we re-allocate the ones we put back, future allocations should be back to failing.
  EXPECT_NULL(arena.Alloc());
  EXPECT_NULL(arena.Alloc());

  // Cleanup.
  for (int i = 0; i < count; i++) {
    arena.Free(allocs[i]);
  }

  END_TEST;
}

static bool does_preserve() {
  BEGIN_TEST;

  constexpr int preserve = 8;
  constexpr char magic[preserve + 1] = "preserve";

  GPArena<preserve, 16> arena;
  constexpr int count = 4;
  ASSERT_EQ(arena.Init("test", count), ZX_OK);
  void* allocs[count];

  // Allocate all our objects, and initialize them with the magic data.
  for (int i = 0; i < count; i++) {
    allocs[i] = arena.Alloc();
    ASSERT_NONNULL(allocs[i]);
    memcpy(allocs[i], magic, preserve);
  }

  // Return the objects back to the allocator.
  for (int i = 0; i < count; i++) {
    arena.Free(allocs[i]);
  }

  // Whilst unallocated the preserve region should be unchanged.
  for (int i = 0; i < count; i++) {
    EXPECT_EQ(memcmp(allocs[i], magic, preserve), 0);
  }

  // Reallocate the object and validate that allocation didn't destroy the preserve region.
  for (int i = 0; i < count; i++) {
    allocs[i] = arena.Alloc();
    ASSERT_NONNULL(allocs[i]);
  }
  for (int i = 0; i < count; i++) {
    EXPECT_EQ(memcmp(allocs[i], magic, preserve), 0);
  }

  // Cleanup.
  for (int i = 0; i < count; i++) {
    arena.Free(allocs[i]);
  }

  END_TEST;
}

// Small helper to do offset arithmetic of an arena Base, keeping it as a void*
template <size_t P, size_t O>
static inline void* base_offset(const GPArena<P, O>& arena, size_t offset) {
  return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(arena.Base()) + offset);
}

static bool committed_monotonic() {
  BEGIN_TEST;
  GPArena<0, 8> arena;
  ASSERT_EQ(arena.Init("test", 4), ZX_OK);

  // Initially Alloc has not been called, and so Committed can never be true.
  EXPECT_FALSE(arena.Committed(base_offset(arena, 0)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 8)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 16)));

  // Perform an allocation check Committed is true for that value, but no other.
  EXPECT_EQ(arena.Alloc(), base_offset(arena, 0));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 0)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 8)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 16)));

  // Perform another allocation, Committed should be true for it and previous allocation.
  EXPECT_EQ(arena.Alloc(), base_offset(arena, 8));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 0)));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 8)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 16)));

  // Returning the allocated objects should have no impact on what Committed returns.
  arena.Free(base_offset(arena, 8));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 0)));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 8)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 16)));

  arena.Free(base_offset(arena, 0));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 0)));
  EXPECT_TRUE(arena.Committed(base_offset(arena, 8)));
  EXPECT_FALSE(arena.Committed(base_offset(arena, 16)));

  END_TEST;
}

// Helper that can be passed to thread_create that continuously allocates and frees a single object.
template <size_t P, size_t O>
static int arena_alloc_helper(void* arg) {
  GPArena<P, O>* arena = static_cast<GPArena<P, O>*>(arg);
  unsigned int allocations = 0;
  while (1) {
    void* v = arena->Alloc();
    // On any failure just return. That we terminated at all is the error signal to our parent.
    if (v == nullptr) {
      return -1;
    }
    arena->Free(v);
    // Check every so often if someone is trying to kill us. We cannot check every iteration
    // since then we would be bouncing the thread_lock back and forth removing most of the
    // chances at actually doing Alloc and Free concurrently.
    allocations++;
    if (allocations % 100 == 0) {
      // The user registers we pass to |thread_process_pending_signals| do not matter because this
      // thread is a pure kernel thread and has no user mode component.
      iframe_t iframe = {};
      Thread::Current::ProcessPendingSignals(GeneralRegsSource::Iframe, &iframe);
    }
  }
}

static bool parallel_alloc() {
  BEGIN_TEST;

  GPArena<0, 8> arena;
  ASSERT_EQ(arena.Init("test", 4), ZX_OK);

  // Spin up two instances of the allocation helper that will run in parallel.
  auto t1 = Thread::Create("gparena worker1", arena_alloc_helper<0, 8>, &arena, DEFAULT_PRIORITY);
  auto t2 = Thread::Create("gparena worker2", arena_alloc_helper<0, 8>, &arena, DEFAULT_PRIORITY);
  t1->Resume();
  t2->Resume();

  // Attempt to join one of the threads, letting it run for a bit. If the join succeeds this means
  // the helper terminated, which indicates it encountered an error.
  zx_status_t status = t1->Join(nullptr, current_time() + ZX_MSEC(500));
  EXPECT_NE(status, ZX_OK);
  // Check that the other thread is still running as well.
  status = t2->Join(nullptr, current_time());
  EXPECT_NE(status, ZX_OK);

  // Cleanup.
  t1->Kill();
  t2->Kill();
  status = t1->Join(nullptr, current_time() + ZX_SEC(5));
  EXPECT_EQ(status, ZX_OK);
  status = t2->Join(nullptr, current_time() + ZX_SEC(5));
  EXPECT_EQ(status, ZX_OK);

  END_TEST;
}

static bool parallel_grow_memory() {
  BEGIN_TEST;
  GPArena<0, 8> arena;
  constexpr int count = PAGE_SIZE * 64 / 8;

  fbl::AllocChecker ac;
  ktl::unique_ptr<void*[]> allocs = ktl::unique_ptr<void*[]>(new (&ac) void*[count]);
  EXPECT_TRUE(ac.check());

  ASSERT_EQ(arena.Init("test", count), ZX_OK);

  // Spin up a worker that will perform allocations in parallel whilst we are causing the arena
  // to need to be grown.
  auto t = Thread::Create("gparena worker", arena_alloc_helper<0, 8>, &arena, DEFAULT_PRIORITY);
  t->Resume();

  // let the worker run for a bit to make sure its started.
  zx_status_t status = t->Join(nullptr, current_time() + ZX_MSEC(10));
  EXPECT_NE(status, ZX_OK);

  // Allocate all the rest of the objects causing arena to have to grow.
  for (int i = 0; i < count - 1; i++) {
    allocs[i] = arena.Alloc();
    EXPECT_NONNULL(allocs[i]);
  }

  // Worker should still be running fine.
  status = t->Join(nullptr, current_time() + ZX_MSEC(10));
  EXPECT_NE(status, ZX_OK);

  // Cleanup.
  t->Kill();
  status = t->Join(nullptr, current_time() + ZX_SEC(5));
  EXPECT_EQ(status, ZX_OK);

  for (int i = 0; i < count - 1; i++) {
    arena.Free(allocs[i]);
  }

  END_TEST;
}

static bool test_confine() {
  BEGIN_TEST;
  constexpr int kMaxItems = 32;
  constexpr int kSize = 64;

  GPArena<0, kSize> arena;
  void* allocs[kMaxItems];

  ASSERT_EQ(arena.Init("test", kMaxItems), ZX_OK);

  for (int i = 0; i < kMaxItems; i++) {
    allocs[i] = arena.Alloc();
  }

  const uintptr_t base = reinterpret_cast<uintptr_t>(arena.Base());
  for (int i = 0; i < 2 * kMaxItems; i++) {
    uintptr_t expected_object = base + i * kSize;
    if (i < kMaxItems) {
      EXPECT_EQ(expected_object, arena.Confine(expected_object));
    } else {
      EXPECT_EQ(base, arena.Confine(expected_object));
    }
  }

  EXPECT_EQ(base, arena.Confine(-1ull));
  EXPECT_EQ(base, arena.Confine(base - 1));
  EXPECT_EQ(base, arena.Confine(base - kSize - 1));

  for (int i = 0; i < kMaxItems; i++) {
    arena.Free(allocs[i]);
  }

  END_TEST;
}

#define GPARENA_UNITTEST(fname) UNITTEST(#fname, fname)

UNITTEST_START_TESTCASE(gparena_tests)
GPARENA_UNITTEST(can_declare_small_objectsize)
GPARENA_UNITTEST(basic_lifo)
GPARENA_UNITTEST(out_of_memory)
GPARENA_UNITTEST(does_preserve)
GPARENA_UNITTEST(committed_monotonic)
GPARENA_UNITTEST(parallel_alloc)
GPARENA_UNITTEST(parallel_grow_memory)
GPARENA_UNITTEST(test_confine)
UNITTEST_END_TESTCASE(gparena_tests, "gparena_tests", "GPArena test")