vulkan/libvulkan/allocator.cpp

/*
 * Copyright 2025 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define ATRACE_TAG ATRACE_TAG_GRAPHICS

#include "allocator.h"

#include <stdlib.h>

#include <algorithm>

#include <log/log.h>

// #define ENABLE_ALLOC_CALLSTACKS 1
#if ENABLE_ALLOC_CALLSTACKS
#include <utils/CallStack.h>
#define ALOGD_CALLSTACK(...)                             \
    do {                                                 \
        ALOGD(__VA_ARGS__);                              \
        android::CallStack callstack;                    \
        callstack.update();                              \
        callstack.log(LOG_TAG, ANDROID_LOG_DEBUG, "  "); \
    } while (false)
#else
#define ALOGD_CALLSTACK(...) \
    do {                     \
    } while (false)
#endif

namespace vulkan {
namespace driver {

namespace {

VKAPI_ATTR void* DefaultAllocate(void*,
                                 size_t size,
                                 size_t alignment,
                                 VkSystemAllocationScope) {
    void* ptr = nullptr;
    // Vulkan requires 'alignment' to be a power of two, but posix_memalign
    // additionally requires that it be at least sizeof(void*).
    int ret = posix_memalign(&ptr, std::max(alignment, sizeof(void*)), size);
    ALOGD_CALLSTACK("Allocate: size=%zu align=%zu => (%d) %p", size, alignment,
                    ret, ptr);
    return ret == 0 ? ptr : nullptr;
}

// This function is marked `noinline` so that LLVM can't infer an object size
// for FORTIFY through it, given that it's abusing malloc_usable_size().
__attribute__((__noinline__))
VKAPI_ATTR void* DefaultReallocate(void*,
                                   void* ptr,
                                   size_t size,
                                   size_t alignment,
                                   VkSystemAllocationScope) {
    if (size == 0) {
        free(ptr);
        return nullptr;
    }

    // TODO(b/143295633): Right now we never shrink allocations; if the new
    // request is smaller than the existing chunk, we just continue using it.
    // Right now the loader never reallocs, so this doesn't matter. If that
    // changes, or if this code is copied into some other project, this should
    // probably have a heuristic to allocate-copy-free when doing so will save
    // "enough" space.
    size_t old_size = ptr ? malloc_usable_size(ptr) : 0;
    if (size <= old_size)
        return ptr;

    void* new_ptr = nullptr;
    if (posix_memalign(&new_ptr, std::max(alignment, sizeof(void*)), size) != 0)
        return nullptr;
    if (ptr) {
        memcpy(new_ptr, ptr, std::min(old_size, size));
        free(ptr);
    }
    return new_ptr;
}

VKAPI_ATTR void DefaultFree(void*, void* ptr) {
    ALOGD_CALLSTACK("Free: %p", ptr);
    free(ptr);
}

}  // anonymous namespace

const VkAllocationCallbacks& GetDefaultAllocator() {
    static const VkAllocationCallbacks kDefaultAllocCallbacks = {
        .pUserData = nullptr,
        .pfnAllocation = DefaultAllocate,
        .pfnReallocation = DefaultReallocate,
        .pfnFree = DefaultFree,
    };

    return kDefaultAllocCallbacks;
}

}  // namespace driver
}  // namespace vulkan