// Copyright (c) 2016-2020 The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <support/lockedpool.h>

#include <support/cleanse.h>

#if defined(HAVE_CONFIG_H)

#include <config/bitcoin-config.h>

#endif

#ifdef WIN32

#ifndef NOMINMAX

#define NOMINMAX

#endif

#include <windows.h>

#else

#include <sys/mman.h> // for mmap

#include <sys/resource.h> // for getrlimit

#include <limits.h> // for PAGESIZE

#include <unistd.h> // for sysconf

#endif

#include <algorithm>

#ifdef ARENA_DEBUG

#include <iomanip>

#include <iostream>

#endif

LockedPoolManager* LockedPoolManager::_instance = nullptr;

/*******************************************************************************/

// Utilities

//

/** Align up to power of 2 */

static inline size_t align_up(size_t x, size_t align)

/*******************************************************************************/

// Implementation: Arena

Arena::Arena(void *base_in, size_t size_in, size_t alignment_in):

    base(static_cast<char*>(base_in)), end(static_cast<char*>(base_in) + size_in), alignment(alignment_in)

    // Start with one free chunk that covers the entire arena

Arena::~Arena()

void* Arena::alloc(size_t size)

    // Round to next multiple of alignment

    // Don't handle zero-sized chunks

    // Pick a large enough free-chunk. Returns an iterator pointing to the first element that is not less than key.

    // This allocation strategy is best-fit. According to "Dynamic Storage Allocation: A Survey and Critical Review",

    // Wilson et. al. 1995, https://www.scs.stanford.edu/14wi-cs140/sched/readings/wilson.pdf, best-fit and first-fit

    // policies seem to work well in practice.

    // Create the used-chunk, taking its space from the end of the free-chunk

        // whole chunk is used up

        // still some memory left in the chunk

void Arena::free(void *ptr)

    // Freeing the nullptr pointer is OK.

    // Remove chunk from used map

    // coalesce freed with previous chunk

    // coalesce freed with chunk after freed

    // Add/set space with coalesced free chunk

Arena::Stats Arena::stats() const

#ifdef ARENA_DEBUG

static void printchunk(void* base, size_t sz, bool used) {

    std::cout <<

        "0x" << std::hex << std::setw(16) << std::setfill('0') << base <<

        " 0x" << std::hex << std::setw(16) << std::setfill('0') << sz <<

        " 0x" << used << std::endl;

}

void Arena::walk() const

{

    for (const auto& chunk: chunks_used)

        printchunk(chunk.first, chunk.second, true);

    std::cout << std::endl;

    for (const auto& chunk: chunks_free)

        printchunk(chunk.first, chunk.second->first, false);

    std::cout << std::endl;

}

#endif

/*******************************************************************************/

// Implementation: Win32LockedPageAllocator

#ifdef WIN32

/** LockedPageAllocator specialized for Windows.

 */

class Win32LockedPageAllocator: public LockedPageAllocator

{

public:

    Win32LockedPageAllocator();

    void* AllocateLocked(size_t len, bool *lockingSuccess) override;

    void FreeLocked(void* addr, size_t len) override;

    size_t GetLimit() override;

private:

    size_t page_size;

};

Win32LockedPageAllocator::Win32LockedPageAllocator()

{

    // Determine system page size in bytes

    SYSTEM_INFO sSysInfo;

    GetSystemInfo(&sSysInfo);

    page_size = sSysInfo.dwPageSize;

}

void *Win32LockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)

{

    len = align_up(len, page_size);

    void *addr = VirtualAlloc(nullptr, len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);

    if (addr) {

        // VirtualLock is used to attempt to keep keying material out of swap. Note

        // that it does not provide this as a guarantee, but, in practice, memory

        // that has been VirtualLock'd almost never gets written to the pagefile

        // except in rare circumstances where memory is extremely low.

        *lockingSuccess = VirtualLock(const_cast<void*>(addr), len) != 0;

    }

    return addr;

}

void Win32LockedPageAllocator::FreeLocked(void* addr, size_t len)

{

    len = align_up(len, page_size);

    memory_cleanse(addr, len);

    VirtualUnlock(const_cast<void*>(addr), len);

}

size_t Win32LockedPageAllocator::GetLimit()

{

    // TODO is there a limit on Windows, how to get it?

    return std::numeric_limits<size_t>::max();

}

#endif

/*******************************************************************************/

// Implementation: PosixLockedPageAllocator

#ifndef WIN32

/** LockedPageAllocator specialized for OSes that don't try to be

 * special snowflakes.

 */

class PosixLockedPageAllocator: public LockedPageAllocator

{

public:

    PosixLockedPageAllocator();

    void* AllocateLocked(size_t len, bool *lockingSuccess) override;

    void FreeLocked(void* addr, size_t len) override;

    size_t GetLimit() override;

private:

    size_t page_size;

};

PosixLockedPageAllocator::PosixLockedPageAllocator()

    // Determine system page size in bytes

#if defined(PAGESIZE) // defined in limits.h

    page_size = PAGESIZE;

#else                   // assume some POSIX OS

void *PosixLockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)

#elif defined(MADV_NOCORE) // FreeBSD

        madvise(addr, len, MADV_NOCORE);

#endif

void PosixLockedPageAllocator::FreeLocked(void* addr, size_t len)

size_t PosixLockedPageAllocator::GetLimit()

#endif

/*******************************************************************************/

// Implementation: LockedPool

LockedPool::LockedPool(std::unique_ptr<LockedPageAllocator> allocator_in, LockingFailed_Callback lf_cb_in):

    allocator(std::move(allocator_in)), lf_cb(lf_cb_in), cumulative_bytes_locked(0)

LockedPool::~LockedPool()

void* LockedPool::alloc(size_t size)

    // Don't handle impossible sizes

    // Try allocating from each current arena

    // If that fails, create a new one

void LockedPool::free(void *ptr)

    // TODO we can do better than this linear search by keeping a map of arena

    // extents to arena, and looking up the address.

LockedPool::Stats LockedPool::stats() const

bool LockedPool::new_arena(size_t size, size_t align)

    // If this is the first arena, handle this specially: Cap the upper size

    // by the process limit. This makes sure that the first arena will at least

    // be locked. An exception to this is if the process limit is 0:

    // in this case no memory can be locked at all so we'll skip past this logic.

LockedPool::LockedPageArena::LockedPageArena(LockedPageAllocator *allocator_in, void *base_in, size_t size_in, size_t align_in):

    Arena(base_in, size_in, align_in), base(base_in), size(size_in), allocator(allocator_in)

LockedPool::LockedPageArena::~LockedPageArena()

/*******************************************************************************/

// Implementation: LockedPoolManager

//

LockedPoolManager::LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator_in):

    LockedPool(std::move(allocator_in), &LockedPoolManager::LockingFailed)

bool LockedPoolManager::LockingFailed()

    // TODO: log something but how? without including util.h

void LockedPoolManager::CreateInstance()

    // Using a local static instance guarantees that the object is initialized

    // when it's first needed and also deinitialized after all objects that use

    // it are done with it.  I can think of one unlikely scenario where we may

    // have a static deinitialization order/problem, but the check in

    // LockedPoolManagerBase's destructor helps us detect if that ever happens.

#ifdef WIN32

    std::unique_ptr<LockedPageAllocator> allocator(new Win32LockedPageAllocator());

#else