Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

258 lines (239 sloc) 8.537 kb
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2012 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_ALLOCATORS_H
#define BITCOIN_ALLOCATORS_H
#include <string.h>
#include <string>
#include <boost/thread/mutex.hpp>
#include <map>
#ifdef WIN32
#ifdef _WIN32_WINNT
#undef _WIN32_WINNT
#endif
#define _WIN32_WINNT 0x0501
#define WIN32_LEAN_AND_MEAN 1
#ifndef NOMINMAX
#define NOMINMAX
#endif
#include <windows.h>
// This is used to attempt to keep keying material out of swap
// Note that VirtualLock does not provide this as a guarantee on Windows,
// 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.
#else
#include <sys/mman.h>
#include <limits.h> // for PAGESIZE
#include <unistd.h> // for sysconf
#endif
/**
* Thread-safe class to keep track of locked (ie, non-swappable) memory pages.
*
* Memory locks do not stack, that is, pages which have been locked several times by calls to mlock()
* will be unlocked by a single call to munlock(). This can result in keying material ending up in swap when
* those functions are used naively. This class simulates stacking memory locks by keeping a counter per page.
*
* @note By using a map from each page base address to lock count, this class is optimized for
* small objects that span up to a few pages, mostly smaller than a page. To support large allocations,
* something like an interval tree would be the preferred data structure.
*/
template <class Locker> class LockedPageManagerBase
{
public:
LockedPageManagerBase(size_t page_size):
page_size(page_size)
{
// Determine bitmask for extracting page from address
assert(!(page_size & (page_size-1))); // size must be power of two
page_mask = ~(page_size - 1);
}
// For all pages in affected range, increase lock count
void LockRange(void *p, size_t size)
{
boost::mutex::scoped_lock lock(mutex);
if(!size) return;
const size_t base_addr = reinterpret_cast<size_t>(p);
const size_t start_page = base_addr & page_mask;
const size_t end_page = (base_addr + size - 1) & page_mask;
for(size_t page = start_page; page <= end_page; page += page_size)
{
Histogram::iterator it = histogram.find(page);
if(it == histogram.end()) // Newly locked page
{
locker.Lock(reinterpret_cast<void*>(page), page_size);
histogram.insert(std::make_pair(page, 1));
}
else // Page was already locked; increase counter
{
it->second += 1;
}
}
}
// For all pages in affected range, decrease lock count
void UnlockRange(void *p, size_t size)
{
boost::mutex::scoped_lock lock(mutex);
if(!size) return;
const size_t base_addr = reinterpret_cast<size_t>(p);
const size_t start_page = base_addr & page_mask;
const size_t end_page = (base_addr + size - 1) & page_mask;
for(size_t page = start_page; page <= end_page; page += page_size)
{
Histogram::iterator it = histogram.find(page);
assert(it != histogram.end()); // Cannot unlock an area that was not locked
// Decrease counter for page, when it is zero, the page will be unlocked
it->second -= 1;
if(it->second == 0) // Nothing on the page anymore that keeps it locked
{
// Unlock page and remove the count from histogram
locker.Unlock(reinterpret_cast<void*>(page), page_size);
histogram.erase(it);
}
}
}
// Get number of locked pages for diagnostics
int GetLockedPageCount()
{
boost::mutex::scoped_lock lock(mutex);
return histogram.size();
}
private:
Locker locker;
boost::mutex mutex;
size_t page_size, page_mask;
// map of page base address to lock count
typedef std::map<size_t,int> Histogram;
Histogram histogram;
};
/** Determine system page size in bytes */
static inline size_t GetSystemPageSize()
{
size_t page_size;
#if defined(WIN32)
SYSTEM_INFO sSysInfo;
GetSystemInfo(&sSysInfo);
page_size = sSysInfo.dwPageSize;
#elif defined(PAGESIZE) // defined in limits.h
page_size = PAGESIZE;
#else // assume some POSIX OS
page_size = sysconf(_SC_PAGESIZE);
#endif
return page_size;
}
/**
* OS-dependent memory page locking/unlocking.
* Defined as policy class to make stubbing for test possible.
*/
class MemoryPageLocker
{
public:
/** Lock memory pages.
* addr and len must be a multiple of the system page size
*/
bool Lock(const void *addr, size_t len)
{
#ifdef WIN32
return VirtualLock(const_cast<void*>(addr), len);
#else
return mlock(addr, len) == 0;
#endif
}
/** Unlock memory pages.
* addr and len must be a multiple of the system page size
*/
bool Unlock(const void *addr, size_t len)
{
#ifdef WIN32
return VirtualUnlock(const_cast<void*>(addr), len);
#else
return munlock(addr, len) == 0;
#endif
}
};
/**
* Singleton class to keep track of locked (ie, non-swappable) memory pages, for use in
* std::allocator templates.
*/
class LockedPageManager: public LockedPageManagerBase<MemoryPageLocker>
{
public:
static LockedPageManager instance; // instantiated in util.cpp
private:
LockedPageManager():
LockedPageManagerBase<MemoryPageLocker>(GetSystemPageSize())
{}
};
//
// Allocator that locks its contents from being paged
// out of memory and clears its contents before deletion.
//
template<typename T>
struct secure_allocator : public std::allocator<T>
{
// MSVC8 default copy constructor is broken
typedef std::allocator<T> base;
typedef typename base::size_type size_type;
typedef typename base::difference_type difference_type;
typedef typename base::pointer pointer;
typedef typename base::const_pointer const_pointer;
typedef typename base::reference reference;
typedef typename base::const_reference const_reference;
typedef typename base::value_type value_type;
secure_allocator() throw() {}
secure_allocator(const secure_allocator& a) throw() : base(a) {}
template <typename U>
secure_allocator(const secure_allocator<U>& a) throw() : base(a) {}
~secure_allocator() throw() {}
template<typename _Other> struct rebind
{ typedef secure_allocator<_Other> other; };
T* allocate(std::size_t n, const void *hint = 0)
{
T *p;
p = std::allocator<T>::allocate(n, hint);
if (p != NULL)
LockedPageManager::instance.LockRange(p, sizeof(T) * n);
return p;
}
void deallocate(T* p, std::size_t n)
{
if (p != NULL)
{
memset(p, 0, sizeof(T) * n);
LockedPageManager::instance.UnlockRange(p, sizeof(T) * n);
}
std::allocator<T>::deallocate(p, n);
}
};
//
// Allocator that clears its contents before deletion.
//
template<typename T>
struct zero_after_free_allocator : public std::allocator<T>
{
// MSVC8 default copy constructor is broken
typedef std::allocator<T> base;
typedef typename base::size_type size_type;
typedef typename base::difference_type difference_type;
typedef typename base::pointer pointer;
typedef typename base::const_pointer const_pointer;
typedef typename base::reference reference;
typedef typename base::const_reference const_reference;
typedef typename base::value_type value_type;
zero_after_free_allocator() throw() {}
zero_after_free_allocator(const zero_after_free_allocator& a) throw() : base(a) {}
template <typename U>
zero_after_free_allocator(const zero_after_free_allocator<U>& a) throw() : base(a) {}
~zero_after_free_allocator() throw() {}
template<typename _Other> struct rebind
{ typedef zero_after_free_allocator<_Other> other; };
void deallocate(T* p, std::size_t n)
{
if (p != NULL)
memset(p, 0, sizeof(T) * n);
std::allocator<T>::deallocate(p, n);
}
};
// This is exactly like std::string, but with a custom allocator.
typedef std::basic_string<char, std::char_traits<char>, secure_allocator<char> > SecureString;
#endif
Jump to Line
Something went wrong with that request. Please try again.