support: Add LockedPool

Add a pool for locked memory chunks, replacing LockedPageManager.

This is something I've been wanting to do for a long time. The current
approach of locking objects where they happen to be on the stack or heap
in-place causes a lot of mlock/munlock system call overhead, slowing
down any handling of keys.

Also locked memory is a limited resource on many operating systems (and
using a lot of it bogs down the system), so the previous approach of
locking every page that may contain any key information (but also other
information) is wasteful.

Author: laanwj

src/Makefile.am

@@ -133,7 +133,7 @@ BITCOIN_CORE_H = \
   support/allocators/secure.h \
   support/allocators/zeroafterfree.h \
   support/cleanse.h \
-  support/pagelocker.h \
+  support/lockedpool.h \
   sync.h \
   threadsafety.h \
   timedata.h \
@@ -310,7 +310,7 @@ libbitcoin_common_a_SOURCES = \
 libbitcoin_util_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_util_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_util_a_SOURCES = \
-  support/pagelocker.cpp \
+  support/lockedpool.cpp \
   chainparamsbase.cpp \
   clientversion.cpp \
   compat/glibc_sanity.cpp \

src/support/allocators/secure.h

@@ -6,7 +6,8 @@
 #ifndef BITCOIN_SUPPORT_ALLOCATORS_SECURE_H
 #define BITCOIN_SUPPORT_ALLOCATORS_SECURE_H
 
-#include "support/pagelocker.h"
+#include "support/lockedpool.h"
+#include "support/cleanse.h"
 
 #include <string>
 
@@ -39,20 +40,15 @@ struct secure_allocator : public std::allocator<T> {
 
     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;
+        return static_cast<T*>(LockedPoolManager::Instance().alloc(sizeof(T) * n));
     }
 
     void deallocate(T* p, std::size_t n)
     {
         if (p != NULL) {
             memory_cleanse(p, sizeof(T) * n);
-            LockedPageManager::Instance().UnlockRange(p, sizeof(T) * n);
         }
-        std::allocator<T>::deallocate(p, n);
+        LockedPoolManager::Instance().free(p);
     }
 };