locking_allocator.cpp

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/*
* Mlock Allocator
* (C) 2012,2014,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/internal/locking_allocator.h>
 
#include <botan/internal/mem_pool.h>
#include <botan/internal/os_utils.h>
#include <botan/internal/safeint.h>
 
namespace Botan {
 
void* mlock_allocator::allocate(size_t num_elems, size_t elem_size) {
   if(!m_pool) {
      return nullptr;
   }
 
   const auto n = BOTAN_CHECKED_MUL(num_elems, elem_size);
   if(!n.has_value()) {
      return nullptr;  // overflow!
   }
 
   return m_pool->allocate(n.value());
}
 
bool mlock_allocator::deallocate(void* p, size_t num_elems, size_t elem_size) noexcept {
   if(!m_pool) {
      return false;
   }
 
   /*
   We return nullptr in allocate if there was an overflow, so if an
   overflow occurs here we know the pointer was not allocated by this pool.
   */
   const auto n = BOTAN_CHECKED_MUL(num_elems, elem_size);
   if(!n.has_value()) {
      return false;
   }
 
   return m_pool->deallocate(p, n.value());
}
 
mlock_allocator::mlock_allocator() {
   const size_t mem_to_lock = OS::get_memory_locking_limit();
   const size_t page_size = OS::system_page_size();
 
   if(mem_to_lock > 0 && mem_to_lock % page_size == 0) {
      m_locked_pages = OS::allocate_locked_pages(mem_to_lock / page_size);
 
      if(!m_locked_pages.empty()) {
         m_pool = std::make_unique<Memory_Pool>(m_locked_pages, page_size);
      }
   }
}
 
mlock_allocator::~mlock_allocator() {
   if(m_pool) {
      m_pool.reset();
      // OS::free_locked_pages scrubs the memory before free
      OS::free_locked_pages(m_locked_pages);
   }
}
 
namespace {
 
// NOLINTNEXTLINE(*-avoid-non-const-global-variables)
BOTAN_EARLY_INIT(101) mlock_allocator g_mlock_allocator;
 
}  // namespace
 
mlock_allocator& mlock_allocator::instance() {
   return g_mlock_allocator;
}
 
}  // namespace Botan