Botan 2.19.1
Crypto and TLS for C&
Public Member Functions | List of all members
Botan::Memory_Pool Class Referencefinal

#include <mem_pool.h>

Public Member Functions

void * allocate (size_t size)
 
bool deallocate (void *p, size_t size) noexcept
 
 Memory_Pool (const Memory_Pool &)=delete
 
 Memory_Pool (const std::vector< void * > &pages, size_t page_size)
 
 Memory_Pool (Memory_Pool &&)=delete
 
Memory_Pooloperator= (const Memory_Pool &)=delete
 
Memory_Pooloperator= (Memory_Pool &&)=delete
 
 ~Memory_Pool ()
 

Detailed Description

Definition at line 20 of file mem_pool.h.

Constructor & Destructor Documentation

◆ Memory_Pool() [1/3]

Botan::Memory_Pool::Memory_Pool ( const std::vector< void * > &  pages,
size_t  page_size 
)

Initialize a memory pool. The memory is not owned by *this, it must be freed by the caller.

Parameters
pagesa list of pages to allocate from
page_sizethe system page size, each page should point to exactly this much memory.

Definition at line 293 of file mem_pool.cpp.

293 :
294 m_page_size(page_size)
295 {
296 m_min_page_ptr = ~static_cast<uintptr_t>(0);
297 m_max_page_ptr = 0;
298
299 for(size_t i = 0; i != pages.size(); ++i)
300 {
301 const uintptr_t p = reinterpret_cast<uintptr_t>(pages[i]);
302
303 m_min_page_ptr = std::min(p, m_min_page_ptr);
304 m_max_page_ptr = std::max(p, m_max_page_ptr);
305
306 clear_bytes(pages[i], m_page_size);
307#if defined(BOTAN_MEM_POOL_USE_MMU_PROTECTIONS)
308 OS::page_prohibit_access(pages[i]);
309#endif
310 m_free_pages.push_back(static_cast<uint8_t*>(pages[i]));
311 }
312
313 /*
314 Right now this points to the start of the last page, adjust it to instead
315 point to the first byte of the following page
316 */
317 m_max_page_ptr += page_size;
318 }
void page_prohibit_access(void *page)
Definition: os_utils.cpp:562
void clear_bytes(void *ptr, size_t bytes)
Definition: mem_ops.h:97

References Botan::clear_bytes(), and Botan::OS::page_prohibit_access().

◆ ~Memory_Pool()

Botan::Memory_Pool::~Memory_Pool ( )

Definition at line 320 of file mem_pool.cpp.

321 {
322#if defined(BOTAN_MEM_POOL_USE_MMU_PROTECTIONS)
323 for(size_t i = 0; i != m_free_pages.size(); ++i)
324 {
325 OS::page_allow_access(m_free_pages[i]);
326 }
327#endif
328 }
void page_allow_access(void *page)
Definition: os_utils.cpp:547

References Botan::OS::page_allow_access().

◆ Memory_Pool() [2/3]

Botan::Memory_Pool::Memory_Pool ( const Memory_Pool )
delete

◆ Memory_Pool() [3/3]

Botan::Memory_Pool::Memory_Pool ( Memory_Pool &&  )
delete

Member Function Documentation

◆ allocate()

void * Botan::Memory_Pool::allocate ( size_t  size)

Definition at line 330 of file mem_pool.cpp.

331 {
332 if(n > m_page_size)
333 return nullptr;
334
335 const size_t n_bucket = choose_bucket(n);
336
337 if(n_bucket > 0)
338 {
339 lock_guard_type<mutex_type> lock(m_mutex);
340
341 std::deque<Bucket>& buckets = m_buckets_for[n_bucket];
342
343 /*
344 It would be optimal to pick the bucket with the most usage,
345 since a bucket with say 1 item allocated out of it has a high
346 chance of becoming later freed and then the whole page can be
347 recycled.
348 */
349 for(auto& bucket : buckets)
350 {
351 if(uint8_t* p = bucket.alloc())
352 return p;
353
354 // If the bucket is full, maybe move it to the end of the list?
355 // Otoh bucket search should be very fast
356 }
357
358 if(m_free_pages.size() > 0)
359 {
360 uint8_t* ptr = m_free_pages[0];
361 m_free_pages.pop_front();
362#if defined(BOTAN_MEM_POOL_USE_MMU_PROTECTIONS)
364#endif
365 buckets.push_front(Bucket(ptr, m_page_size, n_bucket));
366 void* p = buckets[0].alloc();
367 BOTAN_ASSERT_NOMSG(p != nullptr);
368 return p;
369 }
370 }
371
372 // out of room
373 return nullptr;
374 }
#define BOTAN_ASSERT_NOMSG(expr)
Definition: assert.h:68

References BOTAN_ASSERT_NOMSG, and Botan::OS::page_allow_access().

◆ deallocate()

bool Botan::Memory_Pool::deallocate ( void *  p,
size_t  size 
)
noexcept

Definition at line 376 of file mem_pool.cpp.

377 {
378 // Do a fast range check first, before taking the lock
379 const uintptr_t p_val = reinterpret_cast<uintptr_t>(p);
380 if(p_val < m_min_page_ptr || p_val > m_max_page_ptr)
381 return false;
382
383 const size_t n_bucket = choose_bucket(len);
384
385 if(n_bucket != 0)
386 {
387 try
388 {
389 lock_guard_type<mutex_type> lock(m_mutex);
390
391 std::deque<Bucket>& buckets = m_buckets_for[n_bucket];
392
393 for(size_t i = 0; i != buckets.size(); ++i)
394 {
395 Bucket& bucket = buckets[i];
396 if(bucket.free(p))
397 {
398 if(bucket.empty())
399 {
400#if defined(BOTAN_MEM_POOL_USE_MMU_PROTECTIONS)
401 OS::page_prohibit_access(bucket.ptr());
402#endif
403 m_free_pages.push_back(bucket.ptr());
404
405 if(i != buckets.size() - 1)
406 std::swap(buckets.back(), buckets[i]);
407 buckets.pop_back();
408 }
409 return true;
410 }
411 }
412 }
413 catch(...)
414 {
415 /*
416 * The only exception throws that can occur in the above code are from
417 * either the STL or BOTAN_ASSERT failures. In either case, such an
418 * error indicates a logic error or data corruption in the memory
419 * allocator such that it is no longer safe to continue executing.
420 *
421 * Since this function is noexcept, simply letting the exception escape
422 * is sufficient for terminate to be called. However in this scenario
423 * it is implementation defined if any stack unwinding is performed.
424 * Since stack unwinding could cause further memory deallocations this
425 * could result in further corruption in this allocator state. To prevent
426 * this, call terminate directly.
427 */
428 std::terminate();
429 }
430 }
431
432 return false;
433 }

◆ operator=() [1/2]

Memory_Pool & Botan::Memory_Pool::operator= ( const Memory_Pool )
delete

◆ operator=() [2/2]

Memory_Pool & Botan::Memory_Pool::operator= ( Memory_Pool &&  )
delete

The documentation for this class was generated from the following files: