source: rtems/cpukit/score/src/heapallocate.c @ 9b4422a2

/**
 * @file
 *
 * @ingroup ScoreHeap
 *
 * @brief Heap Handler implementation.
 */

/*
 *  COPYRIGHT (c) 1989-1999.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  Copyright (c) 2009 embedded brains GmbH.
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/system.h>
#include <rtems/score/sysstate.h>
#include <rtems/score/heap.h>

#ifndef HEAP_PROTECTION
  #define _Heap_Protection_free_delayed_blocks( heap, alloc_begin ) false
#else
  static bool _Heap_Protection_free_delayed_blocks(
    Heap_Control *heap,
    uintptr_t alloc_begin
  )
  {
    bool search_again = false;
    uintptr_t const blocks_to_free_count =
      (heap->Protection.delayed_free_block_count + 1) / 2;

    if ( alloc_begin == 0 && blocks_to_free_count > 0 ) {
      Heap_Block *block_to_free = heap->Protection.first_delayed_free_block;
      uintptr_t count = 0;

      for ( count = 0; count < blocks_to_free_count; ++count ) {
        Heap_Block *next_block_to_free =
          block_to_free->Protection_begin.next_delayed_free_block;

        block_to_free->Protection_begin.next_delayed_free_block =
          HEAP_PROTECTION_OBOLUS;

        _Heap_Free(
          heap,
          (void *) _Heap_Alloc_area_of_block( block_to_free )
        );

        block_to_free = next_block_to_free;
      }

      heap->Protection.delayed_free_block_count -= blocks_to_free_count;
      heap->Protection.first_delayed_free_block = block_to_free;

      search_again = true;
    }

    return search_again;
  }
#endif

#ifdef RTEMS_HEAP_DEBUG
  static void _Heap_Check_allocation(
    const Heap_Control *heap,
    const Heap_Block *block,
    uintptr_t alloc_begin,
    uintptr_t alloc_size,
    uintptr_t alignment,
    uintptr_t boundary
  )
  {
    uintptr_t const min_block_size = heap->min_block_size;
    uintptr_t const page_size = heap->page_size;

    uintptr_t const block_begin = (uintptr_t) block;
    uintptr_t const block_size = _Heap_Block_size( block );
    uintptr_t const block_end = block_begin + block_size;

    uintptr_t const alloc_end = alloc_begin + alloc_size;

    uintptr_t const alloc_area_begin = _Heap_Alloc_area_of_block( block );
    uintptr_t const alloc_area_offset = alloc_begin - alloc_area_begin;

    _HAssert( block_size >= min_block_size );
    _HAssert( block_begin < block_end );
    _HAssert(
      _Heap_Is_aligned( block_begin + HEAP_BLOCK_HEADER_SIZE, page_size )
    );
    _HAssert(
      _Heap_Is_aligned( block_size, page_size )
    );

    _HAssert( alloc_end <= block_end + HEAP_ALLOC_BONUS );
    _HAssert( alloc_area_begin == block_begin + HEAP_BLOCK_HEADER_SIZE);
    _HAssert( alloc_area_offset < page_size );

    _HAssert( _Heap_Is_aligned( alloc_area_begin, page_size ) );
    if ( alignment == 0 ) {
      _HAssert( alloc_begin == alloc_area_begin );
    } else {
      _HAssert( _Heap_Is_aligned( alloc_begin, alignment ) );
    }

    if ( boundary != 0 ) {
      uintptr_t boundary_line = _Heap_Align_down( alloc_end, boundary );

      _HAssert( alloc_size <= boundary );
      _HAssert( boundary_line <= alloc_begin || alloc_end <= boundary_line );
    }
  }
#else
  #define _Heap_Check_allocation( h, b, ab, as, ag, bd ) ((void) 0)
#endif

static uintptr_t _Heap_Check_block(
  const Heap_Control *heap,
  const Heap_Block *block,
  uintptr_t alloc_size,
  uintptr_t alignment,
  uintptr_t boundary
)
{
  uintptr_t const page_size = heap->page_size;
  uintptr_t const min_block_size = heap->min_block_size;

  uintptr_t const block_begin = (uintptr_t) block;
  uintptr_t const block_size = _Heap_Block_size( block );
  uintptr_t const block_end = block_begin + block_size;

  uintptr_t const alloc_begin_floor = _Heap_Alloc_area_of_block( block );
  uintptr_t const alloc_begin_ceiling = block_end - min_block_size
    + HEAP_BLOCK_HEADER_SIZE + page_size - 1;

  uintptr_t alloc_end = block_end + HEAP_ALLOC_BONUS;
  uintptr_t alloc_begin = alloc_end - alloc_size;

  alloc_begin = _Heap_Align_down( alloc_begin, alignment );

  /* Ensure that the we have a valid new block at the end */
  if ( alloc_begin > alloc_begin_ceiling ) {
    alloc_begin = _Heap_Align_down( alloc_begin_ceiling, alignment );
  }

  alloc_end = alloc_begin + alloc_size;

  /* Ensure boundary constaint */
  if ( boundary != 0 ) {
    uintptr_t const boundary_floor = alloc_begin_floor + alloc_size;
    uintptr_t boundary_line = _Heap_Align_down( alloc_end, boundary );

    while ( alloc_begin < boundary_line && boundary_line < alloc_end ) {
      if ( boundary_line < boundary_floor ) {
        return 0;
      }
      alloc_begin = boundary_line - alloc_size;
      alloc_begin = _Heap_Align_down( alloc_begin, alignment );
      alloc_end = alloc_begin + alloc_size;
      boundary_line = _Heap_Align_down( alloc_end, boundary );
    }
  }

  /* Ensure that the we have a valid new block at the beginning */
  if ( alloc_begin >= alloc_begin_floor ) {
    uintptr_t const alloc_block_begin =
      (uintptr_t) _Heap_Block_of_alloc_area( alloc_begin, page_size );
    uintptr_t const free_size = alloc_block_begin - block_begin;

    if ( free_size >= min_block_size || free_size == 0 ) {
      return alloc_begin;
    }
  }

  return 0;
}

void *_Heap_Allocate_aligned_with_boundary(
  Heap_Control *heap,
  uintptr_t alloc_size,
  uintptr_t alignment,
  uintptr_t boundary
)
{
  Heap_Statistics *const stats = &heap->stats;
  uintptr_t const block_size_floor = alloc_size + HEAP_BLOCK_HEADER_SIZE
    - HEAP_ALLOC_BONUS;
  uintptr_t const page_size = heap->page_size;
  Heap_Block *block = NULL;
  uintptr_t alloc_begin = 0;
  uint32_t search_count = 0;
  bool search_again = false;

  if ( block_size_floor < alloc_size ) {
    /* Integer overflow occured */
    return NULL;
  }

  if ( boundary != 0 ) {
    if ( boundary < alloc_size ) {
      return NULL;
    }

    if ( alignment == 0 ) {
      alignment = page_size;
    }
  }

  do {
    Heap_Block *const free_list_tail = _Heap_Free_list_tail( heap );

    block = _Heap_Free_list_first( heap );
    while ( block != free_list_tail ) {
      _HAssert( _Heap_Is_prev_used( block ) );

      _Heap_Protection_block_check( heap, block );

      /*
       * The HEAP_PREV_BLOCK_USED flag is always set in the block size_and_flag
       * field.  Thus the value is about one unit larger than the real block
       * size.  The greater than operator takes this into account.
       */
      if ( block->size_and_flag > block_size_floor ) {
        if ( alignment == 0 ) {
          alloc_begin = _Heap_Alloc_area_of_block( block );
        } else {
          alloc_begin = _Heap_Check_block(
            heap,
            block,
            alloc_size,
            alignment,
            boundary
          );
        }
      }

      /* Statistics */
      ++search_count;

      if ( alloc_begin != 0 ) {
        break;
      }

      block = block->next;
    }

    search_again = _Heap_Protection_free_delayed_blocks( heap, alloc_begin );
  } while ( search_again );

  if ( alloc_begin != 0 ) {
    /* Statistics */
    ++stats->allocs;
    stats->searches += search_count;

    block = _Heap_Block_allocate( heap, block, alloc_begin, alloc_size );

    _Heap_Check_allocation(
      heap,
      block,
      alloc_begin,
      alloc_size,
      alignment,
      boundary
    );
  }

  /* Statistics */
  if ( stats->max_search < search_count ) {
    stats->max_search = search_count;
  }

  return (void *) alloc_begin;
}