/**
* @file
*
* @ingroup RTEMSScoreHeap
*
* @brief Heap Handler API
*/
/*
* COPYRIGHT (c) 1989-2006.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#ifndef _RTEMS_SCORE_HEAP_H
#define _RTEMS_SCORE_HEAP_H
#include <rtems/score/cpu.h>
#include <rtems/score/heapinfo.h>
#ifdef __cplusplus
extern "C" {
#endif
#ifdef RTEMS_DEBUG
#define HEAP_PROTECTION
#endif
/**
* @defgroup RTEMSScoreHeap Heap Handler
*
* @ingroup RTEMSScore
*
* @brief The Heap Handler provides a heap.
*
* A heap is a doubly linked list of variable size blocks which are allocated
* using the first fit method. Garbage collection is performed each time a
* block is returned to the heap by coalescing neighbor blocks. Control
* information for both allocated and free blocks is contained in the heap
* area. A heap control structure contains control information for the heap.
*
* The alignment routines could be made faster should we require only powers of
* two to be supported for page size, alignment and boundary arguments. The
* minimum alignment requirement for pages is currently CPU_ALIGNMENT and this
* value is only required to be multiple of two and explicitly not required to
* be a power of two.
*
* There are two kinds of blocks. One sort describes a free block from which
* we can allocate memory. The other blocks are used and provide an allocated
* memory area. The free blocks are accessible via a list of free blocks.
*
* Blocks or areas cover a continuous set of memory addresses. They have a
* begin and end address. The end address is not part of the set. The size of
* a block or area equals the distance between the begin and end address in
* units of bytes.
*
* Free blocks look like:
* <table>
* <tr>
* <td rowspan=4>@ref Heap_Block</td><td>previous block size in case the
* previous block is free, <br> otherwise it may contain data used by
* the previous block</td>
* </tr>
* <tr>
* <td>block size and a flag which indicates if the previous block is free
* or used, <br> this field contains always valid data regardless of the
* block usage</td>
* </tr>
* <tr><td>pointer to next block (this field is page size aligned)</td></tr>
* <tr><td>pointer to previous block</td></tr>
* <tr><td colspan=2>free space</td></tr>
* </table>
*
* Used blocks look like:
* <table>
* <tr>
* <td rowspan=4>@ref Heap_Block</td><td>previous block size in case the
* previous block is free,<br>otherwise it may contain data used by
* the previous block</td>
* </tr>
* <tr>
* <td>block size and a flag which indicates if the previous block is free
* or used, <br> this field contains always valid data regardless of the
* block usage</td>
* </tr>
* <tr><td>begin of allocated area (this field is page size aligned)</td></tr>
* <tr><td>allocated space</td></tr>
* <tr><td colspan=2>allocated space</td></tr>
* </table>
*
* The heap area after initialization contains two blocks and looks like:
* <table>
* <tr><th>Label</th><th colspan=2>Content</th></tr>
* <tr><td>heap->area_begin</td><td colspan=2>heap area begin address</td></tr>
* <tr>
* <td>first_block->prev_size</td>
* <td colspan=2>
* subordinate heap area end address (this will be used to maintain a
* linked list of scattered heap areas)
* </td>
* </tr>
* <tr>
* <td>first_block->size</td>
* <td colspan=2>size available for allocation
* | @c HEAP_PREV_BLOCK_USED</td>
* </tr>
* <tr>
* <td>first_block->next</td><td>_Heap_Free_list_tail(heap)</td>
* <td rowspan=3>memory area available for allocation</td>
* </tr>
* <tr><td>first_block->prev</td><td>_Heap_Free_list_head(heap)</td></tr>
* <tr><td>...</td></tr>
* <tr>
* <td>last_block->prev_size</td><td colspan=2>size of first block</td>
* </tr>
* <tr>
* <td>last_block->size</td>
* <td colspan=2>first block begin address - last block begin address</td>
* </tr>
* <tr><td>heap->area_end</td><td colspan=2>heap area end address</td></tr>
* </table>
* The next block of the last block is the first block. Since the first
* block indicates that the previous block is used, this ensures that the
* last block appears as used for the _Heap_Is_used() and _Heap_Is_free()
* functions.
*/
/**@{**/
typedef struct Heap_Control Heap_Control;
typedef struct Heap_Block Heap_Block;
#ifndef HEAP_PROTECTION
#define HEAP_PROTECTION_HEADER_SIZE 0
#else
#define HEAP_PROTECTOR_COUNT 2
#define HEAP_BEGIN_PROTECTOR_0 ((uintptr_t) 0xfd75a98f)
#define HEAP_BEGIN_PROTECTOR_1 ((uintptr_t) 0xbfa1f177)
#define HEAP_END_PROTECTOR_0 ((uintptr_t) 0xd6b8855e)
#define HEAP_END_PROTECTOR_1 ((uintptr_t) 0x13a44a5b)
#define HEAP_FREE_PATTERN ((uintptr_t) 0xe7093cdf)
#define HEAP_PROTECTION_OBOLUS ((Heap_Block *) 1)
typedef void (*_Heap_Protection_handler)(
Heap_Control *heap,
Heap_Block *block
);
typedef struct {
_Heap_Protection_handler block_initialize;
_Heap_Protection_handler block_check;
_Heap_Protection_handler block_error;
void *handler_data;
Heap_Block *first_delayed_free_block;
Heap_Block *last_delayed_free_block;
uintptr_t delayed_free_block_count;
uintptr_t delayed_free_fraction;
} Heap_Protection;
struct _Thread_Control;
typedef struct {
uintptr_t protector [HEAP_PROTECTOR_COUNT];
Heap_Block *next_delayed_free_block;
struct _Thread_Control *task;
void *tag;
} Heap_Protection_block_begin;
typedef struct {
uintptr_t protector [HEAP_PROTECTOR_COUNT];
} Heap_Protection_block_end;
#define HEAP_PROTECTION_HEADER_SIZE \
(sizeof(Heap_Protection_block_begin) + sizeof(Heap_Protection_block_end))
#endif
/**
* @brief The block header consists of the two size fields
* (@ref Heap_Block.prev_size and @ref Heap_Block.size_and_flag).
*/
#define HEAP_BLOCK_HEADER_SIZE \
(2 * sizeof(uintptr_t) + HEAP_PROTECTION_HEADER_SIZE)
/**
* @brief Description for free or used blocks.
*/
struct Heap_Block {
/**
* @brief Size of the previous block or part of the allocated area of the
* previous block.
*
* This field is only valid if the previous block is free. This case is
* indicated by a cleared @c HEAP_PREV_BLOCK_USED flag in the
* @a size_and_flag field of the current block.
*
* In a used block only the @a size_and_flag field needs to be valid. The
* @a prev_size field of the current block is maintained by the previous
* block. The current block can use the @a prev_size field in the next block
* for allocation.
*/
uintptr_t prev_size;
#ifdef HEAP_PROTECTION
Heap_Protection_block_begin Protection_begin;
#endif
/**
* @brief Contains the size of the current block and a flag which indicates
* if the previous block is free or used.
*
* If the flag @c HEAP_PREV_BLOCK_USED is set, then the previous block is
* used, otherwise the previous block is free. A used previous block may
* claim the @a prev_size field for allocation. This trick allows to
* decrease the overhead in the used blocks by the size of the @a prev_size
* field. As sizes are required to be multiples of two, the least
* significant bits would be always zero. We use this bit to store the flag.
*
* This field is always valid.
*/
uintptr_t size_and_flag;
#ifdef HEAP_PROTECTION
Heap_Protection_block_end Protection_end;
#endif
/**
* @brief Pointer to the next free block or part of the allocated area.
*
* This field is page size aligned and begins of the allocated area in case
* the block is used.
*
* This field is only valid if the block is free and thus part of the free
* block list.
*/
Heap_Block *next;
/**
* @brief Pointer to the previous free block or part of the allocated area.
*
* This field is only valid if the block is free and thus part of the free
* block list.
*/
Heap_Block *prev;
};
/**
* @brief Control block used to manage a heap.
*/
struct Heap_Control {
Heap_Block free_list;
uintptr_t page_size;
uintptr_t min_block_size;
uintptr_t area_begin;
uintptr_t area_end;
Heap_Block *first_block;
Heap_Block *last_block;
Heap_Statistics stats;
#ifdef HEAP_PROTECTION
Heap_Protection Protection;
#endif
};
/**
* @brief Heap area structure for table based heap initialization and
* extension.
*
* @see Heap_Initialization_or_extend_handler.
*/
typedef struct {
void *begin;
uintptr_t size;
} Heap_Area;
/**
* @brief Heap initialization and extend handler type.
*
* This helps to do a table based heap initialization and extension. Create a
* table of Heap_Area elements and iterate through it. Set the handler to
* _Heap_Initialize() in the first iteration and then to _Heap_Extend().
*
* @see Heap_Area, _Heap_Initialize(), _Heap_Extend(), or _Heap_No_extend().
*/
typedef uintptr_t (*Heap_Initialization_or_extend_handler)(
Heap_Control *heap,
void *area_begin,
uintptr_t area_size,
uintptr_t page_size_or_unused
);
/**
* @brief Extends the memory available for the heap @a heap using the memory
* area starting at @a area_begin of size @a area_size bytes.
*
* There are no alignment requirements for the memory area. The memory area
* must be big enough to contain some maintenance blocks. It must not overlap
* parts of the current heap memory areas. Disconnected memory areas added to
* the heap will lead to used blocks which cover the gaps. Extending with an
* inappropriate memory area will corrupt the heap resulting in undefined
* behaviour.
*
* The unused fourth parameter is provided to have the same signature as
* _Heap_Initialize().
*
* Returns the extended space available for allocation, or zero in case of failure.
*
* @see Heap_Initialization_or_extend_handler.
*/
uintptr_t _Heap_Extend(
Heap_Control *heap,
void *area_begin,
uintptr_t area_size,
uintptr_t unused
);
/**
* @brief This function returns always zero.
*
* This function only returns zero and does nothing else.
*
* Returns always zero.
*
* @see Heap_Initialization_or_extend_handler.
*/
uintptr_t _Heap_No_extend(
Heap_Control *unused_0,
void *unused_1,
uintptr_t unused_2,
uintptr_t unused_3
);
RTEMS_INLINE_ROUTINE uintptr_t _Heap_Align_up(
uintptr_t value,
uintptr_t alignment
)
{
uintptr_t remainder = value % alignment;
if ( remainder != 0 ) {
return value - remainder + alignment;
} else {
return value;
}
}
RTEMS_INLINE_ROUTINE uintptr_t _Heap_Min_block_size( uintptr_t page_size )
{
return _Heap_Align_up( sizeof( Heap_Block ), page_size );
}
/**
* @brief Returns the worst case overhead to manage a memory area.
*/
RTEMS_INLINE_ROUTINE uintptr_t _Heap_Area_overhead(
uintptr_t page_size
)
{
if ( page_size != 0 ) {
page_size = _Heap_Align_up( page_size, CPU_ALIGNMENT );
} else {
page_size = CPU_ALIGNMENT;
}
return 2 * (page_size - 1) + HEAP_BLOCK_HEADER_SIZE;
}
/**
* @brief Returns the size with administration and alignment overhead for one
* allocation.
*/
RTEMS_INLINE_ROUTINE uintptr_t _Heap_Size_with_overhead(
uintptr_t page_size,
uintptr_t size,
uintptr_t alignment
)
{
if ( page_size != 0 ) {
page_size = _Heap_Align_up( page_size, CPU_ALIGNMENT );
} else {
page_size = CPU_ALIGNMENT;
}
if ( page_size < alignment ) {
page_size = alignment;
}
return HEAP_BLOCK_HEADER_SIZE + page_size - 1 + size;
}
/** @} */
#ifdef __cplusplus
}
#endif
#endif
/* end of include file */
