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Heap improvements (#462)

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* Heap improvements

This commit makes the following improvements:

1. Add a check to heap_2 to track if a memory block is allocated to the
   application or not. The MSB of the size field is used for this
   purpose. The same check already exists in heap_4 and heap_5. This
   check prevents against double free.

2. Add a new flag configHEAP_CLEAR_MEMORY_ON_FREE to heap_2, heap_4 and
   heap_5. The application writer can set it to 1 in their
   FreeRTOSConfig.h to ensure that a block of memory allocated using
   pvPortMalloc is cleared (i.e. set to zero) when it is freed using
   vPortFree. If left undefined, configHEAP_CLEAR_MEMORY_ON_FREE
   defaults to 0 for backward compatibility. We recommend setting
   configHEAP_CLEAR_MEMORY_ON_FREE to 1 for better security.

3. Add a new API pvPortCalloc to heap_2, heap_4 and heap_5. This API
   has the following signature:
   void * pvPortCalloc( size_t xNum, size_t xSize );
   It allocates memory for an array of xNum objects each of which is of
   xSize and initializes all bytes in the allocated storage to zero. If
   allocation succeeds, it returns a pointer to the lowest byte in the
   allocated memory block. On failure, it returns a null pointer.

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
This commit is contained in:
Gaurav-Aggarwal-AWS 2022-02-24 10:52:10 -08:00 • committed by GitHub
parent 4539e1c574
commit 82be77995e
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 249 additions and 98 deletions
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66
portable/MemMang/heap_4.c
View file

@ -35,6 +35,7 @@
* memory management pages of https://www.FreeRTOS.org for more information.
*/
#include <stdlib.h>
#include <string.h>
/* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
* all the API functions to use the MPU wrappers. That should only be done when
@ -50,12 +51,31 @@
#error This file must not be used if configSUPPORT_DYNAMIC_ALLOCATION is 0
#endif
#ifndef configHEAP_CLEAR_MEMORY_ON_FREE
#define configHEAP_CLEAR_MEMORY_ON_FREE 0
#endif
/* Block sizes must not get too small. */
#define heapMINIMUM_BLOCK_SIZE ( ( size_t ) ( xHeapStructSize << 1 ) )
/* Assumes 8bit bytes! */
#define heapBITS_PER_BYTE ( ( size_t ) 8 )
/* Check if multiplying a and b will result in overflow. */
#define heapMULTIPLY_WILL_OVERFLOW( a, b, max ) ( ( ( a ) > 0 ) && ( ( b ) > ( ( max ) / ( a ) ) ) )
/* MSB of the xBlockSize member of an BlockLink_t structure is used to track
* the allocation status of a block. When MSB of the xBlockSize member of
* an BlockLink_t structure is set then the block belongs to the application.
* When the bit is free the block is still part of the free heap space. */
#define heapBLOCK_ALLOCATED_BITMASK ( ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 ) )
#define heapBLOCK_SIZE_IS_VALID( xBlockSize ) ( ( ( xBlockSize ) & heapBLOCK_ALLOCATED_BITMASK ) == 0 )
#define heapBLOCK_IS_ALLOCATED( pxBlock ) ( ( ( pxBlock->xBlockSize ) & heapBLOCK_ALLOCATED_BITMASK ) != 0 )
#define heapALLOCATE_BLOCK( pxBlock ) ( ( pxBlock->xBlockSize ) |= heapBLOCK_ALLOCATED_BITMASK )
#define heapFREE_BLOCK( pxBlock ) ( ( pxBlock->xBlockSize ) &= ~heapBLOCK_ALLOCATED_BITMASK )
/*-----------------------------------------------------------*/
/* Allocate the memory for the heap. */
#if ( configAPPLICATION_ALLOCATED_HEAP == 1 )
@ -106,12 +126,6 @@ PRIVILEGED_DATA static size_t xMinimumEverFreeBytesRemaining = 0U;
PRIVILEGED_DATA static size_t xNumberOfSuccessfulAllocations = 0;
PRIVILEGED_DATA static size_t xNumberOfSuccessfulFrees = 0;
/* Gets set to the top bit of an size_t type. When this bit in the xBlockSize
* member of an BlockLink_t structure is set then the block belongs to the
* application. When the bit is free the block is still part of the free heap
* space. */
PRIVILEGED_DATA static size_t xBlockAllocatedBit = 0;
/*-----------------------------------------------------------*/
void * pvPortMalloc( size_t xWantedSize )
@ -136,7 +150,7 @@ void * pvPortMalloc( size_t xWantedSize )
* set. The top bit of the block size member of the BlockLink_t structure
* is used to determine who owns the block - the application or the
* kernel, so it must be free. */
if( ( xWantedSize & xBlockAllocatedBit ) == 0 )
if( heapBLOCK_SIZE_IS_VALID( xWantedSize ) )
{
/* The wanted size must be increased so it can contain a BlockLink_t
* structure in addition to the requested amount of bytes. */
@ -232,7 +246,7 @@ void * pvPortMalloc( size_t xWantedSize )
/* The block is being returned - it is allocated and owned
* by the application and has no "next" block. */
pxBlock->xBlockSize |= xBlockAllocatedBit;
heapALLOCATE_BLOCK( pxBlock );
pxBlock->pxNextFreeBlock = NULL;
xNumberOfSuccessfulAllocations++;
}
@ -288,17 +302,21 @@ void vPortFree( void * pv )
/* This casting is to keep the compiler from issuing warnings. */
pxLink = ( void * ) puc;
/* Check the block is actually allocated. */
configASSERT( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 );
configASSERT( heapBLOCK_IS_ALLOCATED( pxLink ) );
configASSERT( pxLink->pxNextFreeBlock == NULL );
if( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 )
if( heapBLOCK_IS_ALLOCATED( pxLink ) )
{
if( pxLink->pxNextFreeBlock == NULL )
{
/* The block is being returned to the heap - it is no longer
* allocated. */
pxLink->xBlockSize &= ~xBlockAllocatedBit;
heapFREE_BLOCK( pxLink );
#if ( configHEAP_CLEAR_MEMORY_ON_FREE == 1 )
{
( void ) memset( puc + xHeapStructSize, 0, pxLink->xBlockSize - xHeapStructSize );
}
#endif
vTaskSuspendAll();
{
@ -341,6 +359,26 @@ void vPortInitialiseBlocks( void )
}
/*-----------------------------------------------------------*/
void * pvPortCalloc( size_t xNum,
size_t xSize )
{
void * pv = NULL;
const size_t xSizeMaxValue = ~( ( size_t ) 0 );
if( !heapMULTIPLY_WILL_OVERFLOW( xNum, xSize, xSizeMaxValue ) )
{
pv = pvPortMalloc( xNum * xSize );
if( pv != NULL )
{
( void ) memset( pv, 0, xNum * xSize );
}
}
return pv;
}
/*-----------------------------------------------------------*/
static void prvHeapInit( void ) /* PRIVILEGED_FUNCTION */
{
BlockLink_t * pxFirstFreeBlock;
@ -383,9 +421,6 @@ static void prvHeapInit( void ) /* PRIVILEGED_FUNCTION */
/* Only one block exists - and it covers the entire usable heap space. */
xMinimumEverFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
xFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
/* Work out the position of the top bit in a size_t variable. */
xBlockAllocatedBit = ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 );
}
/*-----------------------------------------------------------*/
@ -502,3 +537,4 @@ void vPortGetHeapStats( HeapStats_t * pxHeapStats )
}
taskEXIT_CRITICAL();
}
/*-----------------------------------------------------------*/