8eb3585252
We use the MSB of the size member of a BlockLink_t to track whether not a block is allocated. Consequently, the size must not be so large that the MSB is set. The check to see if the MSB in the size is set needs to be done after the final size (metadata + alignment) is calculated. Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
363 lines
16 KiB
C
363 lines
16 KiB
C
/*
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* FreeRTOS Kernel <DEVELOPMENT BRANCH>
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* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* SPDX-License-Identifier: MIT
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* https://www.FreeRTOS.org
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* https://github.com/FreeRTOS
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*
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*/
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/*
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* A sample implementation of pvPortMalloc() and vPortFree() that permits
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* allocated blocks to be freed, but does not combine adjacent free blocks
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* into a single larger block (and so will fragment memory). See heap_4.c for
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* an equivalent that does combine adjacent blocks into single larger blocks.
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*
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* See heap_1.c, heap_3.c and heap_4.c for alternative implementations, and the
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* memory management pages of https://www.FreeRTOS.org for more information.
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*/
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#include <stdlib.h>
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#include <string.h>
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/* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
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* all the API functions to use the MPU wrappers. That should only be done when
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* task.h is included from an application file. */
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#define MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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#include "FreeRTOS.h"
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#include "task.h"
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#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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#if ( configSUPPORT_DYNAMIC_ALLOCATION == 0 )
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#error This file must not be used if configSUPPORT_DYNAMIC_ALLOCATION is 0
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#endif
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#ifndef configHEAP_CLEAR_MEMORY_ON_FREE
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#define configHEAP_CLEAR_MEMORY_ON_FREE 0
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#endif
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/* A few bytes might be lost to byte aligning the heap start address. */
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#define configADJUSTED_HEAP_SIZE ( configTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT )
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/* Assumes 8bit bytes! */
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#define heapBITS_PER_BYTE ( ( size_t ) 8 )
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/* Check if multiplying a and b will result in overflow. */
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#define heapMULTIPLY_WILL_OVERFLOW( a, b, max ) ( ( ( a ) > 0 ) && ( ( b ) > ( ( max ) / ( a ) ) ) )
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/* MSB of the xBlockSize member of an BlockLink_t structure is used to track
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* the allocation status of a block. When MSB of the xBlockSize member of
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* an BlockLink_t structure is set then the block belongs to the application.
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* When the bit is free the block is still part of the free heap space. */
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#define heapBLOCK_ALLOCATED_BITMASK ( ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 ) )
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#define heapBLOCK_SIZE_IS_VALID( xBlockSize ) ( ( ( xBlockSize ) & heapBLOCK_ALLOCATED_BITMASK ) == 0 )
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#define heapBLOCK_IS_ALLOCATED( pxBlock ) ( ( ( pxBlock->xBlockSize ) & heapBLOCK_ALLOCATED_BITMASK ) != 0 )
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#define heapALLOCATE_BLOCK( pxBlock ) ( ( pxBlock->xBlockSize ) |= heapBLOCK_ALLOCATED_BITMASK )
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#define heapFREE_BLOCK( pxBlock ) ( ( pxBlock->xBlockSize ) &= ~heapBLOCK_ALLOCATED_BITMASK )
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/*-----------------------------------------------------------*/
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/* Allocate the memory for the heap. */
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#if ( configAPPLICATION_ALLOCATED_HEAP == 1 )
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/* The application writer has already defined the array used for the RTOS
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* heap - probably so it can be placed in a special segment or address. */
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extern uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
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#else
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PRIVILEGED_DATA static uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
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#endif /* configAPPLICATION_ALLOCATED_HEAP */
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/* Define the linked list structure. This is used to link free blocks in order
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* of their size. */
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typedef struct A_BLOCK_LINK
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{
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struct A_BLOCK_LINK * pxNextFreeBlock; /*<< The next free block in the list. */
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size_t xBlockSize; /*<< The size of the free block. */
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} BlockLink_t;
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static const uint16_t heapSTRUCT_SIZE = ( ( sizeof( BlockLink_t ) + ( portBYTE_ALIGNMENT - 1 ) ) & ~portBYTE_ALIGNMENT_MASK );
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#define heapMINIMUM_BLOCK_SIZE ( ( size_t ) ( heapSTRUCT_SIZE * 2 ) )
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/* Create a couple of list links to mark the start and end of the list. */
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PRIVILEGED_DATA static BlockLink_t xStart, xEnd;
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/* Keeps track of the number of free bytes remaining, but says nothing about
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* fragmentation. */
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PRIVILEGED_DATA static size_t xFreeBytesRemaining = configADJUSTED_HEAP_SIZE;
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/*-----------------------------------------------------------*/
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/*
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* Initialises the heap structures before their first use.
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*/
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static void prvHeapInit( void ) PRIVILEGED_FUNCTION;
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/*-----------------------------------------------------------*/
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/* STATIC FUNCTIONS ARE DEFINED AS MACROS TO MINIMIZE THE FUNCTION CALL DEPTH. */
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/*
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* Insert a block into the list of free blocks - which is ordered by size of
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* the block. Small blocks at the start of the list and large blocks at the end
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* of the list.
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*/
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#define prvInsertBlockIntoFreeList( pxBlockToInsert ) \
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{ \
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BlockLink_t * pxIterator; \
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size_t xBlockSize; \
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\
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xBlockSize = pxBlockToInsert->xBlockSize; \
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\
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/* Iterate through the list until a block is found that has a larger size */ \
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/* than the block we are inserting. */ \
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for( pxIterator = &xStart; pxIterator->pxNextFreeBlock->xBlockSize < xBlockSize; pxIterator = pxIterator->pxNextFreeBlock ) \
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{ \
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/* There is nothing to do here - just iterate to the correct position. */ \
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} \
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\
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/* Update the list to include the block being inserted in the correct */ \
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/* position. */ \
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pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock; \
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pxIterator->pxNextFreeBlock = pxBlockToInsert; \
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}
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/*-----------------------------------------------------------*/
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void * pvPortMalloc( size_t xWantedSize )
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{
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BlockLink_t * pxBlock, * pxPreviousBlock, * pxNewBlockLink;
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PRIVILEGED_DATA static BaseType_t xHeapHasBeenInitialised = pdFALSE;
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void * pvReturn = NULL;
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vTaskSuspendAll();
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{
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/* If this is the first call to malloc then the heap will require
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* initialisation to setup the list of free blocks. */
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if( xHeapHasBeenInitialised == pdFALSE )
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{
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prvHeapInit();
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xHeapHasBeenInitialised = pdTRUE;
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}
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/* The wanted size must be increased so it can contain a BlockLink_t
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* structure in addition to the requested amount of bytes. */
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if( ( xWantedSize > 0 ) &&
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( ( xWantedSize + heapSTRUCT_SIZE ) > xWantedSize ) ) /* Overflow check. */
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{
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xWantedSize += heapSTRUCT_SIZE;
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/* Byte alignment required. Check for overflow. */
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if( ( xWantedSize + ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) ) )
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> xWantedSize )
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{
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xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
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configASSERT( ( xWantedSize & portBYTE_ALIGNMENT_MASK ) == 0 );
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}
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else
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{
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xWantedSize = 0;
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}
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}
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else
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{
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xWantedSize = 0;
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}
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/* Check the block size we are trying to allocate is not so large that the
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* top bit is set. The top bit of the block size member of the BlockLink_t
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* structure is used to determine who owns the block - the application or
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* the kernel, so it must be free. */
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if( heapBLOCK_SIZE_IS_VALID( xWantedSize ) != 0 )
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{
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if( ( xWantedSize > 0 ) && ( xWantedSize <= xFreeBytesRemaining ) )
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{
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/* Blocks are stored in byte order - traverse the list from the start
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* (smallest) block until one of adequate size is found. */
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pxPreviousBlock = &xStart;
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pxBlock = xStart.pxNextFreeBlock;
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while( ( pxBlock->xBlockSize < xWantedSize ) && ( pxBlock->pxNextFreeBlock != NULL ) )
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{
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pxPreviousBlock = pxBlock;
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pxBlock = pxBlock->pxNextFreeBlock;
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}
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/* If we found the end marker then a block of adequate size was not found. */
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if( pxBlock != &xEnd )
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{
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/* Return the memory space - jumping over the BlockLink_t structure
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* at its start. */
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pvReturn = ( void * ) ( ( ( uint8_t * ) pxPreviousBlock->pxNextFreeBlock ) + heapSTRUCT_SIZE );
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/* This block is being returned for use so must be taken out of the
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* list of free blocks. */
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pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;
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/* If the block is larger than required it can be split into two. */
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if( ( pxBlock->xBlockSize - xWantedSize ) > heapMINIMUM_BLOCK_SIZE )
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{
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/* This block is to be split into two. Create a new block
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* following the number of bytes requested. The void cast is
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* used to prevent byte alignment warnings from the compiler. */
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pxNewBlockLink = ( void * ) ( ( ( uint8_t * ) pxBlock ) + xWantedSize );
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/* Calculate the sizes of two blocks split from the single
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* block. */
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pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
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pxBlock->xBlockSize = xWantedSize;
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/* Insert the new block into the list of free blocks. */
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prvInsertBlockIntoFreeList( ( pxNewBlockLink ) );
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}
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xFreeBytesRemaining -= pxBlock->xBlockSize;
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/* The block is being returned - it is allocated and owned
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* by the application and has no "next" block. */
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heapALLOCATE_BLOCK( pxBlock );
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pxBlock->pxNextFreeBlock = NULL;
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}
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}
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}
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traceMALLOC( pvReturn, xWantedSize );
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}
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( void ) xTaskResumeAll();
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#if ( configUSE_MALLOC_FAILED_HOOK == 1 )
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{
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if( pvReturn == NULL )
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{
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extern void vApplicationMallocFailedHook( void );
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vApplicationMallocFailedHook();
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}
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}
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#endif
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return pvReturn;
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}
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/*-----------------------------------------------------------*/
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void vPortFree( void * pv )
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{
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uint8_t * puc = ( uint8_t * ) pv;
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BlockLink_t * pxLink;
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if( pv != NULL )
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{
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/* The memory being freed will have an BlockLink_t structure immediately
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* before it. */
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puc -= heapSTRUCT_SIZE;
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/* This unexpected casting is to keep some compilers from issuing
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* byte alignment warnings. */
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pxLink = ( void * ) puc;
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configASSERT( heapBLOCK_IS_ALLOCATED( pxLink ) != 0 );
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configASSERT( pxLink->pxNextFreeBlock == NULL );
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if( heapBLOCK_IS_ALLOCATED( pxLink ) != 0 )
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{
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if( pxLink->pxNextFreeBlock == NULL )
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{
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/* The block is being returned to the heap - it is no longer
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* allocated. */
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heapFREE_BLOCK( pxLink );
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#if ( configHEAP_CLEAR_MEMORY_ON_FREE == 1 )
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{
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( void ) memset( puc + heapSTRUCT_SIZE, 0, pxLink->xBlockSize - heapSTRUCT_SIZE );
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}
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#endif
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vTaskSuspendAll();
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{
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/* Add this block to the list of free blocks. */
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prvInsertBlockIntoFreeList( ( ( BlockLink_t * ) pxLink ) );
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xFreeBytesRemaining += pxLink->xBlockSize;
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traceFREE( pv, pxLink->xBlockSize );
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}
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( void ) xTaskResumeAll();
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}
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}
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}
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}
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/*-----------------------------------------------------------*/
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size_t xPortGetFreeHeapSize( void )
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{
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return xFreeBytesRemaining;
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}
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/*-----------------------------------------------------------*/
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void vPortInitialiseBlocks( void )
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{
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/* This just exists to keep the linker quiet. */
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}
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/*-----------------------------------------------------------*/
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void * pvPortCalloc( size_t xNum,
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size_t xSize )
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{
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void * pv = NULL;
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const size_t xSizeMaxValue = ~( ( size_t ) 0 );
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if( !heapMULTIPLY_WILL_OVERFLOW( xNum, xSize, xSizeMaxValue ) )
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{
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pv = pvPortMalloc( xNum * xSize );
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if( pv != NULL )
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{
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( void ) memset( pv, 0, xNum * xSize );
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}
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}
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return pv;
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}
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/*-----------------------------------------------------------*/
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static void prvHeapInit( void ) /* PRIVILEGED_FUNCTION */
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{
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BlockLink_t * pxFirstFreeBlock;
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uint8_t * pucAlignedHeap;
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/* Ensure the heap starts on a correctly aligned boundary. */
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pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT - 1 ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
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/* xStart is used to hold a pointer to the first item in the list of free
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* blocks. The void cast is used to prevent compiler warnings. */
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xStart.pxNextFreeBlock = ( void * ) pucAlignedHeap;
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xStart.xBlockSize = ( size_t ) 0;
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/* xEnd is used to mark the end of the list of free blocks. */
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xEnd.xBlockSize = configADJUSTED_HEAP_SIZE;
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xEnd.pxNextFreeBlock = NULL;
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/* To start with there is a single free block that is sized to take up the
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* entire heap space. */
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pxFirstFreeBlock = ( void * ) pucAlignedHeap;
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pxFirstFreeBlock->xBlockSize = configADJUSTED_HEAP_SIZE;
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pxFirstFreeBlock->pxNextFreeBlock = &xEnd;
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}
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/*-----------------------------------------------------------*/
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