Heap improvements (#462)

* 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>
4 files changed
tree: 182c04016774f439b7ac05e90d633f23a7af4e33
  1. .github/
  2. include/
  3. portable/
  4. .gitmodules
  5. CMakeLists.txt
  6. croutine.c
  7. event_groups.c
  8. GitHub-FreeRTOS-Kernel-Home.url
  9. History.txt
  10. LICENSE.md
  11. list.c
  12. queue.c
  13. Quick_Start_Guide.url
  14. README.md
  15. stream_buffer.c
  16. tasks.c
  17. timers.c
README.md

Getting started

This repository contains FreeRTOS kernel source/header files and kernel ports only. This repository is referenced as a submodule in FreeRTOS/FreeRTOS repository, which contains pre-configured demo application projects under FreeRTOS/Demo directory.

The easiest way to use FreeRTOS is to start with one of the pre-configured demo application projects. That way you will have the correct FreeRTOS source files included, and the correct include paths configured. Once a demo application is building and executing you can remove the demo application files, and start to add in your own application source files. See the FreeRTOS Kernel Quick Start Guide for detailed instructions and other useful links.

Additionally, for FreeRTOS kernel feature information refer to the Developer Documentation, and API Reference.

Getting help

If you have any questions or need assistance troubleshooting your FreeRTOS project, we have an active community that can help on the FreeRTOS Community Support Forum.

Cloning this repository

To clone using HTTPS:

git clone https://github.com/FreeRTOS/FreeRTOS-Kernel.git

Using SSH:

git clone git@github.com:FreeRTOS/FreeRTOS-Kernel.git

Repository structure

  • The root of this repository contains the three files that are common to every port - list.c, queue.c and tasks.c. The kernel is contained within these three files. croutine.c implements the optional co-routine functionality - which is normally only used on very memory limited systems.

  • The ./portable directory contains the files that are specific to a particular microcontroller and/or compiler. See the readme file in the ./portable directory for more information.

  • The ./include directory contains the real time kernel header files.

Code Formatting

FreeRTOS files are formatted using the “uncrustify” tool. The configuration file used by uncrustify can be found in the FreeRTOS/FreeRTOS repository.

Spelling

lexicon.txt contains words that are not traditionally found in an English dictionary. It is used by the spellchecker to verify the various jargon, variable names, and other odd words used in the FreeRTOS code base. If your pull request fails to pass the spelling and you believe this is a mistake, then add the word to lexicon.txt. Note that only the FreeRTOS Kernel source files are checked for proper spelling, the portable section is ignored.