TNKernel-PIC32Stack
An experimental version of TNKernel-PIC32 featuring hardware stack overflow protection.
##Usage
To use TNKernel-PIC32Stack, set up your project as you would a normal TNKernel-PIC32 project, then just add the included linker script (tn_port_linkerscript.x).
##Notes and limitations
The BMXERRDS bit in the bus matrix configuration registers must not be cleared.
Due to hardware limitations, all thread stack allocations will be rounded up to to the nearest kilobyte.
The memory usage gauge in MPLAB X will not accurately report the amount of free memory. Because of how the XC32 linker allocates sections, all unused memory will be allocated to the thread stack memory region.
When debugging, the first 512 bytes of RAM are reserved by the debug executive, rendering the interrupt stack protection ineffective.
##Implementation The stack overflow protection works by making sure that accesses beyond the stack limits will trigger an exception. This is implemented in two ways:
- The interrupt stack is allocated at the start of the KSEG1 data RAM region. Overflowing the interrupt stack will access unmapped memory at the top of KSEG0, triggering an exception.
- The thread stacks are grouped together at the top of RAM. At runtime, the current thread's stack is mapped as user data RAM using the PIC32 bus matrix registers. Overflowing the thread stack will access unmapped USEG memory, again triggering an exception.
The kernel is released under the BSD license as follows:
TNKernel real-time kernel
Copyright © 2004, 2013 Yuri Tiomkin
PIC32 version modifications copyright © 2013, 2014 Anders Montonen
All rights reserved.
Permission to use, copy, modify, and distribute this software in source
and binary forms and its documentation for any purpose and without fee
is hereby granted, provided that the above copyright notice appear
in all copies and that both that copyright notice and this permission
notice appear in supporting documentation.
THIS SOFTWARE IS PROVIDED BY THE YURI TIOMKIN AND CONTRIBUTORS "AS IS" AND
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ARE DISCLAIMED. IN NO EVENT SHALL YURI TIOMKIN OR CONTRIBUTORS BE LIABLE
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OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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