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[FreeRTOS Home] [Live FreeRTOS Forum] [FAQ] [Archive Top] [February 2017 Threads] Extending number of MPU regionsPosted by hdtx on February 21, 2017 I'm using GCC on a Cortex-M4F (LPC43xx family).
I need more than the 3 configurable MPU regions for this port. I decided to do away with the privileged flash area because I don't need it (privileged background map is enabled and my unprivileged flash area does not reach there, so privileged accesses are enabled by default and unprivleged accesses are blocked).
What I did:
- added the fourth area to all my task parameters (all tasks are created using xTaskCreateRestricted);
- took out the lines setting portMPUREGIONBASEADDRESSREG and portMPUREGIONATTRIBUTE_REG for the privileged flash area in prvSetupMPU (mpu/port.c);
- changed a few lines at the start of mpu/portmacro.h from
~~~
#define portUNPRIVILEGEDFLASHREGION ( 0UL )
#define portPRIVILEGEDFLASHREGION ( 1UL )
#define portPRIVILEGEDRAMREGION ( 2UL )
#define portGENERALPERIPHERALSREGION ( 3UL )
#define portSTACKREGION ( 4UL )
#define portFIRSTCONFIGURABLEREGION ( 5UL )
#define portLASTCONFIGURABLEREGION ( 7UL )
~~~
to
~~~
#define portUNPRIVILEGEDFLASHREGION ( 0UL )
#define portPRIVILEGEDRAMREGION ( 1UL )
#define portGENERALPERIPHERALSREGION ( 2UL )
#define portSTACKREGION ( 3UL )
#define portFIRSTCONFIGURABLEREGION ( 4UL )
#define portLASTCONFIGURABLEREGION ( 7UL )
~~~
What did not work: the fourth area is never set (whatever region I put there does not get activated).
I checked portNUMCONFIGURABLEREGIONS, it's obviously 4 instead of 3 now. I looked at the FreeRTOS code and the fourth region should be working, I have no idea why it's not. I appreciate any help.
Extending number of MPU regionsPosted by hdtx on February 21, 2017 Never mind, I found it... xPortPendSVHandler in mpu/port.c only swaps in 4 regions at most (including the stack region), so I added a few lines that fixed it. If anyone has the same problem, delete line 495 and add this in its place (assuming you defined the appropriate symbol):
~~~
if !defined(FREERTOSEXTRAMPU_REGION)
" stmia r2!, {r4-r11} \n" // original line
else
" stmia r2, {r4-r11} \n" // don't update r2
" ldmia r1!, {r4-r5} \n" // load 1 set of MPU regs
" stmia r2, {r4-r5} \n" // write 1 set of MPU regs
endif
~~~
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