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No entry for pvPortMalloc/vPortFree in mpu_wrappers.h

Posted by philpem on January 31, 2017

mpuwrappers.h seems to be missing #define statements for several of the MPU wrapper functions which are defined in mpuwrappers.c. The most notable of these are MPUpvPortMalloc and MPUvPortFree.

The net effect of this is that MPUpvPortMalloc and MPUvPortFree are defined but no prototype is available to MPU-enabled code -- calling pvPortMalloc() results in the "privileged" pvPortMalloc() being called. If this is called from a "normal" task, there will be a memory protection error. I was expecting that the MPU shim in mpu_wrappers.c would be called, until I noticed the define was missing.

Long and short of it: you can't allocate and free memory from MPU-enabled code.

Adding these calls to mpu_wrappers.h is fairly simple -- is there any adverse implication of doing so which I may have overlooked?

Thanks, Phil.


No entry for pvPortMalloc/vPortFree in mpu_wrappers.h

Posted by rtel on January 31, 2017

mpuwrappers.h seems to be missing #define statements for several of the MPU wrapper functions which are defined in mpuwrappers.c. The most notable of these are MPUpvPortMalloc and MPUvPortFree.

Probably deliberate with the rationale that unprivileged tasks should not be allowed to dynamically allocate memory (directly).

The net effect of this is that MPUpvPortMalloc and MPUvPortFree are defined but no prototype is available to MPU-enabled code -- calling pvPortMalloc() results in the "privileged" pvPortMalloc() being called. If this is called from a "normal" task, there will be a memory protection error. I was expecting that the MPU shim in mpu_wrappers.c would be called, until I noticed the define was missing.

This sounds confused. Either an MPU_...() function have both a implementation in a C file and and entry in the header file, or it should not be in either. Possibly it was removed from one (for the reason above) but not the other. Either way it doesn't sound right and needs to be straightened.

I'm not sure how calling pvPortMalloc() could result in MPUpvPortMalloc() being called if the function is not in mpuwrappers.h - I would expect it to result in the normal pvPortMalloc() being called a there is nothing mapping it anywhere else.


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