No entry for pvPortMalloc/vPortFree in mpu_wrappers.h

Kernel
1

philpem wrote on Tuesday, January 31, 2017:

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

The net effect of this is that MPU_pvPortMalloc and MPU_vPortFree 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.

2

rtel wrote on Tuesday, January 31, 2017:

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

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

The net effect of this is that MPU_pvPortMalloc and MPU_vPortFree 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
MPU_pvPortMalloc() being called if the function is not in mpu_wrappers.h

  • I would expect it to result in the normal pvPortMalloc() being called
    a there is nothing mapping it anywhere else.