Question about NRF5340 SRAM execution permission

[David Duan]

HI Devzone

currently my customer would like to get SRAM execution permission in their porject.

we found a config marco to set the SRAM permission "CONFIG_SRAM_REGION_PERMISSIONS", but looks like this marco doesn't grant  execution permission.

Question, is it possible to have the SRAM execution permission on NRF5340?

If yes, May i know how to do it ?

BR

[Amanda Hsieh]

Hi, 

Besides this is a really bad idea the customer probably wants to look at soc/arm/common/cortex_m/arm_mpu_regions.c and in particular to the REGION_RAM_ATTR macro

Regards,
Amanda

[David Duan]

Hi Amanda

Thanks for your suggestion

we found that the RAM excution access is disabled on default setting.

currently we use below two method to enable excution access.(NCS1.5.0)

1. Remove "NOT_EXEC" on line 123 (zephyr\include\arch\arm\aarch32\cortex_m\mpu\arm_mpu_v8m.h)

2. use arm_core_mpu_disable 

my question is do we have some standard method to enable the access ?

for example some marco ?

[Amanda Hsieh]

Hi, 

There is no standard method to enable EXEC on the whole SRAM because this is considered really really bad from a security perspective. What you could do is to define a new contained region in the SRAM and add that region to the mpu_config structure with the proper attributes as done for example in soc/arm/st_stm32/stm32h7/mpu_regions.c (see the SRAM3_ETH_BUF region)

-Amanda