`physBase` isn't aligned properly on `ARM_HYP`

[Nick Spinale]

physBase is required to be aligned to seL4_SuperSectionBits:

seL4/include/arch/arm/arch/32/mode/hardware.h

Lines 98 to 100 in c998966

 /* For alignment conditions to translate over addrFromPPtr, physBase must be 
    aligned to at least the size of a SuperSection. */ 
 compile_assert(physBase_aligned, IS_ALIGNED(PHYS_BASE_RAW, seL4_SuperSectionBits)); 

On ARM_HYP, seL4_SuperSectionBits = 25:

seL4/libsel4/sel4_arch_include/aarch32/sel4/sel4_arch/constants.h

Line 195 in c998966

 #define seL4_SuperSectionBits 25 

However, in hardware/config.py the value of SUPERSECTION_BITS is hard-coded to 24, its value on ARM:

seL4/tools/hardware/config.py

Lines 48 to 51 in c998966

 class ARMConfig(Config): 
     ''' Config class for ARM ''' 
     arch = 'arm' 
     SUPERSECTION_BITS = 24  # 2^24 = 16 MiByte 

While this bug may not have caused issues for currently supported platform, I noticed it when testing #976 on ARM_HYP. In this case, physBase is set to 2**24 by hardware/config.py and the assertion in hardware.h fails.

[Gerwin Klein]

Nice find, and I'm glad that the assert catches it, because that would have been super hard to find at runtime. The value in config.py is just wrong, it needs to depend on whether hyp mode is on or not.