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RE: setup code

 

From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of srinivas bakki
 
 >  ###   here we take the address of the arch.info structure. Then load ( ldmia )the contents at r3 (i.e arch_info structure) into r4,r5,r6 (3 words long) .
 
 >  ###   now since this address pointing to the machine info.is already virtual why do we need to convert it to physical ? 
 
    Probably because as '__lookup_arch_type' can also be invoked when MMU is not yet turned on.

        
   
 
 > ### also when the assembly code is called from the C code in setup.c is it always defined by the compiler that the arguments would go in     > same   register   always ? cause we expect the machine number in the r0 unconditionally !!! my guess is that they should be picked from the stack.
 
lookup_machine_type is called from setup.c with one argument (architecture id), and hence it goes in to r0 register. lookup_machine_type calls __lookup_machine_type which expects the architecture id in r1 and hence in lookup_machine_type, content of r0 is copied to r1 before invoking __lookup_machine_type.