what does this piece of code means in SVC handler and how are the svc number is passed from application to handler ?
SVC_Handler PROC EXPORT SVC_Handler [WEAK] IMPORT SVC_Handler_Main TST lr, #4 ITE EQ MRSEQ r0, MSP MRSNE r0, PSP B SVC_Handler_Main ENDP
/*below code is placed in main*/
void SVC_Handler_Main( unsigned int *svc_args ){ unsigned int svc_number;
svc_number = ( ( char * )svc_args[ 6 ] )[ -2 ] ; switch( svc_number ) { case 0: break; case 1:break; default: /* unknown SVC */ break;
Hello, I believe the below article explain more:developer.arm.com/.../latest
Hello Teggi,
Just a quick look into the code in my understand the svc_args[6] points to the return address. An array index "-2" with the pointer typecast to char will points to 2 bytes earlier the LR. That will be the part of SVC number in the previous instruction which is the SVC.
Chandrasekar