Description
Is your feature request related to a problem? Please describe.
I need to add a custom SystemCall instruction to execute a custom function.
However, the maximum number of system call instructions is 255.
Describe the solution you'd like
....
#define SYSTEM_CALL_User 80
#define SYSTEM_CALL_xUartSend 10001
....
PRIVILEGED_DATA UBaseType_t uxSystemCallImplementations[ NUM_SYSTEM_CALLS ] =
{
...
xUartSendImpl,
}
...
BaseType_t MPU_xUartSend(..... )
{
__asm volatile
(
" .syntax unified \n"
" .extern MPU_xUartSendImpl \n"
" \n"
" push {r0} \n"
" mrs r0, control \n"
" tst r0, #1 \n"
" pop {r0} \n"
" bne MPU_xUartSend_Unpriv \n"
" MPU_xUartSend_Priv: \n"
" b MPU_xUartSendImpl \n"
" MPU_xUartSend_Unpriv \n"
" svc %0 \n"
" \n"
pc+x : "i" ( SYSTEM_CALL_User ) : "memory"
pc+y : "i" ( .word SYSTEM_CALL_xUartSend ) : "memory" //define a word :system call id I am not familiar with assembly syntax.
);
}
...
void vSystemCallEnter( uint32_t * pulTaskStack,
uint32_t ulLR,
uint8_t ucSystemCallNumber )
{
....
ulSystemCallLocation = pulTaskStack[ portOFFSET_TO_PC ];
if( ( ulSystemCallLocation >= ( uint32_t ) __syscalls_flash_start__ ) &&
( ulSystemCallLocation <= ( uint32_t ) __syscalls_flash_end__ ) &&
( pxMpuSettings->xSystemCallStackInfo.pulTaskStack == NULL ) &&
( uxSystemCallImplementations[ ucSystemCallNumber ] != ( UBaseType_t ) 0 ) )
{
...
uint32_t systemCallId=*(pulTaskStack[ portOFFSET_TO_PC ]+x)；//get user system call id
if( systemCallId>=SYSTEM_CALL_User )
{
systemCallId=*(pulTaskStack[ portOFFSET_TO_PC ]+y);
}
.....
......
...
}
....
}
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How many devices will this feature impact?
Expected volume for your product.
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Timeline for milestones such as design completion, testing and validation, and production.
Additional context
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