= GIET-VM  / Syscall Handler functions =

The [source:soft/giet_vm/giet_kernel/sys_handler.c sys_handler.c] and [source:soft/giet_vm/giet_kernel/sys_handler.h sys_handler.h] files define the kernel data structure and functions that are used to handle the system calls. They are prefixed by ''_'' to remind that they can only be executed by a processor in kernel mode.

The [source:soft/giet_vm/giet_kernel/sys_handler.c _syscall_vector![64!]] array contains the 64 kernel functions defined by the GIET-VM to handle system calls. Most of these functions are provided by the peripheral drivers,
but some services are provided by the kernel itself:

=== void        _sys_ukn() ===
Function executed in case of undefined syscall

=== void         _proc_xyp( unsigned int* x,  unsigned int*,   unsigned int* p ) ===
This function returns the processor (x,y,p) identifiers.

=== void         _task_exit() ===
The calling task goes to sleeping state, after printing an exit message.
It is descheduled and enters the "not runable" mode.

 === void         _context_switch() ===
This function deschedules the calling task. It mask interrupts before calling the _ctx_switch, and restore it when the task is rescheduled.

 === unsigned int _local_task_id() ===
Returns current task local index (amongst tasks running on a given processor).

 === unsigned int _global_task_id() ===
Returns current task global index (amongst all tasks running on all processors).

=== unsigned int _thread_id() ===
Returns current thread index (amongst all tasks in a given multi-tasks application).

 === unsigned int _procs_number( unsigned int  cluster_id, unsigned int* number ) ===
Returns in buffer argument the number of processors in cluster specified by the cluster_id argument.

 === unsigned int _get_vobj_ptr( char* vspace_name,  char* vobj_name,  mapping_vobj_t**  pvobj ) ===
This function returns in the res_vobj argument a pointer on a vobj identified by the (vspace_name / vobj_name ) couple. Returns 0 if success, >0 if not found



/////////////////////////////////////////////////////////////////////////////
// This function writes in vobj_vbase the virtual base address of a vobj 
// identified by the (vspace_name / vobj_name ) couple.
// returns 0 if success, >0 if not found
/////////////////////////////////////////////////////////////////////////////
unsigned int _vobj_get_vbase( char*         vspace_name,
                              char*         vobj_name,
                              unsigned int* vobj_vbase );

/////////////////////////////////////////////////////////////////////////////
// This function writes in vobj_length the length of a vobj 
// identified by the (vspace_name / vobj_name ) couple.
// returns 0 if success, >0 if not found
/////////////////////////////////////////////////////////////////////////////
unsigned int _vobj_get_length( char*         vspace_name, 
                               char*         vobj_name,
                               unsigned int* vobj_length );

 === unsigned int _get_xy_from_ptr( void* ptr,  unsigned int*  px,  unsigned int*  py ) ===
This function returns in the (x,y) arguments the coordinates of the  cluster where is mapped the ptr virtual address. It use the _get_context_slot() function to get the calling task page table, and uses the _v2p_translate() function to obtain the physical address. Returns 0 if success, > 0 if ptr not mapped in the calling task vspace.