GIET-VM / Syscall Handler

The sys_handler.c​ and 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 _syscall_vector​ array contains the 64 kernel functions (syscal handlers) defined by the GIET-VM to handle system calls.

Miscelaneous syscall handlers

void _sys_ukn()

Function executed in case of undefined syscall

void _sys_proc_xyp( unsigned int* x, unsigned int*, unsigned int* p )

This function returns the processor (x,y,p) identifiers.

TTY related syscall handlers

int _sys_tty_alloc()

int _sys_tty_write( const char* buffer, unsigned int length, unsigned int channel )

This non-blocking function writes a character string from a fixed-length buffer to a TTY terminal identified by the channel argument. If channel argument is 0xFFFFFFFF, the TTY index is found in the task context. It is non blocking: it tests the TTY_STATUS register, and stops the transfer as soon as the TTY_STATUS[WRITE] bit is set. Returns the number of characters that have been written.

int _sys_tty_read( char* buffer, unsigned int length, unsigned int channel )

This non-blocking function fetches one character from the terminal identified by the channel argument. If the channel argument is 0xFFFFFFFF, the channel index is obtained from the current task context. It uses the TTY_GET_IRQ[tty_id] interrupt and the buffer must have been filled by the TTY_ISR. It test the _tty_rx_full[tty_id] variable, read the _tty_rx_buf[tty_id] buffer, writes this character to the target buffer, and resets the_tty_rx_full[tty_id] register. The length argument is not used. Returns the number of characters that have been read (0/1).

void _sys_tty_get_lock( unsigned int channel, unsigned int* save_sr_ptr )

This blocking function try to take the lock protecting exclusive access to TTY terminal identified by the "channel" argument. It enters a critical section before taking the lock, and save the SR value at address defined by the save_sr_ptr argument. It returns only when the lock has been successfully taken.

void _sys_tty_release_lock( unsigned int channel, unsigned int* save_sr_ptr )

This function releases the lock protecting exclusive access to TTY terminal identified by the channel argument. It exit the critical section after lock release, and restore SR value from address defined by the save_sr_ptr argument.

TIM retated syscall handlers

int _sys_timer_alloc()

This function allocates a private timer to the calling task, and register the timer index in the task context. Return -1 if no timer available.

int _sys_timer_start( unsigned int period )

This function starts the user timer channel allocated to the calling task. Returns -1 if no allocated timer.

int _sys_timer_stop()

This function stops the user timer channel allocated to the calling task. Returns -1 if no allocated timer.

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

unsigned int _vobj_get_vbase( char* vspace_name, char* vobj_name, unsigned int* vobj_vbase )

This function writes in vobj_base 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_length( char* vspace_name, char* vobj_name, unsigned int* vobj_length )

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 _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.