Kernel Utilities

The utils.c​ and util.h​ files define useful kernel functions, that are used both by the boot_loader and by the kernel. They are prefixed by _ to remind that they can only be executed by a processor in kernel mode.

• They are used by the boot-loader in the static phase, to build the page tables and initialize the schedulers and the peripherals.
• They are also used by the kernel in the dynamic phase, to handle events such as interrupts, exceptions and syscalls.

1) CP0 registers access functions

unsigned int _get_sched( void )

Returns the virtual address of the scheduler stored in the SCHED register for the processor running the calling task.

unsigned int _get_epc( void )

Returns the value stored in the EPC register for the processor running the calling task.

unsigned int _get_cr( void )

Returns the value stored in the CR register for the processor running the calling task.

unsigned int _get_sr( void )

Returns the value stored in the SR register for the processor running the calling task.

unsigned int _get_bvar( void )

Returns the value stored in the BVAR register, for the processor running the calling task.

unsigned int _get_procid( void )

Returns the global processor identifier stored in the EBASE register for the processor running the calling task.

void _set_sched( unsigned int value )

Writes value in the SCHED register, for the processor running the calling task.

void _set_sr( unsigned int value )

Writes value in the SR register, for the processor running the calling task.

void _it_disable( unsigned int* save_sr_ptr )

Disables interrupts for the processor running the calling task and save the SR value at address save_sr_ptr.

void _it_restore( unsigned int* save_sr_ptr )

Writes the value pointed by save_sr_ptr into the SR register, for the processor running the calling task.

These functions can be used to access the MIPS32 protected registers

2) Physical addressing functions

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Miscelaneous functions