English
Russian
Contents 4.1 Overview 4.2 Configuration parameters 4.3 System calls
4.1 Overview [up]
The main document for L4 microkernel is L4 Kernel Reference Manual Version X.2. It describes kernel API, ABI and principles of L4 Operation System.
Kernel is the core part of WrmOS witch is executed on target CPUs in privileged mode. The following actions must be doing by kernel:
- complete system initialization
- initialize MMU
- initialize kernel UART
- initialize Interrupt Controller
- create root-pager Sigma0 and execute it
- process system exceptions, IRQs and system calls in runtime
4.2 Configuration parameters [up]
Kernel has the next configuration parameters:
| Name | Location | Description |
|---|---|---|
| usr_krn_dbg | cfg/prj/<project-name>.prj | Kernel debug flag. My be 0 or 1. It allows to use debug configuration with asserts, additional debug outputs and other (for 1) or use release configuration (for 0). |
| usr_krn_log | Kernel logging enable flag. May be 0 or 1. It enables internal kernel logging, that allows to see kernel activities and actions. | |
| krn_vaddr | cfg/plt/<platform-name>.plt | Start of kernel virtual addresses. |
| krn_tick_usec | Kernel tick in microseconds. Kernel periodically timer will tick every krn_tick_usec microseconds. | |
| krn_uart_paddr | Kernel UART physical address. | |
| krn_uart_sz | Kernel UART size in bytes. | |
| krn_uart_bitrate | Kernel UART bitrate. | |
| krn_uart_irq | Kernel UART interrupt number. | |
| krn_intc_paddr | Interrupt Controller physical address. | |
| krn_intc_sz | Interrupt Controller size in bytes. | |
| krn_timer_paddr | Kernel Timer physical address. | |
| krn_timer_sz | Kernel Timer size in bytes. | |
| krn_timer_irq | Kernel Timer interrupt number. |
4.3 System calls [up]
Full description of L4 system calls there is in L4 Kernel Reference Manual Version X.2. Short description of system calls is listed below:
| System call | Privileged | L4 API | Description |
|---|---|---|---|
| Kernel Interface | Any applications | l4_kip() | Get Kernel Interface Page. |
| Exchange Registers | Any applications | l4_exchange_registers() | Read or modify: stack pointer, instruction pointer, thread flags, pager, user defined handle. |
| Thread Control | Root-pager, Root-task | l4_thread_control() | Root-pager Sigma0 or root-task Alpha can create and delete thread. |
| System Clock | Any applications | l4_system_clock() | Get current system clock (system uptime in microseconds). |
| Thread Switch | Any applications | l4_thread_switch() | Release the CPU. |
| Schedule | Any applications | l4_schedule() | Change thread parameters: priority, timeslice length and other scheduling parameters of threads. |
| IPC | Any applications | l4_ipc() l4_send() l4_receive() |
IPC is the fundamental operation for inter-process communication and synchronization. |
| Unmap | Any applications | l4_unmap() | Unmap memory from caller address space. |
| Space Control | Root-pager, Root-task | l4_space_control() | Root-pager Sigma0 or root-task Alpha can configure address space. |
| Processor Control | Root-pager, Root-task | --- | Control the internal frequency, external frequency, or voltage for a system processor. |
| Memory Control | Root-pager, Root-task | l4_memory_control() | Set the page attributes. For example cached or not. |
| Kernel Debugger | Any applications | l4_kdb() | Kernel debugger system call. |