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The Kernel interacts with processes and devices
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| bet | 6/9 | | Sana | 19.05.2023 | | Hajmi | 1.51 Mb. | | #61987 |
Bog'liq process Mode,Space & Context - By modes: some critical resources can be protected.
- Kernel Mode: More privileged, kernel functions
- User Mode: Less privileged, user functions
- Virtual Memory
- VM space
- Address Translation Maps
- Memory Management Unit
Kernel data - Current process & Context switch
- One instance of the kernel
- Global data structure
- Pre-process objects
- System call, Mode Switch
- User area: info. about a process
- Kernel stack:
Context - UNIX kernel is re-entrant: several processes may be involved in kernel activities concurrently.
- Execution context
- Process context:
- System context (Interrupt context):
Executing in Kernel Mode - 3 types of events:
- Dispatch table
- System context: interrupts
- Process context: traps, exceptions & software interrupts
The System Call Interface - syscall(): the starting point
- in kernel mode, but in process context.
- Copy arguments , save hardware context on the kernel stack.
- Use system call number to index dispatch vector
- Return results in registers, restore hardware context, to user mode, control back to the library routine.
UNIX Interrupt Handling - Interrupt handler(interrupt service routine):
- runs in kernel mode and system context,
- not permitted to block.
- the time used to service an interrupt charged to the interrupted process
- The clock interrupt handler charges the clock tick to the current process
- ipl(interrupt priority level)- specified for each interrupt and saved in interrupt register of the processor status word
- Interrupts are preemptive
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