Project 2 Roadmap++

1. Project 2 Roadmap++

2. 1000 A’S Review Process B function handler() { Print “HANDLING” } main() { Signal(&handler, SIGUSR1) for(;;) Print “B” } Process A main() { for(1000) Print “A” Kill(B, SIGUSR1) } Output HANDLING BBBBBBBBBBBBBB….. AABBAABBAABB………

3. System Calls • Sys_Signal:register a signal handler • Sys_Kill:send a signal • Sys_RegDeliver:initialize signal handling for a process • Sys_WaitNoPID:wait for any child process to die • Sys_ReturnSignal:indicate completion of signal handler

4. System Calls • Sys_Signal:register a signal handler • Sys_Kill:send a signal • Sys_RegDeliver:initialize signal handling for a process • Sys_WaitNoPID:wait for any child process to die • Sys_ReturnSignal:indicate completion of signal handler Referenced in user code

5. 1000 A’S Review Process B function handler() { Print “HANDLING” } main() { Signal(&handler, SIGUSR1) for(;;) Print “B” } Process A main() { for(1000) Print “A” Kill(B, SIGUSR1) } Output HANDLING BBBBBBBBBBBBBB….. AABBAABBAABB………

6. System Calls • Sys_Signal:register a signal handler • Sys_Kill:send a signal • Sys_RegDeliver:initialize signal handling for a process • Sys_WaitNoPID:wait for any child process to die • Sys_ReturnSignal:indicate completion of signal handler

7. Executed by stub code once a signal has been handled System Calls • Sys_Signal:register a signal handler • Sys_Kill:send a signal • Sys_RegDeliver:initialize signal handling for a process • Sys_WaitNoPID:wait for any child process to die • Sys_ReturnSignal:indicate completion of signal handler

8. Helper Functions • Send_Signal • Set_Handler • Check_Pending_Signal • Setup_Frame • Complete_Handler

9. Review Process B function handler() { Print “HANDLING” } main() { Signal(&handler, SIGUSR1) for(;;) Print “B” } Process A main() { for(1000) Print “A” Kill(B, SIGUSR1) }

10. Overview A B

11. Overview A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….)

12. Overview libc A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….)

13. Overview libc A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….) Set_handler

14. Overview libc A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….) Set_handler

15. libc A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….) entry point main Kill Signal Overview Send_signal

16. libc A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….) entry point main Kill Signal Overview Send_signal

17. libc A B RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….) entry point main Kill Signal Overview

18. Helper Functions • Send_Signal • Set_Handler • Check_Pending_Signal • Setup_Frame • Complete_Handler Look at Scheduler

19. B Scheduler: w/o signals scheduler A B src/geekos/lowlevel.asm

20. A B Scheduler: w/ signals scheduler B’s user level sig. hand. B

21. A B Scheduler: w/ signals Check Pending Signal scheduler B’s user level sig. hand. B

22. Check Pending Signal • Boolean output • Determines whether to proceed with signal handling

23. true A B false Scheduler: w/ signals Check Pending Signal scheduler B’s user level sig. hand. B

24. A B Scheduler: w/ signals Check Pending Signal Setup Frame scheduler B’s user level sig. hand. B

25. Setup Frame • Sets up state to enable user-level handling code execution

26. A B Scheduler: w/ signals Check Pending Signal Setup Frame scheduler B’s user level sig. hand. B

27. Setup Frame • Sets up state to enable user-level handling code execution • How are function called?

28. Function Calls • Parameter of return address is stored on the stack so when finished • Pop off stack • Continue execution • Setup Frame • Enables user stack to keep: • Interrupt_State Vector • Return address

29. Storing Return Address • Want complete_handler to execute once user level handling done. • Hack • Place address of return_signal as return address on stack • Now return_signal stred as function

30. A B Scheduler: w/ signals Check Pending Signal Setup Frame scheduler CompleteHandler B’s user level sig. hand. B