Pintos Project 2 User Programs. September 28, 2016

Transcription

1 Pintos Project 2 User Programs September 28, 2016

2 Overview

3 What are user programs? Anything you run on the command line: ~$ls ~$git push ~$./my_project arg1 arg2

4 Overview of Part 1: Setup Stack User Hey I wanna run this thing: ~$/bin/ls -l foo bar K cool. Imma setup the stack for you: Kernel bfffffd bfffffd d8 ff ff bf-ed ff ff bf f5 ff ff bf... bfffffe0 f8 ff ff bf fc ff ff bf /bi bffffff0 6e 2f 6c d 6c f 6f n/ls.-l.foo.bar.

5 Overview of Part 2: Syscalls User Hey I wanna run this thing: <insert syscall here> I dun have the authority, so can you plz do it? K. Let me try Kernel Dude you messed up, Imma give you a -1 so you know. Ok cool, I can do this. Imma go do the thing.

6 Requirements Directory Project 2 must be put in a directory named proj2 in your repository Implementation Project 2 will be done in src/userprog/ This means you will run make in src/userprog This means you will run tests in src/userprog/build DesignDoc Project 2 design document can be found in doc/userprog.tmpl Rename the design document as DESIGNDOC and place in src/userprog. Failure to follow the naming & organization convention will result in deductions!!!

7 Due Dates Project 2 Check (October 6 th, no late days allowed) We will only check the argument tests (tests that begin with args- ), which are the first 5 tests Project 2 due date is October 23 rd Both implementation and design document are due.

8 Overview This project aims for you to implement the necessary features for user programs (the test programs) to request kernel functionality. Part 1: Setup Stack In src/userprog/process.c, support the feature of parsing the user program s filename and setup the stack correctly. Part 2: System Calls Implement the required functions in src/userprog/syscall.h/c

9 Prerequisites Setup proj2 Directory Re-copy & paste the pintos-base repository contents into a new directory named proj2 OR copy / paste your proj1 directory and rename it proj2 Keep Alarm Implementation Go back to your project 1 and add in all the alarm code. You do NOT need priority donation implementation, just the alarm. You should pass all the alarm tests in src/threads except alarm-priority Modify the Make.vars In src/userprog/make.vars, comment out: SIMULATOR=--qemu

10 Part 1 Setup Stack

11 Setup Stack Remember: ~$/bin/ls -l foo bar argc = 4 argv[0] = /bin/ls argv[1] = -l argv[2] = foo argv[3] = bar Your job is to setup the stack for the Pintos

12 Setup Stack ~$/bin/ls -l foo bar Will result in the following stack setup: Address Name Data Type 0xbffffffc argv[3][ ] bar\0 char[4] 0xbffffff8 argv[2][ ] foo\0 char[4] 0xbffffff5 argv[1][ ] -l\0 char[3] 0xbfffffed argv[0][ ] /bin/ls\0 char[8] 0xbfffffec word-align 0 uint8_t 0xbfffffe8 argv[4] 0 char* 0xbfffffe4 argv[3] 0xbffffffc char* 0xbfffffe0 argv[2] 0xbffffff8 char* 0xbfffffdc argv[1] 0xbffffff5 char* 0xbfffffd8 argv[0] 0xbfffffed char* 0xbfffffd4 argv 0xbfffffd8 char** 0xbfffffd0 argc 4 int 0xbfffffcc return address 0 void(*)()

13 Address Name Data Type 0xbffffffc argv[3][ ] bar\0 char[4] 0xbffffff8 argv[2][ ] foo\0 char[4] 0xbffffff5 argv[1][ ] -l\0 char[3] 0xbfffffed argv[0][ ] /bin/ls\0 char[8] 0xbfffffec word-align 0 uint8_t 0xbfffffe8 argv[4] 0 char* 0xbfffffe4 argv[3] 0xbffffffc char* 0xbfffffe0 argv[2] 0xbffffff8 char* 0xbfffffdc argv[1] 0xbffffff5 char* 0xbfffffd8 argv[0] 0xbfffffed char* 0xbfffffd4 argv 0xbfffffd8 char** 0xbfffffd0 argc 4 int 0xbfffffcc return address 0 void(*)() bfffffd bfffffd d8 ff ff bf-ed ff ff bf f5 ff ff bf... bfffffe0 f8 ff ff bf fc ff ff bf /bi bffffff0 6e 2f 6c d 6c f 6f n/ls.-l.foo.bar.

14 Setup Stack General steps should be: 1. Parse the argument by white spaces 2. Write each argument (including \0) in reverse 3. Word align to 4 bytes, write the word align 4. Write four 0 s as last argument 5. Write the addresses of each argument 6. Write the address of argv 7. Write argc 8. Write a 0 for the return address You ll need to use a lot of memset and sizeof Double check your setup stack is correct with hex_dump

15 Part 2 System Calls

16 System Calls When a user program wants to execute a command that only the kernel can do (eg. Write to a file), the following steps will occur: User program makes a request to the kernel Kernel recieves a syscall interrupt Kernel handles this interrupt If it s valid, completes the request If invalid, exit and return -1

17 System Calls System calls are interrupts in Pintos, this is handled in src/userprog/syscall.h syscall_handler. static void syscall_handler(struct intr_frame* f); Using the intr_frame f, you ll want to: 1. Extract the program inputs from the pointer (f->esp) 2. Validate the inputs 1. Cannot be NULL 2. Cannot be kernel memory 3. Cannot be unmapped memory 4. Cannot be a bad pointer 3. Run the appropriate system call 4. If there is a return value, store it in f->eax

18 System Calls You have 13 system calls to implement: Halt, exit, exec, wait, create, remove, open, filesize, read, write, seek, tell, close There are two types of syscalls you need to worry about: Process Management Halt, exit, exec, wait File System Create, remove, open, filesize, read, write, seek, tell, close Make sure your syscall_handler can be extended to run more commands (project 3)

19 System Calls File System are messy, but you have the libraries filesys/file.h and filesys/filesys.h to use for all your file system functions. Each file has a file descriptor, an integer ID. File descriptor 0 and 1 are reserved for STDIN and STDOUT

20 Questions & Concerns?