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memo

fs

• Block size(BSIZE): 512B
• inodestart = 32, ninodes = 200
  • inode info: 0x4000~ (= inodestart * BSIZE)
• bmapstart: 57, size=1 (= FSSIZE / (BSIZE * 8) + 1)
• freeblock: 58~

Boot process

• bootasm.S
• bootmain.c: bootmain()
• entry.S
• main.c: main()
• proc.c: userinit() -> Spawn "initcode" proc
• main.c: mpmain()
• proc.c: scheduler()
• initcode.S
• init.c: main() -> Exec "sh" (Loop forever)
• sh.c: main() : Shell process

Process switch

1. Timer interrupt (100ms)
2. trap.c trap(), case T_IRQ0 + IRQ_TIMER:
3. proc.c yield()
4. proc.c shed()
5. swtch.S swtch

write to stdout

Kernel:

• sysfile.c: sys_write()
• file.c: filewrite()
• fs.c: writei() => return devsw[ip->major].write(ip, src, n);
  • console.c: consoleinit() => devsw[1].write = consolewrite
• console.c: consolewrite()
• console.c: consputc()
• uart.c: uartputc()
• console.c: cgaputc()

Pipe

Creation:

• User space:
  • usys.S: pipe(int*)
• Kernel space:
  • vectors.S: vector64 (T_SYSCALL=64)
  • trapasm.S: alltraps
  • trap.c: trap()
  • syscall.c: syscall()
  • sysfile.c: sys_pipe()
  • pipe.c: pipealloc()
    • filealloc x 2, 1 for read, 1 for write
    • kalloc x 1, used to keep pipe struct.

Write:

• sysfile.c: sys_write()
• file.c: filewrite()
• pipe.c: pipewrite()

Read:

• sysfile.c: sys_read()
• file.c: fileread()
• pipe.c: piperead()

TODOs

• Sleep/wakeup mechanism
• Fork/exec mechanism
• Support >> in shell
  • Add file append mode
• Add mtime to file info
  • RTC
• Analyze ELF execution sequence (How to allocate memory, etc.)
• Use .text, .rodata, .data, .bss sections
• POSIX

Memory map

$ memmap
execelf: /bin/memmap
  vaddr=0, memsz=2908, filesz=18d1, sz=2908
  sz=2908
  sp=5000
main: 0x0
bss: 0x18e0
const_data: 0x1800
rw_data: 0x13e0
stack: 0x4f6c
sbrk: 0x5000

Memory Map (kernel)

Address	Entity
0x80100000-	Kernel program

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