2012-04-10

Virtual Memory

• 有 code 有真相
• Page Table entry (PTE)

Page Table Width: 10 bit + 10 bit + 12 bit

- 10 bit 使用較少量的記憶體

修改過的 QEMU 提供 "info pg" monitor 指令，可交叉觀察 CR3 設定前後的 page 變化，檢驗首個與末個 page

Challenge! Extend the JOS kernel monitor with commands -> 開發 in-kernel debugger

"follow the bouncing kernel" on stackoverflow

• method 1 - swap in/out to other storage

boot_alloc

TDD (Test-Driven Development) in JOS

assert() supported in patched QEMU

Hawx

page_alloc() -- the page reference count pp_ref

page_insert()

pp_ref (reference count)

=> hawx's version

page_table 3

• page 1 1
• page 2 1
• page 3 1

page_table 4

• page 1 1
• page 2 1
• page 3 1

=> MIT JOS

page_table 1

• page 1 x
• page 2 x
• page 3 x

How to start to write labs?

• check homework next lecture
• reference the check code for grade calculation

PDOS paper

The exokernel approach to extensibility (panel statement)

Related: http://hypervisor.org/

Ben

Question: 目前兩週舉行一次會不會太頻繁？

• Ans: 比較難的lab分成兩次。

memory verifier -- magic 1 + [mem] + magic 2

• kernel built-in
• gcc library - LD_PRELOAD=./mem_verifier_library.so (replace malloc , dealloc, free ..)
• a tool: valgrind
  • Android 4.0 內建 valgrind: external/valgrind

main/VEX/ => 模擬 host ISA 的行為來作 memory debugging

libvex -> library for dynamic binary instrumentation

Related paper: Bounds Checking with Taint-Based Analysis

http://cseweb.ucsd.edu/~wchuang/HiPEAC-07-TaintBounds.pdf

Jserv

1. OSDC.tw 2012 介紹 ARM virtualization -- http://osdc.tw/schedule
2. Rework Plan 9's protocol to fit the requirements of new products.
3. Linux community: http://www.svlug.org/