• [DN-03]GDB 使用紀錄
  • 編譯可以 debug 的輸出檔
  • 編譯時產生preprocesser
  • 透過 GDB 來追蹤程式
  • 常用命令
  • 參考資料

[DN-03]GDB 使用紀錄

開始試著用 GDB 來檢查追蹤程式流程和記憶體分配，跟著 GDB 來學習…
透過 GDB 來觀察 merge_soft 程式 https://github.com/Lukechin/mergesort_doubly_linked_list/blob/master/mergesort.c

編譯可以 debug 的輸出檔

首先使用 GDB 蹤程式前，需要在編譯階段增加 ”-g” 參數來產生 debugging info
我們先編譯 merge_soft.c 並產生含有 debugging info 的執行檔 ”merge_soft”

$ gcc -g -o merge_soft merge_soft.c

編譯時產生preprocesser

$ gcc -E -P

透過 GDB 來追蹤程式

$ gdb merge_soft

常用命令

• b <line_number> - setting breakpoint at <line_number>

• info b - print breakpoints information

• disable b <break_number> - disable target breakpoint

• continue - run after code…

• Next - run next instruct (no entry sub function)

• Step - run next instruct (entry sub funxtion)

• List - list the source code and each execution’s corresponding line number

• Backtrace - show trace of all function calls in stack

• Info frame - List address, language, address of arguments/local variables and which registers were saved in frame.

  • This will show where the return address is saved
  • Return address is in Register EIP
  • Calling stack pointer is in Register EBP

• x &variable - show the address and value of a local variable (in hex format)

• x address - print binary representation of 4 bytes of memory pointed to by address.

參考資料

• Buffer Overflow : Example of Using GDB to Check Stack Memory