GDB Rocks!
57 likes•13,523 views
This document discusses using the GNU Debugger (GDB) to debug programs. It begins with an introduction to GDB and why it is useful. Examples are then provided of using GDB for interactive debugging, examining core dumps, patching binaries, and advanced tricks. A real-world case study demonstrates using GDB to debug a crash in the GNU C library by examining assembly code and source-level debugging with debug symbols. The document concludes by mentioning another case study involving hijacking file descriptors in GDB.
![Signal Handler
Terminal hang / Reboot PC
You have to close terminal (e.g., PuTTY, iTerm,...)
Conventional solution
(gdb) handle SIGHUP
GNU Screen / Tmux Signal Stop Print Pass to program Description
SIGHUP Yes Yes Yes Hangup
(gdb) handle SIGHUP nopass
Signal Stop Print Pass to program Description
nohup SIGHUP Yes Yes No Hangup
Program received signal SIGHUP, Hangup.
GDB solution 0x0000003ac7a954e0 in __nanosleep_nocancel () from /lib64/libc.so.6
(gdb)
Continuing.
$ gdb [program] [pid]
(gdb) handle SIGHUP nopass
(gdb) continue](https://image.slidesharecdn.com/gdbrocks-130305104330-phpapp01/85/GDB-Rocks-35-320.jpg)
![frame [index] / up / down](https://image.slidesharecdn.com/gdbrocks-130305104330-phpapp01/85/GDB-Rocks-55-320.jpg)
![Reference
快快樂樂學 GNU Debugger (gdb) Part I + II (Jserv)
http://jserv.sayya.org/debugger/
http://pyclewn.sourceforge.net/
http://clewn.sourceforge.net/
http://reverse.put.as/
GDB的妙用 (vgod)
[GDB Tricks] File Descriptor Hijacking / 劫持 FDs 之奇技淫巧](https://image.slidesharecdn.com/gdbrocks-130305104330-phpapp01/85/GDB-Rocks-91-320.jpg)
GDB Rocks!
- 1. GDB Rocks! GDB The GNU Project Kent Chen Debugger
- 2. Kent Chen (chenkaie) [email protected] http://chenkaie.blogspot.com @chenkaie on GitHub @chenkaie on SlideShare @chenkaie on LinkedIn @chenkaie on Twitter
- 3. 為什麼要學 GDB Why everybody learns GDB?
- 4. 非互動式/交談式 Non-Interactive Debugging
- 5. strace - system call, signal ltrace - library call
- 6. printf / printk “打印”久了 也挺煩人的 Debugging by Endless Printing
- 9. 有了Debugger Coding是彩色的 - by Jserv/宅色夫大大 No Debugger, No Happy Coding
- 10. 學會了GDB 我有種山頂洞人 學會用火的感動 - by 張至 張至是誰?! 我也不認識， Google到的，某某鄉民吧!
- 11. GDB Front Ends
- 12. gdbtui
- 13. cgdb
- 14. ddd (Joe’s Fav)
- 15. insight
- 16. clewn / vim + gdb
- 17. pyclewn
- 18. gdbmgr
- 19. 分享小弟 入門經驗 Sharing my real-world GDB experience
- 21. Change memory contents on-the-fly
- 22. Change memory contents on-the-fly
- 23. stack backtrace
- 24. Attach to a process
- 25. Jump $pc (program counter)
- 26. core dump
- 29. Patch binary file
- 30. Patch binary file (cont.) $objdump -d -S -l -shrt dump1.out Change “ef01” to “ef00”
- 32. 奇技淫巧: 奇異而眩人耳目の 技能或事物 (from 教育部國語辭典)
- 33. SIGSEGV + GDB
- 34. C interpreter 1. $ gdb `which gdb` 2. (gdb) start 3. Enjoy your world… • Example: (gdb) p 1 + 2 + abs(-‐3) (gdb) p strcmp("VIVOTEK", "AXIS") (gdb) x/s getenv(“HOME”) (gdb) p (char*)getenv("HOME") (gdb) p (char)*getenv("HOME") (gdb) p printf("%dn", 12345678)
- 35. Signal Handler Terminal hang / Reboot PC You have to close terminal (e.g., PuTTY, iTerm,...) Conventional solution (gdb) handle SIGHUP GNU Screen / Tmux Signal Stop Print Pass to program Description SIGHUP Yes Yes Yes Hangup (gdb) handle SIGHUP nopass Signal Stop Print Pass to program Description nohup SIGHUP Yes Yes No Hangup Program received signal SIGHUP, Hangup. GDB solution 0x0000003ac7a954e0 in __nanosleep_nocancel () from /lib64/libc.so.6 (gdb) Continuing. $ gdb [program] [pid] (gdb) handle SIGHUP nopass (gdb) continue
- 36. 經典案例 實戰探討 A real-world case study
- 37. 案例一、 Case 1
- 38. GNU C Library (glibc) debugging / 除錯
- 39. Why?
- 40. 追求 卓越 Pursuit of excellence :)
- 41. DieLink 呆吝蚵
- 43. 某某 Daemon 之死 Process crash issue
- 44. dmesg
- 47. WTF!! 不會吧(驚)
- 49. 無敵の gdb core dump
- 50. backtrace (bt)
- 51. _IO_strn_overflow () vfprintf () C language !?
- 52. WTF!! 不會吧(驚驚)
- 53. 欲窮千里目 更上一層樓
- 55. frame [index] / up / down
- 58. C Code & ARM assembly
- 59. 看似 專業 Pro Looks “GEEK”
- 60. In fact 實際上
- 61. 發現 gcc -O3 TMD 實在太難看了 It’s god damn hard to read after gcc -O3
- 64. May The Source Be With You
- 65. How?
- 66. RTFM Read The Fucking Manual
- 67. load by symbol-file cmd
- 68. Re-build debug version shared library with "-g"
- 70. Source be with You
- 72. OMFG!
- 74. 到了 /lib/libc.so.6 -> libc-2.5.90.so
- 75. Shit! 若仿照 上面作法
- 77. Oh No !
- 78. 使用大廠の 偷偷Solution
- 79. 你有權利 Say NO
- 82. glibc source level debug
- 83. DEMO
- 84. Null pointer access issue
- 85. 多虧了 神器 GDB
- 86. 我們終於學會 Shared Library Debugging
- 88. 案例二、 Case 2
- 89. 劫持 FDs File Descriptors Hijacking
- 90. 時間有限 下回揭曉 File Descriptor Hijacking / 劫持 FDs 之奇技淫巧
- 91. Reference 快快樂樂學 GNU Debugger (gdb) Part I + II (Jserv) http://jserv.sayya.org/debugger/ http://pyclewn.sourceforge.net/ http://clewn.sourceforge.net/ http://reverse.put.as/ GDB的妙用 (vgod) [GDB Tricks] File Descriptor Hijacking / 劫持 FDs 之奇技淫巧