Difference between revisions of "Gdb"
From Linuxintro
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= Notable functions = | = Notable functions = | ||
info functions | info functions | ||
| + | |||
| + | = Example = | ||
| + | |||
| + | == How to debug vlc == | ||
| + | Here I try to find out where vlc exits because I am root: | ||
| + | gdb /usr/bin/vlc | ||
| + | (gdb) info functions | ||
| + | All defined functions: | ||
| + | |||
| + | Non-debugging symbols: | ||
| + | [...] | ||
| + | 0x0000000000400f40 geteuid | ||
| + | [...] | ||
| + | (gdb) break geteuid | ||
| + | Breakpoint 1 at 0x400f40 | ||
| + | (gdb) run | ||
| + | Starting program: /usr/bin/vlc | ||
| + | |||
| + | Breakpoint 1, 0x00007ffff71cfc70 in geteuid () from /lib64/libc.so.6 | ||
| + | ok, let's trace the program one command at a time: | ||
| + | (gdb) stepi | ||
| + | 0x00007ffff71cfc75 in geteuid () from /lib64/libc.so.6 | ||
| + | (gdb) stepi | ||
| + | 0x00007ffff71cfc77 in geteuid () from /lib64/libc.so.6 | ||
| + | (gdb) | ||
| + | 0x0000000000401103 in ?? () | ||
| + | (gdb) | ||
| + | 0x0000000000401105 in ?? () | ||
| + | (gdb) | ||
| + | 0x000000000040170f in ?? () | ||
| + | [...] | ||
| + | (gdb) break *0x40170e | ||
| + | Breakpoint 3 at 0x40170e | ||
| + | (gdb) continue | ||
| + | |||
= See also = | = See also = | ||
* [[objdump]] -- disassemble a program | * [[objdump]] -- disassemble a program | ||
* [[strace]] -- show syscalls from a running process | * [[strace]] -- show syscalls from a running process | ||
Revision as of 15:07, 26 November 2011
gdb allows you to debug Linux programs.
Notable functions
info functions
Example
How to debug vlc
Here I try to find out where vlc exits because I am root:
gdb /usr/bin/vlc (gdb) info functions All defined functions: Non-debugging symbols: [...] 0x0000000000400f40 geteuid [...] (gdb) break geteuid Breakpoint 1 at 0x400f40 (gdb) run Starting program: /usr/bin/vlc Breakpoint 1, 0x00007ffff71cfc70 in geteuid () from /lib64/libc.so.6
ok, let's trace the program one command at a time:
(gdb) stepi 0x00007ffff71cfc75 in geteuid () from /lib64/libc.so.6 (gdb) stepi 0x00007ffff71cfc77 in geteuid () from /lib64/libc.so.6 (gdb) 0x0000000000401103 in ?? () (gdb) 0x0000000000401105 in ?? () (gdb) 0x000000000040170f in ?? () [...] (gdb) break *0x40170e Breakpoint 3 at 0x40170e (gdb) continue
