Difference between revisions of "Command line GDB"

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(Created page with '===Start gdb=== Open a program in gdb: $ gdb ./my_proggie Open a program in gdb with a '''core dump''': $ gdb ./my_proggie core Open a program in gdb and attach to PID: $ g…')
 
Line 3: Line 3:
 
Open a program in gdb:
 
Open a program in gdb:
  
 +
<source lang=gdb>
 
$ gdb ./my_proggie
 
$ gdb ./my_proggie
 +
</source>
  
 
Open a program in gdb with a '''core dump''':
 
Open a program in gdb with a '''core dump''':
−
 
+
<source lang=gdb>
 
$ gdb ./my_proggie core
 
$ gdb ./my_proggie core
 +
</source>
  
 
Open a program in gdb and attach to PID:
 
Open a program in gdb and attach to PID:
−
 
+
<source lang=gdb>
 
$ gdb ./my_proggie 15835
 
$ gdb ./my_proggie 15835
 +
</source>
  
 
Open a program in gdb and execute all gdb commands in '''commands.gdb''':
 
Open a program in gdb and execute all gdb commands in '''commands.gdb''':
−
 
+
<source lang=gdb>
 
$ gdb -X commands.gdb ./my_proggie
 
$ gdb -X commands.gdb ./my_proggie
 +
</source>
  
 
gdb commands in ./.gdbinit is usually always executed
 
gdb commands in ./.gdbinit is usually always executed
Line 25: Line 30:
 
Use intel style disassembly:
 
Use intel style disassembly:
  
 +
<source lang=gdb>
 
$ set disassembly-flavor intel
 
$ set disassembly-flavor intel
 +
</source>
  
 
If a program fork wrong follow the child process:
 
If a program fork wrong follow the child process:
−
 
+
<source lang=gdb>
 
$ set follow-fork-mode child
 
$ set follow-fork-mode child
 +
</source>
  
 
Allow auto load of .gdbinit from all paths:
 
Allow auto load of .gdbinit from all paths:
−
 
+
<source lang=gdb>
 
$ set auto-load safe-path /
 
$ set auto-load safe-path /
 +
</source>
  
 
===Execute program===
 
===Execute program===
  
 
Execute the program:
 
Execute the program:
−
 
+
<source lang=gdb>
 
$ r
 
$ r
 +
</source>
  
 
Execute the program with arguments:
 
Execute the program with arguments:
−
 
+
<source lang=gdb>
 
$ r hello world
 
$ r hello world
 +
</source>
  
 
Execute the program with more complex arguments:
 
Execute the program with more complex arguments:
−
 
+
<source lang=gdb>
 
$ r $(python -c "print 'A' * 200 + '\xef\xbe\xad\xde'")
 
$ r $(python -c "print 'A' * 200 + '\xef\xbe\xad\xde'")
 +
</source>
  
 
Execute the program with '''stdin''' from a file:
 
Execute the program with '''stdin''' from a file:
−
 
+
<source lang=gdb>
 
$ r < some_file
 
$ r < some_file
 +
</source>
  
−
Kille the running program:
+
Kill the running program:
−
 
+
<source lang=gdb>
 
$ k
 
$ k
 +
</source>
  
 
Execute a shell command:
 
Execute a shell command:
−
 
+
<source lang=gdb>
 
$ shell cyclic 50
 
$ shell cyclic 50
 +
</source>
  
 
===Read memory===
 
===Read memory===
  
 
Disassemble 10 instructions from a specific address:
 
Disassemble 10 instructions from a specific address:
−
 
+
<source lang=gdb>
 
$ x/10i 0x08048956
 
$ x/10i 0x08048956
 +
</source>
  
 
Disassemble 10 instructions from current line:
 
Disassemble 10 instructions from current line:
−
 
+
<source lang=gdb>
 
$ x/10i $eip
 
$ x/10i $eip
 +
</source>
  
 
Dump a string from a specific address:
 
Dump a string from a specific address:
−
 
+
<source lang=gdb>
 
$ x/s 0x080492d4
 
$ x/s 0x080492d4
 +
</source>
  
 
Dump 10 hex words (4 byte integers) from a specific address:
 
Dump 10 hex words (4 byte integers) from a specific address:
−
 
+
<source lang=gdb>
 
$ x/10xw 0x080492d4
 
$ x/10xw 0x080492d4
 +
</source>
  
 
Dump 10 hex words from the stack:
 
Dump 10 hex words from the stack:
−
 
+
<source lang=gdb>
 
$ x/10xw $esp
 
$ x/10xw $esp
 +
</source>
  
 
Dump 100 hex bytes from a specific address:
 
Dump 100 hex bytes from a specific address:
−
 
+
<source lang=gdb>
 
$ x/100xb 0x080492d4
 
$ x/100xb 0x080492d4
 +
</source>
  
 
Dump 2 hex words relative to register:
 
Dump 2 hex words relative to register:
−
 
+
<source lang=gdb>
 
$ x/2xw $ebp - 0x8
 
$ x/2xw $ebp - 0x8
 +
</source>
  
 
===Read or change register===
 
===Read or change register===
  
 
Read register:
 
Read register:
−
 
+
<source lang=gdb>
 
$ i r eax ebx eip esp
 
$ i r eax ebx eip esp
 +
</source>
  
 
Change content of register:
 
Change content of register:
−
 
+
<source lang=gdb>
 
$ set $eax = 0
 
$ set $eax = 0
 +
</source>
  
 
===Breakpoints===
 
===Breakpoints===
  
 
Set breakpoint on a specific address:
 
Set breakpoint on a specific address:
−
 
+
<source lang=gdb>
 
$ b *0x080485ec
 
$ b *0x080485ec
 +
</source>
  
 
Set conditional breakpoint on a specific address:
 
Set conditional breakpoint on a specific address:
−
 
+
<source lang=gdb>
 
$ b *0x080485ec if $eax == 0
 
$ b *0x080485ec if $eax == 0
 +
</source>
  
 
List breakpoints:
 
List breakpoints:
−
 
+
<source lang=gdb>
 
$ i b
 
$ i b
 +
</source>
  
 
Delete breakpoint number 3:
 
Delete breakpoint number 3:
−
 
+
<source lang=gdb>
 
$ d 3
 
$ d 3
 +
</source>
  
 
Execute gdb commandos when a breakpoint is hit:
 
Execute gdb commandos when a breakpoint is hit:
−
 
+
<source lang=gdb>
 
$ b *0x080487cf
 
$ b *0x080487cf
 
commands
 
commands
Line 126: Line 154:
 
     continue
 
     continue
 
end
 
end
 +
</source>
  
 
Step one instruction:
 
Step one instruction:
−
 
+
<source lang=gdb>
 
$ si
 
$ si
 +
</source>
  
 
Step one instruction without following subroutine call (Step over):
 
Step one instruction without following subroutine call (Step over):
−
 
+
<source lang=gdb>
 
$ ni
 
$ ni
 +
</source>
  
 
Continue execution:
 
Continue execution:
−
 
+
<source lang=gdb>
 
$ c
 
$ c
 +
</source>
  
  

Revision as of 11:58, 25 May 2016

Start gdb

Open a program in gdb: 

$ gdb ./my_proggie

Open a program in gdb with a core dump: 

$ gdb ./my_proggie core

Open a program in gdb and attach to PID: 

$ gdb ./my_proggie 15835

Open a program in gdb and execute all gdb commands in commands.gdb: 

$ gdb -X commands.gdb ./my_proggie

gdb commands in ./.gdbinit is usually always executed

gdb commands i ~/.gdbinit is usually always executed

gdb set up

Use intel style disassembly: 

$ set disassembly-flavor intel

If a program fork wrong follow the child process: 

$ set follow-fork-mode child

Allow auto load of .gdbinit from all paths: 

$ set auto-load safe-path /

Execute program

Execute the program: 

$ r

Execute the program with arguments: 

$ r hello world

Execute the program with more complex arguments: 

$ r $(python -c "print 'A' * 200 + '\xef\xbe\xad\xde'")

Execute the program with stdin from a file: 

$ r < some_file

Kill the running program: 

$ k

Execute a shell command: 

$ shell cyclic 50

Read memory

Disassemble 10 instructions from a specific address: 

$ x/10i 0x08048956

Disassemble 10 instructions from current line: 

$ x/10i $eip

Dump a string from a specific address: 

$ x/s 0x080492d4

Dump 10 hex words (4 byte integers) from a specific address: 

$ x/10xw 0x080492d4

Dump 10 hex words from the stack: 

$ x/10xw $esp

Dump 100 hex bytes from a specific address: 

$ x/100xb 0x080492d4

Dump 2 hex words relative to register: 

$ x/2xw $ebp - 0x8

Read or change register

Read register: 

$ i r eax ebx eip esp

Change content of register: 

$ set $eax = 0

Breakpoints

Set breakpoint on a specific address: 

$ b *0x080485ec

Set conditional breakpoint on a specific address: 

$ b *0x080485ec if $eax == 0

List breakpoints: 

$ i b

Delete breakpoint number 3: 

$ d 3

Execute gdb commandos when a breakpoint is hit: 

$ b *0x080487cf
commands
    set $eax = 0
    continue
end

Step one instruction: 

$ si

Step one instruction without following subroutine call (Step over): 

$ ni

Continue execution: 

$ c


Thanks to

Robert Larsen www.the-playground.dk

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