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-rw-r--r-- | docs/re/gdb.txt | 101 |
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diff --git a/docs/re/gdb.txt b/docs/re/gdb.txt new file mode 100644 index 0000000..5772815 --- /dev/null +++ b/docs/re/gdb.txt @@ -0,0 +1,101 @@ +GNU Debugger (gdb) Basic Cheat Sheet +==================================== + +If possible, compile program with '-ggdb' to enable GDB-specific debugging +symbols. + + +Getting started +--------------- +Launch GDB: + > gdb <executable> # note: any arguments to the exe are supplied separately + > gdb -p <process id> # attach to an already running process (requires root) + + (gdb) run <argument0> <argument1> ... # Start running program + +Quit GDB: + (gdb) quit + (gdb) q + + +Breakpoints +----------- +Set a breakpoint: + (gdb) break <function> + (gdb) break <function><+offset> + (gdb) break <address> + (gdb) b <arg> + +List breakpoints: + (gdb) info break + (gdb) i b + +Remove breakpoint: + (gdb) delete <id> + (gdb) d <id> + (gdb) d # deletes all breakpoints + + +Debugging +--------- +Inspect registers: + (gdb) info registers + (gdb) i r + +Get call stack / backtrace: + (gdb) backtrace + (gdb) bt + +Single-step program: + (gdb) display/i $pc # If debugging symbols missing, set prompt to display + current instruction disassembly + (gdb) n # next source code statement + (gdb) s # step source code statement (will follow calls) + (gdb) ni # next machine instruction + (gdb) si # step machine instruction (will follow calls) + + (gdb) continue # resume execution (until next breakpoint) + (gdb) c + + (gdb) finish # resume execution (until ret - step out of function) + (gdb) fin + +Disassemble program: + (gdb) disassemble <function> + (gdb) disassemble <address> + (gdb) disas <arg> + + +Memory +------ +Examine memory: + (gdb) x/nfu <address> # List contents of memory starting at <address> + and interpret data according to n, f, u + + 'n' is a repeat count: Specifies how many values to display + 'f' is the display format: one of + x, d, u, o, t, a, c, f, s, i, m + 'u' is the unit size: one of + b, h, w, g + + Example: + (gdb) x/32xg $sp # Display the first 32 64-bit 'giant' words on the + stack + +Alter memory: + (gdb) set {type}<address> = <value> + + Example: + (gdb) set {int}0x7fffffdead = 69 # Write the value 69 to given address + as a 32-bit integer + + +Process forks +------------- + (gdb) set follow-fork-mode <parent|child> # Define debugging behavior on + fork() + (gdb) set detach-on-fork <on|off> # If set to 'off' gdb will keep a debugger + on both processes - Default is on + + (gdb) show follow-fork-mode # Check config + (gdb) show detach-on-fork # Check config |