I've tried to set breakpoint on every function that makes any sense but program exit before reaching any of those. Is there a way to make program run in step-by-step mode from the start so I can see what's going on?
I'm trying to debug /usr/bin/id if it's important (we have custom plugin for it and it's misbehaved)
P.S. Start command doesn't work for me here(it should be a comment, but I don't have enough rep for it)
Get the program entry point address and insert a breakpoint at that address.
One way to do this is to do info files which gives you for example "Entry point: 0x4045a4". Then do "break *0x4045a4". After run-ning program, it will immediately stop.
From here on you can use single stepping instructions (like step or stepi) to proceed.
You did not tell what system you are trying to debug. If code is in read-only memory you may need to use hardware breakpoints (hbreak) if they are supported by that system.
Use start command
The ‘start’ command does the equivalent of setting a temporary breakpoint at the beginning of the main procedure and then invoking the ‘run’ command.
e.g.
a program with debug info main, and usage like this: main arg1 arg2
gdb main
(gdb) start arg1 arg2
You can type record full right after running the program. This will record all instructions and make them possible for replaying/going back.
For main function, you'd need to type this before reaching the breakpoint so you can set an earlier one by break _start -> _start is a function always called before the standard main function. (apparently applies only to the gcc compiler or similar)
Then continue to main breakpoint and do reverse-stepi to go exactly one instruction back
For more info about recording look here: link
