How to set a breakpoint in an execve'd program in radare2?

Question

If I have a program A, which uses execve to run program B. How can I set a breakpoint in program B's main routine if I'm debugging program A?

After a certain point in the execve routine, program B will be loaded into memory. After that I can see the symbols in the binary and the regions of memory they have been loaded into. However, to get to that point at the moment I just step through some of the execve instructions which is very fiddly and prone to mistakes.

Is there a simpler approach to this?

Answer 1

There's a debugging flag called dbg.execs that setting it to true should stop the execution when an execv is happening. So try this:

> e dbg.execs = true

It looks like it works on Linux, but I couldn't get the same behaviour on OSX.