I have compiled my freebsd libc source with -g option, so that now I can step in into libc functions. 

But I am having trouble stepping into system calls code. I have compiled the freebsd kernel source code with -g. On setting the breakpoint, gdb informs about breakpoint on .S files. On hitting the breakpoint, gdb is unable to step into the syscall source code. 

Also, I have tried: gdb$catch syscall open 

but this is also not working. 

Can you please suggest something?

Thanks.