On Sun, May 09, 2010 at 08:33:03AM +0300, Ali Polatel wrote: > Kostik Belousov yazm??: > > On Sat, May 08, 2010 at 02:15:09PM +0300, Ali Polatel wrote: > > > Does FreeBSD's ptrace have a way to tell the difference between normal > > > traps and those caused by a system call? > > > > > > On Linux? this is possible by passing PTRACE_O_TRACESYSGOOD option to the > > > ptrace request PTRACE_SETOPTIONS which makes the kernel set bit 7 in the > > > syscall number when delivering system call traps, > > > (i.e., deliver (SIGTRAP | 0x80)). > > > > > > I'm not sure if this is possible on FreeBSD. PT_LWPINFO request looks > > > related but can't be sure. > > > > > > ?: http://linux.die.net/man/2/ptrace > > > > There is already procfs(5)-based interface to get a reason for stop. > > Look at the ioctl PIOCSTATUS. Yes, you have to mount procfs. > > > > The interface can be lifted to ptrace(2), but I think using the capacity > > of procfs is not wrong there. > > Hmm ok, I've been playing around with PIOCSTATUS but it doesn't seem to > work, there's not much documentation about it either so I figured I'll > just ask. > > The code is here: http://alip.github.com/code/piocstatus.c > > The traced child is stopped at the beginning of a system call. I await > that the PIOCSTATUS request sets ps.why to S_SCE but it's always zero. > Can you help me figure out what I'm doing wrong? :)
Apparently I missed the fact that S_PT_SCE and S_SCE are different flags. It seems you have to use procfs stop events (PIOCBIS) and procfs-based loop to get p_step set to 1.
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