[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]
Re: kern/43611: kernel-trace (via ktruss) reports wrong parameter/result values
The following reply was made to PR kern/43611; it has been noted by GNATS.
From: David Holland <dholland-bugs%netbsd.org@localhost>
Subject: Re: kern/43611: kernel-trace (via ktruss) reports wrong
Date: Thu, 15 Jul 2010 20:13:45 +0000
On Wed, Jul 14, 2010 at 12:40:03PM +0000, Christos Zoulas wrote:
>|> ktruss probably should be rewritten to use system call entry/exit
>|> breakpoints and then userspace controlled reads of the traced programs
>|> memory (which is how truss works on SYSV).
>| Using ptrace for this purpose is not desirable because it monkeys with
>| the parent/child process relationships and tends to break things,
>| particularly shell scripts.
> It is desirable because it stops the process and lets you examine the
> syscall arguments in detail.
Mm, point. Maybe we ought to invent a new kind of tracing for this
purpose (since supervised execution was trendy in research for a while
and it's getting to the point of moving to production...)
I'm not sure if it makes sense for that to be different from a
debugger interface or not.
> | (I'm not particularly clear on exactly what ktruss does that's
> | different from running kdump afterwards, but then I've never been
> | particularly clear on why ktruss is desirable relative to running
> | kdump afterwards, either.)
> Interactivity; you can watch processes that stop and wait for events
> and see what they do as you supply the different events.
Ah. Yeah, I guess that can be useful. The main problem I've always had
with strace and truss and whatnot is that the trace output gets mixed
with the program's output; when I first found ktrace years ago it was
a big step forward.
David A. Holland
Main Index |
Thread Index |