Re: kern/43611: kernel-trace (via ktruss) reports wrong parameter/result values

[christos%zoulas.com@localhost (Christos Zoulas)]

The following reply was made to PR kern/43611; it has been noted by GNATS.

From: christos%zoulas.com@localhost (Christos Zoulas)
To: gnats-bugs%NetBSD.org@localhost, kern-bug-people%netbsd.org@localhost, 
        gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost, 
        Wolfgang.Stukenbrock%nagler-company.com@localhost
Cc: 
Subject: Re: kern/43611: kernel-trace (via ktruss) reports wrong 
parameter/result values
Date: Wed, 14 Jul 2010 08:36:07 -0400

 On Jul 14,  1:50am, dholland-bugs%netbsd.org@localhost (David Holland) wrote:
 -- Subject: Re: kern/43611: kernel-trace (via ktruss) reports wrong parameter
 
 |  On Tue, Jul 13, 2010 at 05:40:04PM +0000, David Laight 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.
 
 |  (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.
 
 christos