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

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

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