Date: Mon, 18 Feb 2008 15:13:35 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Giorgos Keramidas <keramida@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, Dag-Erling Smorgrav <des@des.no>, freebsd-current@freebsd.org Subject: Re: [src] cvs commit: src/include unistd.h src/lib/libc/sys readlink.2 src/sys/compat/freebsd32 syscalls.master src/sys/kern syscalls.master vfs_syscalls.c src/sys/sys syscallsubr.h Message-ID: <200802181513.42681.doconnor@gsoft.com.au> In-Reply-To: <20080218040625.GA8141@kobe.laptop> References: <200802122009.m1CK94Y8026959@repoman.freebsd.org> <200802181004.21379.doconnor@gsoft.com.au> <20080218040625.GA8141@kobe.laptop>
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--nextPart1353809.8pjBojVj5D Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On Mon, 18 Feb 2008, Giorgos Keramidas wrote: > >>> However, you still keep the file around which can be rather space > >>> consuming :( > >> > >> Yes, but it also means you can do offline analysis later. :) > >> Tradeoffs either way. > > > > Yes, but being able to specify stdout to ktrace would be really, > > really nice.. > > Specifying stdout may be a bit tricky, since the traced application > may be using the same stream to print output. The same is possible > with stderr, but may be a tiny bit less likely. I didn't realise that the file descriptor used to write tracing data out=20 was 'owned' by the process being traced, I always thought ktrace did. > It is probably easy to add an -F flag to ktrace/kdump which would > inhibit the check for a `regular' file, so you could then write: > > ( ktrace -aF -f /dev/stdout ls ) | \ > kdump -F -f /dev/stdin > > ( ktrace -aF -f /dev/stderr ls >/dev/null ) 2>&1 | \ > kdump -F -f /dev/stdin > > But the first will probably fail when kdump tries to parse the output > of ls(1), and the second may fail in a similar manner when kdump > tries to parse an error message like a ktrace record. > > This sort of difficulty in separating the output of the traced > process and the ktrace records themselves is probably at least part > of the reason why nobody has done it yet. I did have a look at the source and the file opening etc is handled by=20 the kernel but I am not sure who 'owns' that file descriptor. If, as you suggest, it is the process being traced then yes it would=20 cause problems. I guess it couldn't be moved to ktrace without rearchitecting how=20 ktracing works so the ktrace process sticks around writing stuff out to=20 disk. =2D-=20 Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C --nextPart1353809.8pjBojVj5D Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQBHuQz+5ZPcIHs/zowRAraHAKCakJJ2Feljucdt/t+LkfmewUt0XwCgib2i LiJ6naAWz9a3Zzue5zR6bUc= =avaK -----END PGP SIGNATURE----- --nextPart1353809.8pjBojVj5D--
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