Re: [PATCH 05/24] Introduce locking functions for block device setup on NetBSD

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

On Wed, Jan 20, 2021 at 04:12:29PM +0000, Ian Jackson wrote:
> Manuel Bouyer writes ("Re: [PATCH 05/24] Introduce locking functions for 
> block device setup on NetBSD"):
> > Yes, at last the stat call will need to be patched.
> > But it seems to rely on a linux-specific behavoir, which is that
> > /dev/stdin points to the real file on redirection:
> > >ls -l /dev/stdin /proc/self/fd/0 < /etc/passwd
> > lrwxrwxrwx 1 root   root      15 Apr 30  2019 /dev/stdin -> /proc/self/fd/0
> > lr-x------ 1 bouyer ita-iatos 64 Jan 20 16:54 /proc/self/fd/0 -> /etc/passwd
> > 
> > On NetBSD (and I guess other BSDs) this won't work, as /dev/stdin is a
> > specific device:
> > >ls -l /dev/stdin 
> > crw-rw-rw-  1 root  wheel  22, 0 Nov 15  2007 /dev/stdin
> > 
> > so stat -L will always return the same data. We can't use the same
> > protocol.
> 
> Ah.
> 
> The manpage I am looking at says:
> 
>      If no argument is given, stat displays information about the
>      file descriptor for standard input.
> 
> Here NetBSD has a better command line API than Linux - Linux requires
> pratting about with /dev/stdin and NetBSD doesn't.  So I think
> where on Linux we have
>    stat .... /dev/stdin
> on NetBsd we can simply have
>    stat ....
> with no filename argument.

Right, thanks. Then it would need to be done with 2 different calls
but I don't think that's a problem (even with the linux version it would
not be atomic anyway).

> 
> I think NetBSD's stat(1) also takes different argumnts to specify the
> format.  NetBSD uses -f, whereas Linux uses -c.  So the exact rune
> will have to be different.

Yes, and NetBSD doens't have %D (only %d)

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--