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Message-ID: <alpine.LNX.2.20.13.1608142302570.11152@monopod.intra.ispras.ru>
Date: Sun, 14 Aug 2016 23:20:21 +0300 (MSK)
From: Alexander Monakov <amonakov@...ras.ru>
To: Rich Felker <dalias@...ifal.cx>
cc: Rob Landley <rob@...dley.net>, musl@...ts.openwall.com
Subject: Re: Re: sysconf(_SC_ARG_MAX) broken in musl.

On Wed, 10 Aug 2016, Rich Felker wrote:
> Has anyone else looked into the issue enough to have a good opinion on
> it, or at least additional information that would add to discussion?

To provide a data point, I've been told that userspace QEmu used to limit the
cumulative args length in a more restrictive way than the kernel (1/4th stack
limit). The observed failure mode was this: xargs running under qemu-user would
build the command line according to what glibc thought would be accepted by the
syscall (based on large stack size), but then the syscall would fail because
qemu-user wouldn't process that many args.

I understand this is not much, since qemu-user is unreliable in other ways, and
this particular issue has been fixed in QEmu regardless, but still I think it
contributes to the general point. Is the concern that 128KB is too low to be
usable? My understanding is that _SC_ARG_MAX is not broken in musl (contrary to
what the subject says), just conservative (in a healthy way in this case imho).

Alexander

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