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From: Florian Weimer <fweimer@redhat.com>
To: Markus Wichmann <nullplan@gmx.net>
Cc: musl@lists.openwall.com
Subject: Re: [musl] insufficient checking in posix_spawn_file_actions_add{open,dup2}
Date: Mon, 25 Jan 2021 20:48:18 +0100	[thread overview]
Message-ID: <87tur4g5ml.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <20210125193758.GC2006@voyager> (Markus Wichmann's message of "Mon, 25 Jan 2021 20:37:58 +0100")

* Markus Wichmann:

> Adding a getpid vDSO call would require adding the code itself, adding
> the PID to the vvar page (isn't that shared among all processes?), and
> adding support for finding the vDSO function into the libcs. All of that
> for rather dubious performance benefits (or can you name a program that
> was not fast enough because getpid() ran too slowly?)

There's some discussion about this in the context of extensible rseq
support, including userspace donating thread-local data for kernel use
(“KTLS”).  Reliable PID/TID/UID caching in userspace and sigprocmask
with a userspace fastpath are potential applications.

Thanks,
Florian
-- 
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Commercial register: Amtsgericht Muenchen, HRB 153243,
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      reply	other threads:[~2021-01-25 19:48 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-25  8:31 Bruno Haible
2021-01-25  8:40 ` [musl] insufficient checking in posix_spawn_file_actions_addclose Bruno Haible
2021-01-25 14:42 ` [musl] insufficient checking in posix_spawn_file_actions_add{open,dup2} Rich Felker
2021-01-25 16:07   ` Bruno Haible
2021-01-25 16:15     ` Rich Felker
2021-01-25 17:58       ` Bruno Haible
2021-01-25 19:33       ` Alexey Izbyshev
2021-01-25 19:37       ` Markus Wichmann
2021-01-25 19:48         ` Florian Weimer [this message]

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