public inbox for libc-alpha@sourceware.org
 help / color / mirror / Atom feed
From: Florian Weimer <fweimer@redhat.com>
To: Zack Weinberg via Libc-alpha <libc-alpha@sourceware.org>
Cc: Zack Weinberg <zack@owlfolio.org>
Subject: Re: RFC PATCH: Don't use /proc/self/maps to calculate size of initial thread stack
Date: Fri, 23 Sep 2022 20:57:35 +0200	[thread overview]
Message-ID: <87y1u9apgg.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <3fb8e41b-8717-4663-9a09-8259211d5d69@www.fastmail.com> (Zack Weinberg via Libc-alpha's message of "Fri, 23 Sep 2022 10:59:29 -0400")

* Zack Weinberg via Libc-alpha:

> On Wed, Sep 21, 2022, at 4:58 PM, Adhemerval Zanella Netto via Libc-alpha wrote:
>> I wonder if we could use inplace mremap (which should be a nop) to inform
>> a more approximate value for the stack (the code only handles grown down
>> architecture):
>
> mremap is unusual enough that I think we'd have the same problem with
> seccomp filters that Florian pointed out regarding process_vm_readv.

glibc uses mremap for realloc in some cases.  And the system call does
not directly permit mapping memory of a separate process.
(process_vm_readv is one of the system calls that looks like it would be
deliberately blocked, not just accidentally.)

But I'd worry about consistent mremap semantics for this particular use
case here.

Thanks,
Florian


      parent reply	other threads:[~2022-09-23 18:57 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-09 21:03 Zack Weinberg
2022-09-13  9:52 ` Florian Weimer
2022-09-13 22:03   ` Michael Hudson-Doyle
2022-09-15 16:09   ` Zack Weinberg
2022-09-20 12:16     ` Florian Weimer
2022-09-21 12:41       ` Zack Weinberg
2022-09-21 13:01         ` Florian Weimer
2022-09-21 20:58     ` Adhemerval Zanella Netto
2022-09-23 14:59       ` Zack Weinberg
2022-09-23 15:24         ` Adhemerval Zanella Netto
2022-09-23 18:57         ` Florian Weimer [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87y1u9apgg.fsf@oldenburg.str.redhat.com \
    --to=fweimer@redhat.com \
    --cc=libc-alpha@sourceware.org \
    --cc=zack@owlfolio.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).