From: Eli Zaretskii <eliz@gnu.org>
To: Pip Cet <pipcet@gmail.com>
Cc: 47125@debbugs.gnu.org
Subject: bug#47125: 28.0.50; pdumper assumes compile time page size remains valid
Date: Sun, 14 Mar 2021 07:37:07 +0200 [thread overview]
Message-ID: <83r1kigut8.fsf@gnu.org> (raw)
In-Reply-To: <CAOqdjBfBLDW65iZfnExMOU5suadYzB7THLSaj1_hHz010M3zQA@mail.gmail.com> (message from Pip Cet on Sat, 13 Mar 2021 21:38:16 +0000)
> From: Pip Cet <pipcet@gmail.com>
> Date: Sat, 13 Mar 2021 21:38:16 +0000
>
> I'm running Debian GNU/Linux (the Linux part is not provided by
> Debian) on an Apple M1-based machine. This currently involves running
> a kernel compiled with a 16 KB page size (the only fully functional
> kernel is currently available as a binary as recompilation of the
> alleged source fails to produce a fully working kernel).
>
> The Debian-packaged Emacs version does not start. Compiling from
> scratch works fine.
>
> After some investigation, this is because pdumper assumes that an
> address aligned according to the page size at build time is
> sufficiently aligned for mmap to work with the MAP_FIXED flag, when it
> comes to loading the dump. That's not true because the Debian Emacs
> was apparently built with a 4 KB page size, so it will not run on a
> system with a 16 KB page size.
>
> I've confirmed that I get the same error on current master if I modify
> getpagesize to return 4096 rather than the correct value.
>
> I think it would be best to handle this case gracefully, and I thought
> pdumper already did that, but it appears to simply fail.
>
> There are good reasons for increasing the page size, so this is likely
> to happen more often and on other architectures with varying page
> sizes.
CC'ing Daniel, in case he has comments and/or suggestions.
> We're currently enforcing a page size of 64 KB on Windows
We do? can you point me to the code which does that?
> so maybe it already has.
next prev parent reply other threads:[~2021-03-14 5:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-13 21:38 bug#47125: 28.0.50; pdumper assumes compile time page size remains valid Pip Cet
2021-03-14 5:37 ` Eli Zaretskii [this message]
2021-03-14 5:43 ` Daniel Colascione
2021-03-14 7:34 ` Andreas Schwab
2021-03-14 7:36 ` Daniel Colascione
2021-03-14 8:16 ` Pip Cet
2021-03-28 15:46 ` Lars Ingebrigtsen
2021-03-28 16:16 ` Eli Zaretskii
2021-03-28 17:13 ` Lars Ingebrigtsen
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