bug#49495: 27.2; portable dumper incompatible with 64K pages on aarch64

[Eli Zaretskii <eliz@gnu.org>]

> From: Dan Čermák <dan.cermak@cgc-instruments.com>
> Date: Fri, 09 Jul 2021 18:38:10 +0200
> 
> I am forwarding a bugreport from Fedora, about the portable dumper
> causing issues when launching Emacs in a RHEL 8 chroot on aarch64:
> (from https://bugzilla.redhat.com/show_bug.cgi?id=1974244)
> 
> --8<---------------cut here---------------start------------->8---
> The emacs binary from emacs-nox-27.2-2.fc33.aarch64 cannot start in a chroot on Red Hat Enterprise Linux 8 because it assumes 4K pages:
> 
> openat(AT_FDCWD, "/usr/bin/emacs-27.2-nox.pdmp", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=10124128, ...}) = 0
> read(3, "DUMPEDGNUEMACS\0\0(\304wp;D\330G%\f\265\337\214\264VO"..., 80) = 80
> mmap(NULL, 10124128, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xffff92240000
> mmap(0xffff92240000, 6946816, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0xffff92240000
> mmap(0xffff928e0000, 90112, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x6a0000) = 0xffff928e0000
> mmap(0xffff928f6000, 3087200, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x6b6000) = -1 EINVAL (Invalid argument)
> 
> Map offsets and addresses must be a multiple of the page size.
> --8<---------------cut here---------------end--------------->8---
> 
> 
> Unfortunately, I am not really familiar with Emacs' internals to know
> how to handle this bug report.

Thanks.  Can you try the latest master branch and see if this problem
still happens there?

Daniel, could you please look into this?