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Date:   Wed, 20 Apr 2022 16:23:22 -0400
From:   Rich Felker <dalias@libc.org>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Kees Cook <keescook@chromium.org>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
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Subject: Re: [PATCH] binfmt_flat: Remove shared library support
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On Wed, Apr 20, 2022 at 10:04:32PM +0200, Arnd Bergmann wrote:
> On Wed, Apr 20, 2022 at 7:47 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > Yeah, I was trying to understand why systems were using binfmt_flat and
> > not binfmt_elf, given the mention of elf2flat -- is there really such a
> > large kernel memory footprint savings to be had from removing
> > binfmt_elf?
> 
> I think the main reason for using flat binaries is nommu support on
> m68k, xtensa and risc-v. The regular binfmt_elf support requires
> an MMU, and the elf-fdpic variant is only available for arm and sh
> at this point (the other nommu architectures got removed over time).

I believe I made the elf-fdpic loader so that it's capable of loading
normal non-fdpic elf files on nommu (1bde925d23), unless somebody
broke that. I also seem to recall that capability being added to the
main elf loader later.

Rich