linux-kernel - Re: [PATCH] um: Fix overlapping ELF segments when statically linked

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Message-ID: <CAFLxGvw6Sp899NN3CMvC4R9Uz1dSiKw4mdwnKRUvnGg-mr7ttw@mail.gmail.com>
Date:   Sun, 29 Mar 2020 23:38:53 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Brendan Higgins <brendanhiggins@...gle.com>
Cc:     David Gow <davidgow@...gle.com>,
        Patricia Alfonso <trishalfonso@...gle.com>,
        Richard Weinberger <richard@....at>,
        Jeff Dike <jdike@...toit.com>,
        linux-um <linux-um@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>
Subject: Re: [PATCH] um: Fix overlapping ELF segments when statically linked

On Tue, Mar 10, 2020 at 10:24 PM Brendan Higgins
<brendanhiggins@...gle.com> wrote:
>
> On Thu, Mar 5, 2020 at 10:39 AM David Gow <davidgow@...gle.com> wrote:
> >
> > When statically linked, the .text section in UML kernels is not page
> > aligned, causing it to share a page with the executable headers. As
> > .text and the executable headers have different permissions, this causes
> > the kernel to wish to map the same page twice (once as headers with r--
> > permissions, once as .text with r-x permissions), causing a segfault,
> > and a nasty message printed to the host kernel's dmesg:
> >
> > "Uhuuh, elf segment at 0000000060000000 requested but the memory is
> > mapped already"
> >
> > By aligning the .text to a page boundary (as in the dynamically linked
> > version in dyn.lds.S), there is no such overlap, and the kernel runs
> > correctly.
> >
> > Signed-off-by: David Gow <davidgow@...gle.com>
>
> I can confirm that I am seeing this problem as well. (I know we run
> the same Linux distro; nevertheless, this is a real problem for some
> population of users.)
>
> Reviewed-by: Brendan Higgins <brendanhiggins@...gle.com>

Applied, thanks!

-- 
Thanks,
//richard