Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20200305183939.256241-1-davidgow@google.com> <CAFd5g45XJLXYfXB-FJhFYnBYUdqM4ztC=p=Akj3+GbHXfHxzgQ@mail.gmail.com>
In-Reply-To: <CAFd5g45XJLXYfXB-FJhFYnBYUdqM4ztC=p=Akj3+GbHXfHxzgQ@mail.gmail.com>
From:   Richard Weinberger <richard.weinberger@gmail.com>
Date:   Sun, 29 Mar 2020 23:38:53 +0200
Message-ID: <CAFLxGvw6Sp899NN3CMvC4R9Uz1dSiKw4mdwnKRUvnGg-mr7ttw@mail.gmail.com>
Subject: Re: [PATCH] um: Fix overlapping ELF segments when statically linked
To:     Brendan Higgins <brendanhiggins@google.com>
Cc:     David Gow <davidgow@google.com>,
        Patricia Alfonso <trishalfonso@google.com>,
        Richard Weinberger <richard@nod.at>,
        Jeff Dike <jdike@addtoit.com>,
        linux-um <linux-um@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Mar 10, 2020 at 10:24 PM Brendan Higgins
<brendanhiggins@google.com> wrote:
>
> On Thu, Mar 5, 2020 at 10:39 AM David Gow <davidgow@google.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@google.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@google.com>

Applied, thanks!

-- 
Thanks,
//richard