From: Kees Cook <keescook@chromium.org>
To: Segher Boessenkool <segher@kernel.crashing.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: David Laight <David.Laight@aculab.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Jinbum Park <jinb.park7@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] mm: fix RODATA_TEST failure "rodata_test: test data was not read only"
Date: Mon, 2 Oct 2017 12:29:45 -0700 [thread overview]
Message-ID: <CAGXu5j+bj1NHmrrEmcwPavKubavLh1b01AyyJEFRvycg9FkLpg@mail.gmail.com> (raw)
In-Reply-To: <20170925194130.GV8421@gate.crashing.org>
On Mon, Sep 25, 2017 at 12:41 PM, Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> On Mon, Sep 25, 2017 at 04:01:55PM +0000, David Laight wrote:
>> From: Segher Boessenkool
>> > The compiler puts this item in .sdata, for 32-bit. There is no .srodata,
>> > so if it wants to use a small data section, it must use .sdata .
>> >
>> > Non-external, non-referenced symbols are not put in .sdata, that is the
>> > difference you see with the "static".
>> >
>> > I don't think there is a bug here. If you think there is, please open
>> > a GCC bug.
>>
>> The .sxxx sections are for 'small' data that can be accessed (typically)
>> using small offsets from a global register.
>> This means that all sections must be adjacent in the image.
>> So you can't really have readonly small data.
>>
>> My guess is that the linker script is putting .srodata in with .sdata.
>
> .srodata does not *exist* (in the ABI).
So, I still think this is a bug. The variable is marked const: this is
not a _suggestion_. :) If the compiler produces output where the
variable is writable, that's a bug.
I can't tell if this bug is related:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=9571
-Kees
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2017-10-02 19:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-21 9:37 [PATCH] mm: fix RODATA_TEST failure "rodata_test: test data was not read only" Christophe Leroy
2017-09-24 19:17 ` Kees Cook
2017-09-25 7:37 ` Segher Boessenkool
2017-09-25 16:01 ` David Laight
2017-09-25 19:41 ` Segher Boessenkool
2017-10-02 19:29 ` Kees Cook [this message]
2017-10-02 20:08 ` Segher Boessenkool
2017-10-02 20:27 ` Kees Cook
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