linux-kernel - Re: [PATCH] mm: fix RODATA_TEST failure "rodata

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Message-ID: <20170925194130.GV8421@gate.crashing.org>
Date:   Mon, 25 Sep 2017 14:41:31 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Kees Cook <keescook@...omium.org>, Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jinbum Park <jinb.park7@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] mm: fix RODATA_TEST failure "rodata_test: test data was not read only"

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).


Segher