linux-kernel - Re: powerpc: Keep const vars out of writable .sdata

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Date:   Wed,  7 Mar 2018 00:31:17 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: powerpc: Keep const vars out of writable .sdata

On Thu, 2018-03-01 at 01:02:49 UTC, Kees Cook wrote:
> From: Segher Boessenkool <segher@...nel.crashing.org>
> 
> Newer gcc will support "-mno-readonly-in-sdata"[1], which makes sure that
> the optimization on PPC32 for variables getting moved into the .sdata
> section will not apply to const variables (which must be in .rodata).
> 
> This was originally noticed in mm/rodata_test.c when rodata_test_data
> was not static:
> 
> c0695034 g     O .data	00000004 rodata_test_data
> 
> After this patch with an updated compiler, this is correctly in .rodata.
> 
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82411
> 
> Reported-by: Christophe Leroy <christophe.leroy@....fr>
> Signed-off-by: Segher Boessenkool <segher@...nel.crashing.org>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/51d42f0f5fd6c74144d19bf6a66352

cheers