Subject: [PATCH] arm64: page-align sections for DEBUG_RODATA

From: [email-masked] (Mark Rutland)
Date: Tue, 27 Oct 2015 10:56:33 +0000

On Tue, Oct 27, 2015 at 11:37:04AM +0900, Ard Biesheuvel wrote:
> On 27 October 2015 at 06:42, Mark Rutland <[email-masked]> wrote:
> > A kernel built with DEBUG_RO_DATA && !CONFIG_DEBUG_ALIGN_RODATA doesn't
> > have .text aligned to a page boundary, though fixup_executable works at
> > page-granularity thanks to its use of create_mapping. If .text is not
> > page-aligned, the first page it exists in may be marked non-executable,
> > leading to failures when an attempt is made to execute code in said
> > page.
> >
> > This patch upgrades ALIGN_DEBUG_RO and ALIGN_DEBUG_RO_MIN to force page
> > alignment for DEBUG_RO_DATA && !CONFIG_DEBUG_ALIGN_RODATA kernels,
> > ensuring that all sections with specific RWX permission requirements are
> > mapped with the correct permissions.
> >
> > Signed-off-by: Mark Rutland <[email-masked]>
> > Reported-by: Jeremy Linton <[email-masked]>
> > Reviewed-by: Laura Abbott <[email-masked]>
> > Cc: Ard Biesheuvel <[email-masked]>
> > Cc: Catalin Marinas <[email-masked]>
> > Cc: Suzuki Poulose <[email-masked]>
> > Cc: Will Deacon <[email-masked]>
> > ---
> >  arch/arm64/kernel/vmlinux.lds.S | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > Note: this is intended to supercede [1,2].
> >
> > [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/380486.html
> > [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/380999.html
> >
> > diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> > index 9807333..4d77757 100644
> > --- a/arch/arm64/kernel/vmlinux.lds.S
> > +++ b/arch/arm64/kernel/vmlinux.lds.S
> > @@ -60,9 +60,12 @@ PECOFF_FILE_ALIGNMENT = 0x200;
> >  #define PECOFF_EDATA_PADDING
> >  #endif
> >
> > -#ifdef CONFIG_DEBUG_ALIGN_RODATA
> > +#if defined(CONFIG_DEBUG_ALIGN_RODATA)
> >  #define ALIGN_DEBUG_RO                 . = ALIGN(1<<SECTION_SHIFT);
> >  #define ALIGN_DEBUG_RO_MIN(min)                ALIGN_DEBUG_RO
> > +#elif defined(CONFIG_DEBUG_RODATA)
> > +#define ALIGN_DEBUG_RO                 . = ALIGN(1<<PAGE_SHIFT);
> > +#define ALIGN_DEBUG_RO_MIN(min)                ALIGN_DEBUG_RO
> >  #else
> >  #define ALIGN_DEBUG_RO
> >  #define ALIGN_DEBUG_RO_MIN(min)                . = ALIGN(min);
> 
> Acked-by: Ard Biesheuvel <[email-masked]>

Cheers, Ard.

Jeremy, does this work for you?

If so, I expect Catalin will take this for 4.4, with the addition of any
Acks and:

Fixes: da141706aea52c1a ("arm64: add better page protections to arm64")
Cc: <[email-masked]>

Thanks,
Mark.