linux-kernel - Re: [PATCH] ARM: fix __start_rodata_section

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Date:	Tue, 16 Feb 2016 20:20:50 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Chris Brandt <Chris.Brandt@...esas.com>,
	Will Deacon <will.deacon@....com>,
	Nicolas Pitre <nico@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: fix __start_rodata_section_aligned on XIP

Hi Kees,

On Tue, Feb 16, 2016 at 7:38 PM, Kees Cook <keescook@...omium.org> wrote:
> This fixes the build for both allnoconfig (!CONFIG_MMU) and with
> XIP_KERNEL (due to missing pieces in the linker script), as seen after
> both "ARM: 8502/1: mm: mark section-aligned portion of rodata NX" and
> "ARM: 8513/1: xip: Move XIP linking to a separate file".
>
> Reported-by: Russell King <linux@....linux.org.uk>
> Reported-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Kees Cook <keescook@...omium.org>

> diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
> index 40bc4cadb959..2da60cd1b295 100644
> --- a/arch/arm/kernel/vmlinux-xip.lds.S
> +++ b/arch/arm/kernel/vmlinux-xip.lds.S

> @@ -310,6 +311,17 @@ SECTIONS
>  }
>
>  /*
> + * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
> + * be the first section-aligned location after __start_rodata. Otherwise,
> + * it will be equal to __start_rodata.
> + */
> +#ifdef CONFIG_MMU

CONFIG_DEBUG_ALIGN_RODATA or CONFIG_MMU?

> +__start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
> +#else
> +__start_rodata_section_aligned = __start_rodata;
> +#endif
> +
> +/*
>   * These must never be empty
>   * If you have to comment these two assert statements out, your
>   * binutils is too old (for other reasons as well)
> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
> index 1707b9431761..f13960e44955 100644
> --- a/arch/arm/kernel/vmlinux.lds.S
> +++ b/arch/arm/kernel/vmlinux.lds.S
> @@ -328,7 +328,11 @@ SECTIONS
>   * be the first section-aligned location after __start_rodata. Otherwise,
>   * it will be equal to __start_rodata.
>   */
> +#ifdef CONFIG_MMU

Likewise (the out-of-scope comment says CONFIG_DEBUG_ALIGN_RODATA)?

>  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
> +#else
> +__start_rodata_section_aligned = __start_rodata;
> +#endif

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds