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Date: Mon, 4 Sep 2017 14:30:13 -0400 (EDT)
From: Nicolas Pitre <nicolas.pitre@...aro.org>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
cc: linux-arm-kernel@...ts.infradead.org, kernel-hardening@...ts.openwall.com,
Arnd Bergmann <arnd@...db.de>, Russell King <linux@...linux.org.uk>,
Kees Cook <keescook@...omium.org>, Thomas Garnier <thgarnie@...gle.com>,
Marc Zyngier <marc.zyngier@....com>, Mark Rutland <mark.rutland@....com>,
Tony Lindgren <tony@...mide.com>, Matt Fleming <matt@...eblueprint.co.uk>,
Dave Martin <dave.martin@....com>
Subject: Re: [PATCH v2 23/29] ARM: kernel: refer to swapper_pg_dir via its
symbol
On Sun, 3 Sep 2017, Ard Biesheuvel wrote:
> The location of swapper_pg_dir is relative to the kernel, not to
> PAGE_OFFSET or PHYS_OFFSET. So define the symbol relative to the
> start of the kernel image, and refer to it via its name.
Could it cause a section access mismatch if defined in the __HEAD
section?
Otherwise
Acked-by: Nicolas Pitre <nico@...aro.org>
>
> Cc: Russell King <linux@...linux.org.uk>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
> arch/arm/kernel/head.S | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
> index 5d685e86148c..71bc0d037bc9 100644
> --- a/arch/arm/kernel/head.S
> +++ b/arch/arm/kernel/head.S
> @@ -48,14 +48,6 @@
> #define PMD_ORDER 2
> #endif
>
> - .globl swapper_pg_dir
> - .equ swapper_pg_dir, KERNEL_RAM_VADDR - PG_DIR_SIZE
> -
> - .macro pgtbl, rd, phys
> - add \rd, \phys, #TEXT_OFFSET
> - sub \rd, \rd, #PG_DIR_SIZE
> - .endm
> -
> /*
> * Kernel startup entry point.
> * ---------------------------
> @@ -77,6 +69,9 @@
> .arm
>
> __HEAD
> + .globl swapper_pg_dir
> + .equ swapper_pg_dir, . - PG_DIR_SIZE
> +
> ENTRY(stext)
> ARM_BE8(setend be ) @ ensure we are in BE8 mode
>
> @@ -172,7 +167,7 @@ ENDPROC(stext)
> * r4 = physical page table address
> */
> __create_page_tables:
> - pgtbl r4, r8 @ page table address
> + adr_l r4, swapper_pg_dir @ page table address
>
> /*
> * Clear the swapper page table
> --
> 2.11.0
>
>
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