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Date: Fri, 1 Dec 2017 13:59:48 -0800
From: Laura Abbott <labbott@...hat.com>
To: Jinbum Park <jinb.park7@...il.com>, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Cc: afzal.mohd.ma@...il.com, mark.rutland@....com, linux@...linux.org.uk,
gregkh@...uxfoundation.org, keescook@...omium.org, vladimir.murzin@....com,
arnd@...db.de
Subject: Re: [PATCH v2 3/3] arm: mm: dump: add checking for
writable and executable pages
On 12/01/2017 03:34 AM, Jinbum Park wrote:
> +static inline bool is_prot_ro(struct pg_state *st)
> +{
> + if (st->level < 4) {
> + #ifdef CONFIG_ARM_LPAE
> + if ((st->current_prot &
> + (L_PMD_SECT_RDONLY | PMD_SECT_AP2)) ==
> + (L_PMD_SECT_RDONLY | PMD_SECT_AP2))
> + return true;
> + #elif __LINUX_ARM_ARCH__ >= 6
> + if ((st->current_prot &
> + (PMD_SECT_APX | PMD_SECT_AP_READ | PMD_SECT_AP_WRITE)) ==
> + (PMD_SECT_APX | PMD_SECT_AP_WRITE))
> + return true;
> + #else
> + if ((st->current_prot &
> + (PMD_SECT_AP_READ | PMD_SECT_AP_WRITE)) == 0)
> + return true;
> + #endif
> + } else {
> + if ((st->current_prot & L_PTE_RDONLY) == L_PTE_RDONLY)
> + return true;
> + }
> +
> + return false;
> +}
> +
> +static inline bool is_prot_nx(struct pg_state *st)
> +{
> + if (st->level < 4) {
> + if ((st->current_prot & PMD_SECT_XN) == PMD_SECT_XN)
> + return true;
> + } else {
> + if ((st->current_prot & L_PTE_XN) == L_PTE_XN)
> + return true;
> + }
> +
> + return false;
> +}
I know arm64 checks the bits directly, but the arm32 code is a bit
more fiddly and I have mixed feelings about copying and pasting
the checks. It would be cleaner if we could take advantage of
the existing pg_level and bits arrays. I also don't have my heart
set on this so if nobody else objects, the code can stay as is.
Thanks,
Laura
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