linux-kernel - Re: [PATCH v6 0/8] arm: support CONFIG

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Date:	Thu, 25 Sep 2014 22:58:05 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Will Deacon <will.deacon@....com>
Cc:	Kees Cook <keescook@...omium.org>, Rabin Vincent <rabin@....in>,
	Laura Abbott <lauraa@...eaurora.org>,
	Rob Herring <robh@...nel.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Mark Salter <msalter@...hat.com>, Liu hua <sdu.liu@...wei.com>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Doug Anderson <dianders@...gle.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 0/8] arm: support CONFIG_RODATA

On Thu, Sep 18, 2014 at 12:19 PM, Kees Cook <keescook@...omium.org> wrote:
> This is a series of patches to support CONFIG_RODATA on ARM, so that
> the kernel text is RO, and non-text sections default to NX. To support
> on-the-fly kernel text patching (via ftrace, kprobes, etc), fixmap
> support has been finalized based on several versions of various patches
> that are floating around on the mailing list. This series attempts to
> include the least intrusive version, so that others can build on it for
> future fixmap work.
>
> The series has been heavily tested, and appears to be working correctly:
>
> With CONFIG_ARM_PTDUMP, expected page table permissions are seen in
> /sys/kernel/debug/kernel_page_tables.
>
> Using CONFIG_LKDTM, the kernel now correctly detects bad accesses for
> for the following lkdtm tests via /sys/kernel/debug/provoke-crash/DIRECT:
>         EXEC_DATA
>         WRITE_RO
>         WRITE_KERN
>
> ftrace works:
>         CONFIG_FTRACE_STARTUP_TEST passes
>         Enabling tracing works:
>                 echo function > /sys/kernel/debug/tracing/current_tracer
> kprobes works:
>         CONFIG_ARM_KPROBES_TEST passes
>
> kexec works:
>         kexec will load and start a new kernel
>
> Built with and without CONFIG_HIGHMEM, CONFIG_HIGHMEM_DEBUG, and
> CONFIG_NR_CPUS=32.
>
> Thanks to everyone who has been testing this series and working on its
> various pieces!
>
> Hopefully this should address Will's last concerns. :)
>
> Thanks!
>
> -Kees
>
> v6:
> - always run patch_text under stop_machine (will.deacon)
> - document set_fixmap's TLB flushing situation (will.deacon)

Hi Will,

Does this version look good to you? Should I turn it into a pull request?

Thanks!

-Kees

>
> v5:
> - clean up #includes in mmu.c (will.deacon)
> - optimize get_cr() test (will.deacon)
> - created free_tcmmem to avoid excessive #ifdefs (will.deacon)
> - explicitly test irqs_disabled in set_fixmap (will.deacon)
>
> v4:
> - expanded fixmap to 3MB to support 32 CPUs (robh)
> - corrected pmd-finding via vaddr instead of FIXMAP_START (robh)
> - switched structure size test to BUILD_BUG_ON (sboyd)
> - added locking annotations to keep sparse happy (sboyd)
> - adding missing "static" declarations noticed by sparse
> - reorganized fixmap portion of patches
>
> v3:
> - more cleanups in switch to generic fixmap (lauraa, robh)
> - fixed kexec merge hunk glitch (will.deacon)
> - added tested-by tags where appropriate from v2 testing
>
> v2:
> - fix typo in kexec merge (buildbot)
> - flip index order for highmem pte access (lauraa)
> - added kgdb updates (dianders)
>



-- 
Kees Cook
Chrome OS Security
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