linux-kernel - Re: [PATCH v3 3/7] arm: use fixmap for text patching when text is RO

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Date:	Tue, 12 Aug 2014 14:39:09 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Kees Cook <keescook@...omium.org>
CC:	linux-kernel@...r.kernel.org,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Liu hua <sdu.liu@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Tomasz Figa <t.figa@...sung.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Will Deacon <will.deacon@....com>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Doug Anderson <dianders@...gle.com>,
	Rabin Vincent <rabin@....in>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Mark Salter <msalter@...hat.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 3/7] arm: use fixmap for text patching when text is
 RO

On 08/12/14 11:24, Kees Cook wrote:
> diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
> index 07314af47733..03dd4e39c833 100644
> --- a/arch/arm/kernel/patch.c
> +++ b/arch/arm/kernel/patch.c
> @@ -13,21 +16,69 @@ struct patch {
>  	unsigned int insn;
>  };
>  
> -void __kprobes __patch_text(void *addr, unsigned int insn)
> +static DEFINE_SPINLOCK(patch_lock);
> +
> +static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
> +{
> +	unsigned int uintaddr = (uintptr_t) addr;
> +	bool module = !core_kernel_text(uintaddr);
> +	struct page *page;
> +
> +	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
> +		page = vmalloc_to_page(addr);
> +	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
> +		page = virt_to_page(addr);
> +	else
> +		return addr;
> +
> +	if (flags)
> +		spin_lock_irqsave(&patch_lock, *flags);
> +
> +	set_fixmap(fixmap, page_to_phys(page));
> +
> +	return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
> +}
> +
> +static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
> +{
> +	clear_fixmap(fixmap);
> +
> +	if (flags)
> +		spin_unlock_irqrestore(&patch_lock, *flags);
> +}

Has the kbuildbot complained about this one yet?

  CHECK  arch/arm/kernel/patch.c
  arch/arm/kernel/patch.c:47:39: warning: context imbalance in
'patch_unmap' - unexpected unlock

I guess we're going to ignore it.

-- 
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hosted by The Linux Foundation

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