linux-kernel - Re: [PATCH 14(16] pramfs: memory protection

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Date:	Mon, 11 Oct 2010 08:57:45 +0200
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Embedded <linux-embedded@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Tim Bird <tim.bird@...sony.com>, linux-mm@...ck.org
Subject: Re: [PATCH 14(16] pramfs: memory protection

2010/10/10 Andi Kleen <andi@...stfloor.org>:
> Marco Stornelli <marco.stornelli@...il.com> writes:
>> +
>> +     do {
>> +             pgd = pgd_offset(&init_mm, address);
>> +             if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
>> +                     goto out;
>> +
>> +             pud = pud_offset(pgd, address);
>> +             if (pud_none(*pud) || unlikely(pud_bad(*pud)))
>> +                     goto out;
>> +
>> +             pmd = pmd_offset(pud, address);
>> +             if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
>> +                     goto out;
>> +
>> +             ptep = pte_offset_kernel(pmd, addr);
>> +             pte = *ptep;
>> +             if (pte_present(pte)) {
>
> This won't work at all on x86 because you don't handle large
> pages.

On x86 works because I tested. Maybe there's a particular
configuration with large pages. Sincerly I'm only an "user", so if
you/Linus or others want to change it or rewrite it, for me it's ok.
The pte manipulation are a bit out of scope for a fs, so I let the
things to the mm experts.
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