[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAGXu5jKimGaupwyUwt0Zwa3OtjeoED8-uBeMX0MwXjBYP6ssAg@mail.gmail.com>
Date: Thu, 4 Sep 2014 10:23:42 -0700
From: Kees Cook <keescook@...omium.org>
To: Will Deacon <will.deacon@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Rabin Vincent <rabin@....in>,
Laura Abbott <lauraa@...eaurora.org>,
Rob Herring <robh@...nel.org>,
Leif Lindholm <leif.lindholm@...aro.org>,
"msalter@...hat.com" <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>
Subject: Re: [PATCH v5 3/8] arm: fixmap: implement __set_fixmap()
On Thu, Sep 4, 2014 at 10:03 AM, Will Deacon <will.deacon@....com> wrote:
> Hi Kees,
>
> On Wed, Sep 03, 2014 at 10:57:04PM +0100, Kees Cook wrote:
>> This is used from set_fixmap() and clear_fixmap() via asm-generic/fixmap.h.
>> Also makes sure that the fixmap allocation fits into the expected range.
>>
>> Based on patch by Rabin Vincent.
>
> [...]
>
>> +void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>> +{
>> + unsigned long vaddr = __fix_to_virt(idx);
>> + pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
>> +
>> + /* Make sure fixmap region does not exceed available allocation. */
>> + BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) >
>> + FIXADDR_END);
>> + BUG_ON(idx >= __end_of_fixed_addresses);
>> +
>> + if (pgprot_val(prot))
>> + set_pte_at(NULL, vaddr, pte,
>> + pfn_pte(phys >> PAGE_SHIFT, prot));
>> + else
>> + pte_clear(NULL, vaddr, pte);
>> +
>> + /*
>> + * Given the potential a15 tlbi errata, we can only do tlb flushes
>> + * with interrupts disabled. Callers must have taken care of this.
>> + */
>> + WARN_ON_ONCE(!irqs_disabled());
>> + flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
>
> Aha, this explains why we were confusing each other! The issue is that
> interrupts must be *enabled*, so this code does the exact opposite of
> what we need.
>
> I think this got lost in a sea of double negatives during the last round
> of review.
Ah! If this is the case, perhaps we can get away with
local_flush_tlb_kernel_range() then?
-Kees
--
Kees Cook
Chrome OS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists