From: Laura Abbott <labbott@redhat.com>
To: Xishi Qiu <qiuxishi@huawei.com>,
Laura Abbott <labbott@fedoraproject.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH 1/2] arm64: Get existing page protections in split_pmd
Date: Thu, 5 Nov 2015 17:24:01 -0800 [thread overview]
Message-ID: <563C0131.2060707@redhat.com> (raw)
In-Reply-To: <563B2C32.10307@huawei.com>
On 11/05/2015 02:15 AM, Xishi Qiu wrote:
> On 2015/11/4 5:48, Laura Abbott wrote:
>
>>
>> Rather than always putting the least restrictived permissions
>> (PAGE_KERNEL_EXEC) when spliting a pmd into pages, use
>> the existing permissions from the pmd for the page.
>>
>> Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
>> ---
>> arch/arm64/mm/mmu.c | 9 ++++-----
>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 9211b85..ff41efa 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -75,14 +75,13 @@ static void __init *early_alloc(unsigned long sz)
>> static void split_pmd(pmd_t *pmd, pte_t *pte)
>> {
>> unsigned long pfn = pmd_pfn(*pmd);
>> + unsigned long addr = pfn << PAGE_SHIFT;
>> + pgprot_t prot = __pgprot(pmd_val(*pmd) ^ addr) | PTE_TYPE_PAGE;
>> +
>
> Hi Laura,
>
> I'm not quite understand, I find split_pud() doesn't set the flag
> PMD_TYPE_TABLE. If we clear xx_TABLE_BIT, does that means the page
> is large page?
I'm assuming by large page you mean a block mapping. Yes, without
that entry the kernel treats this as a block mapping
> And what is the different from the flag xx_TYPE_SECT?
That would mark it this as a block mapping which is not what we want
here.
>
> Thanks,
> Xishi Qiu
>
next prev parent reply other threads:[~2015-11-06 1:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-03 21:48 [PATCH 0/2] Support for set_memory_* outside of module space Laura Abbott
2015-11-03 21:48 ` [PATCH 1/2] arm64: Get existing page protections in split_pmd Laura Abbott
2015-11-05 7:07 ` Ard Biesheuvel
2015-11-05 10:15 ` Xishi Qiu
2015-11-06 1:24 ` Laura Abbott [this message]
2015-11-03 21:48 ` [PATCH 2/2] arm64: Allow changing of attributes outside of modules Laura Abbott
2015-11-04 3:17 ` zhong jiang
2015-11-05 7:44 ` Ard Biesheuvel
2015-11-06 1:35 ` Laura Abbott
[not found] ` <563974A8.3060306@huawei.com>
[not found] ` <563A4A74.60900@redhat.com>
2015-11-05 11:10 ` Xishi Qiu
2015-11-06 1:11 ` Laura Abbott
2015-11-05 11:29 ` Xishi Qiu
2015-11-03 23:42 ` [PATCH 0/2] Support for set_memory_* outside of module space Kees Cook
2015-11-04 18:51 ` Laura Abbott
2015-11-04 19:06 ` Kees Cook
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