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Date: Thu, 5 Nov 2015 17:24:01 -0800 From: Laura Abbott <labbott@...hat.com> To: Xishi Qiu <qiuxishi@...wei.com>, Laura Abbott <labbott@...oraproject.org> Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Mark Rutland <mark.rutland@....com> Subject: Re: [PATCH 1/2] arm64: Get existing page protections in split_pmd 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@...oraproject.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 > -- 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/
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