linux-kernel - Re: [PATCH V4 3/7] arm64/mm: Enable ARCH_HAS_VM_GET_PAGE

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Date:   Fri, 8 Apr 2022 16:49:36 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        Christoph Hellwig <hch@...radead.org>,
        linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, sparclinux@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH V4 3/7] arm64/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT



On 4/8/22 15:58, Catalin Marinas wrote:
> On Thu, Apr 07, 2022 at 04:02:47PM +0530, Anshuman Khandual wrote:
>> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
>> index 77ada00280d9..307534fcec00 100644
>> --- a/arch/arm64/mm/mmap.c
>> +++ b/arch/arm64/mm/mmap.c
>> @@ -55,3 +55,36 @@ static int __init adjust_protection_map(void)
>>  	return 0;
>>  }
>>  arch_initcall(adjust_protection_map);
>> +
>> +static pgprot_t arm64_arch_vm_get_page_prot(unsigned long vm_flags)
>> +{
>> +	pteval_t prot = 0;
>> +
>> +	if (vm_flags & VM_ARM64_BTI)
>> +		prot |= PTE_GP;
>> +
>> +	/*
>> +	 * There are two conditions required for returning a Normal Tagged
>> +	 * memory type: (1) the user requested it via PROT_MTE passed to
>> +	 * mmap() or mprotect() and (2) the corresponding vma supports MTE. We
>> +	 * register (1) as VM_MTE in the vma->vm_flags and (2) as
>> +	 * VM_MTE_ALLOWED. Note that the latter can only be set during the
>> +	 * mmap() call since mprotect() does not accept MAP_* flags.
>> +	 * Checking for VM_MTE only is sufficient since arch_validate_flags()
>> +	 * does not permit (VM_MTE & !VM_MTE_ALLOWED).
>> +	 */
>> +	if (vm_flags & VM_MTE)
>> +		prot |= PTE_ATTRINDX(MT_NORMAL_TAGGED);
>> +
>> +	return __pgprot(prot);
>> +}
>> +
>> +pgprot_t vm_get_page_prot(unsigned long vm_flags)
>> +{
>> +	pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
>> +				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
>> +				pgprot_val(arm64_arch_vm_get_page_prot(vm_flags)));
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(vm_get_page_prot);
> 
> Could you write all this in a single function? I think I mentioned it in
> a previous series (untested):

Right, missed that.

> 
> pgprot_t vm_get_page_prot(unsigned long vm_flags)
> {
> 	pteval_t prot = pgprot_val(protection_map[vm_flags &
> 				   (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]);
> 
> 	if (vm_flags & VM_ARM64_BTI)
> 		prot |= PTE_GP;
> 
> 	/*
> 	 * There are two conditions required for returning a Normal Tagged
> 	 * memory type: (1) the user requested it via PROT_MTE passed to
> 	 * mmap() or mprotect() and (2) the corresponding vma supports MTE. We
> 	 * register (1) as VM_MTE in the vma->vm_flags and (2) as
> 	 * VM_MTE_ALLOWED. Note that the latter can only be set during the
> 	 * mmap() call since mprotect() does not accept MAP_* flags.
> 	 * Checking for VM_MTE only is sufficient since arch_validate_flags()
> 	 * does not permit (VM_MTE & !VM_MTE_ALLOWED).
> 	 */
> 	if (vm_flags & VM_MTE)
> 		prot |= PTE_ATTRINDX(MT_NORMAL_TAGGED);
> 
> 	return __pgprot(prot);
> }
> EXPORT_SYMBOL(vm_get_page_prot);
> 
> With that:

Sure, will change them into a single function.

> 
> Reviewed-by: Catalin Marinas <catalin.marinas@....com>
>