Balbir Singh <[email protected]> writes:
> [ text/plain ]
>
>
> On 27/03/16 19:23, Aneesh Kumar K.V wrote:
>> This split _PAGE_RW bit to _PAGE_READ and _PAGE_WRITE. It also remove
>> the dependency on _PAGE_USER for implying read only. Few things to note
>> here is that, we have read implied with write and execute permission.
>> Hence we should always find _PAGE_READ set on hash pte fault.
>>
>> We still can't switch PROT_NONE to !(_PAGE_RWX). Auto numa do depend
>> on marking a prot none pte _PAGE_WRITE. (For more details look at
>> b191f9b106ea "mm: numa: preserve PTE write permissions across a NUMA hinting
>> fault")
>>
......
>> diff --git a/arch/powerpc/mm/hash_utils_64.c
>> b/arch/powerpc/mm/hash_utils_64.c
>> index 90dd9280894f..ea23403b3fc0 100644
>> --- a/arch/powerpc/mm/hash_utils_64.c
>> +++ b/arch/powerpc/mm/hash_utils_64.c
>> @@ -175,8 +175,9 @@ unsigned long htab_convert_pte_flags(unsigned long
>> pteflags)
>> * or PP=0x3 for read-only (including writeable but clean pages).
>> */
>> if (pteflags & _PAGE_USER) {
>> - rflags |= 0x2;
>> - if (!((pteflags & _PAGE_RW) && (pteflags & _PAGE_DIRTY)))
>> + if (pteflags & _PAGE_RWX)
> Should this be pteflags & _PAGE_RW?
That will work, because we always have _PAGE_READ set for _PAGE_EXEC.
But what we really need to check here is READ/WRITE/EXEC.
>> + rflags |= 0x2;
>> + if (!((pteflags & _PAGE_WRITE) && (pteflags & _PAGE_DIRTY)))
>> rflags |= 0x1;
> if pteflags == _PAGE_USER | _PAGE_WRITE | _PAGE_DIRTY, what is rflags set to?
>
rflags will be 0x2. and for readlyonly 0x3. That is documented above.
>
>
>> }
>> /*
>> @@ -1205,7 +1206,7 @@ EXPORT_SYMBOL_GPL(hash_page);
>> int __hash_page(unsigned long ea, unsigned long msr, unsigned long trap,
>> unsigned long dsisr)
>> {
>> - unsigned long access = _PAGE_PRESENT;
>> + unsigned long access = _PAGE_PRESENT | _PAGE_READ;
>> unsigned long flags = 0;
>> struct mm_struct *mm = current->mm;
....
>> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
>> index 83dfd7925c72..98b5c03e344d 100644
>> --- a/arch/powerpc/mm/pgtable.c
>> +++ b/arch/powerpc/mm/pgtable.c
>> @@ -177,8 +177,8 @@ void set_pte_at(struct mm_struct *mm, unsigned long
>> addr, pte_t *ptep,
>> * _PAGE_PRESENT, but we can be sure that it is not in hpte.
>> * Hence we can use set_pte_at for them.
>> */
>> - VM_WARN_ON((pte_val(*ptep) & (_PAGE_PRESENT | _PAGE_USER)) ==
>> - (_PAGE_PRESENT | _PAGE_USER));
>> + VM_WARN_ON(pte_present(*ptep) && !pte_protnone(*ptep));
>> +
> What was wrong with the previous check? The compiler will optimize it, but
> the new
> check uses two pte_val() calls on *ptep
That was confusing, even though we documented it clearly above, it does
confuse, because checking for _PAGE_USER is an indirect hint for prot
numa ptes.
>> /*
>> * Add the pte bit when tryint set a pte
>> */
>> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
>> index aa742aa35b64..00d8d985bba3 100644
>> --- a/arch/powerpc/mm/pgtable_64.c
>> +++ b/arch/powerpc/mm/pgtable_64.c
>> @@ -277,7 +277,7 @@ void __iomem * ioremap_prot(phys_addr_t addr, unsigned
>> long size,
>> void *caller = __builtin_return_address(0);
>>
>> /* writeable implies dirty for kernel addresses */
>> - if (flags & _PAGE_RW)
>> + if (flags & _PAGE_WRITE)
>> flags |= _PAGE_DIRTY;
>>
>> /* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
>> @@ -681,8 +681,7 @@ void set_pmd_at(struct mm_struct *mm, unsigned long addr,
>> pmd_t *pmdp, pmd_t pmd)
>> {
>> #ifdef CONFIG_DEBUG_VM
>> - WARN_ON((pmd_val(*pmdp) & (_PAGE_PRESENT | _PAGE_USER)) ==
>> - (_PAGE_PRESENT | _PAGE_USER));
>> + WARN_ON(pte_present(pmd_pte(*pmdp)) && !pte_protnone(pmd_pte(*pmdp)));
> Same as above, plus I think we can move these to VM_WARN_ON just to be
> consistent
We already have #ifdef CONFIG_DEBUG_VM around, hence we can avoid using
VM_WARN_ON.
-aneesh
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