On Tue, Jun 30, 2020 at 02:44:00PM +0200, David Hildenbrand wrote:
>On 30.06.20 05:18, Wei Yang wrote:
>> When walking page tables, we define several helpers to get the address of
>> the next boundary. But we don't have one for pte level.
>>
>> Let's define it and consolidate the code in several places.
>>
>> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
>> ---
>> arch/x86/mm/init_64.c | 6 ++----
>> include/linux/pgtable.h | 7 +++++++
>> mm/kasan/init.c | 4 +---
>> 3 files changed, 10 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>> index dbae185511cd..f902fbd17f27 100644
>> --- a/arch/x86/mm/init_64.c
>> +++ b/arch/x86/mm/init_64.c
>> @@ -973,9 +973,7 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,
>>
>> pte = pte_start + pte_index(addr);
>> for (; addr < end; addr = next, pte++) {
>> - next = (addr + PAGE_SIZE) & PAGE_MASK;
>> - if (next > end)
>> - next = end;
>> + next = pte_addr_end(addr, end);
>>
>> if (!pte_present(*pte))
>> continue;
>> @@ -1558,7 +1556,7 @@ void register_page_bootmem_memmap(unsigned long section_nr,
>> get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO);
>>
>> if (!boot_cpu_has(X86_FEATURE_PSE)) {
>> - next = (addr + PAGE_SIZE) & PAGE_MASK;
>> + next = pte_addr_end(addr, end);
>> pmd = pmd_offset(pud, addr);
>> if (pmd_none(*pmd))
>> continue;
>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>> index 32b6c52d41b9..0de09c6c89d2 100644
>> --- a/include/linux/pgtable.h
>> +++ b/include/linux/pgtable.h
>> @@ -706,6 +706,13 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
>> })
>> #endif
>>
>> +#ifndef pte_addr_end
>> +#define pte_addr_end(addr, end) \
>> +({ unsigned long __boundary = ((addr) + PAGE_SIZE) & PAGE_MASK; \
>> + (__boundary - 1 < (end) - 1) ? __boundary : (end); \
>> +})
>> +#endif
>> +
>> /*
>> * When walking page tables, we usually want to skip any p?d_none entries;
>> * and any p?d_bad entries - reporting the error before resetting to none.
>> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
>> index fe6be0be1f76..89f748601f74 100644
>> --- a/mm/kasan/init.c
>> +++ b/mm/kasan/init.c
>> @@ -349,9 +349,7 @@ static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
>> unsigned long next;
>>
>> for (; addr < end; addr = next, pte++) {
>> - next = (addr + PAGE_SIZE) & PAGE_MASK;
>> - if (next > end)
>> - next = end;
>> + next = pte_addr_end(addr, end);
>>
>> if (!pte_present(*pte))
>> continue;
>>
>
>I'm not really a friend of this I have to say. We're simply iterating
>over single pages, not much magic ....
Hmm... yes, we are iterating on Page boundary, while we many have the case
when addr or end is not PAGE_ALIGN.
>
>What would definitely make sense is replacing (addr + PAGE_SIZE) &
>PAGE_MASK; by PAGE_ALIGN() ...
>
No, PAGE_ALIGN() is expanded to be
(addr + PAGE_SIZE - 1) & PAGE_MASK;
If we change the code to PAGE_ALIGN(), we would end up with infinite loop.
>--
>Thanks,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
