On Fri, Aug 4, 2017 at 1:38 PM, Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> wrote: > Balbir Singh <bsinghar...@gmail.com> writes: > >> On Wed, Aug 2, 2017 at 8:09 PM, Aneesh Kumar K.V >> <aneesh.ku...@linux.vnet.ibm.com> wrote: >>> Balbir Singh <bsinghar...@gmail.com> writes: >>> >>>> Add support for set_memory_xx routines. With the STRICT_KERNEL_RWX >>>> feature support we got support for changing the page permissions >>>> for pte ranges. This patch adds support for both radix and hash >>>> so that we can change their permissions via set/clear masks. >>>> >>>> A new helper is required for hash (hash__change_memory_range() >>>> is changed to hash__change_boot_memory_range() as it deals with >>>> bolted PTE's). >>>> >>>> hash__change_memory_range() works with vmalloc'ed PAGE_SIZE requests >>>> for permission changes. hash__change_memory_range() does not invoke >>>> updatepp, instead it changes the software PTE and invalidates the PTE. >>>> >>>> For radix, radix__change_memory_range() is setup to do the right >>>> thing for vmalloc'd addresses. It takes a new parameter to decide >>>> what attributes to set. >>>> >>> .... >>> >>>> +int hash__change_memory_range(unsigned long start, unsigned long end, >>>> + unsigned long set, unsigned long clear) >>>> +{ >>>> + unsigned long idx; >>>> + pgd_t *pgdp; >>>> + pud_t *pudp; >>>> + pmd_t *pmdp; >>>> + pte_t *ptep; >>>> + >>>> + start = ALIGN_DOWN(start, PAGE_SIZE); >>>> + end = PAGE_ALIGN(end); // aligns up >>>> + >>>> + /* >>>> + * Update the software PTE and flush the entry. >>>> + * This should cause a new fault with the right >>>> + * things setup in the hash page table >>>> + */ >>>> + pr_debug("Changing flags on range %lx-%lx setting 0x%lx removing >>>> 0x%lx\n", >>>> + start, end, set, clear); >>>> + >>>> + for (idx = start; idx < end; idx += PAGE_SIZE) { >>> >>> >>>> + pgdp = pgd_offset_k(idx); >>>> + pudp = pud_alloc(&init_mm, pgdp, idx); >>>> + if (!pudp) >>>> + return -1; >>>> + pmdp = pmd_alloc(&init_mm, pudp, idx); >>>> + if (!pmdp) >>>> + return -1; >>>> + ptep = pte_alloc_kernel(pmdp, idx); >>>> + if (!ptep) >>>> + return -1; >>>> + hash__pte_update(&init_mm, idx, ptep, clear, set, 0); >> >> I think this does the needful, if H_PAGE_HASHPTE is set, the flush >> will happen >> >>>> + hash__flush_tlb_kernel_range(idx, idx + PAGE_SIZE); >>>> + } >>> >>> You can use find_linux_pte_or_hugepte. with my recent patch series >>> find_init_mm_pte() ? >>> >> >> for pte_mkwrite and pte_wrprotect? > > For walking page table. I am not sure you really want to allocate page > table in that function. If you do, then what will be the initial value > of PTE ? We are requesting to set an clear from and existing PTE entry > right ? If you find a none page table entry you should handle it via a > fault ? >
Fair enough, I've been lazy with that check, I'll fix it in v2 Balbir Singh.