| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * This file contains common routines for dealing with free of page tables |
| * Along with common page table handling code |
| * |
| * Derived from arch/powerpc/mm/tlb_64.c: |
| * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) |
| * |
| * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) |
| * and Cort Dougan (PReP) (cort@cs.nmt.edu) |
| * Copyright (C) 1996 Paul Mackerras |
| * |
| * Derived from "arch/i386/mm/init.c" |
| * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| * |
| * Dave Engebretsen <engebret@us.ibm.com> |
| * Rework for PPC64 port. |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/gfp.h> |
| #include <linux/mm.h> |
| #include <linux/percpu.h> |
| #include <linux/hardirq.h> |
| #include <linux/hugetlb.h> |
| #include <asm/pgalloc.h> |
| #include <asm/tlbflush.h> |
| #include <asm/tlb.h> |
| #include <asm/hugetlb.h> |
| |
| static inline int is_exec_fault(void) |
| { |
| return current->thread.regs && TRAP(current->thread.regs) == 0x400; |
| } |
| |
| /* We only try to do i/d cache coherency on stuff that looks like |
| * reasonably "normal" PTEs. We currently require a PTE to be present |
| * and we avoid _PAGE_SPECIAL and cache inhibited pte. We also only do that |
| * on userspace PTEs |
| */ |
| static inline int pte_looks_normal(pte_t pte) |
| { |
| |
| if (pte_present(pte) && !pte_special(pte)) { |
| if (pte_ci(pte)) |
| return 0; |
| if (pte_user(pte)) |
| return 1; |
| } |
| return 0; |
| } |
| |
| static struct page *maybe_pte_to_page(pte_t pte) |
| { |
| unsigned long pfn = pte_pfn(pte); |
| struct page *page; |
| |
| if (unlikely(!pfn_valid(pfn))) |
| return NULL; |
| page = pfn_to_page(pfn); |
| if (PageReserved(page)) |
| return NULL; |
| return page; |
| } |
| |
| #ifdef CONFIG_PPC_BOOK3S |
| |
| /* Server-style MMU handles coherency when hashing if HW exec permission |
| * is supposed per page (currently 64-bit only). If not, then, we always |
| * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec |
| * support falls into the same category. |
| */ |
| |
| static pte_t set_pte_filter_hash(pte_t pte) |
| { |
| if (radix_enabled()) |
| return pte; |
| |
| pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); |
| if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || |
| cpu_has_feature(CPU_FTR_NOEXECUTE))) { |
| struct page *pg = maybe_pte_to_page(pte); |
| if (!pg) |
| return pte; |
| if (!test_bit(PG_arch_1, &pg->flags)) { |
| flush_dcache_icache_page(pg); |
| set_bit(PG_arch_1, &pg->flags); |
| } |
| } |
| return pte; |
| } |
| |
| #else /* CONFIG_PPC_BOOK3S */ |
| |
| static pte_t set_pte_filter_hash(pte_t pte) { return pte; } |
| |
| #endif /* CONFIG_PPC_BOOK3S */ |
| |
| /* Embedded type MMU with HW exec support. This is a bit more complicated |
| * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so |
| * instead we "filter out" the exec permission for non clean pages. |
| */ |
| static pte_t set_pte_filter(pte_t pte) |
| { |
| struct page *pg; |
| |
| if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) |
| return set_pte_filter_hash(pte); |
| |
| /* No exec permission in the first place, move on */ |
| if (!pte_exec(pte) || !pte_looks_normal(pte)) |
| return pte; |
| |
| /* If you set _PAGE_EXEC on weird pages you're on your own */ |
| pg = maybe_pte_to_page(pte); |
| if (unlikely(!pg)) |
| return pte; |
| |
| /* If the page clean, we move on */ |
| if (test_bit(PG_arch_1, &pg->flags)) |
| return pte; |
| |
| /* If it's an exec fault, we flush the cache and make it clean */ |
| if (is_exec_fault()) { |
| flush_dcache_icache_page(pg); |
| set_bit(PG_arch_1, &pg->flags); |
| return pte; |
| } |
| |
| /* Else, we filter out _PAGE_EXEC */ |
| return pte_exprotect(pte); |
| } |
| |
| static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, |
| int dirty) |
| { |
| struct page *pg; |
| |
| if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) |
| return pte; |
| |
| /* So here, we only care about exec faults, as we use them |
| * to recover lost _PAGE_EXEC and perform I$/D$ coherency |
| * if necessary. Also if _PAGE_EXEC is already set, same deal, |
| * we just bail out |
| */ |
| if (dirty || pte_exec(pte) || !is_exec_fault()) |
| return pte; |
| |
| #ifdef CONFIG_DEBUG_VM |
| /* So this is an exec fault, _PAGE_EXEC is not set. If it was |
| * an error we would have bailed out earlier in do_page_fault() |
| * but let's make sure of it |
| */ |
| if (WARN_ON(!(vma->vm_flags & VM_EXEC))) |
| return pte; |
| #endif /* CONFIG_DEBUG_VM */ |
| |
| /* If you set _PAGE_EXEC on weird pages you're on your own */ |
| pg = maybe_pte_to_page(pte); |
| if (unlikely(!pg)) |
| goto bail; |
| |
| /* If the page is already clean, we move on */ |
| if (test_bit(PG_arch_1, &pg->flags)) |
| goto bail; |
| |
| /* Clean the page and set PG_arch_1 */ |
| flush_dcache_icache_page(pg); |
| set_bit(PG_arch_1, &pg->flags); |
| |
| bail: |
| return pte_mkexec(pte); |
| } |
| |
| /* |
| * set_pte stores a linux PTE into the linux page table. |
| */ |
| void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, |
| pte_t pte) |
| { |
| /* |
| * Make sure hardware valid bit is not set. We don't do |
| * tlb flush for this update. |
| */ |
| VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); |
| |
| /* Add the pte bit when trying to set a pte */ |
| pte = pte_mkpte(pte); |
| |
| /* Note: mm->context.id might not yet have been assigned as |
| * this context might not have been activated yet when this |
| * is called. |
| */ |
| pte = set_pte_filter(pte); |
| |
| /* Perform the setting of the PTE */ |
| __set_pte_at(mm, addr, ptep, pte, 0); |
| } |
| |
| /* |
| * This is called when relaxing access to a PTE. It's also called in the page |
| * fault path when we don't hit any of the major fault cases, ie, a minor |
| * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have |
| * handled those two for us, we additionally deal with missing execute |
| * permission here on some processors |
| */ |
| int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, |
| pte_t *ptep, pte_t entry, int dirty) |
| { |
| int changed; |
| entry = set_access_flags_filter(entry, vma, dirty); |
| changed = !pte_same(*(ptep), entry); |
| if (changed) { |
| assert_pte_locked(vma->vm_mm, address); |
| __ptep_set_access_flags(vma, ptep, entry, |
| address, mmu_virtual_psize); |
| } |
| return changed; |
| } |
| |
| #ifdef CONFIG_HUGETLB_PAGE |
| int huge_ptep_set_access_flags(struct vm_area_struct *vma, |
| unsigned long addr, pte_t *ptep, |
| pte_t pte, int dirty) |
| { |
| #ifdef HUGETLB_NEED_PRELOAD |
| /* |
| * The "return 1" forces a call of update_mmu_cache, which will write a |
| * TLB entry. Without this, platforms that don't do a write of the TLB |
| * entry in the TLB miss handler asm will fault ad infinitum. |
| */ |
| ptep_set_access_flags(vma, addr, ptep, pte, dirty); |
| return 1; |
| #else |
| int changed, psize; |
| |
| pte = set_access_flags_filter(pte, vma, dirty); |
| changed = !pte_same(*(ptep), pte); |
| if (changed) { |
| |
| #ifdef CONFIG_PPC_BOOK3S_64 |
| struct hstate *h = hstate_vma(vma); |
| |
| psize = hstate_get_psize(h); |
| #ifdef CONFIG_DEBUG_VM |
| assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); |
| #endif |
| |
| #else |
| /* |
| * Not used on non book3s64 platforms. But 8xx |
| * can possibly use tsize derived from hstate. |
| */ |
| psize = 0; |
| #endif |
| __ptep_set_access_flags(vma, ptep, pte, addr, psize); |
| } |
| return changed; |
| #endif |
| } |
| #endif /* CONFIG_HUGETLB_PAGE */ |
| |
| #ifdef CONFIG_DEBUG_VM |
| void assert_pte_locked(struct mm_struct *mm, unsigned long addr) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd; |
| |
| if (mm == &init_mm) |
| return; |
| pgd = mm->pgd + pgd_index(addr); |
| BUG_ON(pgd_none(*pgd)); |
| pud = pud_offset(pgd, addr); |
| BUG_ON(pud_none(*pud)); |
| pmd = pmd_offset(pud, addr); |
| /* |
| * khugepaged to collapse normal pages to hugepage, first set |
| * pmd to none to force page fault/gup to take mmap_sem. After |
| * pmd is set to none, we do a pte_clear which does this assertion |
| * so if we find pmd none, return. |
| */ |
| if (pmd_none(*pmd)) |
| return; |
| BUG_ON(!pmd_present(*pmd)); |
| assert_spin_locked(pte_lockptr(mm, pmd)); |
| } |
| #endif /* CONFIG_DEBUG_VM */ |
| |
| unsigned long vmalloc_to_phys(void *va) |
| { |
| unsigned long pfn = vmalloc_to_pfn(va); |
| |
| BUG_ON(!pfn); |
| return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); |
| } |
| EXPORT_SYMBOL_GPL(vmalloc_to_phys); |
| |
| /* |
| * We have 4 cases for pgds and pmds: |
| * (1) invalid (all zeroes) |
| * (2) pointer to next table, as normal; bottom 6 bits == 0 |
| * (3) leaf pte for huge page _PAGE_PTE set |
| * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table |
| * |
| * So long as we atomically load page table pointers we are safe against teardown, |
| * we can follow the address down to the the page and take a ref on it. |
| * This function need to be called with interrupts disabled. We use this variant |
| * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED |
| */ |
| pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, |
| bool *is_thp, unsigned *hpage_shift) |
| { |
| pgd_t pgd, *pgdp; |
| pud_t pud, *pudp; |
| pmd_t pmd, *pmdp; |
| pte_t *ret_pte; |
| hugepd_t *hpdp = NULL; |
| unsigned pdshift = PGDIR_SHIFT; |
| |
| if (hpage_shift) |
| *hpage_shift = 0; |
| |
| if (is_thp) |
| *is_thp = false; |
| |
| pgdp = pgdir + pgd_index(ea); |
| pgd = READ_ONCE(*pgdp); |
| /* |
| * Always operate on the local stack value. This make sure the |
| * value don't get updated by a parallel THP split/collapse, |
| * page fault or a page unmap. The return pte_t * is still not |
| * stable. So should be checked there for above conditions. |
| */ |
| if (pgd_none(pgd)) |
| return NULL; |
| |
| if (pgd_huge(pgd)) { |
| ret_pte = (pte_t *)pgdp; |
| goto out; |
| } |
| if (is_hugepd(__hugepd(pgd_val(pgd)))) { |
| hpdp = (hugepd_t *)&pgd; |
| goto out_huge; |
| } |
| |
| /* |
| * Even if we end up with an unmap, the pgtable will not |
| * be freed, because we do an rcu free and here we are |
| * irq disabled |
| */ |
| pdshift = PUD_SHIFT; |
| pudp = pud_offset(&pgd, ea); |
| pud = READ_ONCE(*pudp); |
| |
| if (pud_none(pud)) |
| return NULL; |
| |
| if (pud_huge(pud)) { |
| ret_pte = (pte_t *)pudp; |
| goto out; |
| } |
| if (is_hugepd(__hugepd(pud_val(pud)))) { |
| hpdp = (hugepd_t *)&pud; |
| goto out_huge; |
| } |
| pdshift = PMD_SHIFT; |
| pmdp = pmd_offset(&pud, ea); |
| pmd = READ_ONCE(*pmdp); |
| |
| /* |
| * A hugepage collapse is captured by this condition, see |
| * pmdp_collapse_flush. |
| */ |
| if (pmd_none(pmd)) |
| return NULL; |
| |
| #ifdef CONFIG_PPC_BOOK3S_64 |
| /* |
| * A hugepage split is captured by this condition, see |
| * pmdp_invalidate. |
| * |
| * Huge page modification can be caught here too. |
| */ |
| if (pmd_is_serializing(pmd)) |
| return NULL; |
| #endif |
| |
| if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { |
| if (is_thp) |
| *is_thp = true; |
| ret_pte = (pte_t *)pmdp; |
| goto out; |
| } |
| /* |
| * pmd_large check below will handle the swap pmd pte |
| * we need to do both the check because they are config |
| * dependent. |
| */ |
| if (pmd_huge(pmd) || pmd_large(pmd)) { |
| ret_pte = (pte_t *)pmdp; |
| goto out; |
| } |
| if (is_hugepd(__hugepd(pmd_val(pmd)))) { |
| hpdp = (hugepd_t *)&pmd; |
| goto out_huge; |
| } |
| |
| return pte_offset_kernel(&pmd, ea); |
| |
| out_huge: |
| if (!hpdp) |
| return NULL; |
| |
| ret_pte = hugepte_offset(*hpdp, ea, pdshift); |
| pdshift = hugepd_shift(*hpdp); |
| out: |
| if (hpage_shift) |
| *hpage_shift = pdshift; |
| return ret_pte; |
| } |
| EXPORT_SYMBOL_GPL(__find_linux_pte); |