/* * 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 * Rework for PPC64 port. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include #include #include #include #include #include #include #include #include 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 _PAGE_NO_CACHE. We also only do that * on userspace PTEs */ static inline int pte_looks_normal(pte_t pte) { return (pte_val(pte) & (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER)) == (_PAGE_PRESENT | _PAGE_USER); } 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; } #if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 /* 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(pte_t 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; } static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, int dirty) { return pte; } #else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */ /* 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; /* No exec permission in the first place, move on */ if (!(pte_val(pte) & _PAGE_EXEC) || !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(pte_val(pte) & ~_PAGE_EXEC); } static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, int dirty) { struct page *pg; /* 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_val(pte) & _PAGE_EXEC) || !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(pte_val(pte) | _PAGE_EXEC); } #endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */ /* * 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) { /* * When handling numa faults, we already have the pte marked * _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)); /* 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) { if (!is_vm_hugetlb_page(vma)) assert_pte_locked(vma->vm_mm, address); __ptep_set_access_flags(ptep, entry); flush_tlb_page_nohash(vma, address); } return changed; } #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 */