1 /* 2 * This file contains common routines for dealing with free of page tables 3 * Along with common page table handling code 4 * 5 * Derived from arch/powerpc/mm/tlb_64.c: 6 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 7 * 8 * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) 9 * and Cort Dougan (PReP) (cort@cs.nmt.edu) 10 * Copyright (C) 1996 Paul Mackerras 11 * 12 * Derived from "arch/i386/mm/init.c" 13 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 14 * 15 * Dave Engebretsen <engebret@us.ibm.com> 16 * Rework for PPC64 port. 17 * 18 * This program is free software; you can redistribute it and/or 19 * modify it under the terms of the GNU General Public License 20 * as published by the Free Software Foundation; either version 21 * 2 of the License, or (at your option) any later version. 22 */ 23 24 #include <linux/kernel.h> 25 #include <linux/gfp.h> 26 #include <linux/mm.h> 27 #include <linux/init.h> 28 #include <linux/percpu.h> 29 #include <linux/hardirq.h> 30 #include <linux/hugetlb.h> 31 #include <asm/pgalloc.h> 32 #include <asm/tlbflush.h> 33 #include <asm/tlb.h> 34 35 static inline int is_exec_fault(void) 36 { 37 return current->thread.regs && TRAP(current->thread.regs) == 0x400; 38 } 39 40 /* We only try to do i/d cache coherency on stuff that looks like 41 * reasonably "normal" PTEs. We currently require a PTE to be present 42 * and we avoid _PAGE_SPECIAL and _PAGE_NO_CACHE. We also only do that 43 * on userspace PTEs 44 */ 45 static inline int pte_looks_normal(pte_t pte) 46 { 47 return (pte_val(pte) & 48 (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER)) == 49 (_PAGE_PRESENT | _PAGE_USER); 50 } 51 52 struct page * maybe_pte_to_page(pte_t pte) 53 { 54 unsigned long pfn = pte_pfn(pte); 55 struct page *page; 56 57 if (unlikely(!pfn_valid(pfn))) 58 return NULL; 59 page = pfn_to_page(pfn); 60 if (PageReserved(page)) 61 return NULL; 62 return page; 63 } 64 65 #if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 66 67 /* Server-style MMU handles coherency when hashing if HW exec permission 68 * is supposed per page (currently 64-bit only). If not, then, we always 69 * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec 70 * support falls into the same category. 71 */ 72 73 static pte_t set_pte_filter(pte_t pte) 74 { 75 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 76 if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 77 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 78 struct page *pg = maybe_pte_to_page(pte); 79 if (!pg) 80 return pte; 81 if (!test_bit(PG_arch_1, &pg->flags)) { 82 flush_dcache_icache_page(pg); 83 set_bit(PG_arch_1, &pg->flags); 84 } 85 } 86 return pte; 87 } 88 89 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 90 int dirty) 91 { 92 return pte; 93 } 94 95 #else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */ 96 97 /* Embedded type MMU with HW exec support. This is a bit more complicated 98 * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so 99 * instead we "filter out" the exec permission for non clean pages. 100 */ 101 static pte_t set_pte_filter(pte_t pte) 102 { 103 struct page *pg; 104 105 /* No exec permission in the first place, move on */ 106 if (!(pte_val(pte) & _PAGE_EXEC) || !pte_looks_normal(pte)) 107 return pte; 108 109 /* If you set _PAGE_EXEC on weird pages you're on your own */ 110 pg = maybe_pte_to_page(pte); 111 if (unlikely(!pg)) 112 return pte; 113 114 /* If the page clean, we move on */ 115 if (test_bit(PG_arch_1, &pg->flags)) 116 return pte; 117 118 /* If it's an exec fault, we flush the cache and make it clean */ 119 if (is_exec_fault()) { 120 flush_dcache_icache_page(pg); 121 set_bit(PG_arch_1, &pg->flags); 122 return pte; 123 } 124 125 /* Else, we filter out _PAGE_EXEC */ 126 return __pte(pte_val(pte) & ~_PAGE_EXEC); 127 } 128 129 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 130 int dirty) 131 { 132 struct page *pg; 133 134 /* So here, we only care about exec faults, as we use them 135 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 136 * if necessary. Also if _PAGE_EXEC is already set, same deal, 137 * we just bail out 138 */ 139 if (dirty || (pte_val(pte) & _PAGE_EXEC) || !is_exec_fault()) 140 return pte; 141 142 #ifdef CONFIG_DEBUG_VM 143 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 144 * an error we would have bailed out earlier in do_page_fault() 145 * but let's make sure of it 146 */ 147 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 148 return pte; 149 #endif /* CONFIG_DEBUG_VM */ 150 151 /* If you set _PAGE_EXEC on weird pages you're on your own */ 152 pg = maybe_pte_to_page(pte); 153 if (unlikely(!pg)) 154 goto bail; 155 156 /* If the page is already clean, we move on */ 157 if (test_bit(PG_arch_1, &pg->flags)) 158 goto bail; 159 160 /* Clean the page and set PG_arch_1 */ 161 flush_dcache_icache_page(pg); 162 set_bit(PG_arch_1, &pg->flags); 163 164 bail: 165 return __pte(pte_val(pte) | _PAGE_EXEC); 166 } 167 168 #endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */ 169 170 /* 171 * set_pte stores a linux PTE into the linux page table. 172 */ 173 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 174 pte_t pte) 175 { 176 #ifdef CONFIG_DEBUG_VM 177 WARN_ON(pte_present(*ptep)); 178 #endif 179 /* Note: mm->context.id might not yet have been assigned as 180 * this context might not have been activated yet when this 181 * is called. 182 */ 183 pte = set_pte_filter(pte); 184 185 /* Perform the setting of the PTE */ 186 __set_pte_at(mm, addr, ptep, pte, 0); 187 } 188 189 /* 190 * This is called when relaxing access to a PTE. It's also called in the page 191 * fault path when we don't hit any of the major fault cases, ie, a minor 192 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 193 * handled those two for us, we additionally deal with missing execute 194 * permission here on some processors 195 */ 196 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 197 pte_t *ptep, pte_t entry, int dirty) 198 { 199 int changed; 200 entry = set_access_flags_filter(entry, vma, dirty); 201 changed = !pte_same(*(ptep), entry); 202 if (changed) { 203 if (!is_vm_hugetlb_page(vma)) 204 assert_pte_locked(vma->vm_mm, address); 205 __ptep_set_access_flags(ptep, entry); 206 flush_tlb_page_nohash(vma, address); 207 } 208 return changed; 209 } 210 211 #ifdef CONFIG_DEBUG_VM 212 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 213 { 214 pgd_t *pgd; 215 pud_t *pud; 216 pmd_t *pmd; 217 218 if (mm == &init_mm) 219 return; 220 pgd = mm->pgd + pgd_index(addr); 221 BUG_ON(pgd_none(*pgd)); 222 pud = pud_offset(pgd, addr); 223 BUG_ON(pud_none(*pud)); 224 pmd = pmd_offset(pud, addr); 225 /* 226 * khugepaged to collapse normal pages to hugepage, first set 227 * pmd to none to force page fault/gup to take mmap_sem. After 228 * pmd is set to none, we do a pte_clear which does this assertion 229 * so if we find pmd none, return. 230 */ 231 if (pmd_none(*pmd)) 232 return; 233 BUG_ON(!pmd_present(*pmd)); 234 assert_spin_locked(pte_lockptr(mm, pmd)); 235 } 236 #endif /* CONFIG_DEBUG_VM */ 237 238