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/percpu.h> 28 #include <linux/hardirq.h> 29 #include <linux/hugetlb.h> 30 #include <asm/pgalloc.h> 31 #include <asm/tlbflush.h> 32 #include <asm/tlb.h> 33 34 static inline int is_exec_fault(void) 35 { 36 return current->thread.regs && TRAP(current->thread.regs) == 0x400; 37 } 38 39 /* We only try to do i/d cache coherency on stuff that looks like 40 * reasonably "normal" PTEs. We currently require a PTE to be present 41 * and we avoid _PAGE_SPECIAL and _PAGE_NO_CACHE. We also only do that 42 * on userspace PTEs 43 */ 44 static inline int pte_looks_normal(pte_t pte) 45 { 46 return (pte_val(pte) & 47 (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER)) == 48 (_PAGE_PRESENT | _PAGE_USER); 49 } 50 51 static struct page *maybe_pte_to_page(pte_t pte) 52 { 53 unsigned long pfn = pte_pfn(pte); 54 struct page *page; 55 56 if (unlikely(!pfn_valid(pfn))) 57 return NULL; 58 page = pfn_to_page(pfn); 59 if (PageReserved(page)) 60 return NULL; 61 return page; 62 } 63 64 #if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 65 66 /* Server-style MMU handles coherency when hashing if HW exec permission 67 * is supposed per page (currently 64-bit only). If not, then, we always 68 * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec 69 * support falls into the same category. 70 */ 71 72 static pte_t set_pte_filter(pte_t pte) 73 { 74 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 75 if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 76 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 77 struct page *pg = maybe_pte_to_page(pte); 78 if (!pg) 79 return pte; 80 if (!test_bit(PG_arch_1, &pg->flags)) { 81 flush_dcache_icache_page(pg); 82 set_bit(PG_arch_1, &pg->flags); 83 } 84 } 85 return pte; 86 } 87 88 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 89 int dirty) 90 { 91 return pte; 92 } 93 94 #else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */ 95 96 /* Embedded type MMU with HW exec support. This is a bit more complicated 97 * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so 98 * instead we "filter out" the exec permission for non clean pages. 99 */ 100 static pte_t set_pte_filter(pte_t pte) 101 { 102 struct page *pg; 103 104 /* No exec permission in the first place, move on */ 105 if (!(pte_val(pte) & _PAGE_EXEC) || !pte_looks_normal(pte)) 106 return pte; 107 108 /* If you set _PAGE_EXEC on weird pages you're on your own */ 109 pg = maybe_pte_to_page(pte); 110 if (unlikely(!pg)) 111 return pte; 112 113 /* If the page clean, we move on */ 114 if (test_bit(PG_arch_1, &pg->flags)) 115 return pte; 116 117 /* If it's an exec fault, we flush the cache and make it clean */ 118 if (is_exec_fault()) { 119 flush_dcache_icache_page(pg); 120 set_bit(PG_arch_1, &pg->flags); 121 return pte; 122 } 123 124 /* Else, we filter out _PAGE_EXEC */ 125 return __pte(pte_val(pte) & ~_PAGE_EXEC); 126 } 127 128 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 129 int dirty) 130 { 131 struct page *pg; 132 133 /* So here, we only care about exec faults, as we use them 134 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 135 * if necessary. Also if _PAGE_EXEC is already set, same deal, 136 * we just bail out 137 */ 138 if (dirty || (pte_val(pte) & _PAGE_EXEC) || !is_exec_fault()) 139 return pte; 140 141 #ifdef CONFIG_DEBUG_VM 142 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 143 * an error we would have bailed out earlier in do_page_fault() 144 * but let's make sure of it 145 */ 146 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 147 return pte; 148 #endif /* CONFIG_DEBUG_VM */ 149 150 /* If you set _PAGE_EXEC on weird pages you're on your own */ 151 pg = maybe_pte_to_page(pte); 152 if (unlikely(!pg)) 153 goto bail; 154 155 /* If the page is already clean, we move on */ 156 if (test_bit(PG_arch_1, &pg->flags)) 157 goto bail; 158 159 /* Clean the page and set PG_arch_1 */ 160 flush_dcache_icache_page(pg); 161 set_bit(PG_arch_1, &pg->flags); 162 163 bail: 164 return __pte(pte_val(pte) | _PAGE_EXEC); 165 } 166 167 #endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */ 168 169 /* 170 * set_pte stores a linux PTE into the linux page table. 171 */ 172 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 173 pte_t pte) 174 { 175 /* 176 * When handling numa faults, we already have the pte marked 177 * _PAGE_PRESENT, but we can be sure that it is not in hpte. 178 * Hence we can use set_pte_at for them. 179 */ 180 VM_WARN_ON((pte_val(*ptep) & (_PAGE_PRESENT | _PAGE_USER)) == 181 (_PAGE_PRESENT | _PAGE_USER)); 182 /* 183 * Add the pte bit when tryint set a pte 184 */ 185 pte = __pte(pte_val(pte) | _PAGE_PTE); 186 187 /* Note: mm->context.id might not yet have been assigned as 188 * this context might not have been activated yet when this 189 * is called. 190 */ 191 pte = set_pte_filter(pte); 192 193 /* Perform the setting of the PTE */ 194 __set_pte_at(mm, addr, ptep, pte, 0); 195 } 196 197 /* 198 * This is called when relaxing access to a PTE. It's also called in the page 199 * fault path when we don't hit any of the major fault cases, ie, a minor 200 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 201 * handled those two for us, we additionally deal with missing execute 202 * permission here on some processors 203 */ 204 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 205 pte_t *ptep, pte_t entry, int dirty) 206 { 207 int changed; 208 entry = set_access_flags_filter(entry, vma, dirty); 209 changed = !pte_same(*(ptep), entry); 210 if (changed) { 211 if (!is_vm_hugetlb_page(vma)) 212 assert_pte_locked(vma->vm_mm, address); 213 __ptep_set_access_flags(ptep, entry); 214 flush_tlb_page_nohash(vma, address); 215 } 216 return changed; 217 } 218 219 #ifdef CONFIG_DEBUG_VM 220 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 221 { 222 pgd_t *pgd; 223 pud_t *pud; 224 pmd_t *pmd; 225 226 if (mm == &init_mm) 227 return; 228 pgd = mm->pgd + pgd_index(addr); 229 BUG_ON(pgd_none(*pgd)); 230 pud = pud_offset(pgd, addr); 231 BUG_ON(pud_none(*pud)); 232 pmd = pmd_offset(pud, addr); 233 /* 234 * khugepaged to collapse normal pages to hugepage, first set 235 * pmd to none to force page fault/gup to take mmap_sem. After 236 * pmd is set to none, we do a pte_clear which does this assertion 237 * so if we find pmd none, return. 238 */ 239 if (pmd_none(*pmd)) 240 return; 241 BUG_ON(!pmd_present(*pmd)); 242 assert_spin_locked(pte_lockptr(mm, pmd)); 243 } 244 #endif /* CONFIG_DEBUG_VM */ 245 246