arch/powerpc/mm/pgtable.c

   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 cache inhibited pte. We also only do that
  42  * on userspace PTEs
  43  */
  44 static inline int pte_looks_normal(pte_t pte)
  45 {
  46
  47 #if defined(CONFIG_PPC_BOOK3S_64)
  48         if ((pte_val(pte) & (_PAGE_PRESENT | _PAGE_SPECIAL)) == _PAGE_PRESENT) {
  49                 if (pte_ci(pte))
  50                         return 0;
  51                 if (pte_user(pte))
  52                         return 1;
  53         }
  54         return 0;
  55 #else
  56         return (pte_val(pte) &
  57                 (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER |
  58                  _PAGE_PRIVILEGED)) ==
  59                 (_PAGE_PRESENT | _PAGE_USER);
  60 #endif
  61 }
  62
  63 static struct page *maybe_pte_to_page(pte_t pte)
  64 {
  65         unsigned long pfn = pte_pfn(pte);
  66         struct page *page;
  67
  68         if (unlikely(!pfn_valid(pfn)))
  69                 return NULL;
  70         page = pfn_to_page(pfn);
  71         if (PageReserved(page))
  72                 return NULL;
  73         return page;
  74 }
  75
  76 #if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0
  77
  78 /* Server-style MMU handles coherency when hashing if HW exec permission
  79  * is supposed per page (currently 64-bit only). If not, then, we always
  80  * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec
  81  * support falls into the same category.
  82  */
  83
  84 static pte_t set_pte_filter(pte_t pte)
  85 {
  86         if (radix_enabled())
  87                 return pte;
  88
  89         pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
  90         if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) ||
  91                                        cpu_has_feature(CPU_FTR_NOEXECUTE))) {
  92                 struct page *pg = maybe_pte_to_page(pte);
  93                 if (!pg)
  94                         return pte;
  95                 if (!test_bit(PG_arch_1, &pg->flags)) {
  96                         flush_dcache_icache_page(pg);
  97                         set_bit(PG_arch_1, &pg->flags);
  98                 }
  99         }
 100         return pte;
 101 }
 102
 103 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
 104                                      int dirty)
 105 {
 106         return pte;
 107 }
 108
 109 #else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */
 110
 111 /* Embedded type MMU with HW exec support. This is a bit more complicated
 112  * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so
 113  * instead we "filter out" the exec permission for non clean pages.
 114  */
 115 static pte_t set_pte_filter(pte_t pte)
 116 {
 117         struct page *pg;
 118
 119         /* No exec permission in the first place, move on */
 120         if (!(pte_val(pte) & _PAGE_EXEC) || !pte_looks_normal(pte))
 121                 return pte;
 122
 123         /* If you set _PAGE_EXEC on weird pages you're on your own */
 124         pg = maybe_pte_to_page(pte);
 125         if (unlikely(!pg))
 126                 return pte;
 127
 128         /* If the page clean, we move on */
 129         if (test_bit(PG_arch_1, &pg->flags))
 130                 return pte;
 131
 132         /* If it's an exec fault, we flush the cache and make it clean */
 133         if (is_exec_fault()) {
 134                 flush_dcache_icache_page(pg);
 135                 set_bit(PG_arch_1, &pg->flags);
 136                 return pte;
 137         }
 138
 139         /* Else, we filter out _PAGE_EXEC */
 140         return __pte(pte_val(pte) & ~_PAGE_EXEC);
 141 }
 142
 143 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
 144                                      int dirty)
 145 {
 146         struct page *pg;
 147
 148         /* So here, we only care about exec faults, as we use them
 149          * to recover lost _PAGE_EXEC and perform I$/D$ coherency
 150          * if necessary. Also if _PAGE_EXEC is already set, same deal,
 151          * we just bail out
 152          */
 153         if (dirty || (pte_val(pte) & _PAGE_EXEC) || !is_exec_fault())
 154                 return pte;
 155
 156 #ifdef CONFIG_DEBUG_VM
 157         /* So this is an exec fault, _PAGE_EXEC is not set. If it was
 158          * an error we would have bailed out earlier in do_page_fault()
 159          * but let's make sure of it
 160          */
 161         if (WARN_ON(!(vma->vm_flags & VM_EXEC)))
 162                 return pte;
 163 #endif /* CONFIG_DEBUG_VM */
 164
 165         /* If you set _PAGE_EXEC on weird pages you're on your own */
 166         pg = maybe_pte_to_page(pte);
 167         if (unlikely(!pg))
 168                 goto bail;
 169
 170         /* If the page is already clean, we move on */
 171         if (test_bit(PG_arch_1, &pg->flags))
 172                 goto bail;
 173
 174         /* Clean the page and set PG_arch_1 */
 175         flush_dcache_icache_page(pg);
 176         set_bit(PG_arch_1, &pg->flags);
 177
 178  bail:
 179         return __pte(pte_val(pte) | _PAGE_EXEC);
 180 }
 181
 182 #endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */
 183
 184 /*
 185  * set_pte stores a linux PTE into the linux page table.
 186  */
 187 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
 188                 pte_t pte)
 189 {
 190         /*
 191          * When handling numa faults, we already have the pte marked
 192          * _PAGE_PRESENT, but we can be sure that it is not in hpte.
 193          * Hence we can use set_pte_at for them.
 194          */
 195         VM_WARN_ON(pte_present(*ptep) && !pte_protnone(*ptep));
 196
 197         /* Add the pte bit when trying to set a pte */
 198         pte = __pte(pte_val(pte) | _PAGE_PTE);
 199
 200         /* Note: mm->context.id might not yet have been assigned as
 201          * this context might not have been activated yet when this
 202          * is called.
 203          */
 204         pte = set_pte_filter(pte);
 205
 206         /* Perform the setting of the PTE */
 207         __set_pte_at(mm, addr, ptep, pte, 0);
 208 }
 209
 210 /*
 211  * This is called when relaxing access to a PTE. It's also called in the page
 212  * fault path when we don't hit any of the major fault cases, ie, a minor
 213  * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have
 214  * handled those two for us, we additionally deal with missing execute
 215  * permission here on some processors
 216  */
 217 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address,
 218                           pte_t *ptep, pte_t entry, int dirty)
 219 {
 220         int changed;
 221         entry = set_access_flags_filter(entry, vma, dirty);
 222         changed = !pte_same(*(ptep), entry);
 223         if (changed) {
 224                 if (!is_vm_hugetlb_page(vma))
 225                         assert_pte_locked(vma->vm_mm, address);
 226                 __ptep_set_access_flags(vma->vm_mm, ptep, entry, address);
 227                 flush_tlb_page(vma, address);
 228         }
 229         return changed;
 230 }
 231
 232 #ifdef CONFIG_DEBUG_VM
 233 void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
 234 {
 235         pgd_t *pgd;
 236         pud_t *pud;
 237         pmd_t *pmd;
 238
 239         if (mm == &init_mm)
 240                 return;
 241         pgd = mm->pgd + pgd_index(addr);
 242         BUG_ON(pgd_none(*pgd));
 243         pud = pud_offset(pgd, addr);
 244         BUG_ON(pud_none(*pud));
 245         pmd = pmd_offset(pud, addr);
 246         /*
 247          * khugepaged to collapse normal pages to hugepage, first set
 248          * pmd to none to force page fault/gup to take mmap_sem. After
 249          * pmd is set to none, we do a pte_clear which does this assertion
 250          * so if we find pmd none, return.
 251          */
 252         if (pmd_none(*pmd))
 253                 return;
 254         BUG_ON(!pmd_present(*pmd));
 255         assert_spin_locked(pte_lockptr(mm, pmd));
 256 }
 257 #endif /* CONFIG_DEBUG_VM */
 258
 259 unsigned long vmalloc_to_phys(void *va)
 260 {
 261         unsigned long pfn = vmalloc_to_pfn(va);
 262
 263         BUG_ON(!pfn);
 264         return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va);
 265 }
 266 EXPORT_SYMBOL_GPL(vmalloc_to_phys);