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