1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright 2007-2008 Paul Mackerras, IBM Corp.
4 */
5
6 #include <linux/errno.h>
7 #include <linux/kernel.h>
8 #include <linux/gfp.h>
9 #include <linux/types.h>
10 #include <linux/pagewalk.h>
11 #include <linux/hugetlb.h>
12 #include <linux/syscalls.h>
13
14 #include <linux/pgtable.h>
15 #include <linux/uaccess.h>
16
17 /*
18 * Free all pages allocated for subpage protection maps and pointers.
19 * Also makes sure that the subpage_prot_table structure is
20 * reinitialized for the next user.
21 */
subpage_prot_free(struct mm_struct * mm)22 void subpage_prot_free(struct mm_struct *mm)
23 {
24 struct subpage_prot_table *spt = mm_ctx_subpage_prot(&mm->context);
25 unsigned long i, j, addr;
26 u32 **p;
27
28 if (!spt)
29 return;
30
31 for (i = 0; i < 4; ++i) {
32 if (spt->low_prot[i]) {
33 free_page((unsigned long)spt->low_prot[i]);
34 spt->low_prot[i] = NULL;
35 }
36 }
37 addr = 0;
38 for (i = 0; i < (TASK_SIZE_USER64 >> 43); ++i) {
39 p = spt->protptrs[i];
40 if (!p)
41 continue;
42 spt->protptrs[i] = NULL;
43 for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
44 ++j, addr += PAGE_SIZE)
45 if (p[j])
46 free_page((unsigned long)p[j]);
47 free_page((unsigned long)p);
48 }
49 spt->maxaddr = 0;
50 kfree(spt);
51 }
52
hpte_flush_range(struct mm_struct * mm,unsigned long addr,int npages)53 static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
54 int npages)
55 {
56 pgd_t *pgd;
57 p4d_t *p4d;
58 pud_t *pud;
59 pmd_t *pmd;
60 pte_t *pte;
61 spinlock_t *ptl;
62
63 pgd = pgd_offset(mm, addr);
64 p4d = p4d_offset(pgd, addr);
65 if (p4d_none(*p4d))
66 return;
67 pud = pud_offset(p4d, addr);
68 if (pud_none(*pud))
69 return;
70 pmd = pmd_offset(pud, addr);
71 if (pmd_none(*pmd))
72 return;
73 pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
74 arch_enter_lazy_mmu_mode();
75 for (; npages > 0; --npages) {
76 pte_update(mm, addr, pte, 0, 0, 0);
77 addr += PAGE_SIZE;
78 ++pte;
79 }
80 arch_leave_lazy_mmu_mode();
81 pte_unmap_unlock(pte - 1, ptl);
82 }
83
84 /*
85 * Clear the subpage protection map for an address range, allowing
86 * all accesses that are allowed by the pte permissions.
87 */
subpage_prot_clear(unsigned long addr,unsigned long len)88 static void subpage_prot_clear(unsigned long addr, unsigned long len)
89 {
90 struct mm_struct *mm = current->mm;
91 struct subpage_prot_table *spt;
92 u32 **spm, *spp;
93 unsigned long i;
94 size_t nw;
95 unsigned long next, limit;
96
97 mmap_write_lock(mm);
98
99 spt = mm_ctx_subpage_prot(&mm->context);
100 if (!spt)
101 goto err_out;
102
103 limit = addr + len;
104 if (limit > spt->maxaddr)
105 limit = spt->maxaddr;
106 for (; addr < limit; addr = next) {
107 next = pmd_addr_end(addr, limit);
108 if (addr < 0x100000000UL) {
109 spm = spt->low_prot;
110 } else {
111 spm = spt->protptrs[addr >> SBP_L3_SHIFT];
112 if (!spm)
113 continue;
114 }
115 spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
116 if (!spp)
117 continue;
118 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
119
120 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
121 nw = PTRS_PER_PTE - i;
122 if (addr + (nw << PAGE_SHIFT) > next)
123 nw = (next - addr) >> PAGE_SHIFT;
124
125 memset(spp, 0, nw * sizeof(u32));
126
127 /* now flush any existing HPTEs for the range */
128 hpte_flush_range(mm, addr, nw);
129 }
130
131 err_out:
132 mmap_write_unlock(mm);
133 }
134
135 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
subpage_walk_pmd_entry(pmd_t * pmd,unsigned long addr,unsigned long end,struct mm_walk * walk)136 static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
137 unsigned long end, struct mm_walk *walk)
138 {
139 struct vm_area_struct *vma = walk->vma;
140 split_huge_pmd(vma, pmd, addr);
141 return 0;
142 }
143
144 static const struct mm_walk_ops subpage_walk_ops = {
145 .pmd_entry = subpage_walk_pmd_entry,
146 };
147
subpage_mark_vma_nohuge(struct mm_struct * mm,unsigned long addr,unsigned long len)148 static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
149 unsigned long len)
150 {
151 struct vm_area_struct *vma;
152
153 /*
154 * We don't try too hard, we just mark all the vma in that range
155 * VM_NOHUGEPAGE and split them.
156 */
157 vma = find_vma(mm, addr);
158 /*
159 * If the range is in unmapped range, just return
160 */
161 if (vma && ((addr + len) <= vma->vm_start))
162 return;
163
164 while (vma) {
165 if (vma->vm_start >= (addr + len))
166 break;
167 vma->vm_flags |= VM_NOHUGEPAGE;
168 walk_page_vma(vma, &subpage_walk_ops, NULL);
169 vma = vma->vm_next;
170 }
171 }
172 #else
subpage_mark_vma_nohuge(struct mm_struct * mm,unsigned long addr,unsigned long len)173 static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
174 unsigned long len)
175 {
176 return;
177 }
178 #endif
179
180 /*
181 * Copy in a subpage protection map for an address range.
182 * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
183 * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
184 * 2 or 3 to prevent all accesses.
185 * Note that the normal page protections also apply; the subpage
186 * protection mechanism is an additional constraint, so putting 0
187 * in a 2-bit field won't allow writes to a page that is otherwise
188 * write-protected.
189 */
SYSCALL_DEFINE3(subpage_prot,unsigned long,addr,unsigned long,len,u32 __user *,map)190 SYSCALL_DEFINE3(subpage_prot, unsigned long, addr,
191 unsigned long, len, u32 __user *, map)
192 {
193 struct mm_struct *mm = current->mm;
194 struct subpage_prot_table *spt;
195 u32 **spm, *spp;
196 unsigned long i;
197 size_t nw;
198 unsigned long next, limit;
199 int err;
200
201 if (radix_enabled())
202 return -ENOENT;
203
204 /* Check parameters */
205 if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
206 addr >= mm->task_size || len >= mm->task_size ||
207 addr + len > mm->task_size)
208 return -EINVAL;
209
210 if (is_hugepage_only_range(mm, addr, len))
211 return -EINVAL;
212
213 if (!map) {
214 /* Clear out the protection map for the address range */
215 subpage_prot_clear(addr, len);
216 return 0;
217 }
218
219 if (!access_ok(map, (len >> PAGE_SHIFT) * sizeof(u32)))
220 return -EFAULT;
221
222 mmap_write_lock(mm);
223
224 spt = mm_ctx_subpage_prot(&mm->context);
225 if (!spt) {
226 /*
227 * Allocate subpage prot table if not already done.
228 * Do this with mmap_lock held
229 */
230 spt = kzalloc(sizeof(struct subpage_prot_table), GFP_KERNEL);
231 if (!spt) {
232 err = -ENOMEM;
233 goto out;
234 }
235 mm->context.hash_context->spt = spt;
236 }
237
238 subpage_mark_vma_nohuge(mm, addr, len);
239 for (limit = addr + len; addr < limit; addr = next) {
240 next = pmd_addr_end(addr, limit);
241 err = -ENOMEM;
242 if (addr < 0x100000000UL) {
243 spm = spt->low_prot;
244 } else {
245 spm = spt->protptrs[addr >> SBP_L3_SHIFT];
246 if (!spm) {
247 spm = (u32 **)get_zeroed_page(GFP_KERNEL);
248 if (!spm)
249 goto out;
250 spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
251 }
252 }
253 spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
254 spp = *spm;
255 if (!spp) {
256 spp = (u32 *)get_zeroed_page(GFP_KERNEL);
257 if (!spp)
258 goto out;
259 *spm = spp;
260 }
261 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
262
263 local_irq_disable();
264 demote_segment_4k(mm, addr);
265 local_irq_enable();
266
267 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
268 nw = PTRS_PER_PTE - i;
269 if (addr + (nw << PAGE_SHIFT) > next)
270 nw = (next - addr) >> PAGE_SHIFT;
271
272 mmap_write_unlock(mm);
273 if (__copy_from_user(spp, map, nw * sizeof(u32)))
274 return -EFAULT;
275 map += nw;
276 mmap_write_lock(mm);
277
278 /* now flush any existing HPTEs for the range */
279 hpte_flush_range(mm, addr, nw);
280 }
281 if (limit > spt->maxaddr)
282 spt->maxaddr = limit;
283 err = 0;
284 out:
285 mmap_write_unlock(mm);
286 return err;
287 }
288