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  */
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 
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  */
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
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 
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 	VMA_ITERATOR(vmi, mm, addr);
153 
154 	/*
155 	 * We don't try too hard, we just mark all the vma in that range
156 	 * VM_NOHUGEPAGE and split them.
157 	 */
158 	for_each_vma_range(vmi, vma, addr + len) {
159 		vma->vm_flags |= VM_NOHUGEPAGE;
160 		walk_page_vma(vma, &subpage_walk_ops, NULL);
161 	}
162 }
163 #else
164 static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
165 				    unsigned long len)
166 {
167 	return;
168 }
169 #endif
170 
171 /*
172  * Copy in a subpage protection map for an address range.
173  * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
174  * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
175  * 2 or 3 to prevent all accesses.
176  * Note that the normal page protections also apply; the subpage
177  * protection mechanism is an additional constraint, so putting 0
178  * in a 2-bit field won't allow writes to a page that is otherwise
179  * write-protected.
180  */
181 SYSCALL_DEFINE3(subpage_prot, unsigned long, addr,
182 		unsigned long, len, u32 __user *, map)
183 {
184 	struct mm_struct *mm = current->mm;
185 	struct subpage_prot_table *spt;
186 	u32 **spm, *spp;
187 	unsigned long i;
188 	size_t nw;
189 	unsigned long next, limit;
190 	int err;
191 
192 	if (radix_enabled())
193 		return -ENOENT;
194 
195 	/* Check parameters */
196 	if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
197 	    addr >= mm->task_size || len >= mm->task_size ||
198 	    addr + len > mm->task_size)
199 		return -EINVAL;
200 
201 	if (is_hugepage_only_range(mm, addr, len))
202 		return -EINVAL;
203 
204 	if (!map) {
205 		/* Clear out the protection map for the address range */
206 		subpage_prot_clear(addr, len);
207 		return 0;
208 	}
209 
210 	if (!access_ok(map, (len >> PAGE_SHIFT) * sizeof(u32)))
211 		return -EFAULT;
212 
213 	mmap_write_lock(mm);
214 
215 	spt = mm_ctx_subpage_prot(&mm->context);
216 	if (!spt) {
217 		/*
218 		 * Allocate subpage prot table if not already done.
219 		 * Do this with mmap_lock held
220 		 */
221 		spt = kzalloc(sizeof(struct subpage_prot_table), GFP_KERNEL);
222 		if (!spt) {
223 			err = -ENOMEM;
224 			goto out;
225 		}
226 		mm->context.hash_context->spt = spt;
227 	}
228 
229 	subpage_mark_vma_nohuge(mm, addr, len);
230 	for (limit = addr + len; addr < limit; addr = next) {
231 		next = pmd_addr_end(addr, limit);
232 		err = -ENOMEM;
233 		if (addr < 0x100000000UL) {
234 			spm = spt->low_prot;
235 		} else {
236 			spm = spt->protptrs[addr >> SBP_L3_SHIFT];
237 			if (!spm) {
238 				spm = (u32 **)get_zeroed_page(GFP_KERNEL);
239 				if (!spm)
240 					goto out;
241 				spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
242 			}
243 		}
244 		spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
245 		spp = *spm;
246 		if (!spp) {
247 			spp = (u32 *)get_zeroed_page(GFP_KERNEL);
248 			if (!spp)
249 				goto out;
250 			*spm = spp;
251 		}
252 		spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
253 
254 		local_irq_disable();
255 		demote_segment_4k(mm, addr);
256 		local_irq_enable();
257 
258 		i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
259 		nw = PTRS_PER_PTE - i;
260 		if (addr + (nw << PAGE_SHIFT) > next)
261 			nw = (next - addr) >> PAGE_SHIFT;
262 
263 		mmap_write_unlock(mm);
264 		if (__copy_from_user(spp, map, nw * sizeof(u32)))
265 			return -EFAULT;
266 		map += nw;
267 		mmap_write_lock(mm);
268 
269 		/* now flush any existing HPTEs for the range */
270 		hpte_flush_range(mm, addr, nw);
271 	}
272 	if (limit > spt->maxaddr)
273 		spt->maxaddr = limit;
274 	err = 0;
275  out:
276 	mmap_write_unlock(mm);
277 	return err;
278 }
279