xref: /openbmc/linux/arch/arm64/mm/pageattr.c (revision 9a234a2a)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (c) 2014, The Linux Foundation. All rights reserved.
4  */
5 #include <linux/kernel.h>
6 #include <linux/mm.h>
7 #include <linux/module.h>
8 #include <linux/sched.h>
9 #include <linux/vmalloc.h>
10 
11 #include <asm/cacheflush.h>
12 #include <asm/set_memory.h>
13 #include <asm/tlbflush.h>
14 
15 struct page_change_data {
16 	pgprot_t set_mask;
17 	pgprot_t clear_mask;
18 };
19 
20 bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
21 
22 bool can_set_direct_map(void)
23 {
24 	/*
25 	 * rodata_full, DEBUG_PAGEALLOC and KFENCE require linear map to be
26 	 * mapped at page granularity, so that it is possible to
27 	 * protect/unprotect single pages.
28 	 */
29 	return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() ||
30 		IS_ENABLED(CONFIG_KFENCE);
31 }
32 
33 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
34 {
35 	struct page_change_data *cdata = data;
36 	pte_t pte = READ_ONCE(*ptep);
37 
38 	pte = clear_pte_bit(pte, cdata->clear_mask);
39 	pte = set_pte_bit(pte, cdata->set_mask);
40 
41 	set_pte(ptep, pte);
42 	return 0;
43 }
44 
45 /*
46  * This function assumes that the range is mapped with PAGE_SIZE pages.
47  */
48 static int __change_memory_common(unsigned long start, unsigned long size,
49 				pgprot_t set_mask, pgprot_t clear_mask)
50 {
51 	struct page_change_data data;
52 	int ret;
53 
54 	data.set_mask = set_mask;
55 	data.clear_mask = clear_mask;
56 
57 	ret = apply_to_page_range(&init_mm, start, size, change_page_range,
58 					&data);
59 
60 	flush_tlb_kernel_range(start, start + size);
61 	return ret;
62 }
63 
64 static int change_memory_common(unsigned long addr, int numpages,
65 				pgprot_t set_mask, pgprot_t clear_mask)
66 {
67 	unsigned long start = addr;
68 	unsigned long size = PAGE_SIZE * numpages;
69 	unsigned long end = start + size;
70 	struct vm_struct *area;
71 	int i;
72 
73 	if (!PAGE_ALIGNED(addr)) {
74 		start &= PAGE_MASK;
75 		end = start + size;
76 		WARN_ON_ONCE(1);
77 	}
78 
79 	/*
80 	 * Kernel VA mappings are always live, and splitting live section
81 	 * mappings into page mappings may cause TLB conflicts. This means
82 	 * we have to ensure that changing the permission bits of the range
83 	 * we are operating on does not result in such splitting.
84 	 *
85 	 * Let's restrict ourselves to mappings created by vmalloc (or vmap).
86 	 * Those are guaranteed to consist entirely of page mappings, and
87 	 * splitting is never needed.
88 	 *
89 	 * So check whether the [addr, addr + size) interval is entirely
90 	 * covered by precisely one VM area that has the VM_ALLOC flag set.
91 	 */
92 	area = find_vm_area((void *)addr);
93 	if (!area ||
94 	    end > (unsigned long)kasan_reset_tag(area->addr) + area->size ||
95 	    !(area->flags & VM_ALLOC))
96 		return -EINVAL;
97 
98 	if (!numpages)
99 		return 0;
100 
101 	/*
102 	 * If we are manipulating read-only permissions, apply the same
103 	 * change to the linear mapping of the pages that back this VM area.
104 	 */
105 	if (rodata_enabled &&
106 	    rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
107 			    pgprot_val(clear_mask) == PTE_RDONLY)) {
108 		for (i = 0; i < area->nr_pages; i++) {
109 			__change_memory_common((u64)page_address(area->pages[i]),
110 					       PAGE_SIZE, set_mask, clear_mask);
111 		}
112 	}
113 
114 	/*
115 	 * Get rid of potentially aliasing lazily unmapped vm areas that may
116 	 * have permissions set that deviate from the ones we are setting here.
117 	 */
118 	vm_unmap_aliases();
119 
120 	return __change_memory_common(start, size, set_mask, clear_mask);
121 }
122 
123 int set_memory_ro(unsigned long addr, int numpages)
124 {
125 	return change_memory_common(addr, numpages,
126 					__pgprot(PTE_RDONLY),
127 					__pgprot(PTE_WRITE));
128 }
129 
130 int set_memory_rw(unsigned long addr, int numpages)
131 {
132 	return change_memory_common(addr, numpages,
133 					__pgprot(PTE_WRITE),
134 					__pgprot(PTE_RDONLY));
135 }
136 
137 int set_memory_nx(unsigned long addr, int numpages)
138 {
139 	return change_memory_common(addr, numpages,
140 					__pgprot(PTE_PXN),
141 					__pgprot(PTE_MAYBE_GP));
142 }
143 
144 int set_memory_x(unsigned long addr, int numpages)
145 {
146 	return change_memory_common(addr, numpages,
147 					__pgprot(PTE_MAYBE_GP),
148 					__pgprot(PTE_PXN));
149 }
150 
151 int set_memory_valid(unsigned long addr, int numpages, int enable)
152 {
153 	if (enable)
154 		return __change_memory_common(addr, PAGE_SIZE * numpages,
155 					__pgprot(PTE_VALID),
156 					__pgprot(0));
157 	else
158 		return __change_memory_common(addr, PAGE_SIZE * numpages,
159 					__pgprot(0),
160 					__pgprot(PTE_VALID));
161 }
162 
163 int set_direct_map_invalid_noflush(struct page *page)
164 {
165 	struct page_change_data data = {
166 		.set_mask = __pgprot(0),
167 		.clear_mask = __pgprot(PTE_VALID),
168 	};
169 
170 	if (!can_set_direct_map())
171 		return 0;
172 
173 	return apply_to_page_range(&init_mm,
174 				   (unsigned long)page_address(page),
175 				   PAGE_SIZE, change_page_range, &data);
176 }
177 
178 int set_direct_map_default_noflush(struct page *page)
179 {
180 	struct page_change_data data = {
181 		.set_mask = __pgprot(PTE_VALID | PTE_WRITE),
182 		.clear_mask = __pgprot(PTE_RDONLY),
183 	};
184 
185 	if (!can_set_direct_map())
186 		return 0;
187 
188 	return apply_to_page_range(&init_mm,
189 				   (unsigned long)page_address(page),
190 				   PAGE_SIZE, change_page_range, &data);
191 }
192 
193 #ifdef CONFIG_DEBUG_PAGEALLOC
194 void __kernel_map_pages(struct page *page, int numpages, int enable)
195 {
196 	if (!can_set_direct_map())
197 		return;
198 
199 	set_memory_valid((unsigned long)page_address(page), numpages, enable);
200 }
201 #endif /* CONFIG_DEBUG_PAGEALLOC */
202 
203 /*
204  * This function is used to determine if a linear map page has been marked as
205  * not-valid. Walk the page table and check the PTE_VALID bit. This is based
206  * on kern_addr_valid(), which almost does what we need.
207  *
208  * Because this is only called on the kernel linear map,  p?d_sect() implies
209  * p?d_present(). When debug_pagealloc is enabled, sections mappings are
210  * disabled.
211  */
212 bool kernel_page_present(struct page *page)
213 {
214 	pgd_t *pgdp;
215 	p4d_t *p4dp;
216 	pud_t *pudp, pud;
217 	pmd_t *pmdp, pmd;
218 	pte_t *ptep;
219 	unsigned long addr = (unsigned long)page_address(page);
220 
221 	if (!can_set_direct_map())
222 		return true;
223 
224 	pgdp = pgd_offset_k(addr);
225 	if (pgd_none(READ_ONCE(*pgdp)))
226 		return false;
227 
228 	p4dp = p4d_offset(pgdp, addr);
229 	if (p4d_none(READ_ONCE(*p4dp)))
230 		return false;
231 
232 	pudp = pud_offset(p4dp, addr);
233 	pud = READ_ONCE(*pudp);
234 	if (pud_none(pud))
235 		return false;
236 	if (pud_sect(pud))
237 		return true;
238 
239 	pmdp = pmd_offset(pudp, addr);
240 	pmd = READ_ONCE(*pmdp);
241 	if (pmd_none(pmd))
242 		return false;
243 	if (pmd_sect(pmd))
244 		return true;
245 
246 	ptep = pte_offset_kernel(pmdp, addr);
247 	return pte_valid(READ_ONCE(*ptep));
248 }
249