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#include <asm/kfence.h>
15
16struct page_change_data {
17	pgprot_t set_mask;
18	pgprot_t clear_mask;
19};
20
21bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
22
23bool can_set_direct_map(void)
24{
25	/*
26	 * rodata_full and DEBUG_PAGEALLOC require linear map to be
27	 * mapped at page granularity, so that it is possible to
28	 * protect/unprotect single pages.
29	 *
30	 * KFENCE pool requires page-granular mapping if initialized late.
31	 */
32	return rodata_full || debug_pagealloc_enabled() ||
33	       arm64_kfence_can_set_direct_map();
34}
35
36static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
37{
38	struct page_change_data *cdata = data;
39	pte_t pte = __ptep_get(ptep);
40
41	pte = clear_pte_bit(pte, cdata->clear_mask);
42	pte = set_pte_bit(pte, cdata->set_mask);
43
44	__set_pte(ptep, pte);
45	return 0;
46}
47
48/*
49 * This function assumes that the range is mapped with PAGE_SIZE pages.
50 */
51static int __change_memory_common(unsigned long start, unsigned long size,
52				pgprot_t set_mask, pgprot_t clear_mask)
53{
54	struct page_change_data data;
55	int ret;
56
57	data.set_mask = set_mask;
58	data.clear_mask = clear_mask;
59
60	ret = apply_to_page_range(&init_mm, start, size, change_page_range,
61					&data);
62
63	flush_tlb_kernel_range(start, start + size);
64	return ret;
65}
66
67static int change_memory_common(unsigned long addr, int numpages,
68				pgprot_t set_mask, pgprot_t clear_mask)
69{
70	unsigned long start = addr;
71	unsigned long size = PAGE_SIZE * numpages;
72	unsigned long end = start + size;
73	struct vm_struct *area;
74	int i;
75
76	if (!PAGE_ALIGNED(addr)) {
77		start &= PAGE_MASK;
78		end = start + size;
79		WARN_ON_ONCE(1);
80	}
81
82	/*
83	 * Kernel VA mappings are always live, and splitting live section
84	 * mappings into page mappings may cause TLB conflicts. This means
85	 * we have to ensure that changing the permission bits of the range
86	 * we are operating on does not result in such splitting.
87	 *
88	 * Let's restrict ourselves to mappings created by vmalloc (or vmap).
89	 * Those are guaranteed to consist entirely of page mappings, and
90	 * splitting is never needed.
91	 *
92	 * So check whether the [addr, addr + size) interval is entirely
93	 * covered by precisely one VM area that has the VM_ALLOC flag set.
94	 */
95	area = find_vm_area((void *)addr);
96	if (!area ||
97	    end > (unsigned long)kasan_reset_tag(area->addr) + area->size ||
98	    !(area->flags & VM_ALLOC))
99		return -EINVAL;
100
101	if (!numpages)
102		return 0;
103
104	/*
105	 * If we are manipulating read-only permissions, apply the same
106	 * change to the linear mapping of the pages that back this VM area.
107	 */
108	if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
109			    pgprot_val(clear_mask) == PTE_RDONLY)) {
110		for (i = 0; i < area->nr_pages; i++) {
111			__change_memory_common((u64)page_address(area->pages[i]),
112					       PAGE_SIZE, set_mask, clear_mask);
113		}
114	}
115
116	/*
117	 * Get rid of potentially aliasing lazily unmapped vm areas that may
118	 * have permissions set that deviate from the ones we are setting here.
119	 */
120	vm_unmap_aliases();
121
122	return __change_memory_common(start, size, set_mask, clear_mask);
123}
124
125int set_memory_ro(unsigned long addr, int numpages)
126{
127	return change_memory_common(addr, numpages,
128					__pgprot(PTE_RDONLY),
129					__pgprot(PTE_WRITE));
130}
131
132int set_memory_rw(unsigned long addr, int numpages)
133{
134	return change_memory_common(addr, numpages,
135					__pgprot(PTE_WRITE),
136					__pgprot(PTE_RDONLY));
137}
138
139int set_memory_nx(unsigned long addr, int numpages)
140{
141	return change_memory_common(addr, numpages,
142					__pgprot(PTE_PXN),
143					__pgprot(PTE_MAYBE_GP));
144}
145
146int set_memory_x(unsigned long addr, int numpages)
147{
148	return change_memory_common(addr, numpages,
149					__pgprot(PTE_MAYBE_GP),
150					__pgprot(PTE_PXN));
151}
152
153int set_memory_valid(unsigned long addr, int numpages, int enable)
154{
155	if (enable)
156		return __change_memory_common(addr, PAGE_SIZE * numpages,
157					__pgprot(PTE_VALID),
158					__pgprot(0));
159	else
160		return __change_memory_common(addr, PAGE_SIZE * numpages,
161					__pgprot(0),
162					__pgprot(PTE_VALID));
163}
164
165int set_direct_map_invalid_noflush(struct page *page)
166{
167	struct page_change_data data = {
168		.set_mask = __pgprot(0),
169		.clear_mask = __pgprot(PTE_VALID),
170	};
171
172	if (!can_set_direct_map())
173		return 0;
174
175	return apply_to_page_range(&init_mm,
176				   (unsigned long)page_address(page),
177				   PAGE_SIZE, change_page_range, &data);
178}
179
180int set_direct_map_default_noflush(struct page *page)
181{
182	struct page_change_data data = {
183		.set_mask = __pgprot(PTE_VALID | PTE_WRITE),
184		.clear_mask = __pgprot(PTE_RDONLY),
185	};
186
187	if (!can_set_direct_map())
188		return 0;
189
190	return apply_to_page_range(&init_mm,
191				   (unsigned long)page_address(page),
192				   PAGE_SIZE, change_page_range, &data);
193}
194
195#ifdef CONFIG_DEBUG_PAGEALLOC
196void __kernel_map_pages(struct page *page, int numpages, int enable)
197{
198	if (!can_set_direct_map())
199		return;
200
201	set_memory_valid((unsigned long)page_address(page), numpages, enable);
202}
203#endif /* CONFIG_DEBUG_PAGEALLOC */
204
205/*
206 * This function is used to determine if a linear map page has been marked as
207 * not-valid. Walk the page table and check the PTE_VALID bit.
208 *
209 * Because this is only called on the kernel linear map,  p?d_sect() implies
210 * p?d_present(). When debug_pagealloc is enabled, sections mappings are
211 * disabled.
212 */
213bool kernel_page_present(struct page *page)
214{
215	pgd_t *pgdp;
216	p4d_t *p4dp;
217	pud_t *pudp, pud;
218	pmd_t *pmdp, pmd;
219	pte_t *ptep;
220	unsigned long addr = (unsigned long)page_address(page);
221
222	pgdp = pgd_offset_k(addr);
223	if (pgd_none(READ_ONCE(*pgdp)))
224		return false;
225
226	p4dp = p4d_offset(pgdp, addr);
227	if (p4d_none(READ_ONCE(*p4dp)))
228		return false;
229
230	pudp = pud_offset(p4dp, addr);
231	pud = READ_ONCE(*pudp);
232	if (pud_none(pud))
233		return false;
234	if (pud_sect(pud))
235		return true;
236
237	pmdp = pmd_offset(pudp, addr);
238	pmd = READ_ONCE(*pmdp);
239	if (pmd_none(pmd))
240		return false;
241	if (pmd_sect(pmd))
242		return true;
243
244	ptep = pte_offset_kernel(pmdp, addr);
245	return pte_valid(__ptep_get(ptep));
246}
247