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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Copyright (C) 2020 ARM Ltd.
4 */
5#ifndef __ASM_MTE_H
6#define __ASM_MTE_H
7
8#include <asm/compiler.h>
9#include <asm/mte-def.h>
10
11#ifndef __ASSEMBLER__
12
13#include <linux/bitfield.h>
14#include <linux/kasan-enabled.h>
15#include <linux/page-flags.h>
16#include <linux/sched.h>
17#include <linux/types.h>
18
19#include <asm/pgtable-types.h>
20
21void mte_clear_page_tags(void *addr);
22unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
23 unsigned long n);
24unsigned long mte_copy_tags_to_user(void __user *to, void *from,
25 unsigned long n);
26int mte_save_tags(struct page *page);
27void mte_save_page_tags(const void *page_addr, void *tag_storage);
28void mte_restore_tags(swp_entry_t entry, struct page *page);
29void mte_restore_page_tags(void *page_addr, const void *tag_storage);
30void mte_invalidate_tags(int type, pgoff_t offset);
31void mte_invalidate_tags_area(int type);
32void *mte_allocate_tag_storage(void);
33void mte_free_tag_storage(char *storage);
34
35#ifdef CONFIG_ARM64_MTE
36
37/* track which pages have valid allocation tags */
38#define PG_mte_tagged PG_arch_2
39/* simple lock to avoid multiple threads tagging the same page */
40#define PG_mte_lock PG_arch_3
41
42static inline void set_page_mte_tagged(struct page *page)
43{
44 VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page)));
45
46 /*
47 * Ensure that the tags written prior to this function are visible
48 * before the page flags update.
49 */
50 smp_wmb();
51 set_bit(PG_mte_tagged, &page->flags.f);
52}
53
54static inline bool page_mte_tagged(struct page *page)
55{
56 bool ret = test_bit(PG_mte_tagged, &page->flags.f);
57
58 VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page)));
59
60 /*
61 * If the page is tagged, ensure ordering with a likely subsequent
62 * read of the tags.
63 */
64 if (ret)
65 smp_rmb();
66 return ret;
67}
68
69/*
70 * Lock the page for tagging and return 'true' if the page can be tagged,
71 * 'false' if already tagged. PG_mte_tagged is never cleared and therefore the
72 * locking only happens once for page initialisation.
73 *
74 * The page MTE lock state:
75 *
76 * Locked: PG_mte_lock && !PG_mte_tagged
77 * Unlocked: !PG_mte_lock || PG_mte_tagged
78 *
79 * Acquire semantics only if the page is tagged (returning 'false').
80 */
81static inline bool try_page_mte_tagging(struct page *page)
82{
83 VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page)));
84
85 if (!test_and_set_bit(PG_mte_lock, &page->flags.f))
86 return true;
87
88 /*
89 * The tags are either being initialised or may have been initialised
90 * already. Check if the PG_mte_tagged flag has been set or wait
91 * otherwise.
92 */
93 smp_cond_load_acquire(&page->flags.f, VAL & (1UL << PG_mte_tagged));
94
95 return false;
96}
97
98void mte_zero_clear_page_tags(void *addr);
99void mte_sync_tags(pte_t pte, unsigned int nr_pages);
100void mte_copy_page_tags(void *kto, const void *kfrom);
101void mte_thread_init_user(void);
102void mte_thread_switch(struct task_struct *next);
103void mte_cpu_setup(void);
104void mte_suspend_enter(void);
105void mte_suspend_exit(void);
106long set_mte_ctrl(struct task_struct *task, unsigned long arg);
107long get_mte_ctrl(struct task_struct *task);
108int mte_ptrace_copy_tags(struct task_struct *child, long request,
109 unsigned long addr, unsigned long data);
110size_t mte_probe_user_range(const char __user *uaddr, size_t size);
111
112#else /* CONFIG_ARM64_MTE */
113
114/* unused if !CONFIG_ARM64_MTE, silence the compiler */
115#define PG_mte_tagged 0
116
117static inline void set_page_mte_tagged(struct page *page)
118{
119}
120static inline bool page_mte_tagged(struct page *page)
121{
122 return false;
123}
124static inline bool try_page_mte_tagging(struct page *page)
125{
126 return false;
127}
128static inline void mte_zero_clear_page_tags(void *addr)
129{
130}
131static inline void mte_sync_tags(pte_t pte, unsigned int nr_pages)
132{
133}
134static inline void mte_copy_page_tags(void *kto, const void *kfrom)
135{
136}
137static inline void mte_thread_init_user(void)
138{
139}
140static inline void mte_thread_switch(struct task_struct *next)
141{
142}
143static inline void mte_suspend_enter(void)
144{
145}
146static inline void mte_suspend_exit(void)
147{
148}
149static inline long set_mte_ctrl(struct task_struct *task, unsigned long arg)
150{
151 return 0;
152}
153static inline long get_mte_ctrl(struct task_struct *task)
154{
155 return 0;
156}
157static inline int mte_ptrace_copy_tags(struct task_struct *child,
158 long request, unsigned long addr,
159 unsigned long data)
160{
161 return -EIO;
162}
163
164#endif /* CONFIG_ARM64_MTE */
165
166#if defined(CONFIG_HUGETLB_PAGE) && defined(CONFIG_ARM64_MTE)
167static inline void folio_set_hugetlb_mte_tagged(struct folio *folio)
168{
169 VM_WARN_ON_ONCE(!folio_test_hugetlb(folio));
170
171 /*
172 * Ensure that the tags written prior to this function are visible
173 * before the folio flags update.
174 */
175 smp_wmb();
176 set_bit(PG_mte_tagged, &folio->flags.f);
177
178}
179
180static inline bool folio_test_hugetlb_mte_tagged(struct folio *folio)
181{
182 bool ret = test_bit(PG_mte_tagged, &folio->flags.f);
183
184 VM_WARN_ON_ONCE(!folio_test_hugetlb(folio));
185
186 /*
187 * If the folio is tagged, ensure ordering with a likely subsequent
188 * read of the tags.
189 */
190 if (ret)
191 smp_rmb();
192 return ret;
193}
194
195static inline bool folio_try_hugetlb_mte_tagging(struct folio *folio)
196{
197 VM_WARN_ON_ONCE(!folio_test_hugetlb(folio));
198
199 if (!test_and_set_bit(PG_mte_lock, &folio->flags.f))
200 return true;
201
202 /*
203 * The tags are either being initialised or may have been initialised
204 * already. Check if the PG_mte_tagged flag has been set or wait
205 * otherwise.
206 */
207 smp_cond_load_acquire(&folio->flags.f, VAL & (1UL << PG_mte_tagged));
208
209 return false;
210}
211#else
212static inline void folio_set_hugetlb_mte_tagged(struct folio *folio)
213{
214}
215
216static inline bool folio_test_hugetlb_mte_tagged(struct folio *folio)
217{
218 return false;
219}
220
221static inline bool folio_try_hugetlb_mte_tagging(struct folio *folio)
222{
223 return false;
224}
225#endif
226
227static inline void mte_disable_tco_entry(struct task_struct *task)
228{
229 if (!system_supports_mte())
230 return;
231
232 /*
233 * Re-enable tag checking (TCO set on exception entry). This is only
234 * necessary if MTE is enabled in either the kernel or the userspace
235 * task in synchronous or asymmetric mode (SCTLR_EL1.TCF0 bit 0 is set
236 * for both). With MTE disabled in the kernel and disabled or
237 * asynchronous in userspace, tag check faults (including in uaccesses)
238 * are not reported, therefore there is no need to re-enable checking.
239 * This is beneficial on microarchitectures where re-enabling TCO is
240 * expensive.
241 */
242 if (kasan_hw_tags_enabled() ||
243 (task->thread.sctlr_user & (1UL << SCTLR_EL1_TCF0_SHIFT)))
244 asm volatile(SET_PSTATE_TCO(0));
245}
246
247#ifdef CONFIG_KASAN_HW_TAGS
248void mte_check_tfsr_el1(void);
249
250static inline void mte_check_tfsr_entry(void)
251{
252 if (!kasan_hw_tags_enabled())
253 return;
254
255 mte_check_tfsr_el1();
256}
257
258static inline void mte_check_tfsr_exit(void)
259{
260 if (!kasan_hw_tags_enabled())
261 return;
262
263 /*
264 * The asynchronous faults are sync'ed automatically with
265 * TFSR_EL1 on kernel entry but for exit an explicit dsb()
266 * is required.
267 */
268 dsb(nsh);
269 isb();
270
271 mte_check_tfsr_el1();
272}
273#else
274static inline void mte_check_tfsr_el1(void)
275{
276}
277static inline void mte_check_tfsr_entry(void)
278{
279}
280static inline void mte_check_tfsr_exit(void)
281{
282}
283#endif /* CONFIG_KASAN_HW_TAGS */
284
285#endif /* __ASSEMBLER__ */
286#endif /* __ASM_MTE_H */
287

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source code of linux/arch/arm64/include/asm/mte.h