1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Based on arch/arm/include/asm/mmu_context.h
4 *
5 * Copyright (C) 1996 Russell King.
6 * Copyright (C) 2012 ARM Ltd.
7 */
8 #ifndef __ASM_MMU_CONTEXT_H
9 #define __ASM_MMU_CONTEXT_H
10
11 #ifndef __ASSEMBLY__
12
13 #include <linux/compiler.h>
14 #include <linux/sched.h>
15 #include <linux/sched/hotplug.h>
16 #include <linux/mm_types.h>
17 #include <linux/pgtable.h>
18
19 #include <asm/cacheflush.h>
20 #include <asm/cpufeature.h>
21 #include <asm/daifflags.h>
22 #include <asm/proc-fns.h>
23 #include <asm-generic/mm_hooks.h>
24 #include <asm/cputype.h>
25 #include <asm/sysreg.h>
26 #include <asm/tlbflush.h>
27
28 extern bool rodata_full;
29
contextidr_thread_switch(struct task_struct * next)30 static inline void contextidr_thread_switch(struct task_struct *next)
31 {
32 if (!IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR))
33 return;
34
35 write_sysreg(task_pid_nr(next), contextidr_el1);
36 isb();
37 }
38
39 /*
40 * Set TTBR0 to reserved_pg_dir. No translations will be possible via TTBR0.
41 */
cpu_set_reserved_ttbr0_nosync(void)42 static inline void cpu_set_reserved_ttbr0_nosync(void)
43 {
44 unsigned long ttbr = phys_to_ttbr(__pa_symbol(reserved_pg_dir));
45
46 write_sysreg(ttbr, ttbr0_el1);
47 }
48
cpu_set_reserved_ttbr0(void)49 static inline void cpu_set_reserved_ttbr0(void)
50 {
51 cpu_set_reserved_ttbr0_nosync();
52 isb();
53 }
54
55 void cpu_do_switch_mm(phys_addr_t pgd_phys, struct mm_struct *mm);
56
cpu_switch_mm(pgd_t * pgd,struct mm_struct * mm)57 static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
58 {
59 BUG_ON(pgd == swapper_pg_dir);
60 cpu_do_switch_mm(virt_to_phys(pgd),mm);
61 }
62
63 /*
64 * TCR.T0SZ value to use when the ID map is active. Usually equals
65 * TCR_T0SZ(VA_BITS), unless system RAM is positioned very high in
66 * physical memory, in which case it will be smaller.
67 */
68 extern int idmap_t0sz;
69
70 /*
71 * Ensure TCR.T0SZ is set to the provided value.
72 */
__cpu_set_tcr_t0sz(unsigned long t0sz)73 static inline void __cpu_set_tcr_t0sz(unsigned long t0sz)
74 {
75 unsigned long tcr = read_sysreg(tcr_el1);
76
77 if ((tcr & TCR_T0SZ_MASK) >> TCR_T0SZ_OFFSET == t0sz)
78 return;
79
80 tcr &= ~TCR_T0SZ_MASK;
81 tcr |= t0sz << TCR_T0SZ_OFFSET;
82 write_sysreg(tcr, tcr_el1);
83 isb();
84 }
85
86 #define cpu_set_default_tcr_t0sz() __cpu_set_tcr_t0sz(TCR_T0SZ(vabits_actual))
87 #define cpu_set_idmap_tcr_t0sz() __cpu_set_tcr_t0sz(idmap_t0sz)
88
89 /*
90 * Remove the idmap from TTBR0_EL1 and install the pgd of the active mm.
91 *
92 * The idmap lives in the same VA range as userspace, but uses global entries
93 * and may use a different TCR_EL1.T0SZ. To avoid issues resulting from
94 * speculative TLB fetches, we must temporarily install the reserved page
95 * tables while we invalidate the TLBs and set up the correct TCR_EL1.T0SZ.
96 *
97 * If current is a not a user task, the mm covers the TTBR1_EL1 page tables,
98 * which should not be installed in TTBR0_EL1. In this case we can leave the
99 * reserved page tables in place.
100 */
cpu_uninstall_idmap(void)101 static inline void cpu_uninstall_idmap(void)
102 {
103 struct mm_struct *mm = current->active_mm;
104
105 cpu_set_reserved_ttbr0();
106 local_flush_tlb_all();
107 cpu_set_default_tcr_t0sz();
108
109 if (mm != &init_mm && !system_uses_ttbr0_pan())
110 cpu_switch_mm(mm->pgd, mm);
111 }
112
__cpu_install_idmap(pgd_t * idmap)113 static inline void __cpu_install_idmap(pgd_t *idmap)
114 {
115 cpu_set_reserved_ttbr0();
116 local_flush_tlb_all();
117 cpu_set_idmap_tcr_t0sz();
118
119 cpu_switch_mm(lm_alias(idmap), &init_mm);
120 }
121
cpu_install_idmap(void)122 static inline void cpu_install_idmap(void)
123 {
124 __cpu_install_idmap(idmap_pg_dir);
125 }
126
127 /*
128 * Load our new page tables. A strict BBM approach requires that we ensure that
129 * TLBs are free of any entries that may overlap with the global mappings we are
130 * about to install.
131 *
132 * For a real hibernate/resume/kexec cycle TTBR0 currently points to a zero
133 * page, but TLBs may contain stale ASID-tagged entries (e.g. for EFI runtime
134 * services), while for a userspace-driven test_resume cycle it points to
135 * userspace page tables (and we must point it at a zero page ourselves).
136 *
137 * We change T0SZ as part of installing the idmap. This is undone by
138 * cpu_uninstall_idmap() in __cpu_suspend_exit().
139 */
cpu_install_ttbr0(phys_addr_t ttbr0,unsigned long t0sz)140 static inline void cpu_install_ttbr0(phys_addr_t ttbr0, unsigned long t0sz)
141 {
142 cpu_set_reserved_ttbr0();
143 local_flush_tlb_all();
144 __cpu_set_tcr_t0sz(t0sz);
145
146 /* avoid cpu_switch_mm() and its SW-PAN and CNP interactions */
147 write_sysreg(ttbr0, ttbr0_el1);
148 isb();
149 }
150
151 /*
152 * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
153 * avoiding the possibility of conflicting TLB entries being allocated.
154 */
__cpu_replace_ttbr1(pgd_t * pgdp,pgd_t * idmap,bool cnp)155 static inline void __cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap, bool cnp)
156 {
157 typedef void (ttbr_replace_func)(phys_addr_t);
158 extern ttbr_replace_func idmap_cpu_replace_ttbr1;
159 ttbr_replace_func *replace_phys;
160 unsigned long daif;
161
162 /* phys_to_ttbr() zeros lower 2 bits of ttbr with 52-bit PA */
163 phys_addr_t ttbr1 = phys_to_ttbr(virt_to_phys(pgdp));
164
165 if (cnp)
166 ttbr1 |= TTBR_CNP_BIT;
167
168 replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);
169
170 __cpu_install_idmap(idmap);
171
172 /*
173 * We really don't want to take *any* exceptions while TTBR1 is
174 * in the process of being replaced so mask everything.
175 */
176 daif = local_daif_save();
177 replace_phys(ttbr1);
178 local_daif_restore(daif);
179
180 cpu_uninstall_idmap();
181 }
182
cpu_enable_swapper_cnp(void)183 static inline void cpu_enable_swapper_cnp(void)
184 {
185 __cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir, true);
186 }
187
cpu_replace_ttbr1(pgd_t * pgdp,pgd_t * idmap)188 static inline void cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap)
189 {
190 /*
191 * Only for early TTBR1 replacement before cpucaps are finalized and
192 * before we've decided whether to use CNP.
193 */
194 WARN_ON(system_capabilities_finalized());
195 __cpu_replace_ttbr1(pgdp, idmap, false);
196 }
197
198 /*
199 * It would be nice to return ASIDs back to the allocator, but unfortunately
200 * that introduces a race with a generation rollover where we could erroneously
201 * free an ASID allocated in a future generation. We could workaround this by
202 * freeing the ASID from the context of the dying mm (e.g. in arch_exit_mmap),
203 * but we'd then need to make sure that we didn't dirty any TLBs afterwards.
204 * Setting a reserved TTBR0 or EPD0 would work, but it all gets ugly when you
205 * take CPU migration into account.
206 */
207 void check_and_switch_context(struct mm_struct *mm);
208
209 #define init_new_context(tsk, mm) init_new_context(tsk, mm)
210 static inline int
init_new_context(struct task_struct * tsk,struct mm_struct * mm)211 init_new_context(struct task_struct *tsk, struct mm_struct *mm)
212 {
213 atomic64_set(&mm->context.id, 0);
214 refcount_set(&mm->context.pinned, 0);
215 return 0;
216 }
217
218 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
update_saved_ttbr0(struct task_struct * tsk,struct mm_struct * mm)219 static inline void update_saved_ttbr0(struct task_struct *tsk,
220 struct mm_struct *mm)
221 {
222 u64 ttbr;
223
224 if (!system_uses_ttbr0_pan())
225 return;
226
227 if (mm == &init_mm)
228 ttbr = phys_to_ttbr(__pa_symbol(reserved_pg_dir));
229 else
230 ttbr = phys_to_ttbr(virt_to_phys(mm->pgd)) | ASID(mm) << 48;
231
232 WRITE_ONCE(task_thread_info(tsk)->ttbr0, ttbr);
233 }
234 #else
update_saved_ttbr0(struct task_struct * tsk,struct mm_struct * mm)235 static inline void update_saved_ttbr0(struct task_struct *tsk,
236 struct mm_struct *mm)
237 {
238 }
239 #endif
240
241 #define enter_lazy_tlb enter_lazy_tlb
242 static inline void
enter_lazy_tlb(struct mm_struct * mm,struct task_struct * tsk)243 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
244 {
245 /*
246 * We don't actually care about the ttbr0 mapping, so point it at the
247 * zero page.
248 */
249 update_saved_ttbr0(tsk, &init_mm);
250 }
251
__switch_mm(struct mm_struct * next)252 static inline void __switch_mm(struct mm_struct *next)
253 {
254 /*
255 * init_mm.pgd does not contain any user mappings and it is always
256 * active for kernel addresses in TTBR1. Just set the reserved TTBR0.
257 */
258 if (next == &init_mm) {
259 cpu_set_reserved_ttbr0();
260 return;
261 }
262
263 check_and_switch_context(next);
264 }
265
266 static inline void
switch_mm(struct mm_struct * prev,struct mm_struct * next,struct task_struct * tsk)267 switch_mm(struct mm_struct *prev, struct mm_struct *next,
268 struct task_struct *tsk)
269 {
270 if (prev != next)
271 __switch_mm(next);
272
273 /*
274 * Update the saved TTBR0_EL1 of the scheduled-in task as the previous
275 * value may have not been initialised yet (activate_mm caller) or the
276 * ASID has changed since the last run (following the context switch
277 * of another thread of the same process).
278 */
279 update_saved_ttbr0(tsk, next);
280 }
281
282 static inline const struct cpumask *
task_cpu_possible_mask(struct task_struct * p)283 task_cpu_possible_mask(struct task_struct *p)
284 {
285 if (!static_branch_unlikely(&arm64_mismatched_32bit_el0))
286 return cpu_possible_mask;
287
288 if (!is_compat_thread(task_thread_info(p)))
289 return cpu_possible_mask;
290
291 return system_32bit_el0_cpumask();
292 }
293 #define task_cpu_possible_mask task_cpu_possible_mask
294
295 void verify_cpu_asid_bits(void);
296 void post_ttbr_update_workaround(void);
297
298 unsigned long arm64_mm_context_get(struct mm_struct *mm);
299 void arm64_mm_context_put(struct mm_struct *mm);
300
301 #define mm_untag_mask mm_untag_mask
mm_untag_mask(struct mm_struct * mm)302 static inline unsigned long mm_untag_mask(struct mm_struct *mm)
303 {
304 return -1UL >> 8;
305 }
306
307 #include <asm-generic/mmu_context.h>
308
309 #endif /* !__ASSEMBLY__ */
310
311 #endif /* !__ASM_MMU_CONTEXT_H */
312