1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * MMU context allocation for 64-bit kernels.
4 *
5 * Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
6 */
7
8#include <linux/sched.h>
9#include <linux/kernel.h>
10#include <linux/errno.h>
11#include <linux/string.h>
12#include <linux/types.h>
13#include <linux/mm.h>
14#include <linux/pkeys.h>
15#include <linux/spinlock.h>
16#include <linux/idr.h>
17#include <linux/export.h>
18#include <linux/gfp.h>
19#include <linux/slab.h>
20#include <linux/cpu.h>
21
22#include <asm/mmu_context.h>
23#include <asm/pgalloc.h>
24
25#include "internal.h"
26
27static DEFINE_IDA(mmu_context_ida);
28
29static int alloc_context_id(int min_id, int max_id)
30{
31 return ida_alloc_range(&mmu_context_ida, min: min_id, max: max_id, GFP_KERNEL);
32}
33
34#ifdef CONFIG_PPC_64S_HASH_MMU
35void __init hash__reserve_context_id(int id)
36{
37 int result = ida_alloc_range(&mmu_context_ida, id, id, GFP_KERNEL);
38
39 WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result);
40}
41
42int hash__alloc_context_id(void)
43{
44 unsigned long max;
45
46 if (mmu_has_feature(MMU_FTR_68_BIT_VA))
47 max = MAX_USER_CONTEXT;
48 else
49 max = MAX_USER_CONTEXT_65BIT_VA;
50
51 return alloc_context_id(MIN_USER_CONTEXT, max);
52}
53EXPORT_SYMBOL_GPL(hash__alloc_context_id);
54#endif
55
56#ifdef CONFIG_PPC_64S_HASH_MMU
57static int realloc_context_ids(mm_context_t *ctx)
58{
59 int i, id;
60
61 /*
62 * id 0 (aka. ctx->id) is special, we always allocate a new one, even if
63 * there wasn't one allocated previously (which happens in the exec
64 * case where ctx is newly allocated).
65 *
66 * We have to be a bit careful here. We must keep the existing ids in
67 * the array, so that we can test if they're non-zero to decide if we
68 * need to allocate a new one. However in case of error we must free the
69 * ids we've allocated but *not* any of the existing ones (or risk a
70 * UAF). That's why we decrement i at the start of the error handling
71 * loop, to skip the id that we just tested but couldn't reallocate.
72 */
73 for (i = 0; i < ARRAY_SIZE(ctx->extended_id); i++) {
74 if (i == 0 || ctx->extended_id[i]) {
75 id = hash__alloc_context_id();
76 if (id < 0)
77 goto error;
78
79 ctx->extended_id[i] = id;
80 }
81 }
82
83 /* The caller expects us to return id */
84 return ctx->id;
85
86error:
87 for (i--; i >= 0; i--) {
88 if (ctx->extended_id[i])
89 ida_free(&mmu_context_ida, ctx->extended_id[i]);
90 }
91
92 return id;
93}
94
95static int hash__init_new_context(struct mm_struct *mm)
96{
97 int index;
98
99 mm->context.hash_context = kmalloc(sizeof(struct hash_mm_context),
100 GFP_KERNEL);
101 if (!mm->context.hash_context)
102 return -ENOMEM;
103
104 /*
105 * The old code would re-promote on fork, we don't do that when using
106 * slices as it could cause problem promoting slices that have been
107 * forced down to 4K.
108 *
109 * For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
110 * explicitly against context.id == 0. This ensures that we properly
111 * initialize context slice details for newly allocated mm's (which will
112 * have id == 0) and don't alter context slice inherited via fork (which
113 * will have id != 0).
114 *
115 * We should not be calling init_new_context() on init_mm. Hence a
116 * check against 0 is OK.
117 */
118 if (mm->context.id == 0) {
119 memset(mm->context.hash_context, 0, sizeof(struct hash_mm_context));
120 slice_init_new_context_exec(mm);
121 } else {
122 /* This is fork. Copy hash_context details from current->mm */
123 memcpy(mm->context.hash_context, current->mm->context.hash_context, sizeof(struct hash_mm_context));
124#ifdef CONFIG_PPC_SUBPAGE_PROT
125 /* inherit subpage prot details if we have one. */
126 if (current->mm->context.hash_context->spt) {
127 mm->context.hash_context->spt = kmalloc(sizeof(struct subpage_prot_table),
128 GFP_KERNEL);
129 if (!mm->context.hash_context->spt) {
130 kfree(mm->context.hash_context);
131 return -ENOMEM;
132 }
133 }
134#endif
135 }
136
137 index = realloc_context_ids(&mm->context);
138 if (index < 0) {
139#ifdef CONFIG_PPC_SUBPAGE_PROT
140 kfree(mm->context.hash_context->spt);
141#endif
142 kfree(mm->context.hash_context);
143 return index;
144 }
145
146 pkey_mm_init(mm);
147 return index;
148}
149
150void hash__setup_new_exec(void)
151{
152 slice_setup_new_exec();
153}
154#else
155static inline int hash__init_new_context(struct mm_struct *mm)
156{
157 BUILD_BUG();
158 return 0;
159}
160#endif
161
162static int radix__init_new_context(struct mm_struct *mm)
163{
164 unsigned long rts_field;
165 int index, max_id;
166
167 max_id = (1 << mmu_pid_bits) - 1;
168 index = alloc_context_id(min_id: mmu_base_pid, max_id);
169 if (index < 0)
170 return index;
171
172 /*
173 * set the process table entry,
174 */
175 rts_field = radix__get_tree_size();
176 process_tb[index].prtb0 = cpu_to_be64(rts_field | __pa(mm->pgd) | RADIX_PGD_INDEX_SIZE);
177
178 /*
179 * Order the above store with subsequent update of the PID
180 * register (at which point HW can start loading/caching
181 * the entry) and the corresponding load by the MMU from
182 * the L2 cache.
183 */
184 asm volatile("ptesync;isync" : : : "memory");
185
186#ifdef CONFIG_PPC_64S_HASH_MMU
187 mm->context.hash_context = NULL;
188#endif
189
190 return index;
191}
192
193int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
194{
195 int index;
196
197 if (radix_enabled())
198 index = radix__init_new_context(mm);
199 else
200 index = hash__init_new_context(mm);
201
202 if (index < 0)
203 return index;
204
205 mm->context.id = index;
206
207 mm->context.pte_frag = NULL;
208 mm->context.pmd_frag = NULL;
209#ifdef CONFIG_SPAPR_TCE_IOMMU
210 mm_iommu_init(mm);
211#endif
212 atomic_set(v: &mm->context.active_cpus, i: 0);
213 atomic_set(v: &mm->context.copros, i: 0);
214
215 return 0;
216}
217
218void __destroy_context(int context_id)
219{
220 ida_free(&mmu_context_ida, id: context_id);
221}
222EXPORT_SYMBOL_GPL(__destroy_context);
223
224static void destroy_contexts(mm_context_t *ctx)
225{
226 if (radix_enabled()) {
227 ida_free(&mmu_context_ida, id: ctx->id);
228 } else {
229#ifdef CONFIG_PPC_64S_HASH_MMU
230 int index, context_id;
231
232 for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
233 context_id = ctx->extended_id[index];
234 if (context_id)
235 ida_free(&mmu_context_ida, context_id);
236 }
237 kfree(ctx->hash_context);
238#else
239 BUILD_BUG(); // radix_enabled() should be constant true
240#endif
241 }
242}
243
244static void pmd_frag_destroy(void *pmd_frag)
245{
246 int count;
247 struct ptdesc *ptdesc;
248
249 ptdesc = virt_to_ptdesc(x: pmd_frag);
250 /* drop all the pending references */
251 count = ((unsigned long)pmd_frag & ~PAGE_MASK) >> PMD_FRAG_SIZE_SHIFT;
252 /* We allow PTE_FRAG_NR fragments from a PTE page */
253 if (atomic_sub_and_test(i: PMD_FRAG_NR - count, v: &ptdesc->pt_frag_refcount)) {
254 pagetable_dtor(ptdesc);
255 pagetable_free(pt: ptdesc);
256 }
257}
258
259static void destroy_pagetable_cache(struct mm_struct *mm)
260{
261 void *frag;
262
263 frag = mm->context.pte_frag;
264 if (frag)
265 pte_frag_destroy(frag);
266
267 frag = mm->context.pmd_frag;
268 if (frag)
269 pmd_frag_destroy(pmd_frag: frag);
270 return;
271}
272
273void destroy_context(struct mm_struct *mm)
274{
275#ifdef CONFIG_SPAPR_TCE_IOMMU
276 WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
277#endif
278 /*
279 * For tasks which were successfully initialized we end up calling
280 * arch_exit_mmap() which clears the process table entry. And
281 * arch_exit_mmap() is called before the required fullmm TLB flush
282 * which does a RIC=2 flush. Hence for an initialized task, we do clear
283 * any cached process table entries.
284 *
285 * The condition below handles the error case during task init. We have
286 * set the process table entry early and if we fail a task
287 * initialization, we need to ensure the process table entry is zeroed.
288 * We need not worry about process table entry caches because the task
289 * never ran with the PID value.
290 */
291 if (radix_enabled())
292 process_tb[mm->context.id].prtb0 = 0;
293 else
294 subpage_prot_free(mm);
295 destroy_contexts(ctx: &mm->context);
296 mm->context.id = MMU_NO_CONTEXT;
297}
298
299void arch_exit_mmap(struct mm_struct *mm)
300{
301 destroy_pagetable_cache(mm);
302
303 if (radix_enabled()) {
304 /*
305 * Radix doesn't have a valid bit in the process table
306 * entries. However we know that at least P9 implementation
307 * will avoid caching an entry with an invalid RTS field,
308 * and 0 is invalid. So this will do.
309 *
310 * This runs before the "fullmm" tlb flush in exit_mmap,
311 * which does a RIC=2 tlbie to clear the process table
312 * entry. See the "fullmm" comments in tlb-radix.c.
313 *
314 * No barrier required here after the store because
315 * this process will do the invalidate, which starts with
316 * ptesync.
317 */
318 process_tb[mm->context.id].prtb0 = 0;
319 }
320}
321
322#ifdef CONFIG_PPC_RADIX_MMU
323void radix__switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
324{
325 mtspr(SPRN_PID, next->context.id);
326 isync();
327}
328#endif
329
330/**
331 * cleanup_cpu_mmu_context - Clean up MMU details for this CPU (newly offlined)
332 *
333 * This clears the CPU from mm_cpumask for all processes, and then flushes the
334 * local TLB to ensure TLB coherency in case the CPU is onlined again.
335 *
336 * KVM guest translations are not necessarily flushed here. If KVM started
337 * using mm_cpumask or the Linux APIs which do, this would have to be resolved.
338 */
339#ifdef CONFIG_HOTPLUG_CPU
340void cleanup_cpu_mmu_context(void)
341{
342 int cpu = smp_processor_id();
343
344 clear_tasks_mm_cpumask(cpu);
345 tlbiel_all();
346}
347#endif
348

source code of linux/arch/powerpc/mm/book3s64/mmu_context.c