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 
27 static DEFINE_IDA(mmu_context_ida);
28 
29 static int alloc_context_id(int min_id, int max_id)
30 {
31 	return ida_alloc_range(&mmu_context_ida, min_id, max_id, GFP_KERNEL);
32 }
33 
34 #ifdef CONFIG_PPC_64S_HASH_MMU
35 void __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 
42 int 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 }
53 EXPORT_SYMBOL_GPL(hash__alloc_context_id);
54 #endif
55 
56 #ifdef CONFIG_PPC_64S_HASH_MMU
57 static 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 
86 error:
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 
95 static 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 
150 void hash__setup_new_exec(void)
151 {
152 	slice_setup_new_exec();
153 
154 	slb_setup_new_exec();
155 }
156 #else
157 static inline int hash__init_new_context(struct mm_struct *mm)
158 {
159 	BUILD_BUG();
160 	return 0;
161 }
162 #endif
163 
164 static int radix__init_new_context(struct mm_struct *mm)
165 {
166 	unsigned long rts_field;
167 	int index, max_id;
168 
169 	max_id = (1 << mmu_pid_bits) - 1;
170 	index = alloc_context_id(mmu_base_pid, max_id);
171 	if (index < 0)
172 		return index;
173 
174 	/*
175 	 * set the process table entry,
176 	 */
177 	rts_field = radix__get_tree_size();
178 	process_tb[index].prtb0 = cpu_to_be64(rts_field | __pa(mm->pgd) | RADIX_PGD_INDEX_SIZE);
179 
180 	/*
181 	 * Order the above store with subsequent update of the PID
182 	 * register (at which point HW can start loading/caching
183 	 * the entry) and the corresponding load by the MMU from
184 	 * the L2 cache.
185 	 */
186 	asm volatile("ptesync;isync" : : : "memory");
187 
188 #ifdef CONFIG_PPC_64S_HASH_MMU
189 	mm->context.hash_context = NULL;
190 #endif
191 
192 	return index;
193 }
194 
195 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
196 {
197 	int index;
198 
199 	if (radix_enabled())
200 		index = radix__init_new_context(mm);
201 	else
202 		index = hash__init_new_context(mm);
203 
204 	if (index < 0)
205 		return index;
206 
207 	mm->context.id = index;
208 
209 	mm->context.pte_frag = NULL;
210 	mm->context.pmd_frag = NULL;
211 #ifdef CONFIG_SPAPR_TCE_IOMMU
212 	mm_iommu_init(mm);
213 #endif
214 	atomic_set(&mm->context.active_cpus, 0);
215 	atomic_set(&mm->context.copros, 0);
216 
217 	return 0;
218 }
219 
220 void __destroy_context(int context_id)
221 {
222 	ida_free(&mmu_context_ida, context_id);
223 }
224 EXPORT_SYMBOL_GPL(__destroy_context);
225 
226 static void destroy_contexts(mm_context_t *ctx)
227 {
228 	if (radix_enabled()) {
229 		ida_free(&mmu_context_ida, ctx->id);
230 	} else {
231 #ifdef CONFIG_PPC_64S_HASH_MMU
232 		int index, context_id;
233 
234 		for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
235 			context_id = ctx->extended_id[index];
236 			if (context_id)
237 				ida_free(&mmu_context_ida, context_id);
238 		}
239 		kfree(ctx->hash_context);
240 #else
241 		BUILD_BUG(); // radix_enabled() should be constant true
242 #endif
243 	}
244 }
245 
246 static void pmd_frag_destroy(void *pmd_frag)
247 {
248 	int count;
249 	struct page *page;
250 
251 	page = virt_to_page(pmd_frag);
252 	/* drop all the pending references */
253 	count = ((unsigned long)pmd_frag & ~PAGE_MASK) >> PMD_FRAG_SIZE_SHIFT;
254 	/* We allow PTE_FRAG_NR fragments from a PTE page */
255 	if (atomic_sub_and_test(PMD_FRAG_NR - count, &page->pt_frag_refcount)) {
256 		pgtable_pmd_page_dtor(page);
257 		__free_page(page);
258 	}
259 }
260 
261 static void destroy_pagetable_cache(struct mm_struct *mm)
262 {
263 	void *frag;
264 
265 	frag = mm->context.pte_frag;
266 	if (frag)
267 		pte_frag_destroy(frag);
268 
269 	frag = mm->context.pmd_frag;
270 	if (frag)
271 		pmd_frag_destroy(frag);
272 	return;
273 }
274 
275 void destroy_context(struct mm_struct *mm)
276 {
277 #ifdef CONFIG_SPAPR_TCE_IOMMU
278 	WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
279 #endif
280 	/*
281 	 * For tasks which were successfully initialized we end up calling
282 	 * arch_exit_mmap() which clears the process table entry. And
283 	 * arch_exit_mmap() is called before the required fullmm TLB flush
284 	 * which does a RIC=2 flush. Hence for an initialized task, we do clear
285 	 * any cached process table entries.
286 	 *
287 	 * The condition below handles the error case during task init. We have
288 	 * set the process table entry early and if we fail a task
289 	 * initialization, we need to ensure the process table entry is zeroed.
290 	 * We need not worry about process table entry caches because the task
291 	 * never ran with the PID value.
292 	 */
293 	if (radix_enabled())
294 		process_tb[mm->context.id].prtb0 = 0;
295 	else
296 		subpage_prot_free(mm);
297 	destroy_contexts(&mm->context);
298 	mm->context.id = MMU_NO_CONTEXT;
299 }
300 
301 void arch_exit_mmap(struct mm_struct *mm)
302 {
303 	destroy_pagetable_cache(mm);
304 
305 	if (radix_enabled()) {
306 		/*
307 		 * Radix doesn't have a valid bit in the process table
308 		 * entries. However we know that at least P9 implementation
309 		 * will avoid caching an entry with an invalid RTS field,
310 		 * and 0 is invalid. So this will do.
311 		 *
312 		 * This runs before the "fullmm" tlb flush in exit_mmap,
313 		 * which does a RIC=2 tlbie to clear the process table
314 		 * entry. See the "fullmm" comments in tlb-radix.c.
315 		 *
316 		 * No barrier required here after the store because
317 		 * this process will do the invalidate, which starts with
318 		 * ptesync.
319 		 */
320 		process_tb[mm->context.id].prtb0 = 0;
321 	}
322 }
323 
324 #ifdef CONFIG_PPC_RADIX_MMU
325 void radix__switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
326 {
327 	mtspr(SPRN_PID, next->context.id);
328 	isync();
329 }
330 #endif
331 
332 /**
333  * cleanup_cpu_mmu_context - Clean up MMU details for this CPU (newly offlined)
334  *
335  * This clears the CPU from mm_cpumask for all processes, and then flushes the
336  * local TLB to ensure TLB coherency in case the CPU is onlined again.
337  *
338  * KVM guest translations are not necessarily flushed here. If KVM started
339  * using mm_cpumask or the Linux APIs which do, this would have to be resolved.
340  */
341 #ifdef CONFIG_HOTPLUG_CPU
342 void cleanup_cpu_mmu_context(void)
343 {
344 	int cpu = smp_processor_id();
345 
346 	clear_tasks_mm_cpumask(cpu);
347 	tlbiel_all();
348 }
349 #endif
350