arch/powerpc/mm/book3s64/mmu_context.c

   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 ptdesc *ptdesc;
 250
 251         ptdesc = virt_to_ptdesc(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, &ptdesc->pt_frag_refcount)) {
 256                 pagetable_pmd_dtor(ptdesc);
 257                 pagetable_free(ptdesc);
 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