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