arch/powerpc/mm/book3s64/pkeys.c

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This source file includes following definitions.
scan_pkey_feature
pkey_mmu_enabled
pkey_initialize
pkey_mm_init
read_amr
write_amr
read_iamr
write_iamr
read_uamor
write_uamor
is_pkey_enabled
init_amr
init_iamr
__arch_set_user_pkey_access
thread_pkey_regs_save
thread_pkey_regs_restore
thread_pkey_regs_init
pkey_allows_readwrite
__execute_only_pkey
vma_is_pkey_exec_only
__arch_override_mprotect_pkey
pkey_access_permitted
arch_pte_access_permitted
vma_is_foreign
arch_vma_access_permitted
arch_dup_pkeys
   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * PowerPC Memory Protection Keys management
   4  *
   5  * Copyright 2017, Ram Pai, IBM Corporation.
   6  */
   7 
   8 #include <asm/mman.h>
   9 #include <asm/mmu_context.h>
  10 #include <asm/mmu.h>
  11 #include <asm/setup.h>
  12 #include <linux/pkeys.h>
  13 #include <linux/of_device.h>
  14 
  15 DEFINE_STATIC_KEY_TRUE(pkey_disabled);
  16 int  pkeys_total;               /* Total pkeys as per device tree */
  17 u32  initial_allocation_mask;   /* Bits set for the initially allocated keys */
  18 u32  reserved_allocation_mask;  /* Bits set for reserved keys */
  19 static bool pkey_execute_disable_supported;
  20 static bool pkeys_devtree_defined;      /* property exported by device tree */
  21 static u64 pkey_amr_mask;               /* Bits in AMR not to be touched */
  22 static u64 pkey_iamr_mask;              /* Bits in AMR not to be touched */
  23 static u64 pkey_uamor_mask;             /* Bits in UMOR not to be touched */
  24 static int execute_only_key = 2;
  25 
  26 #define AMR_BITS_PER_PKEY 2
  27 #define AMR_RD_BIT 0x1UL
  28 #define AMR_WR_BIT 0x2UL
  29 #define IAMR_EX_BIT 0x1UL
  30 #define PKEY_REG_BITS (sizeof(u64)*8)
  31 #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY))
  32 
  33 static void scan_pkey_feature(void)
  34 {
  35         u32 vals[2];
  36         struct device_node *cpu;
  37 
  38         cpu = of_find_node_by_type(NULL, "cpu");
  39         if (!cpu)
  40                 return;
  41 
  42         if (of_property_read_u32_array(cpu,
  43                         "ibm,processor-storage-keys", vals, 2))
  44                 return;
  45 
  46         /*
  47          * Since any pkey can be used for data or execute, we will just treat
  48          * all keys as equal and track them as one entity.
  49          */
  50         pkeys_total = vals[0];
  51         pkeys_devtree_defined = true;
  52 }
  53 
  54 static inline bool pkey_mmu_enabled(void)
  55 {
  56         if (firmware_has_feature(FW_FEATURE_LPAR))
  57                 return pkeys_total;
  58         else
  59                 return cpu_has_feature(CPU_FTR_PKEY);
  60 }
  61 
  62 static int pkey_initialize(void)
  63 {
  64         int os_reserved, i;
  65 
  66         /*
  67          * We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral
  68          * generic defines for PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
  69          * Ensure that the bits a distinct.
  70          */
  71         BUILD_BUG_ON(PKEY_DISABLE_EXECUTE &
  72                      (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
  73 
  74         /*
  75          * pkey_to_vmflag_bits() assumes that the pkey bits are contiguous
  76          * in the vmaflag. Make sure that is really the case.
  77          */
  78         BUILD_BUG_ON(__builtin_clzl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) +
  79                      __builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)
  80                                 != (sizeof(u64) * BITS_PER_BYTE));
  81 
  82         /* scan the device tree for pkey feature */
  83         scan_pkey_feature();
  84 
  85         /*
  86          * Let's assume 32 pkeys on P8 bare metal, if its not defined by device
  87          * tree. We make this exception since skiboot forgot to expose this
  88          * property on power8.
  89          */
  90         if (!pkeys_devtree_defined && !firmware_has_feature(FW_FEATURE_LPAR) &&
  91                         cpu_has_feature(CPU_FTRS_POWER8))
  92                 pkeys_total = 32;
  93 
  94         /*
  95          * Adjust the upper limit, based on the number of bits supported by
  96          * arch-neutral code.
  97          */
  98         pkeys_total = min_t(int, pkeys_total,
  99                         ((ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)+1));
 100 
 101         if (!pkey_mmu_enabled() || radix_enabled() || !pkeys_total)
 102                 static_branch_enable(&pkey_disabled);
 103         else
 104                 static_branch_disable(&pkey_disabled);
 105 
 106         if (static_branch_likely(&pkey_disabled))
 107                 return 0;
 108 
 109         /*
 110          * The device tree cannot be relied to indicate support for
 111          * execute_disable support. Instead we use a PVR check.
 112          */
 113         if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p))
 114                 pkey_execute_disable_supported = false;
 115         else
 116                 pkey_execute_disable_supported = true;
 117 
 118 #ifdef CONFIG_PPC_4K_PAGES
 119         /*
 120          * The OS can manage only 8 pkeys due to its inability to represent them
 121          * in the Linux 4K PTE.
 122          */
 123         os_reserved = pkeys_total - 8;
 124 #else
 125         os_reserved = 0;
 126 #endif
 127         /* Bits are in LE format. */
 128         reserved_allocation_mask = (0x1 << 1) | (0x1 << execute_only_key);
 129 
 130         /* register mask is in BE format */
 131         pkey_amr_mask = ~0x0ul;
 132         pkey_amr_mask &= ~(0x3ul << pkeyshift(0));
 133 
 134         pkey_iamr_mask = ~0x0ul;
 135         pkey_iamr_mask &= ~(0x3ul << pkeyshift(0));
 136         pkey_iamr_mask &= ~(0x3ul << pkeyshift(execute_only_key));
 137 
 138         pkey_uamor_mask = ~0x0ul;
 139         pkey_uamor_mask &= ~(0x3ul << pkeyshift(0));
 140         pkey_uamor_mask &= ~(0x3ul << pkeyshift(execute_only_key));
 141 
 142         /* mark the rest of the keys as reserved and hence unavailable */
 143         for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) {
 144                 reserved_allocation_mask |= (0x1 << i);
 145                 pkey_uamor_mask &= ~(0x3ul << pkeyshift(i));
 146         }
 147         initial_allocation_mask = reserved_allocation_mask | (0x1 << 0);
 148 
 149         if (unlikely((pkeys_total - os_reserved) <= execute_only_key)) {
 150                 /*
 151                  * Insufficient number of keys to support
 152                  * execute only key. Mark it unavailable.
 153                  * Any AMR, UAMOR, IAMR bit set for
 154                  * this key is irrelevant since this key
 155                  * can never be allocated.
 156                  */
 157                 execute_only_key = -1;
 158         }
 159 
 160         return 0;
 161 }
 162 
 163 arch_initcall(pkey_initialize);
 164 
 165 void pkey_mm_init(struct mm_struct *mm)
 166 {
 167         if (static_branch_likely(&pkey_disabled))
 168                 return;
 169         mm_pkey_allocation_map(mm) = initial_allocation_mask;
 170         mm->context.execute_only_pkey = execute_only_key;
 171 }
 172 
 173 static inline u64 read_amr(void)
 174 {
 175         return mfspr(SPRN_AMR);
 176 }
 177 
 178 static inline void write_amr(u64 value)
 179 {
 180         mtspr(SPRN_AMR, value);
 181 }
 182 
 183 static inline u64 read_iamr(void)
 184 {
 185         if (!likely(pkey_execute_disable_supported))
 186                 return 0x0UL;
 187 
 188         return mfspr(SPRN_IAMR);
 189 }
 190 
 191 static inline void write_iamr(u64 value)
 192 {
 193         if (!likely(pkey_execute_disable_supported))
 194                 return;
 195 
 196         mtspr(SPRN_IAMR, value);
 197 }
 198 
 199 static inline u64 read_uamor(void)
 200 {
 201         return mfspr(SPRN_UAMOR);
 202 }
 203 
 204 static inline void write_uamor(u64 value)
 205 {
 206         mtspr(SPRN_UAMOR, value);
 207 }
 208 
 209 static bool is_pkey_enabled(int pkey)
 210 {
 211         u64 uamor = read_uamor();
 212         u64 pkey_bits = 0x3ul << pkeyshift(pkey);
 213         u64 uamor_pkey_bits = (uamor & pkey_bits);
 214 
 215         /*
 216          * Both the bits in UAMOR corresponding to the key should be set or
 217          * reset.
 218          */
 219         WARN_ON(uamor_pkey_bits && (uamor_pkey_bits != pkey_bits));
 220         return !!(uamor_pkey_bits);
 221 }
 222 
 223 static inline void init_amr(int pkey, u8 init_bits)
 224 {
 225         u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
 226         u64 old_amr = read_amr() & ~((u64)(0x3ul) << pkeyshift(pkey));
 227 
 228         write_amr(old_amr | new_amr_bits);
 229 }
 230 
 231 static inline void init_iamr(int pkey, u8 init_bits)
 232 {
 233         u64 new_iamr_bits = (((u64)init_bits & 0x1UL) << pkeyshift(pkey));
 234         u64 old_iamr = read_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey));
 235 
 236         write_iamr(old_iamr | new_iamr_bits);
 237 }
 238 
 239 /*
 240  * Set the access rights in AMR IAMR and UAMOR registers for @pkey to that
 241  * specified in @init_val.
 242  */
 243 int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 244                                 unsigned long init_val)
 245 {
 246         u64 new_amr_bits = 0x0ul;
 247         u64 new_iamr_bits = 0x0ul;
 248 
 249         if (!is_pkey_enabled(pkey))
 250                 return -EINVAL;
 251 
 252         if (init_val & PKEY_DISABLE_EXECUTE) {
 253                 if (!pkey_execute_disable_supported)
 254                         return -EINVAL;
 255                 new_iamr_bits |= IAMR_EX_BIT;
 256         }
 257         init_iamr(pkey, new_iamr_bits);
 258 
 259         /* Set the bits we need in AMR: */
 260         if (init_val & PKEY_DISABLE_ACCESS)
 261                 new_amr_bits |= AMR_RD_BIT | AMR_WR_BIT;
 262         else if (init_val & PKEY_DISABLE_WRITE)
 263                 new_amr_bits |= AMR_WR_BIT;
 264 
 265         init_amr(pkey, new_amr_bits);
 266         return 0;
 267 }
 268 
 269 void thread_pkey_regs_save(struct thread_struct *thread)
 270 {
 271         if (static_branch_likely(&pkey_disabled))
 272                 return;
 273 
 274         /*
 275          * TODO: Skip saving registers if @thread hasn't used any keys yet.
 276          */
 277         thread->amr = read_amr();
 278         thread->iamr = read_iamr();
 279         thread->uamor = read_uamor();
 280 }
 281 
 282 void thread_pkey_regs_restore(struct thread_struct *new_thread,
 283                               struct thread_struct *old_thread)
 284 {
 285         if (static_branch_likely(&pkey_disabled))
 286                 return;
 287 
 288         if (old_thread->amr != new_thread->amr)
 289                 write_amr(new_thread->amr);
 290         if (old_thread->iamr != new_thread->iamr)
 291                 write_iamr(new_thread->iamr);
 292         if (old_thread->uamor != new_thread->uamor)
 293                 write_uamor(new_thread->uamor);
 294 }
 295 
 296 void thread_pkey_regs_init(struct thread_struct *thread)
 297 {
 298         if (static_branch_likely(&pkey_disabled))
 299                 return;
 300 
 301         thread->amr = pkey_amr_mask;
 302         thread->iamr = pkey_iamr_mask;
 303         thread->uamor = pkey_uamor_mask;
 304 
 305         write_uamor(pkey_uamor_mask);
 306         write_amr(pkey_amr_mask);
 307         write_iamr(pkey_iamr_mask);
 308 }
 309 
 310 static inline bool pkey_allows_readwrite(int pkey)
 311 {
 312         int pkey_shift = pkeyshift(pkey);
 313 
 314         if (!is_pkey_enabled(pkey))
 315                 return true;
 316 
 317         return !(read_amr() & ((AMR_RD_BIT|AMR_WR_BIT) << pkey_shift));
 318 }
 319 
 320 int __execute_only_pkey(struct mm_struct *mm)
 321 {
 322         return mm->context.execute_only_pkey;
 323 }
 324 
 325 static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
 326 {
 327         /* Do this check first since the vm_flags should be hot */
 328         if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
 329                 return false;
 330 
 331         return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
 332 }
 333 
 334 /*
 335  * This should only be called for *plain* mprotect calls.
 336  */
 337 int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
 338                                   int pkey)
 339 {
 340         /*
 341          * If the currently associated pkey is execute-only, but the requested
 342          * protection is not execute-only, move it back to the default pkey.
 343          */
 344         if (vma_is_pkey_exec_only(vma) && (prot != PROT_EXEC))
 345                 return 0;
 346 
 347         /*
 348          * The requested protection is execute-only. Hence let's use an
 349          * execute-only pkey.
 350          */
 351         if (prot == PROT_EXEC) {
 352                 pkey = execute_only_pkey(vma->vm_mm);
 353                 if (pkey > 0)
 354                         return pkey;
 355         }
 356 
 357         /* Nothing to override. */
 358         return vma_pkey(vma);
 359 }
 360 
 361 static bool pkey_access_permitted(int pkey, bool write, bool execute)
 362 {
 363         int pkey_shift;
 364         u64 amr;
 365 
 366         if (!is_pkey_enabled(pkey))
 367                 return true;
 368 
 369         pkey_shift = pkeyshift(pkey);
 370         if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift)))
 371                 return true;
 372 
 373         amr = read_amr(); /* Delay reading amr until absolutely needed */
 374         return ((!write && !(amr & (AMR_RD_BIT << pkey_shift))) ||
 375                 (write &&  !(amr & (AMR_WR_BIT << pkey_shift))));
 376 }
 377 
 378 bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
 379 {
 380         if (static_branch_likely(&pkey_disabled))
 381                 return true;
 382 
 383         return pkey_access_permitted(pte_to_pkey_bits(pte), write, execute);
 384 }
 385 
 386 /*
 387  * We only want to enforce protection keys on the current thread because we
 388  * effectively have no access to AMR/IAMR for other threads or any way to tell
 389  * which AMR/IAMR in a threaded process we could use.
 390  *
 391  * So do not enforce things if the VMA is not from the current mm, or if we are
 392  * in a kernel thread.
 393  */
 394 static inline bool vma_is_foreign(struct vm_area_struct *vma)
 395 {
 396         if (!current->mm)
 397                 return true;
 398 
 399         /* if it is not our ->mm, it has to be foreign */
 400         if (current->mm != vma->vm_mm)
 401                 return true;
 402 
 403         return false;
 404 }
 405 
 406 bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
 407                                bool execute, bool foreign)
 408 {
 409         if (static_branch_likely(&pkey_disabled))
 410                 return true;
 411         /*
 412          * Do not enforce our key-permissions on a foreign vma.
 413          */
 414         if (foreign || vma_is_foreign(vma))
 415                 return true;
 416 
 417         return pkey_access_permitted(vma_pkey(vma), write, execute);
 418 }
 419 
 420 void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
 421 {
 422         if (static_branch_likely(&pkey_disabled))
 423                 return;
 424 
 425         /* Duplicate the oldmm pkey state in mm: */
 426         mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
 427         mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;
 428 }
/* [<][>][^][v][top][bottom][index][help] */
root/arch/powerpc/mm/book3s64/pkeys.c

DEFINITIONS
