1 // SPDX-License-Identifier: GPL-2.0+
3 * PowerPC Memory Protection Keys management
5 * Copyright 2017, Ram Pai, IBM Corporation.
10 #include <linux/pkeys.h>
11 #include <linux/of_device.h>
13 DEFINE_STATIC_KEY_TRUE(pkey_disabled);
14 bool pkey_execute_disable_supported;
15 int pkeys_total; /* Total pkeys as per device tree */
16 bool pkeys_devtree_defined; /* pkey property exported by 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 u64 pkey_amr_mask; /* Bits in AMR not to be touched */
20 u64 pkey_iamr_mask; /* Bits in AMR not to be touched */
21 u64 pkey_uamor_mask; /* Bits in UMOR not to be touched */
22 int execute_only_key = 2;
24 #define AMR_BITS_PER_PKEY 2
25 #define AMR_RD_BIT 0x1UL
26 #define AMR_WR_BIT 0x2UL
27 #define IAMR_EX_BIT 0x1UL
28 #define PKEY_REG_BITS (sizeof(u64)*8)
29 #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY))
31 static void scan_pkey_feature(void)
34 struct device_node *cpu;
36 cpu = of_find_node_by_type(NULL, "cpu");
40 if (of_property_read_u32_array(cpu,
41 "ibm,processor-storage-keys", vals, 2))
45 * Since any pkey can be used for data or execute, we will just treat
46 * all keys as equal and track them as one entity.
48 pkeys_total = vals[0];
49 pkeys_devtree_defined = true;
52 static inline bool pkey_mmu_enabled(void)
54 if (firmware_has_feature(FW_FEATURE_LPAR))
57 return cpu_has_feature(CPU_FTR_PKEY);
60 int pkey_initialize(void)
65 * We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral
66 * generic defines for PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
67 * Ensure that the bits a distinct.
69 BUILD_BUG_ON(PKEY_DISABLE_EXECUTE &
70 (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
73 * pkey_to_vmflag_bits() assumes that the pkey bits are contiguous
74 * in the vmaflag. Make sure that is really the case.
76 BUILD_BUG_ON(__builtin_clzl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) +
77 __builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)
78 != (sizeof(u64) * BITS_PER_BYTE));
80 /* scan the device tree for pkey feature */
84 * Let's assume 32 pkeys on P8/P9 bare metal, if its not defined by device
85 * tree. We make this exception since some version of skiboot forgot to
86 * expose this property on power8/9.
88 if (!pkeys_devtree_defined && !firmware_has_feature(FW_FEATURE_LPAR)) {
89 unsigned long pvr = mfspr(SPRN_PVR);
91 if (PVR_VER(pvr) == PVR_POWER8 || PVR_VER(pvr) == PVR_POWER8E ||
92 PVR_VER(pvr) == PVR_POWER8NVL || PVR_VER(pvr) == PVR_POWER9)
97 * Adjust the upper limit, based on the number of bits supported by
100 pkeys_total = min_t(int, pkeys_total,
101 ((ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)+1));
103 if (!pkey_mmu_enabled() || radix_enabled() || !pkeys_total)
104 static_branch_enable(&pkey_disabled);
106 static_branch_disable(&pkey_disabled);
108 if (static_branch_likely(&pkey_disabled))
112 * The device tree cannot be relied to indicate support for
113 * execute_disable support. Instead we use a PVR check.
115 if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p))
116 pkey_execute_disable_supported = false;
118 pkey_execute_disable_supported = true;
120 #ifdef CONFIG_PPC_4K_PAGES
122 * The OS can manage only 8 pkeys due to its inability to represent them
123 * in the Linux 4K PTE.
125 os_reserved = pkeys_total - 8;
129 /* Bits are in LE format. */
130 reserved_allocation_mask = (0x1 << 1) | (0x1 << execute_only_key);
132 /* register mask is in BE format */
133 pkey_amr_mask = ~0x0ul;
134 pkey_amr_mask &= ~(0x3ul << pkeyshift(0));
136 pkey_iamr_mask = ~0x0ul;
137 pkey_iamr_mask &= ~(0x3ul << pkeyshift(0));
138 pkey_iamr_mask &= ~(0x3ul << pkeyshift(execute_only_key));
140 pkey_uamor_mask = ~0x0ul;
141 pkey_uamor_mask &= ~(0x3ul << pkeyshift(0));
142 pkey_uamor_mask &= ~(0x3ul << pkeyshift(execute_only_key));
144 /* mark the rest of the keys as reserved and hence unavailable */
145 for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) {
146 reserved_allocation_mask |= (0x1 << i);
147 pkey_uamor_mask &= ~(0x3ul << pkeyshift(i));
149 initial_allocation_mask = reserved_allocation_mask | (0x1 << 0);
151 if (unlikely((pkeys_total - os_reserved) <= execute_only_key)) {
153 * Insufficient number of keys to support
154 * execute only key. Mark it unavailable.
155 * Any AMR, UAMOR, IAMR bit set for
156 * this key is irrelevant since this key
157 * can never be allocated.
159 execute_only_key = -1;
165 arch_initcall(pkey_initialize);
167 void pkey_mm_init(struct mm_struct *mm)
169 if (static_branch_likely(&pkey_disabled))
171 mm_pkey_allocation_map(mm) = initial_allocation_mask;
172 mm->context.execute_only_pkey = execute_only_key;
175 static inline u64 read_amr(void)
177 return mfspr(SPRN_AMR);
180 static inline void write_amr(u64 value)
182 mtspr(SPRN_AMR, value);
185 static inline u64 read_iamr(void)
187 if (!likely(pkey_execute_disable_supported))
190 return mfspr(SPRN_IAMR);
193 static inline void write_iamr(u64 value)
195 if (!likely(pkey_execute_disable_supported))
198 mtspr(SPRN_IAMR, value);
201 static inline u64 read_uamor(void)
203 return mfspr(SPRN_UAMOR);
206 static inline void write_uamor(u64 value)
208 mtspr(SPRN_UAMOR, value);
211 static bool is_pkey_enabled(int pkey)
213 u64 uamor = read_uamor();
214 u64 pkey_bits = 0x3ul << pkeyshift(pkey);
215 u64 uamor_pkey_bits = (uamor & pkey_bits);
218 * Both the bits in UAMOR corresponding to the key should be set or
221 WARN_ON(uamor_pkey_bits && (uamor_pkey_bits != pkey_bits));
222 return !!(uamor_pkey_bits);
225 static inline void init_amr(int pkey, u8 init_bits)
227 u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
228 u64 old_amr = read_amr() & ~((u64)(0x3ul) << pkeyshift(pkey));
230 write_amr(old_amr | new_amr_bits);
233 static inline void init_iamr(int pkey, u8 init_bits)
235 u64 new_iamr_bits = (((u64)init_bits & 0x1UL) << pkeyshift(pkey));
236 u64 old_iamr = read_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey));
238 write_iamr(old_iamr | new_iamr_bits);
242 * Set the access rights in AMR IAMR and UAMOR registers for @pkey to that
243 * specified in @init_val.
245 int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
246 unsigned long init_val)
248 u64 new_amr_bits = 0x0ul;
249 u64 new_iamr_bits = 0x0ul;
251 if (!is_pkey_enabled(pkey))
254 if (init_val & PKEY_DISABLE_EXECUTE) {
255 if (!pkey_execute_disable_supported)
257 new_iamr_bits |= IAMR_EX_BIT;
259 init_iamr(pkey, new_iamr_bits);
261 /* Set the bits we need in AMR: */
262 if (init_val & PKEY_DISABLE_ACCESS)
263 new_amr_bits |= AMR_RD_BIT | AMR_WR_BIT;
264 else if (init_val & PKEY_DISABLE_WRITE)
265 new_amr_bits |= AMR_WR_BIT;
267 init_amr(pkey, new_amr_bits);
271 void thread_pkey_regs_save(struct thread_struct *thread)
273 if (static_branch_likely(&pkey_disabled))
277 * TODO: Skip saving registers if @thread hasn't used any keys yet.
279 thread->amr = read_amr();
280 thread->iamr = read_iamr();
281 thread->uamor = read_uamor();
284 void thread_pkey_regs_restore(struct thread_struct *new_thread,
285 struct thread_struct *old_thread)
287 if (static_branch_likely(&pkey_disabled))
290 if (old_thread->amr != new_thread->amr)
291 write_amr(new_thread->amr);
292 if (old_thread->iamr != new_thread->iamr)
293 write_iamr(new_thread->iamr);
294 if (old_thread->uamor != new_thread->uamor)
295 write_uamor(new_thread->uamor);
298 void thread_pkey_regs_init(struct thread_struct *thread)
300 if (static_branch_likely(&pkey_disabled))
303 thread->amr = pkey_amr_mask;
304 thread->iamr = pkey_iamr_mask;
305 thread->uamor = pkey_uamor_mask;
307 write_uamor(pkey_uamor_mask);
308 write_amr(pkey_amr_mask);
309 write_iamr(pkey_iamr_mask);
312 static inline bool pkey_allows_readwrite(int pkey)
314 int pkey_shift = pkeyshift(pkey);
316 if (!is_pkey_enabled(pkey))
319 return !(read_amr() & ((AMR_RD_BIT|AMR_WR_BIT) << pkey_shift));
322 int __execute_only_pkey(struct mm_struct *mm)
324 return mm->context.execute_only_pkey;
327 static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
329 /* Do this check first since the vm_flags should be hot */
330 if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
333 return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
337 * This should only be called for *plain* mprotect calls.
339 int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
343 * If the currently associated pkey is execute-only, but the requested
344 * protection is not execute-only, move it back to the default pkey.
346 if (vma_is_pkey_exec_only(vma) && (prot != PROT_EXEC))
350 * The requested protection is execute-only. Hence let's use an
353 if (prot == PROT_EXEC) {
354 pkey = execute_only_pkey(vma->vm_mm);
359 /* Nothing to override. */
360 return vma_pkey(vma);
363 static bool pkey_access_permitted(int pkey, bool write, bool execute)
368 if (!is_pkey_enabled(pkey))
371 pkey_shift = pkeyshift(pkey);
373 return !(read_iamr() & (IAMR_EX_BIT << pkey_shift));
377 return !(amr & (AMR_WR_BIT << pkey_shift));
379 return !(amr & (AMR_RD_BIT << pkey_shift));
382 bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
384 if (static_branch_likely(&pkey_disabled))
387 return pkey_access_permitted(pte_to_pkey_bits(pte), write, execute);
391 * We only want to enforce protection keys on the current thread because we
392 * effectively have no access to AMR/IAMR for other threads or any way to tell
393 * which AMR/IAMR in a threaded process we could use.
395 * So do not enforce things if the VMA is not from the current mm, or if we are
396 * in a kernel thread.
398 static inline bool vma_is_foreign(struct vm_area_struct *vma)
403 /* if it is not our ->mm, it has to be foreign */
404 if (current->mm != vma->vm_mm)
410 bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
411 bool execute, bool foreign)
413 if (static_branch_likely(&pkey_disabled))
416 * Do not enforce our key-permissions on a foreign vma.
418 if (foreign || vma_is_foreign(vma))
421 return pkey_access_permitted(vma_pkey(vma), write, execute);
424 void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
426 if (static_branch_likely(&pkey_disabled))
429 /* Duplicate the oldmm pkey state in mm: */
430 mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
431 mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;