// SPDX-License-Identifier: GPL-2.0+ /* * PowerPC Memory Protection Keys management * * Copyright 2017, Ram Pai, IBM Corporation. */ #include #include #include #include #include #include DEFINE_STATIC_KEY_TRUE(pkey_disabled); int pkeys_total; /* Total pkeys as per device tree */ u32 initial_allocation_mask; /* Bits set for the initially allocated keys */ u32 reserved_allocation_mask; /* Bits set for reserved keys */ static bool pkey_execute_disable_supported; static bool pkeys_devtree_defined; /* property exported by device tree */ static u64 pkey_amr_mask; /* Bits in AMR not to be touched */ static u64 pkey_iamr_mask; /* Bits in AMR not to be touched */ static u64 pkey_uamor_mask; /* Bits in UMOR not to be touched */ static int execute_only_key = 2; #define AMR_BITS_PER_PKEY 2 #define AMR_RD_BIT 0x1UL #define AMR_WR_BIT 0x2UL #define IAMR_EX_BIT 0x1UL #define PKEY_REG_BITS (sizeof(u64)*8) #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY)) static void scan_pkey_feature(void) { u32 vals[2]; struct device_node *cpu; cpu = of_find_node_by_type(NULL, "cpu"); if (!cpu) return; if (of_property_read_u32_array(cpu, "ibm,processor-storage-keys", vals, 2)) return; /* * Since any pkey can be used for data or execute, we will just treat * all keys as equal and track them as one entity. */ pkeys_total = vals[0]; pkeys_devtree_defined = true; } static inline bool pkey_mmu_enabled(void) { if (firmware_has_feature(FW_FEATURE_LPAR)) return pkeys_total; else return cpu_has_feature(CPU_FTR_PKEY); } static int pkey_initialize(void) { int os_reserved, i; /* * We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral * generic defines for PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE. * Ensure that the bits a distinct. */ BUILD_BUG_ON(PKEY_DISABLE_EXECUTE & (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE)); /* * pkey_to_vmflag_bits() assumes that the pkey bits are contiguous * in the vmaflag. Make sure that is really the case. */ BUILD_BUG_ON(__builtin_clzl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) + __builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) != (sizeof(u64) * BITS_PER_BYTE)); /* scan the device tree for pkey feature */ scan_pkey_feature(); /* * Let's assume 32 pkeys on P8 bare metal, if its not defined by device * tree. We make this exception since skiboot forgot to expose this * property on power8. */ if (!pkeys_devtree_defined && !firmware_has_feature(FW_FEATURE_LPAR) && cpu_has_feature(CPU_FTRS_POWER8)) pkeys_total = 32; /* * Adjust the upper limit, based on the number of bits supported by * arch-neutral code. */ pkeys_total = min_t(int, pkeys_total, ((ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)+1)); if (!pkey_mmu_enabled() || radix_enabled() || !pkeys_total) static_branch_enable(&pkey_disabled); else static_branch_disable(&pkey_disabled); if (static_branch_likely(&pkey_disabled)) return 0; /* * The device tree cannot be relied to indicate support for * execute_disable support. Instead we use a PVR check. */ if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p)) pkey_execute_disable_supported = false; else pkey_execute_disable_supported = true; #ifdef CONFIG_PPC_4K_PAGES /* * The OS can manage only 8 pkeys due to its inability to represent them * in the Linux 4K PTE. */ os_reserved = pkeys_total - 8; #else os_reserved = 0; #endif /* Bits are in LE format. */ reserved_allocation_mask = (0x1 << 1) | (0x1 << execute_only_key); /* register mask is in BE format */ pkey_amr_mask = ~0x0ul; pkey_amr_mask &= ~(0x3ul << pkeyshift(0)); pkey_iamr_mask = ~0x0ul; pkey_iamr_mask &= ~(0x3ul << pkeyshift(0)); pkey_iamr_mask &= ~(0x3ul << pkeyshift(execute_only_key)); pkey_uamor_mask = ~0x0ul; pkey_uamor_mask &= ~(0x3ul << pkeyshift(0)); pkey_uamor_mask &= ~(0x3ul << pkeyshift(execute_only_key)); /* mark the rest of the keys as reserved and hence unavailable */ for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) { reserved_allocation_mask |= (0x1 << i); pkey_uamor_mask &= ~(0x3ul << pkeyshift(i)); } initial_allocation_mask = reserved_allocation_mask | (0x1 << 0); if (unlikely((pkeys_total - os_reserved) <= execute_only_key)) { /* * Insufficient number of keys to support * execute only key. Mark it unavailable. * Any AMR, UAMOR, IAMR bit set for * this key is irrelevant since this key * can never be allocated. */ execute_only_key = -1; } return 0; } arch_initcall(pkey_initialize); void pkey_mm_init(struct mm_struct *mm) { if (static_branch_likely(&pkey_disabled)) return; mm_pkey_allocation_map(mm) = initial_allocation_mask; mm->context.execute_only_pkey = execute_only_key; } static inline u64 read_amr(void) { return mfspr(SPRN_AMR); } static inline void write_amr(u64 value) { mtspr(SPRN_AMR, value); } static inline u64 read_iamr(void) { if (!likely(pkey_execute_disable_supported)) return 0x0UL; return mfspr(SPRN_IAMR); } static inline void write_iamr(u64 value) { if (!likely(pkey_execute_disable_supported)) return; mtspr(SPRN_IAMR, value); } static inline u64 read_uamor(void) { return mfspr(SPRN_UAMOR); } static inline void write_uamor(u64 value) { mtspr(SPRN_UAMOR, value); } static bool is_pkey_enabled(int pkey) { u64 uamor = read_uamor(); u64 pkey_bits = 0x3ul << pkeyshift(pkey); u64 uamor_pkey_bits = (uamor & pkey_bits); /* * Both the bits in UAMOR corresponding to the key should be set or * reset. */ WARN_ON(uamor_pkey_bits && (uamor_pkey_bits != pkey_bits)); return !!(uamor_pkey_bits); } static inline void init_amr(int pkey, u8 init_bits) { u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey)); u64 old_amr = read_amr() & ~((u64)(0x3ul) << pkeyshift(pkey)); write_amr(old_amr | new_amr_bits); } static inline void init_iamr(int pkey, u8 init_bits) { u64 new_iamr_bits = (((u64)init_bits & 0x1UL) << pkeyshift(pkey)); u64 old_iamr = read_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey)); write_iamr(old_iamr | new_iamr_bits); } /* * Set the access rights in AMR IAMR and UAMOR registers for @pkey to that * specified in @init_val. */ int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val) { u64 new_amr_bits = 0x0ul; u64 new_iamr_bits = 0x0ul; if (!is_pkey_enabled(pkey)) return -EINVAL; if (init_val & PKEY_DISABLE_EXECUTE) { if (!pkey_execute_disable_supported) return -EINVAL; new_iamr_bits |= IAMR_EX_BIT; } init_iamr(pkey, new_iamr_bits); /* Set the bits we need in AMR: */ if (init_val & PKEY_DISABLE_ACCESS) new_amr_bits |= AMR_RD_BIT | AMR_WR_BIT; else if (init_val & PKEY_DISABLE_WRITE) new_amr_bits |= AMR_WR_BIT; init_amr(pkey, new_amr_bits); return 0; } void thread_pkey_regs_save(struct thread_struct *thread) { if (static_branch_likely(&pkey_disabled)) return; /* * TODO: Skip saving registers if @thread hasn't used any keys yet. */ thread->amr = read_amr(); thread->iamr = read_iamr(); thread->uamor = read_uamor(); } void thread_pkey_regs_restore(struct thread_struct *new_thread, struct thread_struct *old_thread) { if (static_branch_likely(&pkey_disabled)) return; if (old_thread->amr != new_thread->amr) write_amr(new_thread->amr); if (old_thread->iamr != new_thread->iamr) write_iamr(new_thread->iamr); if (old_thread->uamor != new_thread->uamor) write_uamor(new_thread->uamor); } void thread_pkey_regs_init(struct thread_struct *thread) { if (static_branch_likely(&pkey_disabled)) return; thread->amr = pkey_amr_mask; thread->iamr = pkey_iamr_mask; thread->uamor = pkey_uamor_mask; write_uamor(pkey_uamor_mask); write_amr(pkey_amr_mask); write_iamr(pkey_iamr_mask); } static inline bool pkey_allows_readwrite(int pkey) { int pkey_shift = pkeyshift(pkey); if (!is_pkey_enabled(pkey)) return true; return !(read_amr() & ((AMR_RD_BIT|AMR_WR_BIT) << pkey_shift)); } int __execute_only_pkey(struct mm_struct *mm) { return mm->context.execute_only_pkey; } static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma) { /* Do this check first since the vm_flags should be hot */ if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC) return false; return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey); } /* * This should only be called for *plain* mprotect calls. */ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey) { /* * If the currently associated pkey is execute-only, but the requested * protection is not execute-only, move it back to the default pkey. */ if (vma_is_pkey_exec_only(vma) && (prot != PROT_EXEC)) return 0; /* * The requested protection is execute-only. Hence let's use an * execute-only pkey. */ if (prot == PROT_EXEC) { pkey = execute_only_pkey(vma->vm_mm); if (pkey > 0) return pkey; } /* Nothing to override. */ return vma_pkey(vma); } static bool pkey_access_permitted(int pkey, bool write, bool execute) { int pkey_shift; u64 amr; if (!is_pkey_enabled(pkey)) return true; pkey_shift = pkeyshift(pkey); if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift))) return true; amr = read_amr(); /* Delay reading amr until absolutely needed */ return ((!write && !(amr & (AMR_RD_BIT << pkey_shift))) || (write && !(amr & (AMR_WR_BIT << pkey_shift)))); } bool arch_pte_access_permitted(u64 pte, bool write, bool execute) { if (static_branch_likely(&pkey_disabled)) return true; return pkey_access_permitted(pte_to_pkey_bits(pte), write, execute); } /* * We only want to enforce protection keys on the current thread because we * effectively have no access to AMR/IAMR for other threads or any way to tell * which AMR/IAMR in a threaded process we could use. * * So do not enforce things if the VMA is not from the current mm, or if we are * in a kernel thread. */ static inline bool vma_is_foreign(struct vm_area_struct *vma) { if (!current->mm) return true; /* if it is not our ->mm, it has to be foreign */ if (current->mm != vma->vm_mm) return true; return false; } bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write, bool execute, bool foreign) { if (static_branch_likely(&pkey_disabled)) return true; /* * Do not enforce our key-permissions on a foreign vma. */ if (foreign || vma_is_foreign(vma)) return true; return pkey_access_permitted(vma_pkey(vma), write, execute); } void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm) { if (static_branch_likely(&pkey_disabled)) return; /* Duplicate the oldmm pkey state in mm: */ mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm); mm->context.execute_only_pkey = oldmm->context.execute_only_pkey; }