diff options
Diffstat (limited to 'arch/powerpc/mm/pkeys.c')
| -rw-r--r-- | arch/powerpc/mm/pkeys.c | 468 |
1 files changed, 468 insertions, 0 deletions
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c new file mode 100644 index 000000000000..ba71c5481f42 --- /dev/null +++ b/arch/powerpc/mm/pkeys.c @@ -0,0 +1,468 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * PowerPC Memory Protection Keys management + * + * Copyright 2017, Ram Pai, IBM Corporation. + */ + +#include <asm/mman.h> +#include <asm/setup.h> +#include <linux/pkeys.h> +#include <linux/of_device.h> + +DEFINE_STATIC_KEY_TRUE(pkey_disabled); +bool pkey_execute_disable_supported; +int pkeys_total; /* Total pkeys as per device tree */ +bool pkeys_devtree_defined; /* pkey property exported by device tree */ +u32 initial_allocation_mask; /* Bits set for reserved keys */ +u64 pkey_amr_uamor_mask; /* Bits in AMR/UMOR not to be touched */ +u64 pkey_iamr_mask; /* Bits in AMR not to be touched */ + +#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 = be32_to_cpu(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); +} + +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)); + + 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. NOTE: 1, 0 are reserved. + * key 0 is the default key, which allows read/write/execute. + * key 1 is recommended not to be used. PowerISA(3.0) page 1015, + * programming note. + */ + initial_allocation_mask = ~0x0; + + /* register mask is in BE format */ + pkey_amr_uamor_mask = ~0x0ul; + pkey_iamr_mask = ~0x0ul; + + for (i = 2; i < (pkeys_total - os_reserved); i++) { + initial_allocation_mask &= ~(0x1 << i); + pkey_amr_uamor_mask &= ~(0x3ul << pkeyshift(i)); + pkey_iamr_mask &= ~(0x1ul << pkeyshift(i)); + } + 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; + /* -1 means unallocated or invalid */ + mm->context.execute_only_pkey = -1; +} + +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); +} + +static void pkey_status_change(int pkey, bool enable) +{ + u64 old_uamor; + + /* Reset the AMR and IAMR bits for this key */ + init_amr(pkey, 0x0); + init_iamr(pkey, 0x0); + + /* Enable/disable key */ + old_uamor = read_uamor(); + if (enable) + old_uamor |= (0x3ul << pkeyshift(pkey)); + else + old_uamor &= ~(0x3ul << pkeyshift(pkey)); + write_uamor(old_uamor); +} + +void __arch_activate_pkey(int pkey) +{ + pkey_status_change(pkey, true); +} + +void __arch_deactivate_pkey(int pkey) +{ + pkey_status_change(pkey, false); +} + +/* + * 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; + + /* + * TODO: Just set UAMOR to zero if @new_thread hasn't used any keys yet. + */ + 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; + + write_amr(read_amr() & pkey_amr_uamor_mask); + write_iamr(read_iamr() & pkey_iamr_mask); + write_uamor(read_uamor() & pkey_amr_uamor_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) +{ + bool need_to_set_mm_pkey = false; + int execute_only_pkey = mm->context.execute_only_pkey; + int ret; + + /* Do we need to assign a pkey for mm's execute-only maps? */ + if (execute_only_pkey == -1) { + /* Go allocate one to use, which might fail */ + execute_only_pkey = mm_pkey_alloc(mm); + if (execute_only_pkey < 0) + return -1; + need_to_set_mm_pkey = true; + } + + /* + * We do not want to go through the relatively costly dance to set AMR + * if we do not need to. Check it first and assume that if the + * execute-only pkey is readwrite-disabled than we do not have to set it + * ourselves. + */ + if (!need_to_set_mm_pkey && !pkey_allows_readwrite(execute_only_pkey)) + return execute_only_pkey; + + /* + * Set up AMR so that it denies access for everything other than + * execution. + */ + ret = __arch_set_user_pkey_access(current, execute_only_pkey, + PKEY_DISABLE_ACCESS | + PKEY_DISABLE_WRITE); + /* + * If the AMR-set operation failed somehow, just return 0 and + * effectively disable execute-only support. + */ + if (ret) { + mm_pkey_free(mm, execute_only_pkey); + return -1; + } + + /* We got one, store it and use it from here on out */ + if (need_to_set_mm_pkey) + mm->context.execute_only_pkey = execute_only_pkey; + return 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 requires read or write, move it back to the default pkey. + */ + if (vma_is_pkey_exec_only(vma) && (prot & (PROT_READ | PROT_WRITE))) + 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 (!pkey) + return true; + + 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); +} |