WIP FPC-III support

[linux/fpc-iii.git] / arch / powerpc / mm / book3s64 / pkeys.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * PowerPC Memory Protection Keys management
 *
 * Copyright 2017, Ram Pai, IBM Corporation.
 */

#include <asm/mman.h>
#include <asm/mmu_context.h>
#include <asm/mmu.h>
#include <asm/setup.h>
#include <asm/smp.h>

#include <linux/pkeys.h>
#include <linux/of_fdt.h>


int  num_pkey;          /* Max number of pkeys supported */
/*
 *  Keys marked in the reservation list cannot be allocated by  userspace
 */
u32 reserved_allocation_mask __ro_after_init;

/* Bits set for the initially allocated keys */
static u32 initial_allocation_mask __ro_after_init;

/*
 * Even if we allocate keys with sys_pkey_alloc(), we need to make sure
 * other thread still find the access denied using the same keys.
 */
u64 default_amr __ro_after_init  = ~0x0UL;
u64 default_iamr __ro_after_init = 0x5555555555555555UL;
u64 default_uamor __ro_after_init;
/*
 * Key used to implement PROT_EXEC mmap. Denies READ/WRITE
 * We pick key 2 because 0 is special key and 1 is reserved as per ISA.
 */
static int execute_only_key = 2;
static bool pkey_execute_disable_supported;


#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 int __init dt_scan_storage_keys(unsigned long node,
                                       const char *uname, int depth,
                                       void *data)
{
        const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
        const __be32 *prop;
        int *pkeys_total = (int *) data;

        /* We are scanning "cpu" nodes only */
        if (type == NULL || strcmp(type, "cpu") != 0)
                return 0;

        prop = of_get_flat_dt_prop(node, "ibm,processor-storage-keys", NULL);
        if (!prop)
                return 0;
        *pkeys_total = be32_to_cpu(prop[0]);
        return 1;
}

static int scan_pkey_feature(void)
{
        int ret;
        int pkeys_total = 0;

        /*
         * Pkey is not supported with Radix translation.
         */
        if (early_radix_enabled())
                return 0;

        ret = of_scan_flat_dt(dt_scan_storage_keys, &pkeys_total);
        if (ret == 0) {
                /*
                 * Let's assume 32 pkeys on P8/P9 bare metal, if its not defined by device
                 * tree. We make this exception since some version of skiboot forgot to
                 * expose this property on power8/9.
                 */
                if (!firmware_has_feature(FW_FEATURE_LPAR)) {
                        unsigned long pvr = mfspr(SPRN_PVR);

                        if (PVR_VER(pvr) == PVR_POWER8 || PVR_VER(pvr) == PVR_POWER8E ||
                            PVR_VER(pvr) == PVR_POWER8NVL || PVR_VER(pvr) == PVR_POWER9)
                                pkeys_total = 32;
                }
        }

#ifdef CONFIG_PPC_MEM_KEYS
        /*
         * 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));
#endif
        return pkeys_total;
}

void __init pkey_early_init_devtree(void)
{
        int pkeys_total, i;

#ifdef CONFIG_PPC_MEM_KEYS
        /*
         * 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));
#endif
        /*
         * Only P7 and above supports SPRN_AMR update with MSR[PR] = 1
         */
        if (!early_cpu_has_feature(CPU_FTR_ARCH_206))
                return;

        /* scan the device tree for pkey feature */
        pkeys_total = scan_pkey_feature();
        if (!pkeys_total)
                goto out;

        /* Allow all keys to be modified by default */
        default_uamor = ~0x0UL;

        cur_cpu_spec->mmu_features |= MMU_FTR_PKEY;

        /*
         * 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. Mark all other keys reserved.
         */
        num_pkey = min(8, pkeys_total);
#else
        num_pkey = pkeys_total;
#endif

        if (unlikely(num_pkey <= execute_only_key) || !pkey_execute_disable_supported) {
                /*
                 * Insufficient number of keys to support
                 * execute only key. Mark it unavailable.
                 */
                execute_only_key = -1;
        } else {
                /*
                 * Mark the execute_only_pkey as not available for
                 * user allocation via pkey_alloc.
                 */
                reserved_allocation_mask |= (0x1 << execute_only_key);

                /*
                 * Deny READ/WRITE for execute_only_key.
                 * Allow execute in IAMR.
                 */
                default_amr  |= (0x3ul << pkeyshift(execute_only_key));
                default_iamr &= ~(0x1ul << pkeyshift(execute_only_key));

                /*
                 * Clear the uamor bits for this key.
                 */
                default_uamor &= ~(0x3ul << pkeyshift(execute_only_key));
        }

        if (unlikely(num_pkey <= 3)) {
                /*
                 * Insufficient number of keys to support
                 * KUAP/KUEP feature.
                 */
                disable_kuep = true;
                disable_kuap = true;
                WARN(1, "Disabling kernel user protection due to low (%d) max supported keys\n", num_pkey);
        } else {
                /*  handle key which is used by kernel for KAUP */
                reserved_allocation_mask |= (0x1 << 3);
                /*
                 * Mark access for kup_key in default amr so that
                 * we continue to operate with that AMR in
                 * copy_to/from_user().
                 */
                default_amr   &= ~(0x3ul << pkeyshift(3));
                default_iamr  &= ~(0x1ul << pkeyshift(3));
                default_uamor &= ~(0x3ul << pkeyshift(3));
        }

        /*
         * Allow access for only key 0. And prevent any other modification.
         */
        default_amr   &= ~(0x3ul << pkeyshift(0));
        default_iamr  &= ~(0x1ul << pkeyshift(0));
        default_uamor &= ~(0x3ul << pkeyshift(0));
        /*
         * key 0 is special in that we want to consider it an allocated
         * key which is preallocated. We don't allow changing AMR bits
         * w.r.t key 0. But one can pkey_free(key0)
         */
        initial_allocation_mask |= (0x1 << 0);

        /*
         * key 1 is recommended not to be used. PowerISA(3.0) page 1015,
         * programming note.
         */
        reserved_allocation_mask |= (0x1 << 1);
        default_uamor &= ~(0x3ul << pkeyshift(1));

        /*
         * Prevent the usage of OS reserved keys. Update UAMOR
         * for those keys. Also mark the rest of the bits in the
         * 32 bit mask as reserved.
         */
        for (i = num_pkey; i < 32 ; i++) {
                reserved_allocation_mask |= (0x1 << i);
                default_uamor &= ~(0x3ul << pkeyshift(i));
        }
        /*
         * Prevent the allocation of reserved keys too.
         */
        initial_allocation_mask |= reserved_allocation_mask;

        pr_info("Enabling pkeys with max key count %d\n", num_pkey);
out:
        /*
         * Setup uamor on boot cpu
         */
        mtspr(SPRN_UAMOR, default_uamor);

        return;
}

#ifdef CONFIG_PPC_KUEP
void setup_kuep(bool disabled)
{
        if (disabled)
                return;
        /*
         * On hash if PKEY feature is not enabled, disable KUAP too.
         */
        if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))
                return;

        if (smp_processor_id() == boot_cpuid) {
                pr_info("Activating Kernel Userspace Execution Prevention\n");
                cur_cpu_spec->mmu_features |= MMU_FTR_BOOK3S_KUEP;
        }

        /*
         * Radix always uses key0 of the IAMR to determine if an access is
         * allowed. We set bit 0 (IBM bit 1) of key0, to prevent instruction
         * fetch.
         */
        mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
        isync();
}
#endif

#ifdef CONFIG_PPC_KUAP
void setup_kuap(bool disabled)
{
        if (disabled)
                return;
        /*
         * On hash if PKEY feature is not enabled, disable KUAP too.
         */
        if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))
                return;

        if (smp_processor_id() == boot_cpuid) {
                pr_info("Activating Kernel Userspace Access Prevention\n");
                cur_cpu_spec->mmu_features |= MMU_FTR_BOOK3S_KUAP;
        }

        /*
         * Set the default kernel AMR values on all cpus.
         */
        mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
        isync();
}
#endif

static inline void update_current_thread_amr(u64 value)
{
        current->thread.regs->amr = value;
}

static inline void update_current_thread_iamr(u64 value)
{
        if (!likely(pkey_execute_disable_supported))
                return;

        current->thread.regs->iamr = value;
}

#ifdef CONFIG_PPC_MEM_KEYS
void pkey_mm_init(struct mm_struct *mm)
{
        if (!mmu_has_feature(MMU_FTR_PKEY))
                return;
        mm_pkey_allocation_map(mm) = initial_allocation_mask;
        mm->context.execute_only_pkey = execute_only_key;
}

static inline void init_amr(int pkey, u8 init_bits)
{
        u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
        u64 old_amr = current_thread_amr() & ~((u64)(0x3ul) << pkeyshift(pkey));

        update_current_thread_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 = current_thread_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey));

        update_current_thread_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;
        u64 pkey_bits, uamor_pkey_bits;

        /*
         * Check whether the key is disabled by UAMOR.
         */
        pkey_bits = 0x3ul << pkeyshift(pkey);
        uamor_pkey_bits = (default_uamor & pkey_bits);

        /*
         * Both the bits in UAMOR corresponding to the key should be set
         */
        if (uamor_pkey_bits != pkey_bits)
                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;
}

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_ACCESS_FLAGS) != 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;

        pkey_shift = pkeyshift(pkey);
        if (execute)
                return !(current_thread_iamr() & (IAMR_EX_BIT << pkey_shift));

        amr = current_thread_amr();
        if (write)
                return !(amr & (AMR_WR_BIT << pkey_shift));

        return !(amr & (AMR_RD_BIT << pkey_shift));
}

bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
{
        if (!mmu_has_feature(MMU_FTR_PKEY))
                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.
 */
bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
                               bool execute, bool foreign)
{
        if (!mmu_has_feature(MMU_FTR_PKEY))
                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 (!mmu_has_feature(MMU_FTR_PKEY))
                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;
}

#endif /* CONFIG_PPC_MEM_KEYS */