// 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 the initially allocated keys */
u32  reserved_allocation_mask;  /* Bits set for reserved keys */
u64  pkey_amr_mask;             /* Bits in AMR not to be touched */
u64  pkey_iamr_mask;            /* Bits in AMR not to be touched */
u64  pkey_uamor_mask;           /* Bits in UMOR not to be touched */
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);
}

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);
}