// SPDX-License-Identifier: GPL-2.0
/*  Copyright(c) 2016-20 Intel Corporation. */

#include <linux/lockdep.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/shmem_fs.h>
#include <linux/suspend.h>
#include <linux/sched/mm.h>
#include <asm/sgx.h>
#include "encl.h"
#include "encls.h"
#include "sgx.h"

/*
 * ELDU: Load an EPC page as unblocked. For more info, see "OS Management of EPC
 * Pages" in the SDM.
 */
static int __sgx_encl_eldu(struct sgx_encl_page *encl_page,
                           struct sgx_epc_page *epc_page,
                           struct sgx_epc_page *secs_page)
{
        unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK;
        struct sgx_encl *encl = encl_page->encl;
        struct sgx_pageinfo pginfo;
        struct sgx_backing b;
        pgoff_t page_index;
        int ret;

        if (secs_page)
                page_index = PFN_DOWN(encl_page->desc - encl_page->encl->base);
        else
                page_index = PFN_DOWN(encl->size);

        ret = sgx_encl_get_backing(encl, page_index, &b);
        if (ret)
                return ret;

        pginfo.addr = encl_page->desc & PAGE_MASK;
        pginfo.contents = (unsigned long)kmap_atomic(b.contents);
        pginfo.metadata = (unsigned long)kmap_atomic(b.pcmd) +
                          b.pcmd_offset;

        if (secs_page)
                pginfo.secs = (u64)sgx_get_epc_virt_addr(secs_page);
        else
                pginfo.secs = 0;

        ret = __eldu(&pginfo, sgx_get_epc_virt_addr(epc_page),
                     sgx_get_epc_virt_addr(encl_page->va_page->epc_page) + va_offset);
        if (ret) {
                if (encls_failed(ret))
                        ENCLS_WARN(ret, "ELDU");

                ret = -EFAULT;
        }

        kunmap_atomic((void *)(unsigned long)(pginfo.metadata - b.pcmd_offset));
        kunmap_atomic((void *)(unsigned long)pginfo.contents);

        sgx_encl_put_backing(&b, false);

        return ret;
}

static struct sgx_epc_page *sgx_encl_eldu(struct sgx_encl_page *encl_page,
                                          struct sgx_epc_page *secs_page)
{

        unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK;
        struct sgx_encl *encl = encl_page->encl;
        struct sgx_epc_page *epc_page;
        int ret;

        epc_page = sgx_alloc_epc_page(encl_page, false);
        if (IS_ERR(epc_page))
                return epc_page;

        ret = __sgx_encl_eldu(encl_page, epc_page, secs_page);
        if (ret) {
                sgx_encl_free_epc_page(epc_page);
                return ERR_PTR(ret);
        }

        sgx_free_va_slot(encl_page->va_page, va_offset);
        list_move(&encl_page->va_page->list, &encl->va_pages);
        encl_page->desc &= ~SGX_ENCL_PAGE_VA_OFFSET_MASK;
        encl_page->epc_page = epc_page;

        return epc_page;
}

static struct sgx_encl_page *sgx_encl_load_page(struct sgx_encl *encl,
                                                unsigned long addr,
                                                unsigned long vm_flags)
{
        unsigned long vm_prot_bits = vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
        struct sgx_epc_page *epc_page;
        struct sgx_encl_page *entry;

        entry = xa_load(&encl->page_array, PFN_DOWN(addr));
        if (!entry)
                return ERR_PTR(-EFAULT);

        /*
         * Verify that the faulted page has equal or higher build time
         * permissions than the VMA permissions (i.e. the subset of {VM_READ,
         * VM_WRITE, VM_EXECUTE} in vma->vm_flags).
         */
        if ((entry->vm_max_prot_bits & vm_prot_bits) != vm_prot_bits)
                return ERR_PTR(-EFAULT);

        /* Entry successfully located. */
        if (entry->epc_page) {
                if (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)
                        return ERR_PTR(-EBUSY);

                return entry;
        }

        if (!(encl->secs.epc_page)) {
                epc_page = sgx_encl_eldu(&encl->secs, NULL);
                if (IS_ERR(epc_page))
                        return ERR_CAST(epc_page);
        }

        epc_page = sgx_encl_eldu(entry, encl->secs.epc_page);
        if (IS_ERR(epc_page))
                return ERR_CAST(epc_page);

        encl->secs_child_cnt++;
        sgx_mark_page_reclaimable(entry->epc_page);

        return entry;
}

static vm_fault_t sgx_vma_fault(struct vm_fault *vmf)
{
        unsigned long addr = (unsigned long)vmf->address;
        struct vm_area_struct *vma = vmf->vma;
        struct sgx_encl_page *entry;
        unsigned long phys_addr;
        struct sgx_encl *encl;
        vm_fault_t ret;

        encl = vma->vm_private_data;

        /*
         * It's very unlikely but possible that allocating memory for the
         * mm_list entry of a forked process failed in sgx_vma_open(). When
         * this happens, vm_private_data is set to NULL.
         */
        if (unlikely(!encl))
                return VM_FAULT_SIGBUS;

        mutex_lock(&encl->lock);

        entry = sgx_encl_load_page(encl, addr, vma->vm_flags);
        if (IS_ERR(entry)) {
                mutex_unlock(&encl->lock);

                if (PTR_ERR(entry) == -EBUSY)
                        return VM_FAULT_NOPAGE;

                return VM_FAULT_SIGBUS;
        }

        phys_addr = sgx_get_epc_phys_addr(entry->epc_page);

        ret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr));
        if (ret != VM_FAULT_NOPAGE) {
                mutex_unlock(&encl->lock);

                return VM_FAULT_SIGBUS;
        }

        sgx_encl_test_and_clear_young(vma->vm_mm, entry);
        mutex_unlock(&encl->lock);

        return VM_FAULT_NOPAGE;
}

static void sgx_vma_open(struct vm_area_struct *vma)
{
        struct sgx_encl *encl = vma->vm_private_data;

        /*
         * It's possible but unlikely that vm_private_data is NULL. This can
         * happen in a grandchild of a process, when sgx_encl_mm_add() had
         * failed to allocate memory in this callback.
         */
        if (unlikely(!encl))
                return;

        if (sgx_encl_mm_add(encl, vma->vm_mm))
                vma->vm_private_data = NULL;
}


/**
 * sgx_encl_may_map() - Check if a requested VMA mapping is allowed
 * @encl:               an enclave pointer
 * @start:              lower bound of the address range, inclusive
 * @end:                upper bound of the address range, exclusive
 * @vm_flags:           VMA flags
 *
 * Iterate through the enclave pages contained within [@start, @end) to verify
 * that the permissions requested by a subset of {VM_READ, VM_WRITE, VM_EXEC}
 * do not contain any permissions that are not contained in the build time
 * permissions of any of the enclave pages within the given address range.
 *
 * An enclave creator must declare the strongest permissions that will be
 * needed for each enclave page. This ensures that mappings have the identical
 * or weaker permissions than the earlier declared permissions.
 *
 * Return: 0 on success, -EACCES otherwise
 */
int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
                     unsigned long end, unsigned long vm_flags)
{
        unsigned long vm_prot_bits = vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
        struct sgx_encl_page *page;
        unsigned long count = 0;
        int ret = 0;

        XA_STATE(xas, &encl->page_array, PFN_DOWN(start));

        /*
         * Disallow READ_IMPLIES_EXEC tasks as their VMA permissions might
         * conflict with the enclave page permissions.
         */
        if (current->personality & READ_IMPLIES_EXEC)
                return -EACCES;

        mutex_lock(&encl->lock);
        xas_lock(&xas);
        xas_for_each(&xas, page, PFN_DOWN(end - 1)) {
                if (~page->vm_max_prot_bits & vm_prot_bits) {
                        ret = -EACCES;
                        break;
                }

                /* Reschedule on every XA_CHECK_SCHED iteration. */
                if (!(++count % XA_CHECK_SCHED)) {
                        xas_pause(&xas);
                        xas_unlock(&xas);
                        mutex_unlock(&encl->lock);

                        cond_resched();

                        mutex_lock(&encl->lock);
                        xas_lock(&xas);
                }
        }
        xas_unlock(&xas);
        mutex_unlock(&encl->lock);

        return ret;
}

static int sgx_vma_mprotect(struct vm_area_struct *vma, unsigned long start,
                            unsigned long end, unsigned long newflags)
{
        return sgx_encl_may_map(vma->vm_private_data, start, end, newflags);
}

static int sgx_encl_debug_read(struct sgx_encl *encl, struct sgx_encl_page *page,
                               unsigned long addr, void *data)
{
        unsigned long offset = addr & ~PAGE_MASK;
        int ret;


        ret = __edbgrd(sgx_get_epc_virt_addr(page->epc_page) + offset, data);
        if (ret)
                return -EIO;

        return 0;
}

static int sgx_encl_debug_write(struct sgx_encl *encl, struct sgx_encl_page *page,
                                unsigned long addr, void *data)
{
        unsigned long offset = addr & ~PAGE_MASK;
        int ret;

        ret = __edbgwr(sgx_get_epc_virt_addr(page->epc_page) + offset, data);
        if (ret)
                return -EIO;

        return 0;
}

/*
 * Load an enclave page to EPC if required, and take encl->lock.
 */
static struct sgx_encl_page *sgx_encl_reserve_page(struct sgx_encl *encl,
                                                   unsigned long addr,
                                                   unsigned long vm_flags)
{
        struct sgx_encl_page *entry;

        for ( ; ; ) {
                mutex_lock(&encl->lock);

                entry = sgx_encl_load_page(encl, addr, vm_flags);
                if (PTR_ERR(entry) != -EBUSY)
                        break;

                mutex_unlock(&encl->lock);
        }

        if (IS_ERR(entry))
                mutex_unlock(&encl->lock);

        return entry;
}

static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr,
                          void *buf, int len, int write)
{
        struct sgx_encl *encl = vma->vm_private_data;
        struct sgx_encl_page *entry = NULL;
        char data[sizeof(unsigned long)];
        unsigned long align;
        int offset;
        int cnt;
        int ret = 0;
        int i;

        /*
         * If process was forked, VMA is still there but vm_private_data is set
         * to NULL.
         */
        if (!encl)
                return -EFAULT;

        if (!test_bit(SGX_ENCL_DEBUG, &encl->flags))
                return -EFAULT;

        for (i = 0; i < len; i += cnt) {
                entry = sgx_encl_reserve_page(encl, (addr + i) & PAGE_MASK,
                                              vma->vm_flags);
                if (IS_ERR(entry)) {
                        ret = PTR_ERR(entry);
                        break;
                }

                align = ALIGN_DOWN(addr + i, sizeof(unsigned long));
                offset = (addr + i) & (sizeof(unsigned long) - 1);
                cnt = sizeof(unsigned long) - offset;
                cnt = min(cnt, len - i);

                ret = sgx_encl_debug_read(encl, entry, align, data);
                if (ret)
                        goto out;

                if (write) {
                        memcpy(data + offset, buf + i, cnt);
                        ret = sgx_encl_debug_write(encl, entry, align, data);
                        if (ret)
                                goto out;
                } else {
                        memcpy(buf + i, data + offset, cnt);
                }

out:
                mutex_unlock(&encl->lock);

                if (ret)
                        break;
        }

        return ret < 0 ? ret : i;
}

const struct vm_operations_struct sgx_vm_ops = {
        .fault = sgx_vma_fault,
        .mprotect = sgx_vma_mprotect,
        .open = sgx_vma_open,
        .access = sgx_vma_access,
};

/**
 * sgx_encl_release - Destroy an enclave instance
 * @kref:       address of a kref inside &sgx_encl
 *
 * Used together with kref_put(). Frees all the resources associated with the
 * enclave and the instance itself.
 */
void sgx_encl_release(struct kref *ref)
{
        struct sgx_encl *encl = container_of(ref, struct sgx_encl, refcount);
        struct sgx_va_page *va_page;
        struct sgx_encl_page *entry;
        unsigned long index;

        xa_for_each(&encl->page_array, index, entry) {
                if (entry->epc_page) {
                        /*
                         * The page and its radix tree entry cannot be freed
                         * if the page is being held by the reclaimer.
                         */
                        if (sgx_unmark_page_reclaimable(entry->epc_page))
                                continue;

                        sgx_encl_free_epc_page(entry->epc_page);
                        encl->secs_child_cnt--;
                        entry->epc_page = NULL;
                }

                kfree(entry);
        }

        xa_destroy(&encl->page_array);

        if (!encl->secs_child_cnt && encl->secs.epc_page) {
                sgx_encl_free_epc_page(encl->secs.epc_page);
                encl->secs.epc_page = NULL;
        }

        while (!list_empty(&encl->va_pages)) {
                va_page = list_first_entry(&encl->va_pages, struct sgx_va_page,
                                           list);
                list_del(&va_page->list);
                sgx_encl_free_epc_page(va_page->epc_page);
                kfree(va_page);
        }

        if (encl->backing)
                fput(encl->backing);

        cleanup_srcu_struct(&encl->srcu);

        WARN_ON_ONCE(!list_empty(&encl->mm_list));

        /* Detect EPC page leak's. */
        WARN_ON_ONCE(encl->secs_child_cnt);
        WARN_ON_ONCE(encl->secs.epc_page);

        kfree(encl);
}

/*
 * 'mm' is exiting and no longer needs mmu notifications.
 */
static void sgx_mmu_notifier_release(struct mmu_notifier *mn,
                                     struct mm_struct *mm)
{
        struct sgx_encl_mm *encl_mm = container_of(mn, struct sgx_encl_mm, mmu_notifier);
        struct sgx_encl_mm *tmp = NULL;

        /*
         * The enclave itself can remove encl_mm.  Note, objects can't be moved
         * off an RCU protected list, but deletion is ok.
         */
        spin_lock(&encl_mm->encl->mm_lock);
        list_for_each_entry(tmp, &encl_mm->encl->mm_list, list) {
                if (tmp == encl_mm) {
                        list_del_rcu(&encl_mm->list);
                        break;
                }
        }
        spin_unlock(&encl_mm->encl->mm_lock);

        if (tmp == encl_mm) {
                synchronize_srcu(&encl_mm->encl->srcu);
                mmu_notifier_put(mn);
        }
}

static void sgx_mmu_notifier_free(struct mmu_notifier *mn)
{
        struct sgx_encl_mm *encl_mm = container_of(mn, struct sgx_encl_mm, mmu_notifier);

        /* 'encl_mm' is going away, put encl_mm->encl reference: */
        kref_put(&encl_mm->encl->refcount, sgx_encl_release);

        kfree(encl_mm);
}

static const struct mmu_notifier_ops sgx_mmu_notifier_ops = {
        .release                = sgx_mmu_notifier_release,
        .free_notifier          = sgx_mmu_notifier_free,
};

static struct sgx_encl_mm *sgx_encl_find_mm(struct sgx_encl *encl,
                                            struct mm_struct *mm)
{
        struct sgx_encl_mm *encl_mm = NULL;
        struct sgx_encl_mm *tmp;
        int idx;

        idx = srcu_read_lock(&encl->srcu);

        list_for_each_entry_rcu(tmp, &encl->mm_list, list) {
                if (tmp->mm == mm) {
                        encl_mm = tmp;
                        break;
                }
        }

        srcu_read_unlock(&encl->srcu, idx);

        return encl_mm;
}

int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm)
{
        struct sgx_encl_mm *encl_mm;
        int ret;

        /*
         * Even though a single enclave may be mapped into an mm more than once,
         * each 'mm' only appears once on encl->mm_list. This is guaranteed by
         * holding the mm's mmap lock for write before an mm can be added or
         * remove to an encl->mm_list.
         */
        mmap_assert_write_locked(mm);

        /*
         * It's possible that an entry already exists in the mm_list, because it
         * is removed only on VFS release or process exit.
         */
        if (sgx_encl_find_mm(encl, mm))
                return 0;

        encl_mm = kzalloc(sizeof(*encl_mm), GFP_KERNEL);
        if (!encl_mm)
                return -ENOMEM;

        /* Grab a refcount for the encl_mm->encl reference: */
        kref_get(&encl->refcount);
        encl_mm->encl = encl;
        encl_mm->mm = mm;
        encl_mm->mmu_notifier.ops = &sgx_mmu_notifier_ops;

        ret = __mmu_notifier_register(&encl_mm->mmu_notifier, mm);
        if (ret) {
                kfree(encl_mm);
                return ret;
        }

        spin_lock(&encl->mm_lock);
        list_add_rcu(&encl_mm->list, &encl->mm_list);
        /* Pairs with smp_rmb() in sgx_reclaimer_block(). */
        smp_wmb();
        encl->mm_list_version++;
        spin_unlock(&encl->mm_lock);

        return 0;
}

static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl,
                                              pgoff_t index)
{
        struct inode *inode = encl->backing->f_path.dentry->d_inode;
        struct address_space *mapping = inode->i_mapping;
        gfp_t gfpmask = mapping_gfp_mask(mapping);

        return shmem_read_mapping_page_gfp(mapping, index, gfpmask);
}

/**
 * sgx_encl_get_backing() - Pin the backing storage
 * @encl:       an enclave pointer
 * @page_index: enclave page index
 * @backing:    data for accessing backing storage for the page
 *
 * Pin the backing storage pages for storing the encrypted contents and Paging
 * Crypto MetaData (PCMD) of an enclave page.
 *
 * Return:
 *   0 on success,
 *   -errno otherwise.
 */
int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
                         struct sgx_backing *backing)
{
        pgoff_t pcmd_index = PFN_DOWN(encl->size) + 1 + (page_index >> 5);
        struct page *contents;
        struct page *pcmd;

        contents = sgx_encl_get_backing_page(encl, page_index);
        if (IS_ERR(contents))
                return PTR_ERR(contents);

        pcmd = sgx_encl_get_backing_page(encl, pcmd_index);
        if (IS_ERR(pcmd)) {
                put_page(contents);
                return PTR_ERR(pcmd);
        }

        backing->page_index = page_index;
        backing->contents = contents;
        backing->pcmd = pcmd;
        backing->pcmd_offset =
                (page_index & (PAGE_SIZE / sizeof(struct sgx_pcmd) - 1)) *
                sizeof(struct sgx_pcmd);

        return 0;
}

/**
 * sgx_encl_put_backing() - Unpin the backing storage
 * @backing:    data for accessing backing storage for the page
 * @do_write:   mark pages dirty
 */
void sgx_encl_put_backing(struct sgx_backing *backing, bool do_write)
{
        if (do_write) {
                set_page_dirty(backing->pcmd);
                set_page_dirty(backing->contents);
        }

        put_page(backing->pcmd);
        put_page(backing->contents);
}

static int sgx_encl_test_and_clear_young_cb(pte_t *ptep, unsigned long addr,
                                            void *data)
{
        pte_t pte;
        int ret;

        ret = pte_young(*ptep);
        if (ret) {
                pte = pte_mkold(*ptep);
                set_pte_at((struct mm_struct *)data, addr, ptep, pte);
        }

        return ret;
}

/**
 * sgx_encl_test_and_clear_young() - Test and reset the accessed bit
 * @mm:         mm_struct that is checked
 * @page:       enclave page to be tested for recent access
 *
 * Checks the Access (A) bit from the PTE corresponding to the enclave page and
 * clears it.
 *
 * Return: 1 if the page has been recently accessed and 0 if not.
 */
int sgx_encl_test_and_clear_young(struct mm_struct *mm,
                                  struct sgx_encl_page *page)
{
        unsigned long addr = page->desc & PAGE_MASK;
        struct sgx_encl *encl = page->encl;
        struct vm_area_struct *vma;
        int ret;

        ret = sgx_encl_find(mm, addr, &vma);
        if (ret)
                return 0;

        if (encl != vma->vm_private_data)
                return 0;

        ret = apply_to_page_range(vma->vm_mm, addr, PAGE_SIZE,
                                  sgx_encl_test_and_clear_young_cb, vma->vm_mm);
        if (ret < 0)
                return 0;

        return ret;
}

/**
 * sgx_alloc_va_page() - Allocate a Version Array (VA) page
 *
 * Allocate a free EPC page and convert it to a Version Array (VA) page.
 *
 * Return:
 *   a VA page,
 *   -errno otherwise
 */
struct sgx_epc_page *sgx_alloc_va_page(void)
{
        struct sgx_epc_page *epc_page;
        int ret;

        epc_page = sgx_alloc_epc_page(NULL, true);
        if (IS_ERR(epc_page))
                return ERR_CAST(epc_page);

        ret = __epa(sgx_get_epc_virt_addr(epc_page));
        if (ret) {
                WARN_ONCE(1, "EPA returned %d (0x%x)", ret, ret);
                sgx_encl_free_epc_page(epc_page);
                return ERR_PTR(-EFAULT);
        }

        return epc_page;
}

/**
 * sgx_alloc_va_slot - allocate a VA slot
 * @va_page:    a &struct sgx_va_page instance
 *
 * Allocates a slot from a &struct sgx_va_page instance.
 *
 * Return: offset of the slot inside the VA page
 */
unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page)
{
        int slot = find_first_zero_bit(va_page->slots, SGX_VA_SLOT_COUNT);

        if (slot < SGX_VA_SLOT_COUNT)
                set_bit(slot, va_page->slots);

        return slot << 3;
}

/**
 * sgx_free_va_slot - free a VA slot
 * @va_page:    a &struct sgx_va_page instance
 * @offset:     offset of the slot inside the VA page
 *
 * Frees a slot from a &struct sgx_va_page instance.
 */
void sgx_free_va_slot(struct sgx_va_page *va_page, unsigned int offset)
{
        clear_bit(offset >> 3, va_page->slots);
}

/**
 * sgx_va_page_full - is the VA page full?
 * @va_page:    a &struct sgx_va_page instance
 *
 * Return: true if all slots have been taken
 */
bool sgx_va_page_full(struct sgx_va_page *va_page)
{
        int slot = find_first_zero_bit(va_page->slots, SGX_VA_SLOT_COUNT);

        return slot == SGX_VA_SLOT_COUNT;
}

/**
 * sgx_encl_free_epc_page - free an EPC page assigned to an enclave
 * @page:       EPC page to be freed
 *
 * Free an EPC page assigned to an enclave. It does EREMOVE for the page, and
 * only upon success, it puts the page back to free page list.  Otherwise, it
 * gives a WARNING to indicate page is leaked.
 */
void sgx_encl_free_epc_page(struct sgx_epc_page *page)
{
        int ret;

        WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);

        ret = __eremove(sgx_get_epc_virt_addr(page));
        if (WARN_ONCE(ret, EREMOVE_ERROR_MESSAGE, ret, ret))
                return;

        sgx_free_epc_page(page);
}