// 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"

static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
                            struct sgx_backing *backing);

#define PCMDS_PER_PAGE (PAGE_SIZE / sizeof(struct sgx_pcmd))
/*
 * 32 PCMD entries share a PCMD page. PCMD_FIRST_MASK is used to
 * determine the page index associated with the first PCMD entry
 * within a PCMD page.
 */
#define PCMD_FIRST_MASK GENMASK(4, 0)

/**
 * reclaimer_writing_to_pcmd() - Query if any enclave page associated with
 *                               a PCMD page is in process of being reclaimed.
 * @encl:        Enclave to which PCMD page belongs
 * @start_addr:  Address of enclave page using first entry within the PCMD page
 *
 * When an enclave page is reclaimed some Paging Crypto MetaData (PCMD) is
 * stored. The PCMD data of a reclaimed enclave page contains enough
 * information for the processor to verify the page at the time
 * it is loaded back into the Enclave Page Cache (EPC).
 *
 * The backing storage to which enclave pages are reclaimed is laid out as
 * follows:
 * Encrypted enclave pages:SECS page:PCMD pages
 *
 * Each PCMD page contains the PCMD metadata of
 * PAGE_SIZE/sizeof(struct sgx_pcmd) enclave pages.
 *
 * A PCMD page can only be truncated if it is (a) empty, and (b) not in the
 * process of getting data (and thus soon being non-empty). (b) is tested with
 * a check if an enclave page sharing the PCMD page is in the process of being
 * reclaimed.
 *
 * The reclaimer sets the SGX_ENCL_PAGE_BEING_RECLAIMED flag when it
 * intends to reclaim that enclave page - it means that the PCMD page
 * associated with that enclave page is about to get some data and thus
 * even if the PCMD page is empty, it should not be truncated.
 *
 * Context: Enclave mutex (&sgx_encl->lock) must be held.
 * Return: 1 if the reclaimer is about to write to the PCMD page
 *         0 if the reclaimer has no intention to write to the PCMD page
 */
static int reclaimer_writing_to_pcmd(struct sgx_encl *encl,
                                     unsigned long start_addr)
{
        int reclaimed = 0;
        int i;

        /*
         * PCMD_FIRST_MASK is based on number of PCMD entries within
         * PCMD page being 32.
         */
        BUILD_BUG_ON(PCMDS_PER_PAGE != 32);

        for (i = 0; i < PCMDS_PER_PAGE; i++) {
                struct sgx_encl_page *entry;
                unsigned long addr;

                addr = start_addr + i * PAGE_SIZE;

                /*
                 * Stop when reaching the SECS page - it does not
                 * have a page_array entry and its reclaim is
                 * started and completed with enclave mutex held so
                 * it does not use the SGX_ENCL_PAGE_BEING_RECLAIMED
                 * flag.
                 */
                if (addr == encl->base + encl->size)
                        break;

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

                /*
                 * VA page slot ID uses same bit as the flag so it is important
                 * to ensure that the page is not already in backing store.
                 */
                if (entry->epc_page &&
                    (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)) {
                        reclaimed = 1;
                        break;
                }
        }

        return reclaimed;
}

/*
 * Calculate byte offset of a PCMD struct associated with an enclave page. PCMD's
 * follow right after the EPC data in the backing storage. In addition to the
 * visible enclave pages, there's one extra page slot for SECS, before PCMD
 * structs.
 */
static inline pgoff_t sgx_encl_get_backing_page_pcmd_offset(struct sgx_encl *encl,
                                                            unsigned long page_index)
{
        pgoff_t epc_end_off = encl->size + sizeof(struct sgx_secs);

        return epc_end_off + page_index * sizeof(struct sgx_pcmd);
}

/*
 * Free a page from the backing storage in the given page index.
 */
static inline void sgx_encl_truncate_backing_page(struct sgx_encl *encl, unsigned long page_index)
{
        struct inode *inode = file_inode(encl->backing);

        shmem_truncate_range(inode, PFN_PHYS(page_index), PFN_PHYS(page_index) + PAGE_SIZE - 1);
}

/*
 * 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;
        pgoff_t page_index, page_pcmd_off;
        unsigned long pcmd_first_page;
        struct sgx_pageinfo pginfo;
        struct sgx_backing b;
        bool pcmd_page_empty;
        u8 *pcmd_page;
        int ret;

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

        /*
         * Address of enclave page using the first entry within the PCMD page.
         */
        pcmd_first_page = PFN_PHYS(page_index & ~PCMD_FIRST_MASK) + encl->base;

        page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);

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

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

        memset(pcmd_page + b.pcmd_offset, 0, sizeof(struct sgx_pcmd));
        set_page_dirty(b.pcmd);

        /*
         * The area for the PCMD in the page was zeroed above.  Check if the
         * whole page is now empty meaning that all PCMD's have been zeroed:
         */
        pcmd_page_empty = !memchr_inv(pcmd_page, 0, PAGE_SIZE);

        kunmap_local(pcmd_page);
        kunmap_local((void *)(unsigned long)pginfo.contents);

        get_page(b.pcmd);
        sgx_encl_put_backing(&b);

        sgx_encl_truncate_backing_page(encl, page_index);

        if (pcmd_page_empty && !reclaimer_writing_to_pcmd(encl, pcmd_first_page)) {
                sgx_encl_truncate_backing_page(encl, PFN_DOWN(page_pcmd_off));
                pcmd_page = kmap_local_page(b.pcmd);
                if (memchr_inv(pcmd_page, 0, PAGE_SIZE))
                        pr_warn("PCMD page not empty after truncate.\n");
                kunmap_local(pcmd_page);
        }

        put_page(b.pcmd);

        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;
}

/*
 * Ensure the SECS page is not swapped out.  Must be called with encl->lock
 * to protect the enclave states including SECS and ensure the SECS page is
 * not swapped out again while being used.
 */
static struct sgx_epc_page *sgx_encl_load_secs(struct sgx_encl *encl)
{
        struct sgx_epc_page *epc_page = encl->secs.epc_page;

        if (!epc_page)
                epc_page = sgx_encl_eldu(&encl->secs, NULL);

        return epc_page;
}

static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl,
                                                  struct sgx_encl_page *entry)
{
        struct sgx_epc_page *epc_page;

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

                return entry;
        }

        epc_page = sgx_encl_load_secs(encl);
        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 struct sgx_encl_page *sgx_encl_load_page_in_vma(struct sgx_encl *encl,
                                                       unsigned long addr,
                                                       vm_flags_t vm_flags)
{
        unsigned long vm_prot_bits = vm_flags & VM_ACCESS_FLAGS;
        struct sgx_encl_page *entry;

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

        /*
         * Verify that the 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);

        return __sgx_encl_load_page(encl, entry);
}

struct sgx_encl_page *sgx_encl_load_page(struct sgx_encl *encl,
                                         unsigned long addr)
{
        struct sgx_encl_page *entry;

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

        return __sgx_encl_load_page(encl, entry);
}

/**
 * sgx_encl_eaug_page() - Dynamically add page to initialized enclave
 * @vma:        VMA obtained from fault info from where page is accessed
 * @encl:       enclave accessing the page
 * @addr:       address that triggered the page fault
 *
 * When an initialized enclave accesses a page with no backing EPC page
 * on a SGX2 system then the EPC can be added dynamically via the SGX2
 * ENCLS[EAUG] instruction.
 *
 * Returns: Appropriate vm_fault_t: VM_FAULT_NOPAGE when PTE was installed
 * successfully, VM_FAULT_SIGBUS or VM_FAULT_OOM as error otherwise.
 */
static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
                                     struct sgx_encl *encl, unsigned long addr)
{
        vm_fault_t vmret = VM_FAULT_SIGBUS;
        struct sgx_pageinfo pginfo = {0};
        struct sgx_encl_page *encl_page;
        struct sgx_epc_page *epc_page;
        struct sgx_va_page *va_page;
        unsigned long phys_addr;
        u64 secinfo_flags;
        int ret;

        if (!test_bit(SGX_ENCL_INITIALIZED, &encl->flags))
                return VM_FAULT_SIGBUS;

        /*
         * Ignore internal permission checking for dynamically added pages.
         * They matter only for data added during the pre-initialization
         * phase. The enclave decides the permissions by the means of
         * EACCEPT, EACCEPTCOPY and EMODPE.
         */
        secinfo_flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_X;
        encl_page = sgx_encl_page_alloc(encl, addr - encl->base, secinfo_flags);
        if (IS_ERR(encl_page))
                return VM_FAULT_OOM;

        mutex_lock(&encl->lock);

        epc_page = sgx_encl_load_secs(encl);
        if (IS_ERR(epc_page)) {
                if (PTR_ERR(epc_page) == -EBUSY)
                        vmret = VM_FAULT_NOPAGE;
                goto err_out_unlock;
        }

        epc_page = sgx_alloc_epc_page(encl_page, false);
        if (IS_ERR(epc_page)) {
                if (PTR_ERR(epc_page) == -EBUSY)
                        vmret =  VM_FAULT_NOPAGE;
                goto err_out_unlock;
        }

        va_page = sgx_encl_grow(encl, false);
        if (IS_ERR(va_page)) {
                if (PTR_ERR(va_page) == -EBUSY)
                        vmret = VM_FAULT_NOPAGE;
                goto err_out_epc;
        }

        if (va_page)
                list_add(&va_page->list, &encl->va_pages);

        ret = xa_insert(&encl->page_array, PFN_DOWN(encl_page->desc),
                        encl_page, GFP_KERNEL);
        /*
         * If ret == -EBUSY then page was created in another flow while
         * running without encl->lock
         */
        if (ret)
                goto err_out_shrink;

        pginfo.secs = (unsigned long)sgx_get_epc_virt_addr(encl->secs.epc_page);
        pginfo.addr = encl_page->desc & PAGE_MASK;
        pginfo.metadata = 0;

        ret = __eaug(&pginfo, sgx_get_epc_virt_addr(epc_page));
        if (ret)
                goto err_out;

        encl_page->encl = encl;
        encl_page->epc_page = epc_page;
        encl_page->type = SGX_PAGE_TYPE_REG;
        encl->secs_child_cnt++;

        sgx_mark_page_reclaimable(encl_page->epc_page);

        phys_addr = sgx_get_epc_phys_addr(epc_page);
        /*
         * Do not undo everything when creating PTE entry fails - next #PF
         * would find page ready for a PTE.
         */
        vmret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr));
        if (vmret != VM_FAULT_NOPAGE) {
                mutex_unlock(&encl->lock);
                return VM_FAULT_SIGBUS;
        }
        mutex_unlock(&encl->lock);
        return VM_FAULT_NOPAGE;

err_out:
        xa_erase(&encl->page_array, PFN_DOWN(encl_page->desc));

err_out_shrink:
        sgx_encl_shrink(encl, va_page);
err_out_epc:
        sgx_encl_free_epc_page(epc_page);
err_out_unlock:
        mutex_unlock(&encl->lock);
        kfree(encl_page);

        return vmret;
}

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;

        /*
         * The page_array keeps track of all enclave pages, whether they
         * are swapped out or not. If there is no entry for this page and
         * the system supports SGX2 then it is possible to dynamically add
         * a new enclave page. This is only possible for an initialized
         * enclave that will be checked for right away.
         */
        if (cpu_feature_enabled(X86_FEATURE_SGX2) &&
            (!xa_load(&encl->page_array, PFN_DOWN(addr))))
                return sgx_encl_eaug_page(vma, encl, addr);

        mutex_lock(&encl->lock);

        entry = sgx_encl_load_page_in_vma(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, vm_flags_t vm_flags)
{
        vm_flags_t vm_prot_bits = vm_flags & VM_ACCESS_FLAGS;
        struct sgx_encl_page *page;
        unsigned long count = 0;
        int ret = 0;

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

        /* Disallow mapping outside enclave's address range. */
        if (test_bit(SGX_ENCL_INITIALIZED, &encl->flags) &&
            (start < encl->base || end > encl->base + encl->size))
                return -EACCES;

        /*
         * 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,
                                                   vm_flags_t vm_flags)
{
        struct sgx_encl_page *entry;

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

                entry = sgx_encl_load_page_in_vma(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
 * @ref:        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);
        unsigned long max_page_index = PFN_DOWN(encl->base + encl->size - 1);
        struct sgx_va_page *va_page;
        struct sgx_encl_page *entry;
        unsigned long count = 0;

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

        xas_lock(&xas);
        xas_for_each(&xas, entry, max_page_index) {
                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);
                /*
                 * Invoke scheduler on every XA_CHECK_SCHED iteration
                 * to prevent soft lockups.
                 */
                if (!(++count % XA_CHECK_SCHED)) {
                        xas_pause(&xas);
                        xas_unlock(&xas);

                        cond_resched();

                        xas_lock(&xas);
                }
        }
        xas_unlock(&xas);

        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);
        sgx_dec_usage_count();
}

/*
 * '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;
        bool found = false;

        /*
         * 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);
                        found = true;
                        break;
                }
        }
        spin_unlock(&encl_mm->encl->mm_lock);

        if (found) {
                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_obj(*encl_mm);
        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_zap_enclave_ptes(). */
        smp_wmb();
        encl->mm_list_version++;
        spin_unlock(&encl->mm_lock);

        return 0;
}

/**
 * sgx_encl_cpumask() - Query which CPUs might be accessing the enclave
 * @encl: the enclave
 *
 * Some SGX functions require that no cached linear-to-physical address
 * mappings are present before they can succeed. For example, ENCLS[EWB]
 * copies a page from the enclave page cache to regular main memory but
 * it fails if it cannot ensure that there are no cached
 * linear-to-physical address mappings referring to the page.
 *
 * SGX hardware flushes all cached linear-to-physical mappings on a CPU
 * when an enclave is exited via ENCLU[EEXIT] or an Asynchronous Enclave
 * Exit (AEX). Exiting an enclave will thus ensure cached linear-to-physical
 * address mappings are cleared but coordination with the tracking done within
 * the SGX hardware is needed to support the SGX functions that depend on this
 * cache clearing.
 *
 * When the ENCLS[ETRACK] function is issued on an enclave the hardware
 * tracks threads operating inside the enclave at that time. The SGX
 * hardware tracking require that all the identified threads must have
 * exited the enclave in order to flush the mappings before a function such
 * as ENCLS[EWB] will be permitted
 *
 * The following flow is used to support SGX functions that require that
 * no cached linear-to-physical address mappings are present:
 * 1) Execute ENCLS[ETRACK] to initiate hardware tracking.
 * 2) Use this function (sgx_encl_cpumask()) to query which CPUs might be
 *    accessing the enclave.
 * 3) Send IPI to identified CPUs, kicking them out of the enclave and
 *    thus flushing all locally cached linear-to-physical address mappings.
 * 4) Execute SGX function.
 *
 * Context: It is required to call this function after ENCLS[ETRACK].
 *          This will ensure that if any new mm appears (racing with
 *          sgx_encl_mm_add()) then the new mm will enter into the
 *          enclave with fresh linear-to-physical address mappings.
 *
 *          It is required that all IPIs are completed before a new
 *          ENCLS[ETRACK] is issued so be sure to protect steps 1 to 3
 *          of the above flow with the enclave's mutex.
 *
 * Return: cpumask of CPUs that might be accessing @encl
 */
const cpumask_t *sgx_encl_cpumask(struct sgx_encl *encl)
{
        cpumask_t *cpumask = &encl->cpumask;
        struct sgx_encl_mm *encl_mm;
        int idx;

        cpumask_clear(cpumask);

        idx = srcu_read_lock(&encl->srcu);

        list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) {
                if (!mmget_not_zero(encl_mm->mm))
                        continue;

                cpumask_or(cpumask, cpumask, mm_cpumask(encl_mm->mm));

                mmput_async(encl_mm->mm);
        }

        srcu_read_unlock(&encl->srcu, idx);

        return cpumask;
}

static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl,
                                              pgoff_t index)
{
        struct address_space *mapping = encl->backing->f_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.
 */
static int __sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
                         struct sgx_backing *backing)
{
        pgoff_t page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);
        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, PFN_DOWN(page_pcmd_off));
        if (IS_ERR(pcmd)) {
                put_page(contents);
                return PTR_ERR(pcmd);
        }

        backing->contents = contents;
        backing->pcmd = pcmd;
        backing->pcmd_offset = page_pcmd_off & (PAGE_SIZE - 1);

        return 0;
}

/*
 * When called from ksgxd, returns the mem_cgroup of a struct mm stored
 * in the enclave's mm_list. When not called from ksgxd, just returns
 * the mem_cgroup of the current task.
 */
static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
{
        struct mem_cgroup *memcg = NULL;
        struct sgx_encl_mm *encl_mm;
        int idx;

        /*
         * If called from normal task context, return the mem_cgroup
         * of the current task's mm. The remainder of the handling is for
         * ksgxd.
         */
        if (!current_is_ksgxd())
                return get_mem_cgroup_from_mm(current->mm);

        /*
         * Search the enclave's mm_list to find an mm associated with
         * this enclave to charge the allocation to.
         */
        idx = srcu_read_lock(&encl->srcu);

        list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) {
                if (!mmget_not_zero(encl_mm->mm))
                        continue;

                memcg = get_mem_cgroup_from_mm(encl_mm->mm);

                mmput_async(encl_mm->mm);

                break;
        }

        srcu_read_unlock(&encl->srcu, idx);

        /*
         * In the rare case that there isn't an mm associated with
         * the enclave, set memcg to the current active mem_cgroup.
         * This will be the root mem_cgroup if there is no active
         * mem_cgroup.
         */
        if (!memcg)
                return get_mem_cgroup_from_mm(NULL);

        return memcg;
}

/**
 * sgx_encl_alloc_backing() - create a new backing storage page
 * @encl:       an enclave pointer
 * @page_index: enclave page index
 * @backing:    data for accessing backing storage for the page
 *
 * When called from ksgxd, sets the active memcg from one of the
 * mms in the enclave's mm_list prior to any backing page allocation,
 * in order to ensure that shmem page allocations are charged to the
 * enclave.  Create a backing page for loading data back into an EPC page with
 * ELDU.  This function takes a reference on a new backing page which
 * must be dropped with a corresponding call to sgx_encl_put_backing().
 *
 * Return:
 *   0 on success,
 *   -errno otherwise.
 */
int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index,
                           struct sgx_backing *backing)
{
        struct mem_cgroup *encl_memcg = sgx_encl_get_mem_cgroup(encl);
        struct mem_cgroup *memcg = set_active_memcg(encl_memcg);
        int ret;

        ret = __sgx_encl_get_backing(encl, page_index, backing);

        set_active_memcg(memcg);
        mem_cgroup_put(encl_memcg);

        return ret;
}

/**
 * sgx_encl_lookup_backing() - retrieve an existing backing storage page
 * @encl:       an enclave pointer
 * @page_index: enclave page index
 * @backing:    data for accessing backing storage for the page
 *
 * Retrieve a backing page for loading data back into an EPC page with ELDU.
 * It is the caller's responsibility to ensure that it is appropriate to use
 * sgx_encl_lookup_backing() rather than sgx_encl_alloc_backing(). If lookup is
 * not used correctly, this will cause an allocation which is not accounted for.
 * This function takes a reference on an existing backing page which must be
 * dropped with a corresponding call to sgx_encl_put_backing().
 *
 * Return:
 *   0 on success,
 *   -errno otherwise.
 */
static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
                           struct sgx_backing *backing)
{
        return __sgx_encl_get_backing(encl, page_index, backing);
}

/**
 * sgx_encl_put_backing() - Unpin the backing storage
 * @backing:    data for accessing backing storage for the page
 */
void sgx_encl_put_backing(struct sgx_backing *backing)
{
        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;
}

struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
                                          unsigned long offset,
                                          u64 secinfo_flags)
{
        struct sgx_encl_page *encl_page;
        unsigned long prot;

        encl_page = kzalloc_obj(*encl_page);
        if (!encl_page)
                return ERR_PTR(-ENOMEM);

        encl_page->desc = encl->base + offset;
        encl_page->encl = encl;

        prot = _calc_vm_trans(secinfo_flags, SGX_SECINFO_R, PROT_READ)  |
               _calc_vm_trans(secinfo_flags, SGX_SECINFO_W, PROT_WRITE) |
               _calc_vm_trans(secinfo_flags, SGX_SECINFO_X, PROT_EXEC);

        /*
         * TCS pages must always RW set for CPU access while the SECINFO
         * permissions are *always* zero - the CPU ignores the user provided
         * values and silently overwrites them with zero permissions.
         */
        if ((secinfo_flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
                prot |= PROT_READ | PROT_WRITE;

        /* Calculate maximum of the VM flags for the page. */
        encl_page->vm_max_prot_bits = calc_vm_prot_bits(prot, 0);

        return encl_page;
}

/**
 * sgx_zap_enclave_ptes() - remove PTEs mapping the address from enclave
 * @encl: the enclave
 * @addr: page aligned pointer to single page for which PTEs will be removed
 *
 * Multiple VMAs may have an enclave page mapped. Remove the PTE mapping
 * @addr from each VMA. Ensure that page fault handler is ready to handle
 * new mappings of @addr before calling this function.
 */
void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr)
{
        unsigned long mm_list_version;
        struct sgx_encl_mm *encl_mm;
        struct vm_area_struct *vma;
        int idx, ret;

        do {
                mm_list_version = encl->mm_list_version;

                /* Pairs with smp_wmb() in sgx_encl_mm_add(). */
                smp_rmb();

                idx = srcu_read_lock(&encl->srcu);

                list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) {
                        if (!mmget_not_zero(encl_mm->mm))
                                continue;

                        mmap_read_lock(encl_mm->mm);

                        ret = sgx_encl_find(encl_mm->mm, addr, &vma);
                        if (!ret && encl == vma->vm_private_data)
                                zap_vma_ptes(vma, addr, PAGE_SIZE);

                        mmap_read_unlock(encl_mm->mm);

                        mmput_async(encl_mm->mm);
                }

                srcu_read_unlock(&encl->srcu, idx);
        } while (unlikely(encl->mm_list_version != mm_list_version));
}

/**
 * sgx_alloc_va_page() - Allocate a Version Array (VA) page
 * @reclaim: Reclaim EPC pages directly if none available. Enclave
 *           mutex should not be held if this is set.
 *
 * 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(bool reclaim)
{
        struct sgx_epc_page *epc_page;
        int ret;

        epc_page = sgx_alloc_epc_page(NULL, reclaim);
        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);
}