/*
 * EFI capsule loader driver.
 *
 * Copyright 2015 Intel Corporation
 *
 * This file is part of the Linux kernel, and is made available under
 * the terms of the GNU General Public License version 2.
 */

#define pr_fmt(fmt) "efi: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/efi.h>

#define NO_FURTHER_WRITE_ACTION -1

struct capsule_info {
        bool            header_obtained;
        int             reset_type;
        long            index;
        size_t          count;
        size_t          total_size;
        struct page     **pages;
        size_t          page_bytes_remain;
};

/**
 * efi_free_all_buff_pages - free all previous allocated buffer pages
 * @cap_info: pointer to current instance of capsule_info structure
 *
 *      In addition to freeing buffer pages, it flags NO_FURTHER_WRITE_ACTION
 *      to cease processing data in subsequent write(2) calls until close(2)
 *      is called.
 **/
static void efi_free_all_buff_pages(struct capsule_info *cap_info)
{
        while (cap_info->index > 0)
                __free_page(cap_info->pages[--cap_info->index]);

        cap_info->index = NO_FURTHER_WRITE_ACTION;
}

/**
 * efi_capsule_setup_info - obtain the efi capsule header in the binary and
 *                          setup capsule_info structure
 * @cap_info: pointer to current instance of capsule_info structure
 * @kbuff: a mapped first page buffer pointer
 * @hdr_bytes: the total received number of bytes for efi header
 **/
static ssize_t efi_capsule_setup_info(struct capsule_info *cap_info,
                                      void *kbuff, size_t hdr_bytes)
{
        efi_capsule_header_t *cap_hdr;
        size_t pages_needed;
        int ret;
        void *temp_page;

        /* Only process data block that is larger than efi header size */
        if (hdr_bytes < sizeof(efi_capsule_header_t))
                return 0;

        /* Reset back to the correct offset of header */
        cap_hdr = kbuff - cap_info->count;
        pages_needed = ALIGN(cap_hdr->imagesize, PAGE_SIZE) >> PAGE_SHIFT;

        if (pages_needed == 0) {
                pr_err("%s: pages count invalid\n", __func__);
                return -EINVAL;
        }

        /* Check if the capsule binary supported */
        ret = efi_capsule_supported(cap_hdr->guid, cap_hdr->flags,
                                    cap_hdr->imagesize,
                                    &cap_info->reset_type);
        if (ret) {
                pr_err("%s: efi_capsule_supported() failed\n",
                       __func__);
                return ret;
        }

        cap_info->total_size = cap_hdr->imagesize;
        temp_page = krealloc(cap_info->pages,
                             pages_needed * sizeof(void *),
                             GFP_KERNEL | __GFP_ZERO);
        if (!temp_page) {
                pr_debug("%s: krealloc() failed\n", __func__);
                return -ENOMEM;
        }

        cap_info->pages = temp_page;
        cap_info->header_obtained = true;

        return 0;
}

/**
 * efi_capsule_submit_update - invoke the efi_capsule_update API once binary
 *                             upload done
 * @cap_info: pointer to current instance of capsule_info structure
 **/
static ssize_t efi_capsule_submit_update(struct capsule_info *cap_info)
{
        int ret;
        void *cap_hdr_temp;

        cap_hdr_temp = kmap(cap_info->pages[0]);
        if (!cap_hdr_temp) {
                pr_debug("%s: kmap() failed\n", __func__);
                return -EFAULT;
        }

        ret = efi_capsule_update(cap_hdr_temp, cap_info->pages);
        kunmap(cap_info->pages[0]);
        if (ret) {
                pr_err("%s: efi_capsule_update() failed\n", __func__);
                return ret;
        }

        /* Indicate capsule binary uploading is done */
        cap_info->index = NO_FURTHER_WRITE_ACTION;
        pr_info("%s: Successfully upload capsule file with reboot type '%s'\n",
                __func__, !cap_info->reset_type ? "RESET_COLD" :
                cap_info->reset_type == 1 ? "RESET_WARM" :
                "RESET_SHUTDOWN");
        return 0;
}

/**
 * efi_capsule_write - store the capsule binary and pass it to
 *                     efi_capsule_update() API
 * @file: file pointer
 * @buff: buffer pointer
 * @count: number of bytes in @buff
 * @offp: not used
 *
 *      Expectation:
 *      - A user space tool should start at the beginning of capsule binary and
 *        pass data in sequentially.
 *      - Users should close and re-open this file note in order to upload more
 *        capsules.
 *      - After an error returned, user should close the file and restart the
 *        operation for the next try otherwise -EIO will be returned until the
 *        file is closed.
 *      - An EFI capsule header must be located at the beginning of capsule
 *        binary file and passed in as first block data of write operation.
 **/
static ssize_t efi_capsule_write(struct file *file, const char __user *buff,
                                 size_t count, loff_t *offp)
{
        int ret = 0;
        struct capsule_info *cap_info = file->private_data;
        struct page *page;
        void *kbuff = NULL;
        size_t write_byte;

        if (count == 0)
                return 0;

        /* Return error while NO_FURTHER_WRITE_ACTION is flagged */
        if (cap_info->index < 0)
                return -EIO;

        /* Only alloc a new page when previous page is full */
        if (!cap_info->page_bytes_remain) {
                page = alloc_page(GFP_KERNEL);
                if (!page) {
                        pr_debug("%s: alloc_page() failed\n", __func__);
                        ret = -ENOMEM;
                        goto failed;
                }

                cap_info->pages[cap_info->index++] = page;
                cap_info->page_bytes_remain = PAGE_SIZE;
        }

        page = cap_info->pages[cap_info->index - 1];

        kbuff = kmap(page);
        if (!kbuff) {
                pr_debug("%s: kmap() failed\n", __func__);
                ret = -EFAULT;
                goto failed;
        }
        kbuff += PAGE_SIZE - cap_info->page_bytes_remain;

        /* Copy capsule binary data from user space to kernel space buffer */
        write_byte = min_t(size_t, count, cap_info->page_bytes_remain);
        if (copy_from_user(kbuff, buff, write_byte)) {
                pr_debug("%s: copy_from_user() failed\n", __func__);
                ret = -EFAULT;
                goto fail_unmap;
        }
        cap_info->page_bytes_remain -= write_byte;

        /* Setup capsule binary info structure */
        if (!cap_info->header_obtained) {
                ret = efi_capsule_setup_info(cap_info, kbuff,
                                             cap_info->count + write_byte);
                if (ret)
                        goto fail_unmap;
        }

        cap_info->count += write_byte;
        kunmap(page);

        /* Submit the full binary to efi_capsule_update() API */
        if (cap_info->header_obtained &&
            cap_info->count >= cap_info->total_size) {
                if (cap_info->count > cap_info->total_size) {
                        pr_err("%s: upload size exceeded header defined size\n",
                               __func__);
                        ret = -EINVAL;
                        goto failed;
                }

                ret = efi_capsule_submit_update(cap_info);
                if (ret)
                        goto failed;
        }

        return write_byte;

fail_unmap:
        kunmap(page);
failed:
        efi_free_all_buff_pages(cap_info);
        return ret;
}

/**
 * efi_capsule_flush - called by file close or file flush
 * @file: file pointer
 * @id: not used
 *
 *      If a capsule is being partially uploaded then calling this function
 *      will be treated as upload termination and will free those completed
 *      buffer pages and -ECANCELED will be returned.
 **/
static int efi_capsule_flush(struct file *file, fl_owner_t id)
{
        int ret = 0;
        struct capsule_info *cap_info = file->private_data;

        if (cap_info->index > 0) {
                pr_err("%s: capsule upload not complete\n", __func__);
                efi_free_all_buff_pages(cap_info);
                ret = -ECANCELED;
        }

        return ret;
}

/**
 * efi_capsule_release - called by file close
 * @inode: not used
 * @file: file pointer
 *
 *      We will not free successfully submitted pages since efi update
 *      requires data to be maintained across system reboot.
 **/
static int efi_capsule_release(struct inode *inode, struct file *file)
{
        struct capsule_info *cap_info = file->private_data;

        kfree(cap_info->pages);
        kfree(file->private_data);
        file->private_data = NULL;
        return 0;
}

/**
 * efi_capsule_open - called by file open
 * @inode: not used
 * @file: file pointer
 *
 *      Will allocate each capsule_info memory for each file open call.
 *      This provided the capability to support multiple file open feature
 *      where user is not needed to wait for others to finish in order to
 *      upload their capsule binary.
 **/
static int efi_capsule_open(struct inode *inode, struct file *file)
{
        struct capsule_info *cap_info;

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

        cap_info->pages = kzalloc(sizeof(void *), GFP_KERNEL);
        if (!cap_info->pages) {
                kfree(cap_info);
                return -ENOMEM;
        }

        file->private_data = cap_info;

        return 0;
}

static const struct file_operations efi_capsule_fops = {
        .owner = THIS_MODULE,
        .open = efi_capsule_open,
        .write = efi_capsule_write,
        .flush = efi_capsule_flush,
        .release = efi_capsule_release,
        .llseek = no_llseek,
};

static struct miscdevice efi_capsule_misc = {
        .minor = MISC_DYNAMIC_MINOR,
        .name = "efi_capsule_loader",
        .fops = &efi_capsule_fops,
};

static int __init efi_capsule_loader_init(void)
{
        int ret;

        if (!efi_enabled(EFI_RUNTIME_SERVICES))
                return -ENODEV;

        ret = misc_register(&efi_capsule_misc);
        if (ret)
                pr_err("%s: Failed to register misc char file note\n",
                       __func__);

        return ret;
}
module_init(efi_capsule_loader_init);

static void __exit efi_capsule_loader_exit(void)
{
        misc_deregister(&efi_capsule_misc);
}
module_exit(efi_capsule_loader_exit);

MODULE_DESCRIPTION("EFI capsule firmware binary loader");
MODULE_LICENSE("GPL v2");