efi: Add misc char driver interface to update EFI firmware

	  bootloader reads this reboot reason and takes particular

	  action according to its policy.

config EFI_CAPSULE_LOADER

	tristate "EFI capsule loader"

	depends on EFI

	help

	  This option exposes a loader interface "/dev/efi_capsule_loader" for

	  users to load EFI capsules. This driver requires working runtime

	  capsule support in the firmware, which many OEMs do not provide.

	  Most users should say N.

endmenu

config UEFI_CPER

arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o

obj-$(CONFIG_ARM)			+= $(arm-obj-y)

obj-$(CONFIG_ARM64)			+= $(arm-obj-y)

obj-$(CONFIG_EFI_CAPSULE_LOADER)	+= capsule-loader.o

/*

 * 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");