Date:	Mon, 3 Nov 2014 20:32:47 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Andy Lutomirski <luto@...capital.net>,
	Kweh Hock Leong <hock.leong.kweh@...el.com>
Cc:	Matt Fleming <matt.fleming@...el.com>,
	Ming Lei <ming.lei@...onical.com>,
	Sam Protsenko <semen.protsenko@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-efi@...r.kernel.org,
	Ong Boon Leong <boon.leong.ong@...el.com>
Subject: Re: [PATCH v2 3/3] efi: Capsule update with user helper interface

On Mon, Nov 03, 2014 at 11:07:10AM +0800, Kweh Hock Leong wrote:
> From: "Kweh, Hock Leong" <hock.leong.kweh@...el.com>
> 
> Introducing a kernel module to expose user helper interface for
> user to upload capsule binaries. This module leverage the
> request_firmware_nowait() to expose an interface to user.
> 
> Example steps to load the capsule binary:
> 1.) echo 1 > /sys/class/firmware/efi-capsule-file/loading
> 2.) cat capsule.bin > /sys/class/firmware/efi-capsule-file/data
> 3.) echo 0 > /sys/class/firmware/efi-capsule-file/loading
> 
> Whereas, this module does not allow the capsule binaries to be
> obtained from the request_firmware library search path. If any
> capsule binary loaded from firmware seach path, the module will
> stop functioning.
> 
> Besides the request_firmware user helper interface, this module
> also expose a 'capsule_loaded' file note for user to verify
> the number of successfully uploaded capsule binaries. This
> file note has the read only attribute.

Andy, here's the steps to load a capsule.  I don't have a problem with
this, it's userspace driven, no "autoloading" of files in /lib/, and
works with sysfs.

Have any objection to it, I don't.

Full patch left below...

> 
> Cc: Matt Fleming <matt.fleming@...el.com>
> Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@...el.com>
> ---
>  drivers/firmware/efi/Kconfig                   |   13 ++
>  drivers/firmware/efi/Makefile                  |    1 +
>  drivers/firmware/efi/efi-capsule-user-helper.c |  246 ++++++++++++++++++++++++
>  3 files changed, 260 insertions(+)
>  create mode 100644 drivers/firmware/efi/efi-capsule-user-helper.c
> 
> diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
> index f712d47..7dc814e 100644
> --- a/drivers/firmware/efi/Kconfig
> +++ b/drivers/firmware/efi/Kconfig
> @@ -60,6 +60,19 @@ config EFI_RUNTIME_WRAPPERS
>  config EFI_ARMSTUB
>  	bool
>  
> +config EFI_CAPSULE_USER_HELPER
> +	tristate "EFI capsule user mode helper"
> +	depends on EFI
> +	select FW_LOADER
> +	select FW_LOADER_USER_HELPER
> +	help
> +	  This option exposes the user mode helper interface for user to load
> +	  EFI capsule binary and update the EFI firmware after system reboot.
> +	  This feature does not support auto locating capsule binaries at the
> +	  firmware lib search path.
> +
> +	  If unsure, say N.
> +
>  endmenu
>  
>  config UEFI_CPER
> diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
> index 698846e..63f6910 100644
> --- a/drivers/firmware/efi/Makefile
> +++ b/drivers/firmware/efi/Makefile
> @@ -8,3 +8,4 @@ obj-$(CONFIG_UEFI_CPER)			+= cper.o
>  obj-$(CONFIG_EFI_RUNTIME_MAP)		+= runtime-map.o
>  obj-$(CONFIG_EFI_RUNTIME_WRAPPERS)	+= runtime-wrappers.o
>  obj-$(CONFIG_EFI_STUB)			+= libstub/
> +obj-$(CONFIG_EFI_CAPSULE_USER_HELPER)	+= efi-capsule-user-helper.o
> diff --git a/drivers/firmware/efi/efi-capsule-user-helper.c b/drivers/firmware/efi/efi-capsule-user-helper.c
> new file mode 100644
> index 0000000..84a1628
> --- /dev/null
> +++ b/drivers/firmware/efi/efi-capsule-user-helper.c
> @@ -0,0 +1,246 @@
> +/*
> + * EFI capsule user mode helper interface driver.
> + *
> + * Copyright 2014 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) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/delay.h>
> +#include <linux/highmem.h>
> +#include <linux/slab.h>
> +#include <linux/mutex.h>
> +#include <linux/reboot.h>
> +#include <linux/efi.h>
> +#include <linux/firmware.h>
> +
> +#define CAPSULE_NAME "efi-capsule-file"
> +#define DEV_NAME "efi_capsule_user_helper"
> +#define STRING_INTEGER_MAX_LENGTH 13
> +
> +static DEFINE_MUTEX(user_helper_lock);
> +static int capsule_count;
> +static int stop_request;
> +static struct platform_device *efi_capsule_pdev;
> +
> +/*
> + * This function will store the capsule binary and pass it to
> + * efi_capsule_update() API in capsule.c
> + */
> +static int efi_capsule_store(const struct firmware *fw)
> +{
> +	int i;
> +	int ret;
> +	int count = fw->size;
> +	int copy_size = (fw->size > PAGE_SIZE) ? PAGE_SIZE : fw->size;
> +	int pages_needed = ALIGN(fw->size, PAGE_SIZE) >> PAGE_SHIFT;
> +	struct page **pages;
> +	void *page_data;
> +	efi_capsule_header_t *capsule = NULL;
> +
> +	pages = kmalloc_array(pages_needed, sizeof(void *), GFP_KERNEL);
> +	if (!pages) {
> +		pr_err("%s: kmalloc_array() failed\n", __func__);
> +		return -ENOMEM;
> +	}
> +
> +	for (i = 0; i < pages_needed; i++) {
> +		pages[i] = alloc_page(GFP_KERNEL);
> +		if (!pages[i]) {
> +			pr_err("%s: alloc_page() failed\n", __func__);
> +			--i;
> +			ret = -ENOMEM;
> +			goto failed;
> +		}
> +	}
> +
> +	for (i = 0; i < pages_needed; i++) {
> +		page_data = kmap(pages[i]);
> +		memcpy(page_data, fw->data + (i * PAGE_SIZE), copy_size);
> +
> +		if (i == 0)
> +			capsule = (efi_capsule_header_t *)page_data;
> +		else
> +			kunmap(pages[i]);
> +
> +		count -= copy_size;
> +		if (count < PAGE_SIZE)
> +			copy_size = count;
> +	}
> +
> +	ret = efi_capsule_update(capsule, pages);
> +	if (ret) {
> +		pr_err("%s: efi_capsule_update() failed\n", __func__);
> +		--i;
> +		goto failed;
> +	}
> +	++capsule_count;
> +	kunmap(pages[0]);
> +
> +	/*
> +	 * we cannot free the pages here due to reboot need that data
> +	 * maintained.
> +	 */
> +	return 0;
> +
> +failed:
> +	while (i >= 0)
> +		__free_page(pages[i--]);
> +	kfree(pages);
> +	return ret;
> +}
> +
> +/*
> + * This callback function will be called by request_firmware_nowait() when
> + * user has loaded the capsule binary or aborted user helper interface
> + */
> +static void callbackfn_efi_capsule(const struct firmware *fw, void *context)
> +{
> +	int ret = 0;
> +
> +	if (fw) {
> +		/*
> +		 * Binary not getting from user helper interface, fw->pages
> +		 * is equal to NULL
> +		 */
> +		if (!fw->pages) {
> +			pr_err("%s: ERROR: Capsule binary '%s' at %s\n",
> +			       __func__, CAPSULE_NAME,
> +			       "firmware lib search path are not supported");
> +			pr_err("user helper interface disabled\n");
> +			stop_request = 1;
> +		} else {
> +			efi_capsule_store(fw);
> +		}
> +		release_firmware(fw);
> +	}
> +
> +	mutex_lock(&user_helper_lock);
> +	if (!stop_request) {
> +		ret = request_firmware_nowait(THIS_MODULE,
> +					      FW_ACTION_NOHOTPLUG,
> +					      CAPSULE_NAME,
> +					      &efi_capsule_pdev->dev,
> +					      GFP_KERNEL, NULL,
> +					      callbackfn_efi_capsule);
> +		if (ret) {
> +			pr_err("%s: request_firmware_nowait() failed\n",
> +			       __func__);
> +		}
> +	}
> +	mutex_unlock(&user_helper_lock);
> +}
> +
> +static ssize_t capsule_loaded_show(struct device *dev,
> +				   struct device_attribute *attr, char *buf)
> +{
> +	return snprintf(buf, STRING_INTEGER_MAX_LENGTH, "%d\n", capsule_count);
> +}
> +
> +static DEVICE_ATTR_RO(capsule_loaded);
> +
> +/* stop user helper interface for reboot or module unload */
> +static void capsule_stop_user_helper(void)
> +{
> +	mutex_lock(&user_helper_lock);
> +	stop_request = 1;
> +	mutex_unlock(&user_helper_lock);
> +	request_firmware_abort(CAPSULE_NAME);
> +}
> +
> +/* reboot notifier for avoid deadlock with usermode_lock */
> +static int capsule_shutdown_notify(struct notifier_block *nb,
> +				   unsigned long sys_state,
> +				   void *reboot_cmd)
> +{
> +	capsule_stop_user_helper();
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block capsule_shutdown_nb = {
> +	.notifier_call = capsule_shutdown_notify,
> +	/*
> +	 * In order to reboot properly, it is required to ensure the priority
> +	 * here is higher than firmware_class fw_shutdown_nb priority
> +	 */
> +	.priority = 1,
> +};
> +
> +/*
> + * Use request_firmware_nowait() exposing an user helper interface to obtain
> + * capsule binary from user space
> + */
> +static int __init efi_capsule_user_helper_init(void)
> +{
> +	int ret;
> +
> +	register_reboot_notifier(&capsule_shutdown_nb);
> +
> +	efi_capsule_pdev = platform_device_register_simple(DEV_NAME,
> +							   PLATFORM_DEVID_NONE,
> +							   NULL, 0);
> +	if (IS_ERR(efi_capsule_pdev)) {
> +		pr_err("%s: platform_device_register_simple() failed\n",
> +		       __func__);
> +		return PTR_ERR(efi_capsule_pdev);
> +	}
> +
> +	/*
> +	 * create this file node for user to check the number of binaries that
> +	 * are successfully loaded
> +	 */
> +	ret = device_create_file(&efi_capsule_pdev->dev,
> +				 &dev_attr_capsule_loaded);
> +	if (ret) {
> +		pr_err("%s: device_create_file() failed\n", __func__);
> +		return ret;
> +	}
> +
> +	ret = request_firmware_nowait(THIS_MODULE, FW_ACTION_NOHOTPLUG,
> +				      CAPSULE_NAME, &efi_capsule_pdev->dev,
> +				      GFP_KERNEL, NULL, callbackfn_efi_capsule);
> +	if (ret) {
> +		pr_err("%s: request_firmware_nowait() failed\n", __func__);
> +		goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	device_remove_file(&efi_capsule_pdev->dev, &dev_attr_capsule_loaded);
> +	unregister_reboot_notifier(&capsule_shutdown_nb);
> +	return ret;
> +}
> +module_init(efi_capsule_user_helper_init);
> +
> +/*
> + * rmmod app itself will stop you to remove the module if the user
> + * helper interface is still exposing. In order to remove this driver,
> + * you are require to do the command as below:
> + * rmmod -f efi_capsule_user_helper.ko
> + */
> +static void __exit efi_capsule_user_helper_exit(void)
> +{
> +	unregister_reboot_notifier(&capsule_shutdown_nb);
> +
> +	capsule_stop_user_helper();
> +	/*
> +	 * synchronization is needed to make sure request_firmware is fully
> +	 * aborted
> +	 */
> +	while (efi_capsule_pdev->dev.kobj.kref.refcount.counter > 3)
> +		msleep(20); /* avoid busy waiting for cooperative kernel */
> +
> +	device_remove_file(&efi_capsule_pdev->dev, &dev_attr_capsule_loaded);
> +	platform_device_unregister(efi_capsule_pdev);
> +}
> +module_exit(efi_capsule_user_helper_exit);
> +
> +MODULE_DESCRIPTION("EFI Capsule user helper binary load utility");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.7.9.5
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