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Date: Thu, 26 Feb 2015 21:06:46 -0800
From: Roy Franz <roy.franz@...aro.org>
To: 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>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
LKML <linux-kernel@...r.kernel.org>,
"linux-efi@...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 Sun, Nov 2, 2014 at 7:07 PM, Kweh Hock Leong
<hock.leong.kweh@...el.com> 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.
>
> 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;
Hi Hock,
What does the decrement of i do here? I looked at
efi_capsule_update() and didn't see anything
that would account for this. It looks like in this failure case one
page won't get freed.
As an aside, when I was looking at efi_update_capsule, I see that Matt
is doing very similar operations
(array of struct page pointers), but does it like this (snipped from his patch):
+ struct page **block_pgs;
...
+ block_pgs = kzalloc(nr_block_pgs * sizeof(*block_pgs), GFP_KERNEL);
+ if (!block_pgs)
+ return -ENOMEM;
+
+ for (i = 0; i < nr_block_pgs; i++) {
+ block_pgs[i] = alloc_page(GFP_KERNEL);
+ if (!block_pgs[i])
+ goto fail;
+ }
and then can simply free the pages that are not NULL:
+fail:
+ for (i = 0; i < nr_block_pgs; i++) {
+ if (block_pgs[i])
+ __free_page(block_pgs[i]);
+ }
I think this way is preferable since it doesn't rely on 'i' being
unchanged at the end of the function. I also
think it would be nice if the capsule code stuck with one idiom for
dealing with arrays of page pointers.
Roy
> + 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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