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Date: Sat, 3 Oct 2015 16:16:08 -0700
From: Andy Lutomirski <luto@...capital.net>
To: "Kweh, Hock Leong" <hock.leong.kweh@...el.com>
Cc: Matt Fleming <matt@...sole-pimps.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ong Boon Leong <boon.leong.ong@...el.com>,
LKML <linux-kernel@...r.kernel.org>,
"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
Sam Protsenko <semen.protsenko@...aro.org>,
Peter Jones <pjones@...hat.com>,
Roy Franz <roy.franz@...aro.org>,
Borislav Petkov <bp@...en8.de>,
James Bottomley <James.Bottomley@...senpartnership.com>,
Linux FS Devel <linux-fsdevel@...r.kernel.org>,
Fleming Matt <matt.fleming@...el.com>
Subject: Re: [PATCH v6 2/2] efi: a misc char interface for user to update efi firmware
On Thu, Oct 1, 2015 at 2:05 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 capsule loader interface
> (misc char device file note) for user to upload capsule binaries.
>
> Example method to load the capsule binary:
> cat firmware.bin > /dev/efi_capsule_loader
>
> Cc: Matt Fleming <matt.fleming@...el.com>
> Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@...el.com>
> ---
> drivers/firmware/efi/Kconfig | 10 ++
> drivers/firmware/efi/Makefile | 1 +
> drivers/firmware/efi/efi-capsule-loader.c | 246 +++++++++++++++++++++++++++++
> 3 files changed, 257 insertions(+)
> create mode 100644 drivers/firmware/efi/efi-capsule-loader.c
>
> diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
> index f712d47..0be8ee3 100644
> --- a/drivers/firmware/efi/Kconfig
> +++ b/drivers/firmware/efi/Kconfig
> @@ -60,6 +60,16 @@ config EFI_RUNTIME_WRAPPERS
> config EFI_ARMSTUB
> bool
>
> +config EFI_CAPSULE_LOADER
> + tristate "EFI capsule loader"
> + depends on EFI
> + help
> + This option exposes a loader interface "/dev/efi_capsule_loader" for
> + user to load EFI capsule binary and update the EFI firmware through
> + system reboot.
> +
> + If unsure, say N.
> +
> endmenu
>
> config UEFI_CPER
> diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
> index 698846e..5ab031a 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_LOADER) += efi-capsule-loader.o
> diff --git a/drivers/firmware/efi/efi-capsule-loader.c b/drivers/firmware/efi/efi-capsule-loader.c
> new file mode 100644
> index 0000000..571e0c8
> --- /dev/null
> +++ b/drivers/firmware/efi/efi-capsule-loader.c
> @@ -0,0 +1,246 @@
> +/*
> + * 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) KBUILD_MODNAME ": " 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 DEV_NAME "efi_capsule_loader"
> +
> +static struct capsule_info {
> + char header_obtained;
> + long index;
> + unsigned long count;
> + unsigned long total_size;
> + struct page **pages;
> + unsigned long page_count_remain;
> +} cap_info;
> +
Why is this static?
> +static DEFINE_MUTEX(capsule_loader_lock);
> +
> +/*
> + * This function will free the current & all previous allocated buffer pages.
> + * The input parameter is the allocated buffer page for current execution which
> + * has not yet assigned to pages array. The input param can be NULL if the
> + * current execution has not allocated any buffer page.
> + */
> +static void efi_free_all_buff_pages(struct page *kbuff_page)
> +{
> + if (!kbuff_page)
> + __free_page(kbuff_page);
> +
> + if (cap_info.index > 0)
> + while (cap_info.index > 0)
> + __free_page(cap_info.pages[--cap_info.index]);
> +
> + if (cap_info.header_obtained)
> + kfree(cap_info.pages);
> +
> + /* indicate to the next that error had occurred */
> + cap_info.index = -2;
This -2 to too magical.
> +}
> +
> +/*
> + * This function will store the capsule binary and pass it to
> + * efi_capsule_update() API in capsule.c.
> + *
> + * Expectation:
> + * - userspace tool should start at the beginning of capsule binary and pass
> + * data in sequential.
> + * - user should close and re-open this file note in order to upload more
> + * capsules.
> + * - any error occurred, user should close the file and restart the operation
> + * for the next try otherwise -EIO will be returned until the file is closed.
> + */
> +static ssize_t efi_capsule_write(struct file *file, const char __user *buff,
> + size_t count, loff_t *offp)
> +{
> + int ret = 0;
> + struct page *kbuff_page;
> + void *kbuff;
> + size_t write_byte;
> +
> + pr_debug("%s: Entering Write()\n", __func__);
Unnecessary.
> + if (count == 0)
> + return 0;
> +
> + /* return error while error had occurred or capsule uploading is done */
> + if (cap_info.index < 0)
> + return -EIO;
> +
> + /* only alloc a new page when the current page is full */
> + if (!cap_info.page_count_remain) {
> + kbuff_page = alloc_page(GFP_KERNEL);
> + if (!kbuff_page) {
> + pr_debug("%s: alloc_page() failed\n", __func__);
> + efi_free_all_buff_pages(NULL);
> + return -ENOMEM;
> + }
> + cap_info.page_count_remain = PAGE_SIZE;
> + } else {
> + kbuff_page = cap_info.pages[--cap_info.index];
> + }
> + kbuff = kmap(kbuff_page);
> + if (!kbuff) {
> + pr_debug("%s: kmap() failed\n", __func__);
> + efi_free_all_buff_pages(kbuff_page);
> + return -EFAULT;
> + }
> + kbuff += PAGE_SIZE - cap_info.page_count_remain;
> +
> + /* copy capsule binary data from user space to kernel space buffer */
> + write_byte = min_t(size_t, count, cap_info.page_count_remain);
> + if (copy_from_user(kbuff, buff, write_byte)) {
> + pr_debug("%s: copy_from_user() failed\n", __func__);
> + kunmap(kbuff_page);
> + efi_free_all_buff_pages(kbuff_page);
> + return -EFAULT;
> + }
> + cap_info.page_count_remain -= write_byte;
> +
> + /* setup capsule binary info structure */
> + if (cap_info.header_obtained == 0 && cap_info.index == 0) {
> + efi_capsule_header_t *cap_hdr = kbuff;
> + int reset_type;
> + size_t pages_needed = ALIGN(cap_hdr->imagesize, PAGE_SIZE) >>
> + PAGE_SHIFT;
> +
> + if (pages_needed == 0) {
> + pr_err("%s: pages count invalid\n", __func__);
> + kunmap(kbuff_page);
> + efi_free_all_buff_pages(kbuff_page);
> + return -EINVAL;
> + }
> +
> + /* check if the capsule binary supported */
> + ret = efi_capsule_supported(cap_hdr->guid, cap_hdr->flags,
> + cap_hdr->imagesize, &reset_type);
And what if cap_hdr isn't written yet?
> + if (ret) {
> + pr_err("%s: efi_capsule_supported() failed\n",
> + __func__);
> + kunmap(kbuff_page);
> + efi_free_all_buff_pages(kbuff_page);
> + return ret;
> + }
> +
> + cap_info.total_size = cap_hdr->imagesize;
> + cap_info.pages = kmalloc_array(pages_needed, sizeof(void *),
> + GFP_KERNEL);
> + if (!cap_info.pages) {
> + pr_debug("%s: kmalloc_array() failed\n", __func__);
> + kunmap(kbuff_page);
> + efi_free_all_buff_pages(kbuff_page);
> + return -ENOMEM;
> + }
> +
> + cap_info.header_obtained = 1;
I don't see how you know that the header is obtained.
> + }
> +
> + cap_info.pages[cap_info.index++] = kbuff_page;
Huh? You might now have allocated a whole page.
> + cap_info.count += write_byte;
> + kunmap(kbuff_page);
> +
> + /* submit the full binary to efi_capsule_update() API */
> + if (cap_info.count >= cap_info.total_size) {
> + void *cap_hdr_temp;
> +
> + cap_hdr_temp = kmap(cap_info.pages[0]);
> + if (!cap_hdr_temp) {
> + pr_debug("%s: kmap() failed\n", __func__);
> + efi_free_all_buff_pages(NULL);
> + 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__);
> + efi_free_all_buff_pages(NULL);
> + return ret;
> + }
> + /* indicate capsule binary uploading is done */
> + cap_info.index = -1;
Should count > cap_info.total_size be an error?
--Andy
> +static int efi_capsule_release(struct inode *inode, struct file *file)
> +{
> + int ret = 0;
> +
> + pr_debug("%s: Exit in Release()\n", __func__);
> + /* release uncompleted capsule upload */
> + if (cap_info.index > 0) {
> + pr_err("%s: capsule upload not complete\n", __func__);
> + efi_free_all_buff_pages(NULL);
> + ret = -ECANCELED;
> + }
> + mutex_unlock(&capsule_loader_lock);
Holding mutexes in userspace seems like an error. In fact, doesn't
lockdep warn when you do that?
--Andy
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