[PATCH v4 2/2] efi: an sysfs interface for user to update efi firmware

["Kweh, Hock Leong" <hock.leong.kweh@intel.com>]

From: "Kweh, Hock Leong" <hock.leong.kweh@intel.com>

Introducing a kernel module to expose capsule loader interface
for user to upload capsule binaries. This module leverage the
request_firmware_direct_full_path() to obtain the binary at a
specific path input by user.

Example method to load the capsule binary:
echo -n "/path/to/capsule/binary" > /sys/devices/platform/efi_capsule_loader/capsule_loader

Cc: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@intel.com>
---
 drivers/firmware/efi/Kconfig              |   12 ++
 drivers/firmware/efi/Makefile             |    1 +
 drivers/firmware/efi/efi-capsule-loader.c |  169 +++++++++++++++++++++++++++++
 3 files changed, 182 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..3e84ec0 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -60,6 +60,18 @@ config EFI_RUNTIME_WRAPPERS
 config EFI_ARMSTUB
 	bool
 
+config EFI_CAPSULE_LOADER
+	tristate "EFI capsule loader"
+	depends on EFI
+	select FW_LOADER
+	help
+	  This option exposes a loader interface for user to load EFI
+	  capsule binary and update the EFI firmware through 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..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..84b979b
--- /dev/null
+++ b/drivers/firmware/efi/efi-capsule-loader.c
@@ -0,0 +1,169 @@
+/*
+ * 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/platform_device.h>
+#include <linux/highmem.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/efi.h>
+#include <linux/firmware.h>
+
+#define DEV_NAME "efi_capsule_loader"
+
+static DEFINE_MUTEX(capsule_loader_lock);
+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;
+
+	if (!count) {
+		pr_err("%s: Received zero binary size\n", __func__);
+		return -ENOENT;
+	}
+
+	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;
+	}
+	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;
+}
+
+static ssize_t capsule_loader_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	int ret = -EBUSY;
+	const struct firmware *fw;
+
+	pr_debug("%s: Received path = %s\n", __func__, buf);
+	if (mutex_trylock(&capsule_loader_lock)) {
+		ret = request_firmware_direct_full_path(&fw, buf,
+							&efi_capsule_pdev->dev);
+		if (ret) {
+			pr_err("%s: request_firmware_direct_full_path() %s\n",
+			       __func__,
+			       "failed");
+			mutex_unlock(&capsule_loader_lock);
+			return ret;
+		}
+
+		ret = efi_capsule_store(fw);
+		if (ret)
+			pr_err("%s: %s, return error code = %d\n",
+			       __func__,
+			       "Failed to store capsule binary",
+			       ret);
+		release_firmware(fw);
+		mutex_unlock(&capsule_loader_lock);
+	}
+
+	return ret ? ret : count;
+}
+static DEVICE_ATTR_WO(capsule_loader);
+
+static int __init efi_capsule_loader_init(void)
+{
+	int ret = 0;
+
+	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 pass in the full path of the
+	 * capsule binary
+	 */
+	ret = device_create_file(&efi_capsule_pdev->dev,
+				 &dev_attr_capsule_loader);
+	if (ret) {
+		pr_err("%s: device_create_file() failed\n", __func__);
+		platform_device_unregister(efi_capsule_pdev);
+	}
+
+	return ret;
+}
+module_init(efi_capsule_loader_init);
+
+/*
+ * To remove this kernel module, just perform:
+ * rmmod efi_capsule_loader.ko
+ */
+static void __exit efi_capsule_loader_exit(void)
+{
+	platform_device_unregister(efi_capsule_pdev);
+}
+module_exit(efi_capsule_loader_exit);
+
+MODULE_DESCRIPTION("EFI capsule firmware binary loader");
+MODULE_LICENSE("GPL v2");
-- 
1.7.9.5