efi: Add 'capsule' update support

The EFI capsule mechanism allows data blobs to be passed to the EFI
firmware. A common use case is performing firmware updates. This patch
just introduces the main infrastructure for interacting with the
firmware, and a driver that allows users to upload capsules will come
in a later patch.

Once a capsule has been passed to the firmware, the next reboot must
be performed using the ResetSystem() EFI runtime service, which may
involve overriding the reboot type specified by reboot=. This ensures
the reset value returned by QueryCapsuleCapabilities() is used to
reset the system, which is required for the capsule to be processed.
efi_capsule_pending() is provided for this purpose.

At the moment we only allow a single capsule blob to be sent to the
firmware despite the fact that UpdateCapsule() takes a 'CapsuleCount'
parameter. This simplifies the API and shouldn't result in any
downside since it is still possible to send multiple capsules by
repeatedly calling UpdateCapsule().
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Cc: Kweh Hock Leong <hock.leong.kweh@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: joeyli <jlee@suse.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1461614832-17633-28-git-send-email-matt@codeblueprint.co.ukSigned-off-by: Ingo Molnar <mingo@kernel.org>

drivers/firmware/efi/Makefile

@@ -10,6 +10,7 @@
 KASAN_SANITIZE_runtime-wrappers.o	:= n
 
 obj-$(CONFIG_EFI)			+= efi.o vars.o reboot.o memattr.o
+obj-$(CONFIG_EFI)			+= capsule.o
 obj-$(CONFIG_EFI_VARS)			+= efivars.o
 obj-$(CONFIG_EFI_ESRT)			+= esrt.o
 obj-$(CONFIG_EFI_VARS_PSTORE)		+= efi-pstore.o

drivers/firmware/efi/capsule.c

+/*
+ * EFI capsule support.
+ *
+ * Copyright 2013 Intel Corporation; author Matt Fleming
+ *
+ * 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/slab.h>
+#include <linux/mutex.h>
+#include <linux/highmem.h>
+#include <linux/efi.h>
+#include <linux/vmalloc.h>
+#include <asm/io.h>
+
+typedef struct {
+	u64 length;
+	u64 data;
+} efi_capsule_block_desc_t;
+
+static bool capsule_pending;
+static int efi_reset_type = -1;
+
+/*
+ * capsule_mutex serialises access to both capsule_pending and
+ * efi_reset_type.
+ */
+static DEFINE_MUTEX(capsule_mutex);
+
+/**
+ * efi_capsule_pending - has a capsule been passed to the firmware?
+ * @reset_type: store the type of EFI reset if capsule is pending
+ *
+ * To ensure that the registered capsule is processed correctly by the
+ * firmware we need to perform a specific type of reset. If a capsule is
+ * pending return the reset type in @reset_type.
+ *
+ * This function will race with callers of efi_capsule_update(), for
+ * example, calling this function while somebody else is in
+ * efi_capsule_update() but hasn't reached efi_capsue_update_locked()
+ * will miss the updates to capsule_pending and efi_reset_type after
+ * efi_capsule_update_locked() completes.
+ *
+ * A non-racy use is from platform reboot code because we use
+ * system_state to ensure no capsules can be sent to the firmware once
+ * we're at SYSTEM_RESTART. See efi_capsule_update_locked().
+ */
+bool efi_capsule_pending(int *reset_type)
+{
+	bool rv = false;
+
+	mutex_lock(&capsule_mutex);
+	if (!capsule_pending)
+		goto out;
+
+	if (reset_type)
+		*reset_type = efi_reset_type;
+	rv = true;
+out:
+	mutex_unlock(&capsule_mutex);
+	return rv;
+}
+
+/*
+ * Whitelist of EFI capsule flags that we support.
+ *
+ * We do not handle EFI_CAPSULE_INITIATE_RESET because that would
+ * require us to prepare the kernel for reboot. Refuse to load any
+ * capsules with that flag and any other flags that we do not know how
+ * to handle.
+ */
+#define EFI_CAPSULE_SUPPORTED_FLAG_MASK			\
+	(EFI_CAPSULE_PERSIST_ACROSS_RESET | EFI_CAPSULE_POPULATE_SYSTEM_TABLE)
+
+/**
+ * efi_capsule_supported - does the firmware support the capsule?
+ * @guid: vendor guid of capsule
+ * @flags: capsule flags
+ * @size: size of capsule data
+ * @reset: the reset type required for this capsule
+ *
+ * Check whether a capsule with @flags is supported by the firmware
+ * and that @size doesn't exceed the maximum size for a capsule.
+ *
+ * No attempt is made to check @reset against the reset type required
+ * by any pending capsules because of the races involved.
+ */
+int efi_capsule_supported(efi_guid_t guid, u32 flags, size_t size, int *reset)
+{
+	efi_capsule_header_t *capsule;
+	efi_status_t status;
+	u64 max_size;
+	int rv = 0;
+
+	if (flags & ~EFI_CAPSULE_SUPPORTED_FLAG_MASK)
+		return -EINVAL;
+
+	capsule = kmalloc(sizeof(*capsule), GFP_KERNEL);
+	if (!capsule)
+		return -ENOMEM;
+
+	capsule->headersize = capsule->imagesize = sizeof(*capsule);
+	memcpy(&capsule->guid, &guid, sizeof(efi_guid_t));
+	capsule->flags = flags;
+
+	status = efi.query_capsule_caps(&capsule, 1, &max_size, reset);
+	if (status != EFI_SUCCESS) {
+		rv = efi_status_to_err(status);
+		goto out;
+	}
+
+	if (size > max_size)
+		rv = -ENOSPC;
+out:
+	kfree(capsule);
+	return rv;
+}
+EXPORT_SYMBOL_GPL(efi_capsule_supported);
+
+/*
+ * Every scatter gather list (block descriptor) page must end with a
+ * continuation pointer. The last continuation pointer of the last
+ * page must be zero to mark the end of the chain.
+ */
+#define SGLIST_PER_PAGE	((PAGE_SIZE / sizeof(efi_capsule_block_desc_t)) - 1)
+
+/*
+ * How many scatter gather list (block descriptor) pages do we need
+ * to map @count pages?
+ */
+static inline unsigned int sg_pages_num(unsigned int count)
+{
+	return DIV_ROUND_UP(count, SGLIST_PER_PAGE);
+}
+
+/**
+ * efi_capsule_update_locked - pass a single capsule to the firmware
+ * @capsule: capsule to send to the firmware
+ * @sg_pages: array of scatter gather (block descriptor) pages
+ * @reset: the reset type required for @capsule
+ *
+ * Since this function must be called under capsule_mutex check
+ * whether efi_reset_type will conflict with @reset, and atomically
+ * set it and capsule_pending if a capsule was successfully sent to
+ * the firmware.
+ *
+ * We also check to see if the system is about to restart, and if so,
+ * abort. This avoids races between efi_capsule_update() and
+ * efi_capsule_pending().
+ */
+static int
+efi_capsule_update_locked(efi_capsule_header_t *capsule,
+			  struct page **sg_pages, int reset)
+{
+	efi_physical_addr_t sglist_phys;
+	efi_status_t status;
+
+	lockdep_assert_held(&capsule_mutex);
+
+	/*
+	 * If someone has already registered a capsule that requires a
+	 * different reset type, we're out of luck and must abort.
+	 */
+	if (efi_reset_type >= 0 && efi_reset_type != reset) {
+		pr_err("Conflicting capsule reset type %d (%d).\n",
+		       reset, efi_reset_type);
+		return -EINVAL;
+	}
+
+	/*
+	 * If the system is getting ready to restart it may have
+	 * called efi_capsule_pending() to make decisions (such as
+	 * whether to force an EFI reboot), and we're racing against
+	 * that call. Abort in that case.
+	 */
+	if (unlikely(system_state == SYSTEM_RESTART)) {
+		pr_warn("Capsule update raced with reboot, aborting.\n");
+		return -EINVAL;
+	}
+
+	sglist_phys = page_to_phys(sg_pages[0]);
+
+	status = efi.update_capsule(&capsule, 1, sglist_phys);
+	if (status == EFI_SUCCESS) {
+		capsule_pending = true;
+		efi_reset_type = reset;
+	}
+
+	return efi_status_to_err(status);
+}
+
+/**
+ * efi_capsule_update - send a capsule to the firmware
+ * @capsule: capsule to send to firmware
+ * @pages: an array of capsule data pages
+ *
+ * Build a scatter gather list with EFI capsule block descriptors to
+ * map the capsule described by @capsule with its data in @pages and
+ * send it to the firmware via the UpdateCapsule() runtime service.
+ *
+ * @capsule must be a virtual mapping of the first page in @pages
+ * (@pages[0]) in the kernel address space. That is, a
+ * capsule_header_t that describes the entire contents of the capsule
+ * must be at the start of the first data page.
+ *
+ * Even though this function will validate that the firmware supports
+ * the capsule guid, users will likely want to check that
+ * efi_capsule_supported() returns true before calling this function
+ * because it makes it easier to print helpful error messages.
+ *
+ * If the capsule is successfully submitted to the firmware, any
+ * subsequent calls to efi_capsule_pending() will return true. @pages
+ * must not be released or modified if this function returns
+ * successfully.
+ *
+ * Callers must be prepared for this function to fail, which can
+ * happen if we raced with system reboot or if there is already a
+ * pending capsule that has a reset type that conflicts with the one
+ * required by @capsule. Do NOT use efi_capsule_pending() to detect
+ * this conflict since that would be racy. Instead, submit the capsule
+ * to efi_capsule_update() and check the return value.
+ *
+ * Return 0 on success, a converted EFI status code on failure.
+ */
+int efi_capsule_update(efi_capsule_header_t *capsule, struct page **pages)
+{
+	u32 imagesize = capsule->imagesize;
+	efi_guid_t guid = capsule->guid;
+	unsigned int count, sg_count;
+	u32 flags = capsule->flags;
+	struct page **sg_pages;
+	int rv, reset_type;
+	int i, j;
+
+	rv = efi_capsule_supported(guid, flags, imagesize, &reset_type);
+	if (rv)
+		return rv;
+
+	count = DIV_ROUND_UP(imagesize, PAGE_SIZE);
+	sg_count = sg_pages_num(count);
+
+	sg_pages = kzalloc(sg_count * sizeof(*sg_pages), GFP_KERNEL);
+	if (!sg_pages)
+		return -ENOMEM;
+
+	for (i = 0; i < sg_count; i++) {
+		sg_pages[i] = alloc_page(GFP_KERNEL);
+		if (!sg_pages[i]) {
+			rv = -ENOMEM;
+			goto out;
+		}
+	}
+
+	for (i = 0; i < sg_count; i++) {
+		efi_capsule_block_desc_t *sglist;
+
+		sglist = kmap(sg_pages[i]);
+		if (!sglist) {
+			rv = -ENOMEM;
+			goto out;
+		}
+
+		for (j = 0; j < SGLIST_PER_PAGE && count > 0; j++) {
+			u64 sz = min_t(u64, imagesize, PAGE_SIZE);
+
+			sglist[j].length = sz;
+			sglist[j].data = page_to_phys(*pages++);
+
+			imagesize -= sz;
+			count--;
+		}
+
+		/* Continuation pointer */
+		sglist[j].length = 0;
+
+		if (i + 1 == sg_count)
+			sglist[j].data = 0;
+		else
+			sglist[j].data = page_to_phys(sg_pages[i + 1]);
+
+		kunmap(sg_pages[i]);
+	}
+
+	mutex_lock(&capsule_mutex);
+	rv = efi_capsule_update_locked(capsule, sg_pages, reset_type);
+	mutex_unlock(&capsule_mutex);
+
+out:
+	for (i = 0; rv && i < sg_count; i++) {
+		if (sg_pages[i])
+			__free_page(sg_pages[i]);
+	}
+
+	kfree(sg_pages);
+	return rv;
+}
+EXPORT_SYMBOL_GPL(efi_capsule_update);

drivers/firmware/efi/reboot.c

@@ -9,7 +9,8 @@ int efi_reboot_quirk_mode = -1;
 
 void efi_reboot(enum reboot_mode reboot_mode, const char *__unused)
 {
-	int efi_mode;
+	const char *str[] = { "cold", "warm", "shutdown", "platform" };
+	int efi_mode, cap_reset_mode;
 
 	if (!efi_enabled(EFI_RUNTIME_SERVICES))
 		return;
@@ -30,6 +31,15 @@ void efi_reboot(enum reboot_mode reboot_mode, const char *__unused)
 	if (efi_reboot_quirk_mode != -1)
 		efi_mode = efi_reboot_quirk_mode;
 
+	if (efi_capsule_pending(&cap_reset_mode)) {
+		if (efi_mode != cap_reset_mode)
+			printk(KERN_CRIT "efi: %s reset requested but pending "
+			       "capsule update requires %s reset... Performing "
+			       "%s reset.\n", str[efi_mode], str[cap_reset_mode],
+			       str[cap_reset_mode]);
+		efi_mode = cap_reset_mode;
+	}
+
 	efi.reset_system(efi_mode, EFI_SUCCESS, 0, NULL);
 }
 

include/linux/efi.h

@@ -124,6 +124,13 @@ typedef struct {
 	u32 imagesize;
 } efi_capsule_header_t;
 
+/*
+ * EFI capsule flags
+ */
+#define EFI_CAPSULE_PERSIST_ACROSS_RESET	0x00010000
+#define EFI_CAPSULE_POPULATE_SYSTEM_TABLE	0x00020000
+#define EFI_CAPSULE_INITIATE_RESET		0x00040000
+
 /*
  * Allocation types for calls to boottime->allocate_pages.
  */
@@ -1370,6 +1377,13 @@ int efivars_sysfs_init(void);
 #define EFIVARS_DATA_SIZE_MAX 1024
 
 #endif /* CONFIG_EFI_VARS */
+extern bool efi_capsule_pending(int *reset_type);
+
+extern int efi_capsule_supported(efi_guid_t guid, u32 flags,
+				 size_t size, int *reset);
+
+extern int efi_capsule_update(efi_capsule_header_t *capsule,
+			      struct page **pages);
 
 #ifdef CONFIG_EFI_RUNTIME_MAP
 int efi_runtime_map_init(struct kobject *);