1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * EFI capsule support.
  4 *
  5 * Copyright 2013 Intel Corporation; author Matt Fleming
  6 */
  7
  8#define pr_fmt(fmt) "efi: " fmt
  9
 10#include <linux/slab.h>
 11#include <linux/mutex.h>
 12#include <linux/highmem.h>
 13#include <linux/efi.h>
 14#include <linux/vmalloc.h>
 15#include <asm/io.h>
 16
 17typedef struct {
 18	u64 length;
 19	u64 data;
 20} efi_capsule_block_desc_t;
 21
 22static bool capsule_pending;
 23static bool stop_capsules;
 24static int efi_reset_type = -1;
 25
 26/*
 27 * capsule_mutex serialises access to both capsule_pending and
 28 * efi_reset_type and stop_capsules.
 29 */
 30static DEFINE_MUTEX(capsule_mutex);
 31
 32/**
 33 * efi_capsule_pending - has a capsule been passed to the firmware?
 34 * @reset_type: store the type of EFI reset if capsule is pending
 35 *
 36 * To ensure that the registered capsule is processed correctly by the
 37 * firmware we need to perform a specific type of reset. If a capsule is
 38 * pending return the reset type in @reset_type.
 39 *
 40 * This function will race with callers of efi_capsule_update(), for
 41 * example, calling this function while somebody else is in
 42 * efi_capsule_update() but hasn't reached efi_capsue_update_locked()
 43 * will miss the updates to capsule_pending and efi_reset_type after
 44 * efi_capsule_update_locked() completes.
 45 *
 46 * A non-racy use is from platform reboot code because we use
 47 * system_state to ensure no capsules can be sent to the firmware once
 48 * we're at SYSTEM_RESTART. See efi_capsule_update_locked().
 49 */
 50bool efi_capsule_pending(int *reset_type)
 51{
 52	if (!capsule_pending)
 53		return false;
 54
 55	if (reset_type)
 56		*reset_type = efi_reset_type;
 57
 58	return true;
 59}
 60
 61/*
 62 * Whitelist of EFI capsule flags that we support.
 63 *
 64 * We do not handle EFI_CAPSULE_INITIATE_RESET because that would
 65 * require us to prepare the kernel for reboot. Refuse to load any
 66 * capsules with that flag and any other flags that we do not know how
 67 * to handle.
 68 */
 69#define EFI_CAPSULE_SUPPORTED_FLAG_MASK			\
 70	(EFI_CAPSULE_PERSIST_ACROSS_RESET | EFI_CAPSULE_POPULATE_SYSTEM_TABLE)
 71
 72/**
 73 * efi_capsule_supported - does the firmware support the capsule?
 74 * @guid: vendor guid of capsule
 75 * @flags: capsule flags
 76 * @size: size of capsule data
 77 * @reset: the reset type required for this capsule
 78 *
 79 * Check whether a capsule with @flags is supported by the firmware
 80 * and that @size doesn't exceed the maximum size for a capsule.
 81 *
 82 * No attempt is made to check @reset against the reset type required
 83 * by any pending capsules because of the races involved.
 84 */
 85int efi_capsule_supported(efi_guid_t guid, u32 flags, size_t size, int *reset)
 86{
 87	efi_capsule_header_t capsule;
 88	efi_capsule_header_t *cap_list[] = { &capsule };
 89	efi_status_t status;
 90	u64 max_size;
 91
 92	if (flags & ~EFI_CAPSULE_SUPPORTED_FLAG_MASK)
 93		return -EINVAL;
 94
 95	capsule.headersize = capsule.imagesize = sizeof(capsule);
 96	memcpy(&capsule.guid, &guid, sizeof(efi_guid_t));
 97	capsule.flags = flags;
 98
 99	status = efi.query_capsule_caps(cap_list, 1, &max_size, reset);
100	if (status != EFI_SUCCESS)
101		return efi_status_to_err(status);
102
103	if (size > max_size)
104		return -ENOSPC;
105
106	return 0;
107}
108EXPORT_SYMBOL_GPL(efi_capsule_supported);
109
110/*
111 * Every scatter gather list (block descriptor) page must end with a
112 * continuation pointer. The last continuation pointer of the last
113 * page must be zero to mark the end of the chain.
114 */
115#define SGLIST_PER_PAGE	((PAGE_SIZE / sizeof(efi_capsule_block_desc_t)) - 1)
116
117/*
118 * How many scatter gather list (block descriptor) pages do we need
119 * to map @count pages?
120 */
121static inline unsigned int sg_pages_num(unsigned int count)
122{
123	return DIV_ROUND_UP(count, SGLIST_PER_PAGE);
124}
125
126/**
127 * efi_capsule_update_locked - pass a single capsule to the firmware
128 * @capsule: capsule to send to the firmware
129 * @sg_pages: array of scatter gather (block descriptor) pages
130 * @reset: the reset type required for @capsule
131 *
132 * Since this function must be called under capsule_mutex check
133 * whether efi_reset_type will conflict with @reset, and atomically
134 * set it and capsule_pending if a capsule was successfully sent to
135 * the firmware.
136 *
137 * We also check to see if the system is about to restart, and if so,
138 * abort. This avoids races between efi_capsule_update() and
139 * efi_capsule_pending().
140 */
141static int
142efi_capsule_update_locked(efi_capsule_header_t *capsule,
143			  struct page **sg_pages, int reset)
144{
145	efi_physical_addr_t sglist_phys;
146	efi_status_t status;
147
148	lockdep_assert_held(&capsule_mutex);
149
150	/*
151	 * If someone has already registered a capsule that requires a
152	 * different reset type, we're out of luck and must abort.
153	 */
154	if (efi_reset_type >= 0 && efi_reset_type != reset) {
155		pr_err("Conflicting capsule reset type %d (%d).\n",
156		       reset, efi_reset_type);
157		return -EINVAL;
158	}
159
160	/*
161	 * If the system is getting ready to restart it may have
162	 * called efi_capsule_pending() to make decisions (such as
163	 * whether to force an EFI reboot), and we're racing against
164	 * that call. Abort in that case.
165	 */
166	if (unlikely(stop_capsules)) {
167		pr_warn("Capsule update raced with reboot, aborting.\n");
168		return -EINVAL;
169	}
170
171	sglist_phys = page_to_phys(sg_pages[0]);
172
173	status = efi.update_capsule(&capsule, 1, sglist_phys);
174	if (status == EFI_SUCCESS) {
175		capsule_pending = true;
176		efi_reset_type = reset;
177	}
178
179	return efi_status_to_err(status);
180}
181
182/**
183 * efi_capsule_update - send a capsule to the firmware
184 * @capsule: capsule to send to firmware
185 * @pages: an array of capsule data pages
186 *
187 * Build a scatter gather list with EFI capsule block descriptors to
188 * map the capsule described by @capsule with its data in @pages and
189 * send it to the firmware via the UpdateCapsule() runtime service.
190 *
191 * @capsule must be a virtual mapping of the complete capsule update in the
192 * kernel address space, as the capsule can be consumed immediately.
193 * A capsule_header_t that describes the entire contents of the capsule
194 * must be at the start of the first data page.
195 *
196 * Even though this function will validate that the firmware supports
197 * the capsule guid, users will likely want to check that
198 * efi_capsule_supported() returns true before calling this function
199 * because it makes it easier to print helpful error messages.
200 *
201 * If the capsule is successfully submitted to the firmware, any
202 * subsequent calls to efi_capsule_pending() will return true. @pages
203 * must not be released or modified if this function returns
204 * successfully.
205 *
206 * Callers must be prepared for this function to fail, which can
207 * happen if we raced with system reboot or if there is already a
208 * pending capsule that has a reset type that conflicts with the one
209 * required by @capsule. Do NOT use efi_capsule_pending() to detect
210 * this conflict since that would be racy. Instead, submit the capsule
211 * to efi_capsule_update() and check the return value.
212 *
213 * Return 0 on success, a converted EFI status code on failure.
214 */
215int efi_capsule_update(efi_capsule_header_t *capsule, phys_addr_t *pages)
216{
217	u32 imagesize = capsule->imagesize;
218	efi_guid_t guid = capsule->guid;
219	unsigned int count, sg_count;
220	u32 flags = capsule->flags;
221	struct page **sg_pages;
222	int rv, reset_type;
223	int i, j;
224
225	rv = efi_capsule_supported(guid, flags, imagesize, &reset_type);
226	if (rv)
227		return rv;
228
229	count = DIV_ROUND_UP(imagesize, PAGE_SIZE);
230	sg_count = sg_pages_num(count);
231
232	sg_pages = kcalloc(sg_count, sizeof(*sg_pages), GFP_KERNEL);
233	if (!sg_pages)
234		return -ENOMEM;
235
236	for (i = 0; i < sg_count; i++) {
237		sg_pages[i] = alloc_page(GFP_KERNEL);
238		if (!sg_pages[i]) {
239			rv = -ENOMEM;
240			goto out;
241		}
242	}
243
244	for (i = 0; i < sg_count; i++) {
245		efi_capsule_block_desc_t *sglist;
246
247		sglist = kmap(sg_pages[i]);
248
249		for (j = 0; j < SGLIST_PER_PAGE && count > 0; j++) {
250			u64 sz = min_t(u64, imagesize,
251				       PAGE_SIZE - (u64)*pages % PAGE_SIZE);
252
253			sglist[j].length = sz;
254			sglist[j].data = *pages++;
255
256			imagesize -= sz;
257			count--;
258		}
259
260		/* Continuation pointer */
261		sglist[j].length = 0;
262
263		if (i + 1 == sg_count)
264			sglist[j].data = 0;
265		else
266			sglist[j].data = page_to_phys(sg_pages[i + 1]);
267
268		kunmap(sg_pages[i]);
269	}
270
271	mutex_lock(&capsule_mutex);
272	rv = efi_capsule_update_locked(capsule, sg_pages, reset_type);
273	mutex_unlock(&capsule_mutex);
274
275out:
276	for (i = 0; rv && i < sg_count; i++) {
277		if (sg_pages[i])
278			__free_page(sg_pages[i]);
279	}
280
281	kfree(sg_pages);
282	return rv;
283}
284EXPORT_SYMBOL_GPL(efi_capsule_update);
285
286static int capsule_reboot_notify(struct notifier_block *nb, unsigned long event, void *cmd)
287{
288	mutex_lock(&capsule_mutex);
289	stop_capsules = true;
290	mutex_unlock(&capsule_mutex);
291
292	return NOTIFY_DONE;
293}
294
295static struct notifier_block capsule_reboot_nb = {
296	.notifier_call = capsule_reboot_notify,
297};
298
299static int __init capsule_reboot_register(void)
300{
301	return register_reboot_notifier(&capsule_reboot_nb);
302}
303core_initcall(capsule_reboot_register);