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/efi.h>
16 #include <asm/io.h>
17
18 typedef struct {
19 u64 length;
20 u64 data;
21 } efi_capsule_block_desc_t;
22
23 static bool capsule_pending;
24 static bool stop_capsules;
25 static int efi_reset_type = -1;
26
27 /*
28 * capsule_mutex serialises access to both capsule_pending and
29 * efi_reset_type and stop_capsules.
30 */
31 static DEFINE_MUTEX(capsule_mutex);
32
33 /**
34 * efi_capsule_pending - has a capsule been passed to the firmware?
35 * @reset_type: store the type of EFI reset if capsule is pending
36 *
37 * To ensure that the registered capsule is processed correctly by the
38 * firmware we need to perform a specific type of reset. If a capsule is
39 * pending return the reset type in @reset_type.
40 *
41 * This function will race with callers of efi_capsule_update(), for
42 * example, calling this function while somebody else is in
43 * efi_capsule_update() but hasn't reached efi_capsue_update_locked()
44 * will miss the updates to capsule_pending and efi_reset_type after
45 * efi_capsule_update_locked() completes.
46 *
47 * A non-racy use is from platform reboot code because we use
48 * system_state to ensure no capsules can be sent to the firmware once
49 * we're at SYSTEM_RESTART. See efi_capsule_update_locked().
50 */
efi_capsule_pending(int * reset_type)51 bool efi_capsule_pending(int *reset_type)
52 {
53 if (!capsule_pending)
54 return false;
55
56 if (reset_type)
57 *reset_type = efi_reset_type;
58
59 return true;
60 }
61
62 /*
63 * Whitelist of EFI capsule flags that we support.
64 *
65 * We do not handle EFI_CAPSULE_INITIATE_RESET because that would
66 * require us to prepare the kernel for reboot. Refuse to load any
67 * capsules with that flag and any other flags that we do not know how
68 * to handle.
69 */
70 #define EFI_CAPSULE_SUPPORTED_FLAG_MASK \
71 (EFI_CAPSULE_PERSIST_ACROSS_RESET | EFI_CAPSULE_POPULATE_SYSTEM_TABLE)
72
73 /**
74 * efi_capsule_supported - does the firmware support the capsule?
75 * @guid: vendor guid of capsule
76 * @flags: capsule flags
77 * @size: size of capsule data
78 * @reset: the reset type required for this capsule
79 *
80 * Check whether a capsule with @flags is supported by the firmware
81 * and that @size doesn't exceed the maximum size for a capsule.
82 *
83 * No attempt is made to check @reset against the reset type required
84 * by any pending capsules because of the races involved.
85 */
efi_capsule_supported(efi_guid_t guid,u32 flags,size_t size,int * reset)86 int efi_capsule_supported(efi_guid_t guid, u32 flags, size_t size, int *reset)
87 {
88 efi_capsule_header_t capsule;
89 efi_capsule_header_t *cap_list[] = { &capsule };
90 efi_status_t status;
91 u64 max_size;
92
93 if (flags & ~EFI_CAPSULE_SUPPORTED_FLAG_MASK)
94 return -EINVAL;
95
96 capsule.headersize = capsule.imagesize = sizeof(capsule);
97 memcpy(&capsule.guid, &guid, sizeof(efi_guid_t));
98 capsule.flags = flags;
99
100 status = efi.query_capsule_caps(cap_list, 1, &max_size, reset);
101 if (status != EFI_SUCCESS)
102 return efi_status_to_err(status);
103
104 if (size > max_size)
105 return -ENOSPC;
106
107 return 0;
108 }
109 EXPORT_SYMBOL_GPL(efi_capsule_supported);
110
111 /*
112 * Every scatter gather list (block descriptor) page must end with a
113 * continuation pointer. The last continuation pointer of the last
114 * page must be zero to mark the end of the chain.
115 */
116 #define SGLIST_PER_PAGE ((PAGE_SIZE / sizeof(efi_capsule_block_desc_t)) - 1)
117
118 /*
119 * How many scatter gather list (block descriptor) pages do we need
120 * to map @count pages?
121 */
sg_pages_num(unsigned int count)122 static inline unsigned int sg_pages_num(unsigned int count)
123 {
124 return DIV_ROUND_UP(count, SGLIST_PER_PAGE);
125 }
126
127 /**
128 * efi_capsule_update_locked - pass a single capsule to the firmware
129 * @capsule: capsule to send to the firmware
130 * @sg_pages: array of scatter gather (block descriptor) pages
131 * @reset: the reset type required for @capsule
132 *
133 * Since this function must be called under capsule_mutex check
134 * whether efi_reset_type will conflict with @reset, and atomically
135 * set it and capsule_pending if a capsule was successfully sent to
136 * the firmware.
137 *
138 * We also check to see if the system is about to restart, and if so,
139 * abort. This avoids races between efi_capsule_update() and
140 * efi_capsule_pending().
141 */
142 static int
efi_capsule_update_locked(efi_capsule_header_t * capsule,struct page ** sg_pages,int reset)143 efi_capsule_update_locked(efi_capsule_header_t *capsule,
144 struct page **sg_pages, int reset)
145 {
146 efi_physical_addr_t sglist_phys;
147 efi_status_t status;
148
149 lockdep_assert_held(&capsule_mutex);
150
151 /*
152 * If someone has already registered a capsule that requires a
153 * different reset type, we're out of luck and must abort.
154 */
155 if (efi_reset_type >= 0 && efi_reset_type != reset) {
156 pr_err("Conflicting capsule reset type %d (%d).\n",
157 reset, efi_reset_type);
158 return -EINVAL;
159 }
160
161 /*
162 * If the system is getting ready to restart it may have
163 * called efi_capsule_pending() to make decisions (such as
164 * whether to force an EFI reboot), and we're racing against
165 * that call. Abort in that case.
166 */
167 if (unlikely(stop_capsules)) {
168 pr_warn("Capsule update raced with reboot, aborting.\n");
169 return -EINVAL;
170 }
171
172 sglist_phys = page_to_phys(sg_pages[0]);
173
174 status = efi.update_capsule(&capsule, 1, sglist_phys);
175 if (status == EFI_SUCCESS) {
176 capsule_pending = true;
177 efi_reset_type = reset;
178 }
179
180 return efi_status_to_err(status);
181 }
182
183 /**
184 * efi_capsule_update - send a capsule to the firmware
185 * @capsule: capsule to send to firmware
186 * @pages: an array of capsule data pages
187 *
188 * Build a scatter gather list with EFI capsule block descriptors to
189 * map the capsule described by @capsule with its data in @pages and
190 * send it to the firmware via the UpdateCapsule() runtime service.
191 *
192 * @capsule must be a virtual mapping of the complete capsule update in the
193 * kernel address space, as the capsule can be consumed immediately.
194 * A capsule_header_t that describes the entire contents of the capsule
195 * must be at the start of the first data page.
196 *
197 * Even though this function will validate that the firmware supports
198 * the capsule guid, users will likely want to check that
199 * efi_capsule_supported() returns true before calling this function
200 * because it makes it easier to print helpful error messages.
201 *
202 * If the capsule is successfully submitted to the firmware, any
203 * subsequent calls to efi_capsule_pending() will return true. @pages
204 * must not be released or modified if this function returns
205 * successfully.
206 *
207 * Callers must be prepared for this function to fail, which can
208 * happen if we raced with system reboot or if there is already a
209 * pending capsule that has a reset type that conflicts with the one
210 * required by @capsule. Do NOT use efi_capsule_pending() to detect
211 * this conflict since that would be racy. Instead, submit the capsule
212 * to efi_capsule_update() and check the return value.
213 *
214 * Return 0 on success, a converted EFI status code on failure.
215 */
efi_capsule_update(efi_capsule_header_t * capsule,phys_addr_t * pages)216 int efi_capsule_update(efi_capsule_header_t *capsule, phys_addr_t *pages)
217 {
218 u32 imagesize = capsule->imagesize;
219 efi_guid_t guid = capsule->guid;
220 unsigned int count, sg_count;
221 u32 flags = capsule->flags;
222 struct page **sg_pages;
223 int rv, reset_type;
224 int i, j;
225
226 rv = efi_capsule_supported(guid, flags, imagesize, &reset_type);
227 if (rv)
228 return rv;
229
230 count = DIV_ROUND_UP(imagesize, PAGE_SIZE);
231 sg_count = sg_pages_num(count);
232
233 sg_pages = kcalloc(sg_count, sizeof(*sg_pages), GFP_KERNEL);
234 if (!sg_pages)
235 return -ENOMEM;
236
237 for (i = 0; i < sg_count; i++) {
238 sg_pages[i] = alloc_page(GFP_KERNEL);
239 if (!sg_pages[i]) {
240 rv = -ENOMEM;
241 goto out;
242 }
243 }
244
245 for (i = 0; i < sg_count; i++) {
246 efi_capsule_block_desc_t *sglist;
247
248 sglist = kmap_atomic(sg_pages[i]);
249
250 for (j = 0; j < SGLIST_PER_PAGE && count > 0; j++) {
251 u64 sz = min_t(u64, imagesize,
252 PAGE_SIZE - (u64)*pages % PAGE_SIZE);
253
254 sglist[j].length = sz;
255 sglist[j].data = *pages++;
256
257 imagesize -= sz;
258 count--;
259 }
260
261 /* Continuation pointer */
262 sglist[j].length = 0;
263
264 if (i + 1 == sg_count)
265 sglist[j].data = 0;
266 else
267 sglist[j].data = page_to_phys(sg_pages[i + 1]);
268
269 #if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
270 /*
271 * At runtime, the firmware has no way to find out where the
272 * sglist elements are mapped, if they are mapped in the first
273 * place. Therefore, on architectures that can only perform
274 * cache maintenance by virtual address, the firmware is unable
275 * to perform this maintenance, and so it is up to the OS to do
276 * it instead.
277 */
278 efi_capsule_flush_cache_range(sglist, PAGE_SIZE);
279 #endif
280 kunmap_atomic(sglist);
281 }
282
283 mutex_lock(&capsule_mutex);
284 rv = efi_capsule_update_locked(capsule, sg_pages, reset_type);
285 mutex_unlock(&capsule_mutex);
286
287 out:
288 for (i = 0; rv && i < sg_count; i++) {
289 if (sg_pages[i])
290 __free_page(sg_pages[i]);
291 }
292
293 kfree(sg_pages);
294 return rv;
295 }
296 EXPORT_SYMBOL_GPL(efi_capsule_update);
297
capsule_reboot_notify(struct notifier_block * nb,unsigned long event,void * cmd)298 static int capsule_reboot_notify(struct notifier_block *nb, unsigned long event, void *cmd)
299 {
300 mutex_lock(&capsule_mutex);
301 stop_capsules = true;
302 mutex_unlock(&capsule_mutex);
303
304 return NOTIFY_DONE;
305 }
306
307 static struct notifier_block capsule_reboot_nb = {
308 .notifier_call = capsule_reboot_notify,
309 };
310
capsule_reboot_register(void)311 static int __init capsule_reboot_register(void)
312 {
313 return register_reboot_notifier(&capsule_reboot_nb);
314 }
315 core_initcall(capsule_reboot_register);
316