1/*
2 * runtime-wrappers.c - Runtime Services function call wrappers
3 *
4 * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
5 *
6 * Split off from arch/x86/platform/efi/efi.c
7 *
8 * Copyright (C) 1999 VA Linux Systems
9 * Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
10 * Copyright (C) 1999-2002 Hewlett-Packard Co.
11 * Copyright (C) 2005-2008 Intel Co.
12 * Copyright (C) 2013 SuSE Labs
13 *
14 * This file is released under the GPLv2.
15 */
16
17#include <linux/bug.h>
18#include <linux/efi.h>
19#include <linux/mutex.h>
20#include <linux/spinlock.h>
21#include <asm/efi.h>
22
23/*
24 * According to section 7.1 of the UEFI spec, Runtime Services are not fully
25 * reentrant, and there are particular combinations of calls that need to be
26 * serialized. (source: UEFI Specification v2.4A)
27 *
28 * Table 31. Rules for Reentry Into Runtime Services
29 * +------------------------------------+-------------------------------+
30 * | If previous call is busy in	| Forbidden to call		|
31 * +------------------------------------+-------------------------------+
32 * | Any				| SetVirtualAddressMap()	|
33 * +------------------------------------+-------------------------------+
34 * | ConvertPointer()			| ConvertPointer()		|
35 * +------------------------------------+-------------------------------+
36 * | SetVariable()			| ResetSystem()			|
37 * | UpdateCapsule()			|				|
38 * | SetTime()				|				|
39 * | SetWakeupTime()			|				|
40 * | GetNextHighMonotonicCount()	|				|
41 * +------------------------------------+-------------------------------+
42 * | GetVariable()			| GetVariable()			|
43 * | GetNextVariableName()		| GetNextVariableName()		|
44 * | SetVariable()			| SetVariable()			|
45 * | QueryVariableInfo()		| QueryVariableInfo()		|
46 * | UpdateCapsule()			| UpdateCapsule()		|
47 * | QueryCapsuleCapabilities()		| QueryCapsuleCapabilities()	|
48 * | GetNextHighMonotonicCount()	| GetNextHighMonotonicCount()	|
49 * +------------------------------------+-------------------------------+
50 * | GetTime()				| GetTime()			|
51 * | SetTime()				| SetTime()			|
52 * | GetWakeupTime()			| GetWakeupTime()		|
53 * | SetWakeupTime()			| SetWakeupTime()		|
54 * +------------------------------------+-------------------------------+
55 *
56 * Due to the fact that the EFI pstore may write to the variable store in
57 * interrupt context, we need to use a spinlock for at least the groups that
58 * contain SetVariable() and QueryVariableInfo(). That leaves little else, as
59 * none of the remaining functions are actually ever called at runtime.
60 * So let's just use a single spinlock to serialize all Runtime Services calls.
61 */
62static DEFINE_SPINLOCK(efi_runtime_lock);
63
64/*
65 * Some runtime services calls can be reentrant under NMI, even if the table
66 * above says they are not. (source: UEFI Specification v2.4A)
67 *
68 * Table 32. Functions that may be called after Machine Check, INIT and NMI
69 * +----------------------------+------------------------------------------+
70 * | Function			| Called after Machine Check, INIT and NMI |
71 * +----------------------------+------------------------------------------+
72 * | GetTime()			| Yes, even if previously busy.		   |
73 * | GetVariable()		| Yes, even if previously busy		   |
74 * | GetNextVariableName()	| Yes, even if previously busy		   |
75 * | QueryVariableInfo()	| Yes, even if previously busy		   |
76 * | SetVariable()		| Yes, even if previously busy		   |
77 * | UpdateCapsule()		| Yes, even if previously busy		   |
78 * | QueryCapsuleCapabilities()	| Yes, even if previously busy		   |
79 * | ResetSystem()		| Yes, even if previously busy		   |
80 * +----------------------------+------------------------------------------+
81 *
82 * In order to prevent deadlocks under NMI, the wrappers for these functions
83 * may only grab the efi_runtime_lock or rtc_lock spinlocks if !efi_in_nmi().
84 * However, not all of the services listed are reachable through NMI code paths,
85 * so the the special handling as suggested by the UEFI spec is only implemented
86 * for QueryVariableInfo() and SetVariable(), as these can be reached in NMI
87 * context through efi_pstore_write().
88 */
89
90/*
91 * As per commit ef68c8f87ed1 ("x86: Serialize EFI time accesses on rtc_lock"),
92 * the EFI specification requires that callers of the time related runtime
93 * functions serialize with other CMOS accesses in the kernel, as the EFI time
94 * functions may choose to also use the legacy CMOS RTC.
95 */
96__weak DEFINE_SPINLOCK(rtc_lock);
97
98static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
99{
100	unsigned long flags;
101	efi_status_t status;
102
103	spin_lock_irqsave(&rtc_lock, flags);
104	spin_lock(&efi_runtime_lock);
105	status = efi_call_virt(get_time, tm, tc);
106	spin_unlock(&efi_runtime_lock);
107	spin_unlock_irqrestore(&rtc_lock, flags);
108	return status;
109}
110
111static efi_status_t virt_efi_set_time(efi_time_t *tm)
112{
113	unsigned long flags;
114	efi_status_t status;
115
116	spin_lock_irqsave(&rtc_lock, flags);
117	spin_lock(&efi_runtime_lock);
118	status = efi_call_virt(set_time, tm);
119	spin_unlock(&efi_runtime_lock);
120	spin_unlock_irqrestore(&rtc_lock, flags);
121	return status;
122}
123
124static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
125					     efi_bool_t *pending,
126					     efi_time_t *tm)
127{
128	unsigned long flags;
129	efi_status_t status;
130
131	spin_lock_irqsave(&rtc_lock, flags);
132	spin_lock(&efi_runtime_lock);
133	status = efi_call_virt(get_wakeup_time, enabled, pending, tm);
134	spin_unlock(&efi_runtime_lock);
135	spin_unlock_irqrestore(&rtc_lock, flags);
136	return status;
137}
138
139static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
140{
141	unsigned long flags;
142	efi_status_t status;
143
144	spin_lock_irqsave(&rtc_lock, flags);
145	spin_lock(&efi_runtime_lock);
146	status = efi_call_virt(set_wakeup_time, enabled, tm);
147	spin_unlock(&efi_runtime_lock);
148	spin_unlock_irqrestore(&rtc_lock, flags);
149	return status;
150}
151
152static efi_status_t virt_efi_get_variable(efi_char16_t *name,
153					  efi_guid_t *vendor,
154					  u32 *attr,
155					  unsigned long *data_size,
156					  void *data)
157{
158	unsigned long flags;
159	efi_status_t status;
160
161	spin_lock_irqsave(&efi_runtime_lock, flags);
162	status = efi_call_virt(get_variable, name, vendor, attr, data_size,
163			       data);
164	spin_unlock_irqrestore(&efi_runtime_lock, flags);
165	return status;
166}
167
168static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
169					       efi_char16_t *name,
170					       efi_guid_t *vendor)
171{
172	unsigned long flags;
173	efi_status_t status;
174
175	spin_lock_irqsave(&efi_runtime_lock, flags);
176	status = efi_call_virt(get_next_variable, name_size, name, vendor);
177	spin_unlock_irqrestore(&efi_runtime_lock, flags);
178	return status;
179}
180
181static efi_status_t virt_efi_set_variable(efi_char16_t *name,
182					  efi_guid_t *vendor,
183					  u32 attr,
184					  unsigned long data_size,
185					  void *data)
186{
187	unsigned long flags;
188	efi_status_t status;
189
190	spin_lock_irqsave(&efi_runtime_lock, flags);
191	status = efi_call_virt(set_variable, name, vendor, attr, data_size,
192			       data);
193	spin_unlock_irqrestore(&efi_runtime_lock, flags);
194	return status;
195}
196
197static efi_status_t
198virt_efi_set_variable_nonblocking(efi_char16_t *name, efi_guid_t *vendor,
199				  u32 attr, unsigned long data_size,
200				  void *data)
201{
202	unsigned long flags;
203	efi_status_t status;
204
205	if (!spin_trylock_irqsave(&efi_runtime_lock, flags))
206		return EFI_NOT_READY;
207
208	status = efi_call_virt(set_variable, name, vendor, attr, data_size,
209			       data);
210	spin_unlock_irqrestore(&efi_runtime_lock, flags);
211	return status;
212}
213
214
215static efi_status_t virt_efi_query_variable_info(u32 attr,
216						 u64 *storage_space,
217						 u64 *remaining_space,
218						 u64 *max_variable_size)
219{
220	unsigned long flags;
221	efi_status_t status;
222
223	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
224		return EFI_UNSUPPORTED;
225
226	spin_lock_irqsave(&efi_runtime_lock, flags);
227	status = efi_call_virt(query_variable_info, attr, storage_space,
228			       remaining_space, max_variable_size);
229	spin_unlock_irqrestore(&efi_runtime_lock, flags);
230	return status;
231}
232
233static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
234{
235	unsigned long flags;
236	efi_status_t status;
237
238	spin_lock_irqsave(&efi_runtime_lock, flags);
239	status = efi_call_virt(get_next_high_mono_count, count);
240	spin_unlock_irqrestore(&efi_runtime_lock, flags);
241	return status;
242}
243
244static void virt_efi_reset_system(int reset_type,
245				  efi_status_t status,
246				  unsigned long data_size,
247				  efi_char16_t *data)
248{
249	unsigned long flags;
250
251	spin_lock_irqsave(&efi_runtime_lock, flags);
252	__efi_call_virt(reset_system, reset_type, status, data_size, data);
253	spin_unlock_irqrestore(&efi_runtime_lock, flags);
254}
255
256static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
257					    unsigned long count,
258					    unsigned long sg_list)
259{
260	unsigned long flags;
261	efi_status_t status;
262
263	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
264		return EFI_UNSUPPORTED;
265
266	spin_lock_irqsave(&efi_runtime_lock, flags);
267	status = efi_call_virt(update_capsule, capsules, count, sg_list);
268	spin_unlock_irqrestore(&efi_runtime_lock, flags);
269	return status;
270}
271
272static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
273						unsigned long count,
274						u64 *max_size,
275						int *reset_type)
276{
277	unsigned long flags;
278	efi_status_t status;
279
280	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
281		return EFI_UNSUPPORTED;
282
283	spin_lock_irqsave(&efi_runtime_lock, flags);
284	status = efi_call_virt(query_capsule_caps, capsules, count, max_size,
285			       reset_type);
286	spin_unlock_irqrestore(&efi_runtime_lock, flags);
287	return status;
288}
289
290void efi_native_runtime_setup(void)
291{
292	efi.get_time = virt_efi_get_time;
293	efi.set_time = virt_efi_set_time;
294	efi.get_wakeup_time = virt_efi_get_wakeup_time;
295	efi.set_wakeup_time = virt_efi_set_wakeup_time;
296	efi.get_variable = virt_efi_get_variable;
297	efi.get_next_variable = virt_efi_get_next_variable;
298	efi.set_variable = virt_efi_set_variable;
299	efi.set_variable_nonblocking = virt_efi_set_variable_nonblocking;
300	efi.get_next_high_mono_count = virt_efi_get_next_high_mono_count;
301	efi.reset_system = virt_efi_reset_system;
302	efi.query_variable_info = virt_efi_query_variable_info;
303	efi.update_capsule = virt_efi_update_capsule;
304	efi.query_capsule_caps = virt_efi_query_capsule_caps;
305}
306