drivers/firmware/efi/runtime-wrappers.c

   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  */
  62 static 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
  98 static 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
 111 static 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
 124 static 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
 139 static 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
 152 static 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
 168 static 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
 181 static 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
 197 static efi_status_t
 198 virt_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
 215 static 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
 233 static 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
 244 static 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
 256 static 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
 272 static 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
 290 void 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 }