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 #ifndef efi_in_nmi
  90 #define efi_in_nmi()    (0)
  91 #endif
  92
  93 /*
  94  * As per commit ef68c8f87ed1 ("x86: Serialize EFI time accesses on rtc_lock"),
  95  * the EFI specification requires that callers of the time related runtime
  96  * functions serialize with other CMOS accesses in the kernel, as the EFI time
  97  * functions may choose to also use the legacy CMOS RTC.
  98  */
  99 __weak DEFINE_SPINLOCK(rtc_lock);
 100
 101 static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
 102 {
 103         unsigned long flags;
 104         efi_status_t status;
 105
 106         spin_lock_irqsave(&rtc_lock, flags);
 107         spin_lock(&efi_runtime_lock);
 108         status = efi_call_virt(get_time, tm, tc);
 109         spin_unlock(&efi_runtime_lock);
 110         spin_unlock_irqrestore(&rtc_lock, flags);
 111         return status;
 112 }
 113
 114 static efi_status_t virt_efi_set_time(efi_time_t *tm)
 115 {
 116         unsigned long flags;
 117         efi_status_t status;
 118
 119         spin_lock_irqsave(&rtc_lock, flags);
 120         spin_lock(&efi_runtime_lock);
 121         status = efi_call_virt(set_time, tm);
 122         spin_unlock(&efi_runtime_lock);
 123         spin_unlock_irqrestore(&rtc_lock, flags);
 124         return status;
 125 }
 126
 127 static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
 128                                              efi_bool_t *pending,
 129                                              efi_time_t *tm)
 130 {
 131         unsigned long flags;
 132         efi_status_t status;
 133
 134         spin_lock_irqsave(&rtc_lock, flags);
 135         spin_lock(&efi_runtime_lock);
 136         status = efi_call_virt(get_wakeup_time, enabled, pending, tm);
 137         spin_unlock(&efi_runtime_lock);
 138         spin_unlock_irqrestore(&rtc_lock, flags);
 139         return status;
 140 }
 141
 142 static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
 143 {
 144         unsigned long flags;
 145         efi_status_t status;
 146
 147         spin_lock_irqsave(&rtc_lock, flags);
 148         spin_lock(&efi_runtime_lock);
 149         status = efi_call_virt(set_wakeup_time, enabled, tm);
 150         spin_unlock(&efi_runtime_lock);
 151         spin_unlock_irqrestore(&rtc_lock, flags);
 152         return status;
 153 }
 154
 155 static efi_status_t virt_efi_get_variable(efi_char16_t *name,
 156                                           efi_guid_t *vendor,
 157                                           u32 *attr,
 158                                           unsigned long *data_size,
 159                                           void *data)
 160 {
 161         unsigned long flags;
 162         efi_status_t status;
 163
 164         spin_lock_irqsave(&efi_runtime_lock, flags);
 165         status = efi_call_virt(get_variable, name, vendor, attr, data_size,
 166                                data);
 167         spin_unlock_irqrestore(&efi_runtime_lock, flags);
 168         return status;
 169 }
 170
 171 static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
 172                                                efi_char16_t *name,
 173                                                efi_guid_t *vendor)
 174 {
 175         unsigned long flags;
 176         efi_status_t status;
 177
 178         spin_lock_irqsave(&efi_runtime_lock, flags);
 179         status = efi_call_virt(get_next_variable, name_size, name, vendor);
 180         spin_unlock_irqrestore(&efi_runtime_lock, flags);
 181         return status;
 182 }
 183
 184 static efi_status_t virt_efi_set_variable(efi_char16_t *name,
 185                                           efi_guid_t *vendor,
 186                                           u32 attr,
 187                                           unsigned long data_size,
 188                                           void *data)
 189 {
 190         unsigned long flags;
 191         efi_status_t status;
 192         bool __in_nmi = efi_in_nmi();
 193
 194         if (!__in_nmi)
 195                 spin_lock_irqsave(&efi_runtime_lock, flags);
 196         status = efi_call_virt(set_variable, name, vendor, attr, data_size,
 197                                data);
 198         if (!__in_nmi)
 199                 spin_unlock_irqrestore(&efi_runtime_lock, flags);
 200         return status;
 201 }
 202
 203 static efi_status_t virt_efi_query_variable_info(u32 attr,
 204                                                  u64 *storage_space,
 205                                                  u64 *remaining_space,
 206                                                  u64 *max_variable_size)
 207 {
 208         unsigned long flags;
 209         efi_status_t status;
 210         bool __in_nmi = efi_in_nmi();
 211
 212         if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
 213                 return EFI_UNSUPPORTED;
 214
 215         if (!__in_nmi)
 216                 spin_lock_irqsave(&efi_runtime_lock, flags);
 217         status = efi_call_virt(query_variable_info, attr, storage_space,
 218                                remaining_space, max_variable_size);
 219         if (!__in_nmi)
 220                 spin_unlock_irqrestore(&efi_runtime_lock, flags);
 221         return status;
 222 }
 223
 224 static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
 225 {
 226         unsigned long flags;
 227         efi_status_t status;
 228
 229         spin_lock_irqsave(&efi_runtime_lock, flags);
 230         status = efi_call_virt(get_next_high_mono_count, count);
 231         spin_unlock_irqrestore(&efi_runtime_lock, flags);
 232         return status;
 233 }
 234
 235 static void virt_efi_reset_system(int reset_type,
 236                                   efi_status_t status,
 237                                   unsigned long data_size,
 238                                   efi_char16_t *data)
 239 {
 240         unsigned long flags;
 241
 242         spin_lock_irqsave(&efi_runtime_lock, flags);
 243         __efi_call_virt(reset_system, reset_type, status, data_size, data);
 244         spin_unlock_irqrestore(&efi_runtime_lock, flags);
 245 }
 246
 247 static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
 248                                             unsigned long count,
 249                                             unsigned long sg_list)
 250 {
 251         unsigned long flags;
 252         efi_status_t status;
 253
 254         if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
 255                 return EFI_UNSUPPORTED;
 256
 257         spin_lock_irqsave(&efi_runtime_lock, flags);
 258         status = efi_call_virt(update_capsule, capsules, count, sg_list);
 259         spin_unlock_irqrestore(&efi_runtime_lock, flags);
 260         return status;
 261 }
 262
 263 static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
 264                                                 unsigned long count,
 265                                                 u64 *max_size,
 266                                                 int *reset_type)
 267 {
 268         unsigned long flags;
 269         efi_status_t status;
 270
 271         if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
 272                 return EFI_UNSUPPORTED;
 273
 274         spin_lock_irqsave(&efi_runtime_lock, flags);
 275         status = efi_call_virt(query_capsule_caps, capsules, count, max_size,
 276                                reset_type);
 277         spin_unlock_irqrestore(&efi_runtime_lock, flags);
 278         return status;
 279 }
 280
 281 void efi_native_runtime_setup(void)
 282 {
 283         efi.get_time = virt_efi_get_time;
 284         efi.set_time = virt_efi_set_time;
 285         efi.get_wakeup_time = virt_efi_get_wakeup_time;
 286         efi.set_wakeup_time = virt_efi_set_wakeup_time;
 287         efi.get_variable = virt_efi_get_variable;
 288         efi.get_next_variable = virt_efi_get_next_variable;
 289         efi.set_variable = virt_efi_set_variable;
 290         efi.get_next_high_mono_count = virt_efi_get_next_high_mono_count;
 291         efi.reset_system = virt_efi_reset_system;
 292         efi.query_variable_info = virt_efi_query_variable_info;
 293         efi.update_capsule = virt_efi_update_capsule;
 294         efi.query_capsule_caps = virt_efi_query_capsule_caps;
 295 }