ArmPkg/Library/ArmExceptionLib/Arm/ExceptionSupport.S

   1 #------------------------------------------------------------------------------
   2 #
   3 # Use ARMv6 instruction to operate on a single stack
   4 #
   5 # Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
   6 # Copyright (c) 2014, ARM Limited. All rights reserved.<BR>
   7 # Copyright (c) 2016 HP Development Company, L.P.<BR>
   8 #
   9 # SPDX-License-Identifier: BSD-2-Clause-Patent
  10 #
  11 #------------------------------------------------------------------------------
  12
  13 #include <Library/PcdLib.h>
  14
  15 /*
  16
  17 This is the stack constructed by the exception handler (low address to high address)
  18                 # R0 - IFAR is EFI_SYSTEM_CONTEXT for ARM
  19   Reg   Offset
  20   ===   ======
  21   R0    0x00    # stmfd     SP!,{R0-R12}
  22   R1    0x04
  23   R2    0x08
  24   R3    0x0c
  25   R4    0x10
  26   R5    0x14
  27   R6    0x18
  28   R7    0x1c
  29   R8    0x20
  30   R9    0x24
  31   R10   0x28
  32   R11   0x2c
  33   R12   0x30
  34   SP    0x34    # reserved via subtraction 0x20 (32) from SP
  35   LR    0x38
  36   PC    0x3c
  37   CPSR  0x40
  38   DFSR  0x44
  39   DFAR  0x48
  40   IFSR  0x4c
  41   IFAR  0x50
  42
  43   LR    0x54    # SVC Link register (we need to restore it)
  44
  45   LR    0x58    # pushed by srsfd
  46   CPSR  0x5c
  47
  48  */
  49
  50
  51 GCC_ASM_EXPORT(ExceptionHandlersStart)
  52 GCC_ASM_EXPORT(ExceptionHandlersEnd)
  53 GCC_ASM_EXPORT(CommonExceptionEntry)
  54 GCC_ASM_EXPORT(AsmCommonExceptionEntry)
  55 GCC_ASM_EXPORT(CommonCExceptionHandler)
  56
  57 .text
  58 .syntax unified
  59 #if !defined(__APPLE__)
  60 .fpu neon    @ makes vpush/vpop assemble
  61 #endif
  62 .align 5
  63
  64
  65 //
  66 // This code gets copied to the ARM vector table
  67 // ExceptionHandlersStart - ExceptionHandlersEnd gets copied
  68 //
  69 ASM_PFX(ExceptionHandlersStart):
  70
  71 ASM_PFX(Reset):
  72   b ASM_PFX(ResetEntry)
  73
  74 ASM_PFX(UndefinedInstruction):
  75   b ASM_PFX(UndefinedInstructionEntry)
  76
  77 ASM_PFX(SoftwareInterrupt):
  78   b ASM_PFX(SoftwareInterruptEntry)
  79
  80 ASM_PFX(PrefetchAbort):
  81   b ASM_PFX(PrefetchAbortEntry)
  82
  83 ASM_PFX(DataAbort):
  84   b ASM_PFX(DataAbortEntry)
  85
  86 ASM_PFX(ReservedException):
  87   b ASM_PFX(ReservedExceptionEntry)
  88
  89 ASM_PFX(Irq):
  90   b ASM_PFX(IrqEntry)
  91
  92 ASM_PFX(Fiq):
  93   b ASM_PFX(FiqEntry)
  94
  95 ASM_PFX(ResetEntry):
  96   srsdb     #0x13!                    @ Store return state on SVC stack
  97                                       @ We are already in SVC mode
  98
  99   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 100   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 101   stmfd     SP!,{R0-R12}              @ Store the register state
 102
 103   mov       R0,#0                     @ ExceptionType
 104   ldr       R1,ASM_PFX(CommonExceptionEntry)
 105   bx        R1
 106
 107 ASM_PFX(UndefinedInstructionEntry):
 108   sub       LR, LR, #4                @ Only -2 for Thumb, adjust in CommonExceptionEntry
 109   srsdb     #0x13!                    @ Store return state on SVC stack
 110   cps       #0x13                     @ Switch to SVC for common stack
 111   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 112   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 113   stmfd     SP!,{R0-R12}              @ Store the register state
 114
 115   mov       R0,#1                     @ ExceptionType
 116   ldr       R1,ASM_PFX(CommonExceptionEntry)
 117   bx        R1
 118
 119 ASM_PFX(SoftwareInterruptEntry):
 120   srsdb     #0x13!                    @ Store return state on SVC stack
 121                                       @ We are already in SVC mode
 122   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 123   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 124   stmfd     SP!,{R0-R12}              @ Store the register state
 125
 126   mov       R0,#2                     @ ExceptionType
 127   ldr       R1,ASM_PFX(CommonExceptionEntry)
 128   bx        R1
 129
 130 ASM_PFX(PrefetchAbortEntry):
 131   sub       LR,LR,#4
 132   srsdb     #0x13!                    @ Store return state on SVC stack
 133   cps       #0x13                     @ Switch to SVC for common stack
 134   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 135   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 136   stmfd     SP!,{R0-R12}              @ Store the register state
 137
 138   mov       R0,#3                     @ ExceptionType
 139   ldr       R1,ASM_PFX(CommonExceptionEntry)
 140   bx        R1
 141
 142 ASM_PFX(DataAbortEntry):
 143   sub       LR,LR,#8
 144   srsdb     #0x13!                    @ Store return state on SVC stack
 145   cps       #0x13                     @ Switch to SVC for common stack
 146   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 147   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 148   stmfd     SP!,{R0-R12}              @ Store the register state
 149
 150   mov       R0,#4
 151   ldr       R1,ASM_PFX(CommonExceptionEntry)
 152   bx        R1
 153
 154 ASM_PFX(ReservedExceptionEntry):
 155   srsdb     #0x13!                    @ Store return state on SVC stack
 156   cps       #0x13                     @ Switch to SVC for common stack
 157   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 158   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 159   stmfd     SP!,{R0-R12}              @ Store the register state
 160
 161   mov       R0,#5
 162   ldr       R1,ASM_PFX(CommonExceptionEntry)
 163   bx        R1
 164
 165 ASM_PFX(IrqEntry):
 166   sub       LR,LR,#4
 167   srsdb     #0x13!                    @ Store return state on SVC stack
 168   cps       #0x13                     @ Switch to SVC for common stack
 169   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 170   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 171   stmfd     SP!,{R0-R12}              @ Store the register state
 172
 173   mov       R0,#6                     @ ExceptionType
 174   ldr       R1,ASM_PFX(CommonExceptionEntry)
 175   bx        R1
 176
 177 ASM_PFX(FiqEntry):
 178   sub       LR,LR,#4
 179   srsdb     #0x13!                    @ Store return state on SVC stack
 180   cps       #0x13                     @ Switch to SVC for common stack
 181   stmfd     SP!,{LR}                  @ Store the link register for the current mode
 182   sub       SP,SP,#0x20               @ Save space for SP, LR, PC, IFAR - CPSR
 183   stmfd     SP!,{R0-R12}              @ Store the register state
 184                                       @ Since we have already switch to SVC R8_fiq - R12_fiq
 185                                       @ never get used or saved
 186   mov       R0,#7                     @ ExceptionType
 187   ldr       R1,ASM_PFX(CommonExceptionEntry)
 188   bx        R1
 189
 190 //
 191 // This gets patched by the C code that patches in the vector table
 192 //
 193 ASM_PFX(CommonExceptionEntry):
 194   .word       ASM_PFX(AsmCommonExceptionEntry)
 195
 196 ASM_PFX(ExceptionHandlersEnd):
 197
 198 //
 199 // This code runs from CpuDxe driver loaded address. It is patched into
 200 // CommonExceptionEntry.
 201 //
 202 ASM_PFX(AsmCommonExceptionEntry):
 203   mrc       p15, 0, R1, c6, c0, 2   @ Read IFAR
 204   str       R1, [SP, #0x50]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.IFAR
 205
 206   mrc       p15, 0, R1, c5, c0, 1   @ Read IFSR
 207   str       R1, [SP, #0x4c]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.IFSR
 208
 209   mrc       p15, 0, R1, c6, c0, 0   @ Read DFAR
 210   str       R1, [SP, #0x48]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.DFAR
 211
 212   mrc       p15, 0, R1, c5, c0, 0   @ Read DFSR
 213   str       R1, [SP, #0x44]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.DFSR
 214
 215   ldr       R1, [SP, #0x5c]         @ srsdb saved pre-exception CPSR on the stack
 216   str       R1, [SP, #0x40]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.CPSR
 217
 218   add       R2, SP, #0x38           @ Make R2 point to EFI_SYSTEM_CONTEXT_ARM.LR
 219   and       R3, R1, #0x1f           @ Check CPSR to see if User or System Mode
 220   cmp       R3, #0x1f               @ if ((CPSR == 0x10) || (CPSR == 0x1f))
 221   cmpne     R3, #0x10               @
 222   stmdaeq   R2, {lr}^               @   save unbanked lr
 223                                     @ else
 224   stmdane   R2, {lr}                @   save SVC lr
 225
 226
 227   ldr       R5, [SP, #0x58]         @ PC is the LR pushed by srsfd
 228                                     @ Check to see if we have to adjust for Thumb entry
 229   sub       r4, r0, #1              @ if (ExceptionType == 1 || ExceptionType == 2)) {
 230   cmp       r4, #1                  @   // UND & SVC have different LR adjust for Thumb
 231   bhi       NoAdjustNeeded
 232
 233   tst       r1, #0x20               @   if ((CPSR & T)) == T) {  // Thumb Mode on entry
 234   addne     R5, R5, #2              @     PC += 2;
 235   strne     R5,[SP,#0x58]           @ Update LR value pushed by srsfd
 236
 237 NoAdjustNeeded:
 238
 239   str       R5, [SP, #0x3c]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.PC
 240
 241   add       R1, SP, #0x60           @ We pushed 0x60 bytes on the stack
 242   str       R1, [SP, #0x34]         @ Store it in EFI_SYSTEM_CONTEXT_ARM.SP
 243
 244                                     @ R0 is ExceptionType
 245   mov       R1,SP                   @ R1 is SystemContext
 246
 247 #if (FixedPcdGet32(PcdVFPEnabled))
 248   vpush     {d0-d15}                @ save vstm registers in case they are used in optimizations
 249 #endif
 250
 251   mov       R4, SP                  @ Save current SP
 252   tst       R4, #4
 253   subne     SP, SP, #4              @ Adjust SP if not 8-byte aligned
 254
 255 /*
 256 VOID
 257 EFIAPI
 258 CommonCExceptionHandler (
 259   IN     EFI_EXCEPTION_TYPE           ExceptionType,   R0
 260   IN OUT EFI_SYSTEM_CONTEXT           SystemContext    R1
 261   )
 262
 263 */
 264   blx       ASM_PFX(CommonCExceptionHandler)  @ Call exception handler
 265
 266   mov       SP, R4                  @ Restore SP
 267
 268 #if (FixedPcdGet32(PcdVFPEnabled))
 269   vpop      {d0-d15}
 270 #endif
 271
 272   ldr       R1, [SP, #0x4c]         @ Restore EFI_SYSTEM_CONTEXT_ARM.IFSR
 273   mcr       p15, 0, R1, c5, c0, 1   @ Write IFSR
 274
 275   ldr       R1, [SP, #0x44]         @ Restore EFI_SYSTEM_CONTEXT_ARM.DFSR
 276   mcr       p15, 0, R1, c5, c0, 0   @ Write DFSR
 277
 278   ldr       R1,[SP,#0x3c]           @ EFI_SYSTEM_CONTEXT_ARM.PC
 279   str       R1,[SP,#0x58]           @ Store it back to srsfd stack slot so it can be restored
 280
 281   ldr       R1,[SP,#0x40]           @ EFI_SYSTEM_CONTEXT_ARM.CPSR
 282   str       R1,[SP,#0x5c]           @ Store it back to srsfd stack slot so it can be restored
 283
 284   add       R3, SP, #0x54           @ Make R3 point to SVC LR saved on entry
 285   add       R2, SP, #0x38           @ Make R2 point to EFI_SYSTEM_CONTEXT_ARM.LR
 286   and       R1, R1, #0x1f           @ Check to see if User or System Mode
 287   cmp       R1, #0x1f               @ if ((CPSR == 0x10) || (CPSR == 0x1f))
 288   cmpne     R1, #0x10               @
 289   ldmibeq   R2, {lr}^               @   restore unbanked lr
 290                                     @ else
 291   ldmibne   R3, {lr}                @   restore SVC lr, via ldmfd SP!, {LR}
 292
 293   ldmfd     SP!,{R0-R12}            @ Restore general purpose registers
 294                                     @ Exception handler can not change SP
 295
 296   add       SP,SP,#0x20             @ Clear out the remaining stack space
 297   ldmfd     SP!,{LR}                @ restore the link register for this context
 298   rfefd     SP!                     @ return from exception via srsfd stack slot
 299