ArmPkg/Drivers/CpuDxe/ArmV6/ExceptionSupport.asm
//------------------------------------------------------------------------------
//
// Use ARMv6 instruction to operate on a single stack
//
// Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
//
// This program and the accompanying materials
// are licensed and made available under the terms and conditions of the BSD License
// which accompanies this distribution. The full text of the license may be found at
// http://opensource.org/licenses/bsd-license.php
//
// THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
// WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
//
//------------------------------------------------------------------------------
#include <Library/PcdLib.h>
/*
This is the stack constructed by the exception handler (low address to high address)
# R0 - IFAR is EFI_SYSTEM_CONTEXT for ARM
Reg Offset
=== ======
R0 0x00 # stmfd SP!,{R0-R12}
R1 0x04
R2 0x08
R3 0x0c
R4 0x10
R5 0x14
R6 0x18
R7 0x1c
R8 0x20
R9 0x24
R10 0x28
R11 0x2c
R12 0x30
SP 0x34 # reserved via adding 0x20 (32) to the SP
LR 0x38
PC 0x3c
CPSR 0x40
DFSR 0x44
DFAR 0x48
IFSR 0x4c
IFAR 0x50
LR 0x54 # SVC Link register (we need to restore it)
LR 0x58 # pushed by srsfd
CPSR 0x5c
*/
EXPORT ExceptionHandlersStart
EXPORT ExceptionHandlersEnd
EXPORT CommonExceptionEntry
EXPORT AsmCommonExceptionEntry
IMPORT CommonCExceptionHandler
PRESERVE8
AREA DxeExceptionHandlers, CODE, READONLY, CODEALIGN, ALIGN=5
//
// This code gets copied to the ARM vector table
// ExceptionHandlersStart - ExceptionHandlersEnd gets copied
//
ExceptionHandlersStart
Reset
b ResetEntry
UndefinedInstruction
b UndefinedInstructionEntry
SoftwareInterrupt
b SoftwareInterruptEntry
PrefetchAbort
b PrefetchAbortEntry
DataAbort
b DataAbortEntry
ReservedException
b ReservedExceptionEntry
Irq
b IrqEntry
Fiq
b FiqEntry
ResetEntry
srsfd #0x13! ; Store return state on SVC stack
; We are already in SVC mode
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#0 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
UndefinedInstructionEntry
sub LR, LR, #4 ; Only -2 for Thumb, adjust in CommonExceptionEntry
srsfd #0x13! ; Store return state on SVC stack
cps #0x13 ; Switch to SVC for common stack
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#1 ; ExceptionType
ldr R1,CommonExceptionEntry;
bx R1
SoftwareInterruptEntry
srsfd #0x13! ; Store return state on SVC stack
; We are already in SVC mode
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#2 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
PrefetchAbortEntry
sub LR,LR,#4
srsfd #0x13! ; Store return state on SVC stack
cps #0x13 ; Switch to SVC for common stack
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#3 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
DataAbortEntry
sub LR,LR,#8
srsfd #0x13! ; Store return state on SVC stack
cps #0x13 ; Switch to SVC for common stack
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#4 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
ReservedExceptionEntry
srsfd #0x13! ; Store return state on SVC stack
cps #0x13 ; Switch to SVC for common stack
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#5 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
IrqEntry
sub LR,LR,#4
srsfd #0x13! ; Store return state on SVC stack
cps #0x13 ; Switch to SVC for common stack
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
mov R0,#6 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
FiqEntry
sub LR,LR,#4
srsfd #0x13! ; Store return state on SVC stack
cps #0x13 ; Switch to SVC for common stack
stmfd SP!,{LR} ; Store the link register for the current mode
sub SP,SP,#0x20 ; Save space for SP, LR, PC, IFAR - CPSR
stmfd SP!,{R0-R12} ; Store the register state
; Since we have already switch to SVC R8_fiq - R12_fiq
; never get used or saved
mov R0,#7 ; ExceptionType
ldr R1,CommonExceptionEntry
bx R1
//
// This gets patched by the C code that patches in the vector table
//
CommonExceptionEntry
dcd AsmCommonExceptionEntry
ExceptionHandlersEnd
//
// This code runs from CpuDxe driver loaded address. It is patched into
// CommonExceptionEntry.
//
AsmCommonExceptionEntry
mrc p15, 0, R1, c6, c0, 2 ; Read IFAR
str R1, [SP, #0x50] ; Store it in EFI_SYSTEM_CONTEXT_ARM.IFAR
mrc p15, 0, R1, c5, c0, 1 ; Read IFSR
str R1, [SP, #0x4c] ; Store it in EFI_SYSTEM_CONTEXT_ARM.IFSR
mrc p15, 0, R1, c6, c0, 0 ; Read DFAR
str R1, [SP, #0x48] ; Store it in EFI_SYSTEM_CONTEXT_ARM.DFAR
mrc p15, 0, R1, c5, c0, 0 ; Read DFSR
str R1, [SP, #0x44] ; Store it in EFI_SYSTEM_CONTEXT_ARM.DFSR
ldr R1, [SP, #0x5c] ; srsfd saved pre-exception CPSR on the stack
str R1, [SP, #0x40] ; Store it in EFI_SYSTEM_CONTEXT_ARM.CPSR
add R2, SP, #0x38 ; Make R2 point to EFI_SYSTEM_CONTEXT_ARM.LR
and R3, R1, #0x1f ; Check CPSR to see if User or System Mode
cmp R3, #0x1f ; if ((CPSR == 0x10) || (CPSR == 0x1df))
cmpne R3, #0x10 ;
stmeqed R2, {lr}^ ; save unbanked lr
; else
stmneed R2, {lr} ; save SVC lr
ldr R5, [SP, #0x58] ; PC is the LR pushed by srsfd
; Check to see if we have to adjust for Thumb entry
sub r4, r0, #1 ; if (ExceptionType == 1 || ExceptionType ==2)) {
cmp r4, #1 ; // UND & SVC have differnt LR adjust for Thumb
bhi NoAdjustNeeded
tst r1, #0x20 ; if ((CPSR & T)) == T) { // Thumb Mode on entry
addne R5, R5, #2 ; PC += 2;
str R5,[SP,#0x58] ; Update LR value pused by srsfd
NoAdjustNeeded
str R5, [SP, #0x3c] ; Store it in EFI_SYSTEM_CONTEXT_ARM.PC
add R1, SP, #0x60 ; We pushed 0x60 bytes on the stack
str R1, [SP, #0x34] ; Store it in EFI_SYSTEM_CONTEXT_ARM.SP
; R0 is ExceptionType
mov R1,SP ; R1 is SystemContext
#if (FixedPcdGet32(PcdVFPEnabled))
vpush {d0-d15} ; save vstm registers in case they are used in optimizations
#endif
/*
VOID
EFIAPI
CommonCExceptionHandler (
IN EFI_EXCEPTION_TYPE ExceptionType, R0
IN OUT EFI_SYSTEM_CONTEXT SystemContext R1
)
*/
blx CommonCExceptionHandler ; Call exception handler
#if (FixedPcdGet32(PcdVFPEnabled))
vpop {d0-d15}
#endif
ldr R1, [SP, #0x4c] ; Restore EFI_SYSTEM_CONTEXT_ARM.IFSR
mcr p15, 0, R1, c5, c0, 1 ; Write IFSR
ldr R1, [SP, #0x44] ; sRestore EFI_SYSTEM_CONTEXT_ARM.DFSR
mcr p15, 0, R1, c5, c0, 0 ; Write DFSR
ldr R1,[SP,#0x3c] ; EFI_SYSTEM_CONTEXT_ARM.PC
str R1,[SP,#0x58] ; Store it back to srsfd stack slot so it can be restored
ldr R1,[SP,#0x40] ; EFI_SYSTEM_CONTEXT_ARM.CPSR
str R1,[SP,#0x5c] ; Store it back to srsfd stack slot so it can be restored
add R3, SP, #0x54 ; Make R3 point to SVC LR saved on entry
add R2, SP, #0x38 ; Make R2 point to EFI_SYSTEM_CONTEXT_ARM.LR
and R1, R1, #0x1f ; Check to see if User or System Mode
cmp R1, #0x1f ; if ((CPSR == 0x10) || (CPSR == 0x1f))
cmpne R1, #0x10 ;
ldmeqed R2, {lr}^ ; restore unbanked lr
; else
ldmneed R3, {lr} ; restore SVC lr, via ldmfd SP!, {LR}
ldmfd SP!,{R0-R12} ; Restore general purpose registers
; Exception handler can not change SP
add SP,SP,#0x20 ; Clear out the remaining stack space
ldmfd SP!,{LR} ; restore the link register for this context
rfefd SP! ; return from exception via srsfd stack slot
END