ArmPkg/Drivers/CpuDxe/ArmV6/ExceptionSupport.S
#------------------------------------------------------------------------------
#
# 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
*/
GCC_ASM_EXPORT(ExceptionHandlersStart)
GCC_ASM_EXPORT(ExceptionHandlersEnd)
GCC_ASM_EXPORT(CommonExceptionEntry)
GCC_ASM_EXPORT(AsmCommonExceptionEntry)
GCC_ASM_EXPORT(CommonCExceptionHandler)
.text
#if !defined(__APPLE__)
.fpu neon @ makes vpush/vpop assemble
#endif
.align 5
//
// This code gets copied to the ARM vector table
// ExceptionHandlersStart - ExceptionHandlersEnd gets copied
//
ASM_PFX(ExceptionHandlersStart):
ASM_PFX(Reset):
b ASM_PFX(ResetEntry)
ASM_PFX(UndefinedInstruction):
b ASM_PFX(UndefinedInstructionEntry)
ASM_PFX(SoftwareInterrupt):
b ASM_PFX(SoftwareInterruptEntry)
ASM_PFX(PrefetchAbort):
b ASM_PFX(PrefetchAbortEntry)
ASM_PFX(DataAbort):
b ASM_PFX(DataAbortEntry)
ASM_PFX(ReservedException):
b ASM_PFX(ReservedExceptionEntry)
ASM_PFX(Irq):
b ASM_PFX(IrqEntry)
ASM_PFX(Fiq):
b ASM_PFX(FiqEntry)
ASM_PFX(ResetEntry):
srsdb #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,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(UndefinedInstructionEntry):
sub LR, LR, #4 @ Only -2 for Thumb, adjust in CommonExceptionEntry
srsdb #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,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(SoftwareInterruptEntry):
srsdb #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,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(PrefetchAbortEntry):
sub LR,LR,#4
srsdb #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,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(DataAbortEntry):
sub LR,LR,#8
srsdb #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
ldr R1,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(ReservedExceptionEntry):
srsdb #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
ldr R1,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(IrqEntry):
sub LR,LR,#4
srsdb #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,ASM_PFX(CommonExceptionEntry)
bx R1
ASM_PFX(FiqEntry):
sub LR,LR,#4
srsdb #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,ASM_PFX(CommonExceptionEntry)
bx R1
//
// This gets patched by the C code that patches in the vector table
//
ASM_PFX(CommonExceptionEntry):
.word ASM_PFX(AsmCommonExceptionEntry)
ASM_PFX(ExceptionHandlersEnd):
//
// This code runs from CpuDxe driver loaded address. It is patched into
// CommonExceptionEntry.
//
ASM_PFX(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] @ srsdb 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 ASM_PFX(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