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#========================================================================================
# Copyright (c) 2011-2012, ARM Limited. All rights reserved.
#
# 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.
#
#=======================================================================================
#start of the code section
.text
.align 3
GCC_ASM_EXPORT(return_from_exception)
GCC_ASM_EXPORT(enter_monitor_mode)
GCC_ASM_EXPORT(copy_cpsr_into_spsr)
GCC_ASM_EXPORT(set_non_secure_mode)
# r0: Monitor World EntryPoint
# r1: MpId
# r2: Secure Monitor mode stack
ASM_PFX(enter_monitor_mode):
mrs r4, cpsr @ Save current mode (SVC) in r1
bic r3, r4, #0x1f @ Clear all mode bits
orr r3, r3, #0x16 @ Set bits for Monitor mode
msr cpsr_cxsf, r3 @ We are now in Monitor Mode
cmp r2, #0 @ If a Secure Monitor stack base has been passed, used it
movne sp, r2 @ Use the passed sp
mov lr, r0 @ Use the pass entrypoint as lr
msr spsr_cxsf, r4 @ Use saved mode for the MOVS jump to the kernel
mov r4, r0 @ Swap EntryPoint and MpId registers
mov r0, r1
bx r4
# We cannot use the instruction 'movs pc, lr' because the caller can be written either in ARM or Thumb2 assembler.
# When we will jump into this function, we will set the CPSR flag to ARM assembler. By copying directly 'lr' into
# 'pc'; we will not change the CPSR flag and it will crash.
# The way to fix this limitation is to do the movs into the ARM assmbler code and then do a 'bx'.
ASM_PFX(return_from_exception):
ldr lr, returned_exception
#The following instruction breaks the code.
#movs pc, lr
mrs r2, cpsr
bic r2, r2, #0x1f
orr r2, r2, #0x13
msr cpsr_c, r2
returned_exception: @ We are now in non-secure state
bx r0
# Save the current Program Status Register (PSR) into the Saved PSR
ASM_PFX(copy_cpsr_into_spsr):
mrs r0, cpsr
msr spsr_cxsf, r0
bx lr
# Set the Non Secure Mode
ASM_PFX(set_non_secure_mode):
push { r1 }
and r0, r0, #0x1f @ Keep only the mode bits
mrs r1, spsr @ Read the spsr
bic r1, r1, #0x1f @ Clear all mode bits
orr r1, r1, r0
msr spsr_cxsf, r1 @ write back spsr (may have caused a mode switch)
isb
pop { r1 }
bx lr @ return (hopefully thumb-safe!)
dead:
b dead
ASM_FUNCTION_REMOVE_IF_UNREFERENCED
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