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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.
//
//
EXPORT return_from_exception
EXPORT enter_monitor_mode
EXPORT copy_cpsr_into_spsr
EXPORT set_non_secure_mode
AREA Helper, CODE, READONLY
// r0: Monitor World EntryPoint
// r1: MpId
// r2: Secure Monitor mode stack
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'.
return_from_exception
adr lr, returned_exception
movs pc, lr
returned_exception // We are now in non-secure state
bx r0
// Save the current Program Status Register (PSR) into the Saved PSR
copy_cpsr_into_spsr
mrs r0, cpsr
msr spsr_cxsf, r0
bx lr
// Set the Non Secure Mode
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
END
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