mirror of https://github.com/acidanthera/audk.git
67 lines
2.4 KiB
NASM
67 lines
2.4 KiB
NASM
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//
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// Copyright (c) 2011, ARM Limited. All rights reserved.
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//
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// This program and the accompanying materials
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// are licensed and made available under the terms and conditions of the BSD License
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// which accompanies this distribution. The full text of the license may be found at
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// http://opensource.org/licenses/bsd-license.php
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//
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// THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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// WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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//
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//
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EXPORT monitor_vector_table
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EXPORT return_from_exception
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EXPORT enter_monitor_mode
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EXPORT copy_cpsr_into_spsr
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AREA Helper, CODE, READONLY
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ALIGN 32
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monitor_vector_table
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ldr pc, dead
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ldr pc, dead
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ldr pc, dead
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ldr pc, dead
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ldr pc, dead
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ldr pc, dead
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ldr pc, dead
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ldr pc, dead
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// arg0: Secure Monitor mode stack
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enter_monitor_mode
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mov r2, lr // Save current lr
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mrs r1, cpsr // Save current mode (SVC) in r1
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bic r3, r1, #0x1f // Clear all mode bits
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orr r3, r3, #0x16 // Set bits for Monitor mode
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msr cpsr_cxsf, r3 // We are now in Monitor Mode
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mov sp, r0 // Use the passed sp
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mov lr, r2 // Use the same lr as before
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msr spsr_cxsf, r1 // Use saved mode for the MOVS jump to the kernel
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bx lr
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// We cannot use the instruction 'movs pc, lr' because the caller can be written either in ARM or Thumb2 assembler.
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// When we will jump into this function, we will set the CPSR flag to ARM assembler. By copying directly 'lr' into
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// 'pc'; we will not change the CPSR flag and it will crash.
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// The way to fix this limitation is to do the movs into the ARM assmbler code and then do a 'bx'.
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return_from_exception
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adr lr, returned_exception
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movs pc, lr
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returned_exception // We are now in non-secure state
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bx r0
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// Save the current Program Status Register (PSR) into the Saved PSR
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copy_cpsr_into_spsr
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mrs r0, cpsr
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msr spsr_cxsf, r0
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bx lr
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dead
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B dead
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END
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