mirror of https://github.com/acidanthera/audk.git
80 lines
2.9 KiB
NASM
80 lines
2.9 KiB
NASM
//
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// Copyright (c) 2011-2012, 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 return_from_exception
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EXPORT enter_monitor_mode
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EXPORT copy_cpsr_into_spsr
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EXPORT set_non_secure_mode
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AREA Helper, CODE, READONLY
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// r0: Monitor World EntryPoint
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// r1: MpId
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// r2: SecBootMode
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// r3: Secure Monitor mode stack
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enter_monitor_mode FUNCTION
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cmp r3, #0 // If a Secure Monitor stack base has not been defined then use the Secure stack
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moveq r3, sp
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mrs r4, cpsr // Save current mode (SVC) in r4
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bic r5, r4, #0x1f // Clear all mode bits
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orr r5, r5, #0x16 // Set bits for Monitor mode
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msr cpsr_cxsf, r5 // We are now in Monitor Mode
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mov sp, r3 // Set the stack of the Monitor Mode
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mov lr, r0 // Use the pass entrypoint as lr
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msr spsr_cxsf, r4 // Use saved mode for the MOVS jump to the kernel
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mov r4, r0 // Swap EntryPoint and MpId registers
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mov r0, r1
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mov r1, r2
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mov r2, r3
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bx r4
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ENDFUNC
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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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// Set the Non Secure Mode
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set_non_secure_mode
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push { r1 }
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and r0, r0, #0x1f // Keep only the mode bits
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mrs r1, spsr // Read the spsr
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bic r1, r1, #0x1f // Clear all mode bits
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orr r1, r1, r0
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msr spsr_cxsf, r1 // write back spsr (may have caused a mode switch)
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isb
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pop { r1 }
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bx lr // return (hopefully thumb-safe!)
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dead
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B dead
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END
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