ArmPlatformPkg/Sec/Arm/Helper.S

   1 #========================================================================================
   2 #  Copyright (c) 2011-2014, ARM Limited. All rights reserved.
   3 #
   4 #  This program and the accompanying materials
   5 #  are licensed and made available under the terms and conditions of the BSD License
   6 #  which accompanies this distribution.  The full text of the license may be found at
   7 #  http://opensource.org/licenses/bsd-license.php
   8 #
   9 #  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 #  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11 #
  12 #=======================================================================================
  13
  14 #start of the code section
  15 .text
  16 .align 3
  17
  18 GCC_ASM_EXPORT(return_from_exception)
  19 GCC_ASM_EXPORT(enter_monitor_mode)
  20 GCC_ASM_EXPORT(copy_cpsr_into_spsr)
  21 GCC_ASM_EXPORT(set_non_secure_mode)
  22
  23 # r0: Monitor World EntryPoint
  24 # r1: MpId
  25 # r2: SecBootMode
  26 # r3: Secure Monitor mode stack
  27 ASM_PFX(enter_monitor_mode):
  28     cmp     r3, #0                      @ If a Secure Monitor stack base has not been defined then use the Secure stack
  29     moveq   r3, sp
  30
  31     mrs     r4, cpsr                    @ Save current mode (SVC) in r4
  32     bic     r5, r4, #0x1f               @ Clear all mode bits
  33     orr     r5, r5, #0x16               @ Set bits for Monitor mode
  34     msr     cpsr_cxsf, r5               @ We are now in Monitor Mode
  35
  36     mov     sp, r3                      @ Set the stack of the Monitor Mode
  37
  38     mov     lr, r0                      @ Use the pass entrypoint as lr
  39
  40     msr     spsr_cxsf, r4               @ Use saved mode for the MOVS jump to the kernel
  41
  42     mov     r4, r0                      @ Swap EntryPoint and MpId registers
  43     mov     r0, r1
  44     mov     r1, r2
  45     mov     r2, r3
  46
  47     bx      r4
  48
  49 # Return-from-exception is not an interworking return, so we must do it
  50 # in two steps, in case r0 has the Thumb bit set.
  51 ASM_PFX(return_from_exception):
  52     adr     lr, returned_exception
  53     movs    pc, lr
  54 returned_exception:                           @ We are now in non-secure state
  55     bx      r0
  56
  57 # Save the current Program Status Register (PSR) into the Saved PSR
  58 ASM_PFX(copy_cpsr_into_spsr):
  59     mrs     r0, cpsr
  60     msr     spsr_cxsf, r0
  61     bx      lr
  62
  63 # Set the Non Secure Mode
  64 ASM_PFX(set_non_secure_mode):
  65     push    { r1 }
  66     and     r0, r0, #0x1f     @ Keep only the mode bits
  67     mrs     r1, spsr          @ Read the spsr
  68     bic     r1, r1, #0x1f     @ Clear all mode bits
  69     orr     r1, r1, r0
  70     msr     spsr_cxsf, r1     @ write back spsr (may have caused a mode switch)
  71     isb
  72     pop     { r1 }
  73     bx      lr                @ return (hopefully thumb-safe!)
  74
  75 ASM_FUNCTION_REMOVE_IF_UNREFERENCED