ArmPkg/Library/ArmSvcLib/Arm/ArmSvc.asm

   1 //
   2 //  Copyright (c) 2016 - 2020, ARM Limited. All rights reserved.
   3 //
   4 //  SPDX-License-Identifier: BSD-2-Clause-Patent
   5 //
   6 //
   7
   8
   9     INCLUDE AsmMacroExport.inc
  10
  11  RVCT_ASM_EXPORT ArmCallSvc
  12     // r0 will be popped just after the SVC call
  13     push     {r0, r4-r8}
  14
  15     // Load the SVC arguments values into the appropriate registers
  16     ldm     r0, {r0-r7}
  17
  18     svc     #0
  19     // Prevent speculative execution beyond svc instruction
  20     dsb     nsh
  21     isb
  22
  23     // Load the ARM_SVC_ARGS structure address from the stack into r8
  24     ldr     r8, [sp]
  25
  26     // Load the SVC returned values into the appropriate registers
  27     // A SVC call can return up to 4 values - we do not need to store back r4-r7.
  28     stm     r8, {r0-r3}
  29
  30     mov     r0, r8
  31
  32     // Restore the registers r4-r8
  33     pop     {r1, r4-r8}
  34     bx      lr
  35
  36     END