ArmPkg/Library/SemihostLib/Arm/GccSemihost.S

   1 #------------------------------------------------------------------------------
   2 #
   3 # Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
   4 #
   5 # SPDX-License-Identifier: BSD-2-Clause-Patent
   6 #
   7 #------------------------------------------------------------------------------
   8
   9 #include <AsmMacroIoLib.h>
  10
  11 /*
  12   Semihosting operation request mechanism
  13
  14   SVC  0x123456  in ARM state (for all architectures)
  15   SVC  0xAB in Thumb state (excluding ARMv7-M)
  16   BKPT 0xAB for ARMv7-M (Thumb-2 only)
  17
  18   R0 - operation type
  19   R1 - block containing all other parametes
  20
  21   lr - must be saved as svc instruction will cause an svc exception and write
  22        the svc lr register. That happens to be the one we are using, so we must
  23        save it or we will not be able to return.
  24  */
  25 ASM_FUNC(GccSemihostCall)
  26   stmfd   sp!, {lr}
  27   svc     #0x123456
  28   ldmfd   sp!, {lr}
  29   bx      lr
  30
  31