MdePkg/Library/BaseLib/Arm/GccInline.c

   1 /** @file
   2   GCC inline implementation of BaseLib processor specific functions.
   3
   4   Copyright (c) 2006 - 2010, Intel Corporation<BR>
   5   Portions copyright (c) 2008-2009 Apple Inc. All rights reserved.<BR>
   6   All rights reserved. This program and the accompanying materials
   7   are licensed and made available under the terms and conditions of the BSD License
   8   which accompanies this distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include "BaseLibInternals.h"
  17
  18 /**
  19   Requests CPU to pause for a short period of time.
  20
  21   Requests CPU to pause for a short period of time. Typically used in MP
  22   systems to prevent memory starvation while waiting for a spin lock.
  23
  24 **/
  25 VOID
  26 EFIAPI
  27 CpuPause (
  28   VOID
  29   )
  30 {
  31   __asm__ __volatile__ (
  32     "nop\n\t"
  33     "nop\n\t"
  34     "nop\n\t"
  35     "nop\n\t"
  36     "nop\n\t"
  37     );
  38 }
  39
  40 /**
  41   Transfers control to a function starting with a new stack.
  42
  43   This internal worker function transfers control to the function
  44   specified by EntryPoint using the new stack specified by NewStack
  45   and passing in the parameters specified by Context1 and Context2.
  46   Context1 and Context2 are optional and may be NULL.
  47   The function EntryPoint must never return.
  48
  49   @param EntryPoint   The pointer to the function to enter.
  50   @param Context1     The first parameter to pass in.
  51   @param Context2     The second Parameter to pass in
  52   @param NewStack     The new Location of the stack
  53
  54 **/
  55 VOID
  56 EFIAPI
  57 InternalSwitchStackAsm (
  58   SWITCH_STACK_ENTRY_POINT EntryPoint,
  59   VOID  *Context1,
  60   VOID  *Context2,
  61   VOID  *NewStack
  62   )
  63 {
  64   __asm__ __volatile__ (
  65     "mov  lr, %0\n\t"
  66     "mov  sp, %3\n\t"
  67     "mov  %r0, %1\n\t"
  68     "mov  %r1, %2\n\t"
  69     "bx   lr\n\t"
  70     : /* no output operand */
  71     : "r" (EntryPoint),
  72       "r" (Context1),
  73       "r" (Context2),
  74       "r" (NewStack)
  75     );
  76 }