arch/arc/kernel/ctx_sw_asm.S

   1 /*
   2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Vineetg: Aug 2009
   9  *  -Moved core context switch macro out of entry.S into this file.
  10  *  -This is the more "natural" hand written assembler
  11  */
  12
  13 #include <asm/entry.h>       /* For the SAVE_* macros */
  14 #include <asm/asm-offsets.h>
  15 #include <asm/linkage.h>
  16
  17 ;################### Low Level Context Switch ##########################
  18
  19         .section .sched.text,"ax",@progbits
  20         .align 4
  21         .global __switch_to
  22         .type   __switch_to, @function
  23 __switch_to:
  24
  25         /* Save regs on kernel mode stack of task */
  26         st.a    blink, [sp, -4]
  27         st.a    fp, [sp, -4]
  28         SAVE_CALLEE_SAVED_KERNEL
  29
  30         /* Save the now KSP in task->thread.ksp */
  31         st.as  sp, [r0, (TASK_THREAD + THREAD_KSP)/4]
  32
  33         /*
  34         * Return last task in r0 (return reg)
  35         * On ARC, Return reg = First Arg reg = r0.
  36         * Since we already have last task in r0,
  37         * don't need to do anything special to return it
  38         */
  39
  40         /* hardware memory barrier */
  41         sync
  42
  43         /*
  44          * switch to new task, contained in r1
  45          * Temp reg r3 is required to get the ptr to store val
  46          */
  47         SET_CURR_TASK_ON_CPU  r1, r3
  48
  49         /* reload SP with kernel mode stack pointer in task->thread.ksp */
  50         ld.as  sp, [r1, (TASK_THREAD + THREAD_KSP)/4]
  51
  52         /* restore the registers */
  53         RESTORE_CALLEE_SAVED_KERNEL
  54         ld.ab   fp, [sp, 4]
  55         ld.ab   blink, [sp, 4]
  56         j       [blink]
  57
  58 ARC_EXIT __switch_to