root/arch/arc/kernel/ctx_sw_asm.S

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   4  *
   5  * Vineetg: Aug 2009
   6  *  -Moved core context switch macro out of entry.S into this file.
   7  *  -This is the more "natural" hand written assembler
   8  */
   9 
  10 #include <linux/linkage.h>
  11 #include <asm/entry.h>       /* For the SAVE_* macros */
  12 #include <asm/asm-offsets.h>
  13 
  14 #define KSP_WORD_OFF    ((TASK_THREAD + THREAD_KSP) / 4)
  15 
  16 ;################### Low Level Context Switch ##########################
  17 
  18         .section .sched.text,"ax",@progbits
  19         .align 4
  20         .global __switch_to
  21         .type   __switch_to, @function
  22 __switch_to:
  23         CFI_STARTPROC
  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 #if KSP_WORD_OFF  <= 255
  32         st.as  sp, [r0, KSP_WORD_OFF]
  33 #else
  34         /* Workaround for NR_CPUS=4k as ST.as can only take s9 offset */
  35         add2    r24, r0, KSP_WORD_OFF
  36         st      sp, [r24]
  37 #endif
  38         /*
  39         * Return last task in r0 (return reg)
  40         * On ARC, Return reg = First Arg reg = r0.
  41         * Since we already have last task in r0,
  42         * don't need to do anything special to return it
  43         */
  44 
  45         /*
  46          * switch to new task, contained in r1
  47          * Temp reg r3 is required to get the ptr to store val
  48          */
  49         SET_CURR_TASK_ON_CPU  r1, r3
  50 
  51         /* reload SP with kernel mode stack pointer in task->thread.ksp */
  52         ld.as  sp, [r1, (TASK_THREAD + THREAD_KSP)/4]
  53 
  54         /* restore the registers */
  55         RESTORE_CALLEE_SAVED_KERNEL
  56         ld.ab   fp, [sp, 4]
  57         ld.ab   blink, [sp, 4]
  58         j       [blink]
  59 
  60 END_CFI(__switch_to)