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 60END_CFI(__switch_to) 61