// SPDX-License-Identifier: GPL-2.0-only /* * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) * * Vineetg: Aug 2009 * -"C" version of lowest level context switch asm macro called by schedular * gcc doesn't generate the dward CFI info for hand written asm, hence can't * backtrace out of it (e.g. tasks sleeping in kernel). * So we cheat a bit by writing almost similar code in inline-asm. * -This is a hacky way of doing things, but there is no other simple way. * I don't want/intend to extend unwinding code to understand raw asm */ #include <asm/asm-offsets.h> #include <linux/sched.h> #include <linux/sched/debug.h> #ifdef CONFIG_ARC_PLAT_EZNPS #include <plat/ctop.h> #endif #define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4) struct task_struct *__sched __switch_to(struct task_struct *prev_task, struct task_struct *next_task) { unsigned int tmp; unsigned int prev = (unsigned int)prev_task; unsigned int next = (unsigned int)next_task; __asm__ __volatile__( /* FP/BLINK save generated by gcc (standard function prologue */ "st.a r13, [sp, -4] \n\t" "st.a r14, [sp, -4] \n\t" "st.a r15, [sp, -4] \n\t" "st.a r16, [sp, -4] \n\t" "st.a r17, [sp, -4] \n\t" "st.a r18, [sp, -4] \n\t" "st.a r19, [sp, -4] \n\t" "st.a r20, [sp, -4] \n\t" "st.a r21, [sp, -4] \n\t" "st.a r22, [sp, -4] \n\t" "st.a r23, [sp, -4] \n\t" "st.a r24, [sp, -4] \n\t" #ifndef CONFIG_ARC_CURR_IN_REG "st.a r25, [sp, -4] \n\t" #else "sub sp, sp, 4 \n\t" /* usual r25 placeholder */ #endif /* set ksp of outgoing task in tsk->thread.ksp */ #if KSP_WORD_OFF <= 255 "st.as sp, [%3, %1] \n\t" #else /* * Workaround for NR_CPUS=4k * %1 is bigger than 255 (S9 offset for st.as) */ "add2 r24, %3, %1 \n\t" "st sp, [r24] \n\t" #endif /* * setup _current_task with incoming tsk. * optionally, set r25 to that as well * For SMP extra work to get to &_current_task[cpu] * (open coded SET_CURR_TASK_ON_CPU) */ #ifndef CONFIG_SMP "st %2, [@_current_task] \n\t" #else #ifdef CONFIG_ARC_PLAT_EZNPS "lr r24, [%4] \n\t" #ifndef CONFIG_EZNPS_MTM_EXT "lsr r24, r24, 4 \n\t" #endif #else "lr r24, [identity] \n\t" "lsr r24, r24, 8 \n\t" "bmsk r24, r24, 7 \n\t" #endif "add2 r24, @_current_task, r24 \n\t" "st %2, [r24] \n\t" #endif #ifdef CONFIG_ARC_CURR_IN_REG "mov r25, %2 \n\t" #endif /* get ksp of incoming task from tsk->thread.ksp */ "ld.as sp, [%2, %1] \n\t" /* start loading it's CALLEE reg file */ #ifndef CONFIG_ARC_CURR_IN_REG "ld.ab r25, [sp, 4] \n\t" #else "add sp, sp, 4 \n\t" #endif "ld.ab r24, [sp, 4] \n\t" "ld.ab r23, [sp, 4] \n\t" "ld.ab r22, [sp, 4] \n\t" "ld.ab r21, [sp, 4] \n\t" "ld.ab r20, [sp, 4] \n\t" "ld.ab r19, [sp, 4] \n\t" "ld.ab r18, [sp, 4] \n\t" "ld.ab r17, [sp, 4] \n\t" "ld.ab r16, [sp, 4] \n\t" "ld.ab r15, [sp, 4] \n\t" "ld.ab r14, [sp, 4] \n\t" "ld.ab r13, [sp, 4] \n\t" /* last (ret value) = prev : although for ARC it mov r0, r0 */ "mov %0, %3 \n\t" /* FP/BLINK restore generated by gcc (standard func epilogue */ : "=r"(tmp) : "n"(KSP_WORD_OFF), "r"(next), "r"(prev) #ifdef CONFIG_ARC_PLAT_EZNPS , "i"(CTOP_AUX_LOGIC_GLOBAL_ID) #endif : "blink" ); return (struct task_struct *)tmp; }