diff options
Diffstat (limited to 'arch/arc/kernel/ctx_sw.c')
| -rw-r--r-- | arch/arc/kernel/ctx_sw.c | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/arch/arc/kernel/ctx_sw.c b/arch/arc/kernel/ctx_sw.c new file mode 100644 index 0000000..647e37a --- /dev/null +++ b/arch/arc/kernel/ctx_sw.c @@ -0,0 +1,91 @@ +/* + * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * 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> + +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; + int num_words_to_skip = 1; + + __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" + "st.a r25, [sp, -4] \n\t" + "sub sp, sp, %4 \n\t" /* create gutter at top */ + + /* set ksp of outgoing task in tsk->thread.ksp */ + "st.as sp, [%3, %1] \n\t" + + "sync \n\t" + + /* + * 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) + */ + "st %2, [@_current_task] \n\t" + + /* get ksp of incoming task from tsk->thread.ksp */ + "ld.as sp, [%2, %1] \n\t" + + /* start loading it's CALLEE reg file */ + + "add sp, sp, %4 \n\t" /* skip gutter at top */ + + "ld.ab r25, [sp, 4] \n\t" + "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"((TASK_THREAD + THREAD_KSP) / 4), "r"(next), "r"(prev), + "n"(num_words_to_skip * 4) + : "blink" + ); + + return (struct task_struct *)tmp; +} |