| Vineet Gupta | bf90e1e | 2013-01-18 15:12:18 +0530 | [diff] [blame^] | 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 | * -"C" version of lowest level context switch asm macro called by schedular |
| 10 | * gcc doesn't generate the dward CFI info for hand written asm, hence can't |
| 11 | * backtrace out of it (e.g. tasks sleeping in kernel). |
| 12 | * So we cheat a bit by writing almost similar code in inline-asm. |
| 13 | * -This is a hacky way of doing things, but there is no other simple way. |
| 14 | * I don't want/intend to extend unwinding code to understand raw asm |
| 15 | */ |
| 16 | |
| 17 | #include <asm/asm-offsets.h> |
| 18 | #include <linux/sched.h> |
| 19 | |
| 20 | struct task_struct *__sched |
| 21 | __switch_to(struct task_struct *prev_task, struct task_struct *next_task) |
| 22 | { |
| 23 | unsigned int tmp; |
| 24 | unsigned int prev = (unsigned int)prev_task; |
| 25 | unsigned int next = (unsigned int)next_task; |
| 26 | int num_words_to_skip = 1; |
| 27 | |
| 28 | __asm__ __volatile__( |
| 29 | /* FP/BLINK save generated by gcc (standard function prologue */ |
| 30 | "st.a r13, [sp, -4] \n\t" |
| 31 | "st.a r14, [sp, -4] \n\t" |
| 32 | "st.a r15, [sp, -4] \n\t" |
| 33 | "st.a r16, [sp, -4] \n\t" |
| 34 | "st.a r17, [sp, -4] \n\t" |
| 35 | "st.a r18, [sp, -4] \n\t" |
| 36 | "st.a r19, [sp, -4] \n\t" |
| 37 | "st.a r20, [sp, -4] \n\t" |
| 38 | "st.a r21, [sp, -4] \n\t" |
| 39 | "st.a r22, [sp, -4] \n\t" |
| 40 | "st.a r23, [sp, -4] \n\t" |
| 41 | "st.a r24, [sp, -4] \n\t" |
| 42 | "st.a r25, [sp, -4] \n\t" |
| 43 | "sub sp, sp, %4 \n\t" /* create gutter at top */ |
| 44 | |
| 45 | /* set ksp of outgoing task in tsk->thread.ksp */ |
| 46 | "st.as sp, [%3, %1] \n\t" |
| 47 | |
| 48 | "sync \n\t" |
| 49 | |
| 50 | /* |
| 51 | * setup _current_task with incoming tsk. |
| 52 | * optionally, set r25 to that as well |
| 53 | * For SMP extra work to get to &_current_task[cpu] |
| 54 | * (open coded SET_CURR_TASK_ON_CPU) |
| 55 | */ |
| 56 | "st %2, [@_current_task] \n\t" |
| 57 | |
| 58 | /* get ksp of incoming task from tsk->thread.ksp */ |
| 59 | "ld.as sp, [%2, %1] \n\t" |
| 60 | |
| 61 | /* start loading it's CALLEE reg file */ |
| 62 | |
| 63 | "add sp, sp, %4 \n\t" /* skip gutter at top */ |
| 64 | |
| 65 | "ld.ab r25, [sp, 4] \n\t" |
| 66 | "ld.ab r24, [sp, 4] \n\t" |
| 67 | "ld.ab r23, [sp, 4] \n\t" |
| 68 | "ld.ab r22, [sp, 4] \n\t" |
| 69 | "ld.ab r21, [sp, 4] \n\t" |
| 70 | "ld.ab r20, [sp, 4] \n\t" |
| 71 | "ld.ab r19, [sp, 4] \n\t" |
| 72 | "ld.ab r18, [sp, 4] \n\t" |
| 73 | "ld.ab r17, [sp, 4] \n\t" |
| 74 | "ld.ab r16, [sp, 4] \n\t" |
| 75 | "ld.ab r15, [sp, 4] \n\t" |
| 76 | "ld.ab r14, [sp, 4] \n\t" |
| 77 | "ld.ab r13, [sp, 4] \n\t" |
| 78 | |
| 79 | /* last (ret value) = prev : although for ARC it mov r0, r0 */ |
| 80 | "mov %0, %3 \n\t" |
| 81 | |
| 82 | /* FP/BLINK restore generated by gcc (standard func epilogue */ |
| 83 | |
| 84 | : "=r"(tmp) |
| 85 | : "n"((TASK_THREAD + THREAD_KSP) / 4), "r"(next), "r"(prev), |
| 86 | "n"(num_words_to_skip * 4) |
| 87 | : "blink" |
| 88 | ); |
| 89 | |
| 90 | return (struct task_struct *)tmp; |
| 91 | } |