| /* |
| * 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/system.h> |
| #include <asm/asm-offsets.h> |
| #include <linux/sched.h> //__sched |
| |
| 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; |
| #ifdef CONFIG_ARCH_ARC_CURR_IN_REG |
| num_words_to_skip++; |
| #endif |
| |
| __asm__ __volatile__( |
| |
| // The fp, blink stashing is generated by gcc as part of standard |
| // function prelogue |
| |
| //-------------------------------- |
| "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_ARCH_ARC_CURR_IN_REG |
| "st.a r25, [sp, -4] \n\t" |
| #endif |
| "sub sp, sp, %4 \n\t" |
| |
| //-------------------------------- |
| "st.as sp, [%3, %1] \n\t" |
| |
| //-------------------------------- |
| "sync \n\t" |
| |
| //-------------------------------- |
| "st %2, [_current_task] \n\t" |
| #ifdef CONFIG_ARCH_ARC_CURR_IN_REG |
| "mov r25, %2 \n\t" |
| #endif |
| |
| //-------------------------------- |
| "ld.as sp, [%2, %1] \n\t" |
| |
| "add sp, sp, %4 \n\t" |
| //-------------------------------- |
| #ifndef CONFIG_ARCH_ARC_CURR_IN_REG |
| "ld.ab r25, [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 (return value) = prev (1st arg) |
| // (although for ARC it moves r0 to r0 |
| "mov %0, %3 \n\t" |
| |
| // Again fp, blink restoration is generated by gcc as part of standard |
| // function epilogie |
| |
| :"=r" (tmp) |
| :"n" ((TASK_THREAD + THREAD_KSP)/4), |
| "r" (next), |
| "r"(prev), |
| "n" (num_words_to_skip * 4) |
| :"blink" |
| ); |
| |
| return (struct task_struct *) tmp; |
| } |
