diff options
Diffstat (limited to 'arch/hexagon/kernel/vm_switch.S')
| -rw-r--r-- | arch/hexagon/kernel/vm_switch.S | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/arch/hexagon/kernel/vm_switch.S b/arch/hexagon/kernel/vm_switch.S new file mode 100644 index 00000000000..0decf2f58e3 --- /dev/null +++ b/arch/hexagon/kernel/vm_switch.S @@ -0,0 +1,95 @@ +/* + * Context switch support for Hexagon + * + * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 and + * only version 2 as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +#include <asm/asm-offsets.h> + +.text + +/* + * The register used as a fast-path thread information pointer + * is determined as a kernel configuration option. If it happens + * to be a callee-save register, we're going to be saving and + * restoring it twice here. + * + * This code anticipates a revised ABI where R20-23 are added + * to the set of callee-save registers, but this should be + * backward compatible to legacy tools. + */ + + +/* + * void switch_to(struct task_struct *prev, + * struct task_struct *next, struct task_struct *last); + */ + .p2align 2 + .globl __switch_to + .type __switch_to, @function + +/* + * When we exit the wormhole, we need to store the previous task + * in the new R0's pointer. Technically it should be R2, but they should + * be the same; seems like a legacy thing. In short, don't butcher + * R0, let it go back out unmolested. + */ + +__switch_to: + /* + * Push callee-saves onto "prev" stack. + * Here, we're sneaky because the LR and FP + * storage of the thread_stack structure + * is automagically allocated by allocframe, + * so we pass struct size less 8. + */ + allocframe(#(_SWITCH_STACK_SIZE - 8)); + memd(R29+#(_SWITCH_R2726))=R27:26; + memd(R29+#(_SWITCH_R2524))=R25:24; + memd(R29+#(_SWITCH_R2322))=R23:22; + memd(R29+#(_SWITCH_R2120))=R21:20; + memd(R29+#(_SWITCH_R1918))=R19:18; + memd(R29+#(_SWITCH_R1716))=R17:16; + /* Stash thread_info pointer in task_struct */ + memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG; + memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29; + /* Switch to "next" stack and restore callee saves from there */ + R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)); + { + R27:26 = memd(R29+#(_SWITCH_R2726)); + R25:24 = memd(R29+#(_SWITCH_R2524)); + } + { + R23:22 = memd(R29+#(_SWITCH_R2322)); + R21:20 = memd(R29+#(_SWITCH_R2120)); + } + { + R19:18 = memd(R29+#(_SWITCH_R1918)); + R17:16 = memd(R29+#(_SWITCH_R1716)); + } + { + /* THREADINFO_REG is currently one of the callee-saved regs + * above, and so be sure to re-load it last. + */ + THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO); + R31:30 = memd(R29+#_SWITCH_FP); + } + { + R29 = add(R29,#_SWITCH_STACK_SIZE); + jumpr R31; + } + .size __switch_to, .-__switch_to |