/* * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009 * The President and Fellows of Harvard College. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Assembly language context switch code. */ #include <kern/mips/regdefs.h> .text .set noreorder .globl switchframe_switch .type switchframe_switch,@function .ent switchframe_switch switchframe_switch: /* * a0 contains the address of the switchframe pointer in the old thread. * a1 contains the address of the switchframe pointer in the new thread. * * The switchframe pointer is really the stack pointer. The other * registers get saved on the stack, namely: * * s0-s6, s8 * gp, ra * * The order must match <mips/switchframe.h>. * * Note that while we'd ordinarily need to save s7 too, because we * use it to hold curthread saving it would interfere with the way * curthread is managed by thread.c. So we'll just let thread.c * manage it. */ /* Allocate stack space for saving 10 registers. 10*4 = 40 */ addi sp, sp, -40 /* Save the registers */ sw ra, 36(sp) sw gp, 32(sp) sw s8, 28(sp) sw s6, 24(sp) sw s5, 20(sp) sw s4, 16(sp) sw s3, 12(sp) sw s2, 8(sp) sw s1, 4(sp) sw s0, 0(sp) /* Store the old stack pointer in the old thread */ sw sp, 0(a0) /* Get the new stack pointer from the new thread */ lw sp, 0(a1) nop /* delay slot for load */ /* Now, restore the registers */ lw s0, 0(sp) lw s1, 4(sp) lw s2, 8(sp) lw s3, 12(sp) lw s4, 16(sp) lw s5, 20(sp) lw s6, 24(sp) lw s8, 28(sp) lw gp, 32(sp) lw ra, 36(sp) nop /* delay slot for load */ /* and return. */ j ra addi sp, sp, 40 /* in delay slot */ .end switchframe_switch