eduOS/arch/x86/kernel/tasks.c

89 lines
3.2 KiB
C

/*
* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * 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 COPYRIGHT HOLDERS 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 REGENTS 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.
*/
#include <eduos/stdio.h>
#include <eduos/stdlib.h>
#include <eduos/string.h>
#include <eduos/tasks.h>
#include <eduos/errno.h>
#include <eduos/processor.h>
size_t* get_current_stack(void)
{
task_t* curr_task = current_task;
return curr_task->last_stack_pointer;
}
int create_default_frame(task_t* task, entry_point_t ep, void* arg)
{
size_t *stack;
struct state *stptr;
size_t state_size;
if (BUILTIN_EXPECT(!task, 0))
return -EINVAL;
if (BUILTIN_EXPECT(!task->stack, 0))
return -EINVAL;
memset(task->stack, 0xCD, KERNEL_STACK_SIZE);
/* The difference between setting up a task for SW-task-switching
* and not for HW-task-switching is setting up a stack and not a TSS.
* This is the stack which will be activated and popped off for iret later.
*/
stack = (size_t*) (task->stack + KERNEL_STACK_SIZE - 16); // => stack is 16byte aligned
/* Only marker for debugging purposes, ... */
*stack-- = 0xDEADBEEF;
/* the first-function-to-be-called's arguments, ... */
*stack-- = (size_t) arg;
/* and the "caller" we shall return to.
* This procedure cleans the task after exit. */
*stack = (size_t) leave_kernel_task;
/* Next bunch on the stack is the initial register state.
* The stack must look like the stack of a task which was
* scheduled away previously. */
state_size = sizeof(struct state);
stack = (size_t*) ((size_t) stack - state_size);
stptr = (struct state *) stack;
memset(stptr, 0x00, state_size);
stptr->esp = (size_t)stack + state_size;
stptr->eip = (size_t)ep;
stptr->eflags = 0x1202;
/* Set the task's stack pointer entry to the stack we have crafted right now. */
task->last_stack_pointer = (size_t*)stack;
return 0;
}