metalsvm/arch/x86/kernel/gdt.c
2011-08-02 15:58:20 +02:00

259 lines
8.3 KiB
C

/*
* Copyright 2010 Stefan Lankes, Chair for Operating Systems,
* RWTH Aachen University
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of MetalSVM.
*/
#include <metalsvm/string.h>
#include <metalsvm/stdlib.h>
#include <metalsvm/tasks.h>
#include <metalsvm/errno.h>
#include <metalsvm/processor.h>
#include <asm/gdt.h>
#include <asm/tss.h>
#include <asm/page.h>
gdt_ptr_t gp;
static tss_t task_state_segments[MAX_TASKS] __attribute__ ((aligned (PAGE_SIZE)));
static unsigned char kstacks[MAX_TASKS][KERNEL_STACK_SIZE] __attribute__ ((aligned (PAGE_SIZE), section (".data")));
// currently, our kernel has full access to the ioports
static gdt_entry_t gdt[GDT_ENTRIES] = {[0 ... GDT_ENTRIES-1] = {0, 0, 0, 0, 0, 0}};
unsigned char* default_stack_pointer __attribute__ ((section (".data"))) = kstacks[0] + KERNEL_STACK_SIZE - sizeof(size_t);
/*
* This is defined in entry.asm. We use this to properly reload
* the new segment registers
*/
extern void gdt_flush(void);
/*
* This is defined in entry.asm. We use this for a
* hardware-based task switch.
*/
extern void tss_switch(uint32_t id);
size_t get_stack(uint32_t id)
{
if (BUILTIN_EXPECT(id >= MAX_TASKS, 0))
return -EINVAL;
return (size_t) kstacks[id] + KERNEL_STACK_SIZE - sizeof(size_t);
}
int register_task(task_t* task) {
uint16_t sel;
uint32_t id = task->id;
if (BUILTIN_EXPECT(!task, 0))
return -EINVAL;
sel = (task->id+5) << 3;
asm volatile ("mov %0, %%ax; ltr %%ax" : : "ir"(sel) : "%eax");
// initialize the static elements of a TSS
task_state_segments[id].cr3 = (uint32_t) (task->pgd);
task_state_segments[id].ss0 = 0x10;
return 0;
}
int arch_fork(task_t* task)
{
uint16_t cs = 0x08;
uint16_t ds = 0x10;
uint32_t id;
task_t* curr_task = per_core(current_task);
if (BUILTIN_EXPECT(!task, 0))
return -EINVAL;
id = task->id;
// copy kernel stack of the current task
memcpy(kstacks[id], kstacks[curr_task->id], KERNEL_STACK_SIZE);
// reset TSS
memset(task_state_segments+id, 0x00, sizeof(tss_t));
// set default values of all registers
task_state_segments[id].cs = cs;
task_state_segments[id].ss = ds;
task_state_segments[id].ds = ds;
task_state_segments[id].fs = ds;
task_state_segments[id].gs = ds;
task_state_segments[id].es = ds;
task_state_segments[id].cr3 = (uint32_t) (virt_to_phys((size_t)task->pgd));
task_state_segments[id].ss0 = ds;
task_state_segments[id].esp0 = (uint32_t) kstacks[id] + KERNEL_STACK_SIZE - sizeof(size_t);
// save curret task context
asm volatile("mov %%esp, %0" : "=r"(task_state_segments[id].esp));
task_state_segments[id].esp -= (uint32_t) kstacks[curr_task->id];
task_state_segments[id].esp += (uint32_t) kstacks[id];
asm volatile ("pusha");
asm volatile ("pop %0" : "=r"(task_state_segments[id].edi));
asm volatile ("pop %0" : "=r"(task_state_segments[id].esi));
asm volatile ("pop %0" : "=r"(task_state_segments[id].ebp));
#ifdef WITH_FRAME_POINTER
task_state_segments[id].ebp -= (uint32_t) kstacks[curr_task->id];
task_state_segments[id].ebp += (uint32_t) kstacks[id];
#endif
asm volatile ("add $4, %%esp" ::: "%esp");
asm volatile ("pop %0" : "=r"(task_state_segments[id].ebx));
asm volatile ("pop %0" : "=r"(task_state_segments[id].edx));
asm volatile ("pop %0" : "=r"(task_state_segments[id].ecx));
asm volatile ("pop %0" : "=r"(task_state_segments[id].eax));
// store current EFLAGS and set IF flag
// => the parent task will enable the interrupt handling
asm volatile ("pushf; pop %%eax; or $2,%%ah" : "=a"(task_state_segments[id].eflags));
// This will be the entry point for the new task.
asm volatile ("call read_eip" : "=a"(task_state_segments[id].eip));
return 0;
}
int create_default_frame(task_t* task, internal_entry_point_t ep, void* arg)
{
uint16_t cs = 0x08;
uint16_t ds = 0x10;
uint32_t id;
if (BUILTIN_EXPECT(!task, 0))
return -EINVAL;
id = task->id;
/* reset buffers */
memset(task_state_segments+id, 0x00, sizeof(tss_t));
memset(kstacks[id], 0xCD, KERNEL_STACK_SIZE);
/* set default values of all registers */
task_state_segments[id].cs = cs;
task_state_segments[id].ss = ds;
task_state_segments[id].ds = ds;
task_state_segments[id].fs = ds;
task_state_segments[id].gs = ds;
task_state_segments[id].es = ds;
task_state_segments[id].eflags = 0x1202;
task_state_segments[id].cr3 = (uint32_t) (virt_to_phys((size_t)task->pgd));
task_state_segments[id].eip = (uint32_t) ep;
task_state_segments[id].esp = (uint32_t) kstacks[id] + KERNEL_STACK_SIZE - sizeof(size_t);
/* build default stack frame */
*((size_t*)task_state_segments[id].esp) = 0xDEADBEAF; /* dead-end */
task_state_segments[id].ebp = task_state_segments[id].esp;
task_state_segments[id].esp -= sizeof(size_t);
*((size_t*)task_state_segments[id].esp) = (size_t) arg;
task_state_segments[id].esp -= sizeof(size_t);
*((size_t*)task_state_segments[id].esp) = (size_t) leave_kernel_task;
/* setup for the kernel stack frame */
task_state_segments[id].ss0 = 0x10;
task_state_segments[id].esp0 = (uint32_t) kstacks[id] + KERNEL_STACK_SIZE - sizeof(size_t);
return 0;
}
/* Setup a descriptor in the Global Descriptor Table */
static void gdt_set_gate(int num, unsigned long base, unsigned long limit,
unsigned char access, unsigned char gran)
{
gdt[num] = configure_gdt_entry(base, limit, access, gran);
}
gdt_entry_t configure_gdt_entry(unsigned long base, unsigned long limit,
unsigned char access, unsigned char gran)
{
gdt_entry_t desc;
/* Setup the descriptor base address */
desc.base_low = (base & 0xFFFF);
desc.base_middle = (base >> 16) & 0xFF;
desc.base_high = (base >> 24) & 0xFF;
/* Setup the descriptor limits */
desc.limit_low = (limit & 0xFFFF);
desc.granularity = ((limit >> 16) & 0x0F);
/* Finally, set up the granularity and access flags */
desc.granularity |= (gran & 0xF0);
desc.access = access;
return desc;
}
/*
* This will setup the special GDT
* pointer, set up the entries in our GDT, and then
* finally call gdt_flush() in our assembler file in order
* to tell the processor where the new GDT is and update the
* new segment registers
*/
void gdt_install(void)
{
unsigned int i;
memset(task_state_segments, 0x00, MAX_TASKS*sizeof(tss_t));
/* Setup the GDT pointer and limit */
gp.limit = (sizeof(gdt_entry_t) * GDT_ENTRIES) - 1;
gp.base = (unsigned int) &gdt;
/* Our NULL descriptor */
gdt_set_gate(0, 0, 0, 0, 0);
/*
* The second entry is our Code Segment. The base address
* is 0, the limit is 4 GByte, it uses 4KByte granularity,
* uses 32-bit opcodes, and is a Code Segment descriptor.
*/
gdt_set_gate(1, 0, 0xFFFFFFFF,
GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT,
GDT_FLAG_4K_GRAN | GDT_FLAG_32_BIT);
/*
* The third entry is our Data Segment. It's EXACTLY the
* same as our code segment, but the descriptor type in
* this entry's access byte says it's a Data Segment
*/
gdt_set_gate(2, 0, 0xFFFFFFFF,
GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
GDT_FLAG_4K_GRAN | GDT_FLAG_32_BIT);
/*
* Create code segement for userspace applications (ring 3)
*/
gdt_set_gate(3, 0, 0xFFFFFFFF,
GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT,
GDT_FLAG_4K_GRAN | GDT_FLAG_32_BIT);
/*
* Create data segement for userspace applications (ring 3)
*/
gdt_set_gate(4, 0, 0xFFFFFFFF,
GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
GDT_FLAG_4K_GRAN | GDT_FLAG_32_BIT);
/*
* Create TSS for each task at ring0 (we use these segments for task switching)
*/
for(i=0; i<MAX_TASKS; i++) {
gdt_set_gate(5+i, (unsigned long) (task_state_segments+i), sizeof(tss_t)-1,
GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0,
GDT_FLAG_32_BIT);
}
/* Flush out the old GDT and install the new changes! */
gdt_flush();
}