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mm.c
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/*
* mm.c - Memory Management: Paging & segment memory management
*/
#include <types.h>
#include <mm.h>
#include <segment.h>
#include <hardware.h>
#include <sched.h>
Byte phys_mem[TOTAL_PAGES];
/* SEGMENTATION */
/* Memory segements description table */
Descriptor *gdt = (Descriptor *) GDT_START;
/* Register pointing to the memory segments table */
Register gdtR;
/* PAGING */
/* Variables containing the page directory and the page table */
page_table_entry dir_pages[NR_TASKS][TOTAL_PAGES]
__attribute__((__section__(".data.task")));
page_table_entry pagusr_table[NR_TASKS][TOTAL_PAGES]
__attribute__((__section__(".data.task")));
int dir_busy[NR_TASKS];
/* TSS */
TSS tss;
/***********************************************/
/************** PAGING MANAGEMENT **************/
/***********************************************/
/* Init page table directory */
void init_dir_pages()
{
int i;
for (i = 0; i< NR_TASKS; i++) {
dir_pages[i][ENTRY_DIR_PAGES].entry = 0;
dir_pages[i][ENTRY_DIR_PAGES].bits.pbase_addr = (((unsigned int)&pagusr_table[i]) >> 12);
dir_pages[i][ENTRY_DIR_PAGES].bits.user = 1;
dir_pages[i][ENTRY_DIR_PAGES].bits.rw = 1;
dir_pages[i][ENTRY_DIR_PAGES].bits.present = 1;
dir_busy[i] = 0;
}
}
/*
void init_dir_busy()
{
int i;
for (i = 0; i< NR_TASKS; i++) {
dir_busy[i][ENTRY_DIR_PAGES].entry = 0;
}
}*/
/* Initializes the page table (kernel pages only) */
void init_table_pages()
{
int i,j;
/* reset all entries */
for (j=0; j< NR_TASKS; j++) {
for (i=0; i<TOTAL_PAGES; i++)
{
pagusr_table[j][i].entry = 0;
}
/* Init kernel pages */
for (i=1; i<NUM_PAG_KERNEL; i++) // Leave the page inaccessible to comply with NULL convention
{
// Logical page equal to physical page (frame)
pagusr_table[j][i].bits.pbase_addr = i;
pagusr_table[j][i].bits.rw = 1;
pagusr_table[j][i].bits.present = 1;
}
/* Protect the task array by using a couple of invalid pages before and after the task array */
pagusr_table[j][PH_PAGE((DWord)(&protected_tasks[0]))].bits.present = 0;
pagusr_table[j][PH_PAGE((DWord)(&protected_tasks[11]))].bits.present = 0;
}
}
/* Initialize pages for initial process (user pages) */
void set_user_pages( struct task_struct *task )
{
int pag;
int new_ph_pag;
page_table_entry * process_PT = get_PT(task);
/* CODE */
for (pag=0;pag<NUM_PAG_CODE;pag++){
new_ph_pag=alloc_frame();
process_PT[PAG_LOG_INIT_CODE+pag].entry = 0;
process_PT[PAG_LOG_INIT_CODE+pag].bits.pbase_addr = new_ph_pag;
process_PT[PAG_LOG_INIT_CODE+pag].bits.user = 1;
process_PT[PAG_LOG_INIT_CODE+pag].bits.present = 1;
}
/* DATA */
for (pag=0;pag<NUM_PAG_DATA;pag++){
new_ph_pag=alloc_frame();
process_PT[PAG_LOG_INIT_DATA+pag].entry = 0;
process_PT[PAG_LOG_INIT_DATA+pag].bits.pbase_addr = new_ph_pag;
process_PT[PAG_LOG_INIT_DATA+pag].bits.user = 1;
process_PT[PAG_LOG_INIT_DATA+pag].bits.rw = 1;
process_PT[PAG_LOG_INIT_DATA+pag].bits.present = 1;
}
}
/* Writes on CR3 register producing a TLB flush */
void set_cr3(page_table_entry * dir)
{
asm volatile("movl %0,%%cr3": :"r" (dir));
}
/* Macros for reading/writing the CR0 register, where is shown the paging status */
#define read_cr0() ({ \
unsigned int __dummy; \
__asm__( \
"movl %%cr0,%0\n\t" \
:"=r" (__dummy)); \
__dummy; \
})
#define write_cr0(x) \
__asm__("movl %0,%%cr0": :"r" (x));
/* Enable paging, modifying the CR0 register */
void set_pe_flag()
{
unsigned int cr0 = read_cr0();
cr0 |= 0x80000000;
write_cr0(cr0);
}
/* Initializes paging for the system address space */
void init_mm()
{
init_table_pages();
init_frames();
init_dir_pages();
//init_dir_busy();
int pos = allocate_DIR(&task[0].task);
dir_busy[pos] = 0;
set_cr3(get_DIR(&task[0].task));
set_pe_flag();
}
/***********************************************/
/************** SEGMENTATION MANAGEMENT ********/
/***********************************************/
void setGdt()
{
/* Configure TSS base address, that wasn't initialized */
gdt[KERNEL_TSS>>3].lowBase = lowWord((DWord)&(tss));
gdt[KERNEL_TSS>>3].midBase = midByte((DWord)&(tss));
gdt[KERNEL_TSS>>3].highBase = highByte((DWord)&(tss));
gdtR.base = (DWord)gdt;
gdtR.limit = 256 * sizeof(Descriptor);
set_gdt_reg(&gdtR);
}
/***********************************************/
/************* TSS MANAGEMENT*******************/
/***********************************************/
void setTSS()
{
tss.PreviousTaskLink = NULL;
tss.esp0 = INITIAL_ESP;
tss.ss0 = __KERNEL_DS;
tss.esp1 = NULL;
tss.ss1 = NULL;
tss.esp2 = NULL;
tss.ss2 = NULL;
tss.cr3 = NULL;
tss.eip = 0;
tss.eFlags = INITIAL_EFLAGS; /* Enable interrupts */
tss.eax = NULL;
tss.ecx = NULL;
tss.edx = NULL;
tss.ebx = NULL;
tss.esp = USER_ESP;
tss.ebp = tss.esp;
tss.esi = NULL;
tss.edi = NULL;
tss.es = __USER_DS;
tss.cs = __USER_CS;
tss.ss = __USER_DS;
tss.ds = __USER_DS;
tss.fs = NULL;
tss.gs = NULL;
tss.LDTSegmentSelector = KERNEL_TSS;
tss.debugTrap = 0;
tss.IOMapBaseAddress = NULL;
set_task_reg(KERNEL_TSS);
}
/* Initializes the ByteMap of free physical pages.
* The kernel pages are marked as used */
int init_frames( void )
{
int i;
/* Mark pages as Free */
for (i=0; i<TOTAL_PAGES; i++) {
phys_mem[i] = FREE_FRAME;
}
/* Mark kernel pages as Used */
for (i=0; i<NUM_PAG_KERNEL; i++) {
phys_mem[i] = USED_FRAME;
}
return 0;
}
/* alloc_frame - Search a free physical page (== frame) and mark it as USED_FRAME.
* Returns the frame number or -1 if there isn't any frame available. */
int alloc_frame( void )
{
int i;
for (i=NUM_PAG_KERNEL; i<TOTAL_PAGES;) {
if (phys_mem[i] == FREE_FRAME) {
phys_mem[i] = USED_FRAME;
return i;
}
i += 2; /* NOTE: There will be holes! This is intended.
DO NOT MODIFY! */
}
return -1;
}
void free_user_pages( struct task_struct *task )
{
int pag;
page_table_entry * process_PT = get_PT(task);
/* DATA */
for (pag=0;pag<NUM_PAG_DATA;pag++){
free_frame(process_PT[PAG_LOG_INIT_DATA+pag].bits.pbase_addr);
process_PT[PAG_LOG_INIT_DATA+pag].entry = 0;
}
}
/* free_frame - Mark as FREE_FRAME the frame 'frame'.*/
void free_frame( unsigned int frame )
{
if ((frame>NUM_PAG_KERNEL)&&(frame<TOTAL_PAGES))
phys_mem[frame]=FREE_FRAME;
}
/* set_ss_pag - Associates logical page 'page' with physical page 'frame' */
void set_ss_pag(page_table_entry *PT, unsigned page,unsigned frame)
{
PT[page].entry=0;
PT[page].bits.pbase_addr=frame;
PT[page].bits.user=1;
PT[page].bits.rw=1;
PT[page].bits.present=1;
}
/* del_ss_pag - Removes mapping from logical page 'logical_page' */
void del_ss_pag(page_table_entry *PT, unsigned logical_page)
{
PT[logical_page].entry=0;
}
/* get_frame - Returns the physical frame associated to page 'logical_page' */
unsigned int get_frame (page_table_entry *PT, unsigned int logical_page){
return PT[logical_page].bits.pbase_addr;
}