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#include"../include/types.h"
extern void loadPageDirectory(uint32_t*);
extern void enablePaging();
uint32_t page_directory[1024] __attribute__((aligned(4096)));
void set_pd()
{
//set each entry to not present
for(size_t i=0;i<1024;i++)
{
// This sets the following flags to the pages:
// Supervisor: Only kernel-mode can access them
// Write Enabled: It can be both read from and written to
// Not Present: The page table is not present
page_directory[i] = 0x00000002;
}
}
uint32_t page_table[1024][1024] __attribute__((aligned(4096)));
void set_pt(size_t num,uint32_t address)
{
// holds the physical address where we want to start mapping these pages to.
// in this case, we want to map these pages to the very beginning of memory.
//we will fill all 1024 entries in the table, mapping 4 megabytes
for(size_t i=0;i<1024;i++)
{
// As the address is page aligned, it will always leave 12 bits zeroed.
// Those bits are used by the attributes ;)
page_table[num][i] = (address + i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
}
page_directory[num] = ((uint32_t)page_table[num]) | 3;
// attributes: supervisor level, read/write, present
}
void set_paging()
{
set_pd();
for(size_t i=0;i<1024;i++) set_pt(i,0x00400000 * i); // all 4GB mapped
loadPageDirectory(page_directory);
enablePaging();
}
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