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/**
* @file
* http://www.brokenthorn.com/Resources/OSDev18.html
* https://wiki.osdev.org/Memory_Map_(x86)
*
* Paging
* ======
*
* The Smallest Managable Unit is a Page containing 4096 (0x1000) bytes.
*
* A Page Directory holds 1024 tables each mapping 1024 pages, totaling
* in 0x100000000 bytes of addressable space (4gigs).
*
* The first 32megs will get ALWAYS identity mapped (hold kernel code/kernel stack etc)
* This are the first 8 page-tables
*
* Layout
* ======
*
* We are aiming for the following layout:
*
* 0xFFFFFFFF
* 0xC0000000 RESERVED
*
* 0xB0000000 User Stack TOP (Grows down) |
* env, argc, argv ... |
* | alltogether ~2.5gigs
* .......... User Heap (brk()) |
* 0x08000000 User Code |
* |
* | almost 100 megs (in kernel alloc/free?)
* |
* 0x02000000 FoolOS TSS Stack TOP (max ~8mb) GROWS DOWN
* leave few empty pages under stack as guard.
*
* 0x01800000 FoolOS Stack TOP (max ~8mb) GROWS DOWN
* leave few empty pages under stack as guard.
*
* 0x01000000
* 0x00EFFFFF RESERVED
* 0x00100000 FoolOS Kernel (max ~14mb)
* 0x00007BFF RESERVED
* 0x00007000 16-bit SMP entry (max ~3kb)
* 0x00000500
* 0x00000000 RESERVED
*
*/
//! i86 architecture defines 1024 entries per table--do not change
#define PAGES_PER_TABLE 1024
#define PAGES_PER_DIR 1024
#define PAGE_DIRECTORY_INDEX(x) (((x) >> 22) & 0x3ff)
#define PAGE_TABLE_INDEX(x) (((x) >> 12) & 0x3ff)
#define PAGE_GET_PHYSICAL_ADDRESS(x) (*x & ~0xfff)
//! page table represents 4mb address space
#define PTABLE_ADDR_SPACE_SIZE 0x400000
//! directory table represents 4gb address space
#define DTABLE_ADDR_SPACE_SIZE 0x100000000
//! page sizes are 4kb
#define PAGE_SIZE 4096
//! page table entry
typedef uint32_t pt_entry;
//! a page directery entry
typedef uint32_t pd_entry;
//! page table
typedef struct ptable_struct {
pt_entry m_entries[PAGES_PER_TABLE];
}ptable ;
//! page directory
typedef struct pdirectory_struct {
pd_entry m_entries[PAGES_PER_DIR];
}pdirectory;
pdirectory* vmem_init(uint32_t kernel_blocks,uint32_t fb_addr);
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