docs: documents memory management

docs/config/Menu.txt

@@ -81,6 +81,8 @@ Group: Kernel  {
 
       }  # Group: Sys
 
+   File: vm.inc  (kernel/vm/vm.inc)
+   File: pmap.s  (kernel/vm/pmap.s)
    }  # Group: Kernel
 
 Group: Lib  {

docs/img/pmap_bootstrap.mmd

@@ -0,0 +1,89 @@
+---
+title: pmap_bootstrap
+---
+flowchart TD
+
+R_BEGIN("Begin")
+R_GETMMAP["Get Memory Map entry"]
+R_MMAP_LAST{"Last Item ?"}
+R_END("End")
+
+subgraph "entry to pmap_block"
+    C_BEGIN("Begin Proc")
+    C_IS_FREE{"Is
+    entry free?"}
+    C_END("End Proc")
+    C_OVERLAP_KERNEL{"entry
+    overlap
+    kernel?"}
+    C_REMOVE_KRESERVED["Remove Kernel
+    Memory from entry"]
+    C_MEMORY_SIZE_EXCEED{"Is entry size
+    larger than
+    0x0x7f80000 ?"}
+    C_MEMORY_SPLIT["Split entry"]
+    C_MEMORY_LAST["Is last ?"]
+
+    C_BEGIN-->C_IS_FREE
+    C_IS_FREE--No-->C_END
+    C_IS_FREE--Yes-->C_OVERLAP_KERNEL
+    C_OVERLAP_KERNEL--Yes-->C_REMOVE_KRESERVED
+    C_REMOVE_KRESERVED-->C_MEMORY_SIZE_EXCEED
+    C_OVERLAP_KERNEL--No-->C_MEMORY_SIZE_EXCEED
+    C_MEMORY_SIZE_EXCEED--Yes-->C_MEMORY_SPLIT
+    C_MEMORY_SPLIT-->C_MEMORY_LAST
+    C_MEMORY_LAST--Yes-->C_END
+
+end
+
+subgraph "create & store pmap_block"
+    D_BEGIN("Begin Proc")
+    D_BOOSTRAP_EXIST{"Bootstrap
+    pmap_block
+    exist?"}
+    D_SETUP_BOOTSTRAP["Setup bootstrap pmap"]
+    D_END("End Proc")
+    D_SET_HEAD_BOOTSTRAP["Set bootstrap as Head"]
+    D_SEARCH_FREE_PAGE["Search free page in Head->bitmap"]
+    D_FREE_PAGE_FOUND{"Free Page found ?"}
+    D_HEAD_NEXT_NULL{"Head->next == NULL?"}
+    D_HEAD_NEXT["Set Head to Head->next"]
+    D_CREATE_PMAP["Create new pmap_block
+    in free page"]
+    D_APPEND_PMAP["Append pmap_block
+    at end of
+    linked list"]
+
+    D_BEGIN-->D_BOOSTRAP_EXIST
+    D_BOOSTRAP_EXIST--No-->D_SETUP_BOOTSTRAP
+    D_SETUP_BOOTSTRAP-->D_END
+    D_BOOSTRAP_EXIST--Yes-->D_SET_HEAD_BOOTSTRAP
+    D_SET_HEAD_BOOTSTRAP-->D_SEARCH_FREE_PAGE
+    D_SEARCH_FREE_PAGE-->D_FREE_PAGE_FOUND
+    D_FREE_PAGE_FOUND--No-->D_HEAD_NEXT_NULL
+    D_HEAD_NEXT_NULL--No-->D_HEAD_NEXT
+    D_HEAD_NEXT-->D_SEARCH_FREE_PAGE
+    D_FREE_PAGE_FOUND--Yes-->D_CREATE_PMAP
+    D_CREATE_PMAP-->D_APPEND_PMAP
+    D_APPEND_PMAP-->D_END
+end
+
+R_BEGIN-->R_GETMMAP
+R_GETMMAP-->R_MMAP_LAST
+R_MMAP_LAST--Yes-->R_END
+
+R_MMAP_LAST--No-->C_BEGIN
+C_MEMORY_SIZE_EXCEED--No-->D_BEGIN
+D_END--Try get next-->C_MEMORY_LAST
+C_MEMORY_LAST--No-->D_BEGIN
+C_END--Try get next entry-->R_MMAP_LAST
+
+
+style R_BEGIN fill:#6CA300
+style R_END fill:#A30000
+
+style C_BEGIN fill:#6CA300
+style C_END fill:#A30000
+
+style D_BEGIN fill:#6CA300
+style D_END fill:#A30000

kernel/Makefile

@@ -7,4 +7,4 @@ INCS	= sys/multiboot.inc \
 			sys/i386/registers.inc
 
 include $(TOPDIR)/share/mk/stupid.kernel.mk
-include $(TOPDIR)/share/mk/stupid.inc.mk
+#include $(TOPDIR)/share/mk/stupid.inc.mk

kernel/sys/i386/mmu.inc

@@ -1,7 +1,46 @@
 	;; File: mmu.inc
+	;;
+	;; About: Address Translation
+	;;
+	;; Since we don't use segmentation, this is how address translation works
+	;; > 31       21       11       0
+	;; > +--------+--------+--------+
+	;; > |   DIR  |  PAGE  | OFFSET |
+	;; > +--------+--------+--------+
+	;; >               |
+	;; >               v
+	;; >         Page Translation
+	;; >               |
+	;; > 31            v            0
+	;; > +--------------------------+
+	;; > |     Pyshical address     |
+	;; > +--------------------------+
+	;;
+	;; About: Page Translation
+	;;
+	;; > +--------+--------+--------+             +--------+
+	;; > |   DIR  |  PAGE  | OFFSET |-----+       |  Phys  |
+	;; > +--------+--------+--------+     +------>|  addr  |
+	;; >   |             |                        |        |
+	;; >   |             +----+                   +--------+
+	;; >   |   Page Dir       |             +---> Page Frame
+	;; >   |  +---------+     |  +--------+ |
+	;; >   |  |         |     |  |        | |
+	;; >   +->| PDE     |-+   +->| PTE    |-+
+	;; >      |         | |      |        |
+	;; >      +---------+ |      +--------+
+	;; >                  +----> Page Table
+	;; >
+	;;
 
+	;; Macro: V2P(addr)
+	;; Convert Kernel Address to Physical Address
 %define V2P(addr)   (addr - KERNBASE)
+
+	;; Macro: P2V(addr)
+	;; Convert Physical Address to Kernel Address
 %define P2V(addr)   (addr + KERNBASE)
+
 %define P2PDE(addr) ((addr >> 22) & 0x3FF)
 %define PDE2P(addr) (addr << 22)
 %define P2PTE(addr) ((addr >> 12) & 0x3FF)
@@ -26,8 +65,8 @@ PDE_G   equ 1 << 8
 	;; PTE_PCD - Cache Disable
 	;; PTE_A   - Accessed
 	;; PTE_D   - Dirty
-	;; PTE_PAT -
+	;; PTE_PAT - TODO
-	;; PTE_G   -
+	;; PTE_G   - TODO
 PTE_P   equ 1 << 0
 PTE_W   equ 1 << 1
 PTE_U   equ 1 << 2

kernel/vm/pmap.s

@@ -0,0 +1,46 @@
+	;; File: pmap.s
+	;; Physical Memory Map
+
+	;; Structure: pmap_block
+	;; 
+	;; .next        - pointer to next pmap_block struct
+	;; .phys_start  - start physical address of memory range
+	;; .phys_end    - stop address of memory range
+	;; .bitmap_size - bitmap size (max: 0xFF0)
+	;; .last_alloc  - last allocated frame in bitmap
+	;; .bitmap      - bitmap array
+	;;
+	;; >          pmap_block
+	;; > 0x0000 +-------------+
+	;; >        | next        |-----> pmap_block
+	;; > 0x0004 +-------------+       +----------+
+	;; >        | phys start  |       | next     |----> NULL (0x0)
+	;; > 0x0008 +-------------+       +----------+
+	;; >        | phys end    |       | .....    |
+	;; > 0x000C +-------------+       | .....    |
+	;; >        | bitmap size |       | .....    |
+	;; > 0x000e +-------------+       +----------+
+	;; >        | last alloc  |
+	;; > 0x0010 +-------------+
+	;; >        | bitmap      |
+	;; > 0x???? +-------------+ (bitmap size * 4)
+	;;
+struct pmap_block
+	.next:        resd 1
+	.phys_start:  resd 1
+	.phys_end:    resd 1
+	.bitmap_size: resw 1
+	.last_alloc:  resw 1
+	.bitmap:
+endstruc
+
+section .text
+	;; Function: pmap_bootstrap
+	;;
+	;; (see pmap_bootstrap.png)
+pmap_bootstrap:
+	push esp
+	mov esp, ebp
+
+	leave
+	ret

kernel/vm/vm.inc

@@ -0,0 +1,60 @@
+	;; File: vm.inc
+	;; Stupid OS virtual Memory manager
+	;;
+	;; About: Memory Management
+	;;
+	;; Terminology:
+	;; VA  - Virtual Address
+	;; PA  - Physical Address
+	;; PDE - Page Directory Entry
+	;; PTE - Page Table Entry
+	;;
+	;; Memory Layout:
+	;;
+	;; Virtual Memory above `0xC0000000` is mapped as kernel only <PTE_U> flags
+	;;
+	;; >                 Virtual
+	;; > 0xFFFFFFFF +---------------+
+	;; >            |               |
+	;; >            | Device Memory |
+	;; >            |               |
+	;; >            +---------------+
+	;; >            |               |
+	;; >            | Kernel Heap   |
+	;; >            |               |
+	;; >   KERN_END +---------------+
+	;; >            |               |
+	;; >            | Stupid Kernel |
+	;; >            |               |
+	;; > 0xC0100000 +---------------+
+	;; >            | I/O Space and |
+	;; >            | phys memory   |
+	;; >            | Lower than 1M | kernel mode only
+	;; > 0xC0000000 +---------------+
+	;; >            |               | user mode
+	;; >            |  userspace    |
+	;; >            |               |
+	;; > 0x00000000 +---------------+
+	;;
+	;; Page Frame Allocator
+	;;
+%define K2P(addr) (addr - KERNBASE)
+%define P2K(addr) (addr + KERNBASE)
+
+struc vm_kmap
+	.virt: resd 1
+	.phys_start: resd 1
+	.phys_stop:  resd 1
+	.access: resb 1
+endstruc
+
+struc vm_map
+	.pmap: resd 1
+
+endstruc
+
+struc
+	.directory: resd 1
+	.ref_count: resd 1
+	
+endstruc