boot/x86/stage3/loader.s

   1 bits 16
   2 cpu 686
   3
   4 extern enable_paging
   5 extern map_range
   6 extern set_up_page_directory
   7
   8 section .text
   9 %include "../fat32/fat32-structs.s"
  10
  11 %macro print 1
  12         push si
  13         mov si, %1
  14         call print_str
  15         pop si
  16 %endmacro
  17
  18 extern __STACK_BOTTOM__
  19
  20 global _start
  21 _start:
  22         mov sp, __STACK_BOTTOM__
  23         mov [BOOT_DRIVE], dl
  24         call enable_unreal
  25         print begin
  26         call check_a20
  27         jc .a20_enabled
  28         call enable_a20
  29         jnc .a20_enable_fail
  30 .a20_enabled:
  31         print a20_enabled
  32         call get_1st_data_sec
  33         mov ax, 0x1000
  34         mov es, ax
  35         mov eax, BPB_RootClus
  36         xor di, di
  37         call read_cluster_chain
  38         jc critical_error
  39
  40         push cx
  41         push si
  42 .find_kernel:
  43         mov si, kernel_name
  44         cmp byte [es:di], 0 ; end of root directory
  45         je .kernel_missing
  46         cmp byte [es:di], 0xe5 ; unused entry
  47         je .increment
  48         mov cx, 11
  49         push si
  50         push di
  51         repe cmpsb
  52         pop di
  53         pop si
  54         je .kernel_found
  55 .increment:
  56         add di, 32
  57         jno .find_kernel
  58         mov bx, es
  59         add bx, 0x1000
  60         mov es, bx
  61         jmp .find_kernel
  62 .kernel_found:
  63         pop si
  64         pop cx
  65         print kernel_found
  66         mov ax, [es:di+dir_entry.firstclushi]
  67         shl eax, 16
  68         mov ax, [es:di+(dir_entry.firstcluslo)]
  69         call print_dword
  70         mov edi, 0x100000
  71         print kernel_loading
  72         call read_clus_chain_unreal ; load kernel
  73         print kernel_loaded
  74
  75         call get_e820_map
  76         mov ebx, ecx
  77         mov eax, 24
  78         mul ecx
  79         add eax, 20
  80         sub sp, ax
  81
  82         cli
  83         lgdt [gdt]
  84         mov eax, cr0
  85         or al, 1
  86         mov cr0, eax
  87         jmp 0x8:in_protected
  88 .kernel_missing:
  89         print missing_kernel
  90         jmp .halt
  91
  92 .a20_enable_fail:
  93         print a20_fail
  94 .halt:
  95         hlt
  96         jmp $-1
  97
  98 ; eax - start cluster
  99 ; edi - address to load to
 100 read_clus_chain_unreal:
 101         push eax
 102         push edi
 103 .loop:
 104         push di
 105         push es
 106         push ax
 107         xor di, di
 108         mov ax, 0x1000
 109         mov es, ax
 110         pop ax
 111         call read_cluster
 112         pop es
 113         pop di
 114         jc .done
 115         push esi
 116         push eax
 117         push ebx
 118         push ecx
 119         mov esi, 0x10000
 120         xor ebx, ebx
 121         movzx eax, word BPB_BytsPerSec
 122         movzx bx, byte BPB_SecPerClus
 123         mul ebx
 124         mov ecx, eax
 125         call memcpy
 126         add edi, ecx
 127         pop ecx
 128         pop ebx
 129         pop eax
 130         pop esi
 131         cmp eax, 0xffffff7
 132         jl .loop
 133 .done:
 134         pop edi
 135         pop eax
 136         ret
 137
 138 ; esi - copy from
 139 ; edi - copy to
 140 ; ecx - bytes to copy
 141 memcpy:
 142         push esi
 143         push edi
 144         push ecx
 145         push dx
 146
 147 .loop:
 148         mov dl, [esi]
 149         mov [edi], dl
 150         dec ecx
 151         cmp ecx, 0
 152         je .done
 153         inc esi
 154         inc edi
 155         jmp .loop
 156 .done:
 157         pop dx
 158         pop ecx
 159         pop edi
 160         pop esi
 161         ret
 162
 163 %include "unreal.s"
 164 %include "a20.s"
 165 %include "../fat32/fat32.s"
 166 %include "gdt.s"
 167 %include "print.s"
 168 %include "e820.s"
 169
 170 bits 32
 171 section .text
 172 in_protected:
 173         mov ax, 0x10
 174         mov ds, ax
 175         mov es, ax
 176         mov ss, ax
 177         mov fs, ax
 178         mov gs, ax
 179
 180         push dword 0
 181         push 0xc0003000
 182         push 0xc0000000
 183         push 0x103000
 184         push 0x100000
 185         call map_range
 186         cmp eax, 0
 187         jne .error
 188         add esp, 20
 189         push dword 2
 190         push 0xc0009000
 191         push 0xc0003000
 192         push 0x109000
 193         push 0x103000
 194         call map_range
 195         cmp eax, 0
 196         jne .error
 197         add esp, 20
 198         push dword 2
 199         push 0x100000
 200         push dword 0
 201         push 0x100000
 202         push dword 0
 203         call map_range
 204         cmp eax, 0
 205         jne .error
 206         add esp, 20
 207
 208         call set_up_page_directory
 209         call enable_paging
 210
 211         jmp 0xc0000000
 212         nop
 213 .error:
 214         mov dword [0xb8000], 0xcf28cf3a
 215         hlt
 216         jmp $-1
 217
 218 section .rodata
 219
 220 kernel_name: db "KERNEL  BIN"
 221 begin: db "Nameless Bootloader revision ", GIT_REVISION, 0xd, 0xa, 0
 222 a20_enabled: db "A20 has been enabled", 0xd, 0xa, "Searching for kernel...", 0xd, 0xa, 0
 223 a20_fail: db "Failed to enable A20, giving up!", 0xd, 0xa, 0
 224 crit_err: db "A critical error occurred, dumping registers now: ", 0xd, 0xa, 0
 225 kernel_found: db "Found kernel at cluster ", 0
 226 kernel_loading: db 0xd, 0xa, "Loading kernel...", 0xd, 0xa, 0
 227 kernel_loaded: db "Kernel successfully loaded.", 0xd, 0xa, "Setting up kernel environment and running kernel...", 0xd, 0xa, 0
 228 missing_kernel: db "Could not find KERNEL.BIN", 0xd, 0xa, 0
 229 eax_s: db "EAX: ", 0
 230 ebx_s: db "EBX: ", 0
 231 ecx_s: db "ECX: ", 0
 232 edx_s: db "EDX: ", 0
 233 esi_s: db "ESI: ", 0
 234 edi_s: db "EDI: ", 0
 235 cs_s: db "CS: ", 0
 236 ds_s: db "DS: ", 0
 237 es_s: db "ES: ", 0
 238 ss_s: db "SS: ", 0
 239 space: db " ", 0
 240 hex_delm: db "0x", 0
 241 newline: db 0xd, 0xa, 0