reactos/boot/freeldr/freeldr/arch/realmode/amd64.S

   1
   2 #include <asm.inc>
   3 #include "../../include/arch/pc/x86common.h"
   4
   5 #define IMAGE_DOS_HEADER_e_lfanew 60
   6 #define IMAGE_FILE_HEADER_SIZE 20
   7 #define IMAGE_OPTIONAL_HEADER_AddressOfEntryPoint 16
   8
   9
  10 .code16
  11
  12 /* fat helper code */
  13 #include "fathelp.inc"
  14
  15 .org 512
  16 Startup:
  17
  18         cli
  19
  20         /* Setup real mode segment registers */
  21         xor ax, ax
  22         mov     ds, ax
  23         mov es, ax
  24         mov fs, ax
  25         mov     gs, ax
  26         mov ss, ax
  27
  28     /* Save the boot drive and partition */
  29     mov byte ptr ds:[BSS_BootDrive], dl
  30     mov byte ptr ds:[BSS_BootPartition], dh
  31
  32         /* Setup a real mode stack */
  33     mov sp, word ptr ds:[stack16]
  34
  35         /* Output first status */
  36         mov si, offset Msg_Starting
  37         call writestr
  38
  39     /* Enable A20 address line */
  40     call EnableA20
  41
  42     /* Check the CPU */
  43     call CheckFor64BitSupport
  44     test al, al
  45     jnz .LongModeSupported
  46
  47         /* Output failure message */
  48         mov si, offset Msg_Unsupported
  49         call writestr
  50
  51     /* Wait for a keypress */
  52     int HEX(16)
  53     jmp Reboot
  54
  55 Msg_Unsupported:
  56     .ascii "This CPU is not supported.", CR, LF
  57     .ascii "Press any key to reboot...", NUL
  58
  59 Msg_Starting:
  60         .ascii "Starting FreeLoader...", CR, LF, NUL
  61
  62 Msg_LongModeSupported:
  63     .ascii "Long mode support detected.", CR, LF, NUL
  64
  65 .LongModeSupported:
  66         /* Output status */
  67         mov si, offset Msg_LongModeSupported
  68         call writestr
  69
  70         /* Load the GDT */
  71         lgdt fword ptr [gdtptr]
  72
  73     /* Build the startup page tables */
  74         call BuildPageTables
  75
  76     /* Store real mode entry point in shared memory */
  77     mov dword ptr ds:[BSS_RealModeEntry], offset RealModeEntryPoint
  78
  79     /* Address the image with es segment */
  80     mov ax, FREELDR_PE_BASE / 16
  81     mov es, ax
  82
  83     /* Get address of optional header */
  84     mov eax, dword ptr es:[IMAGE_DOS_HEADER_e_lfanew]
  85     add eax, 4 + IMAGE_FILE_HEADER_SIZE
  86
  87     /* Get address of entry point */
  88     mov eax, dword ptr es:[eax + IMAGE_OPTIONAL_HEADER_AddressOfEntryPoint]
  89     add eax, FREELDR_PE_BASE
  90
  91     /* Save entry point */
  92     mov dword ptr ds:[LongModeEntryPoint], eax
  93
  94     /* Restore es */
  95     xor ax, ax
  96     mov es, ax
  97
  98         /* Output status */
  99         mov si, offset Msg_SwitchToLongMode
 100         call writestr
 101
 102     jmp ExitToLongMode
 103
 104 Msg_SwitchToLongMode:
 105     .ascii "Switching to long mode....", CR, LF, NUL
 106
 107 .align 8
 108 gdt:
 109         .word HEX(0000), HEX(0000), HEX(0000), HEX(0000) /* 00: NULL descriptor */
 110         .word HEX(0000), HEX(0000), HEX(0000), HEX(0000) /* 08:  */
 111         .word HEX(0000), HEX(0000), HEX(9800), HEX(0020) /* 10: long mode cs */
 112         .word HEX(ffff), HEX(0000), HEX(f300), HEX(00cf) /* 18: long mode ds */
 113         .word HEX(FFFF), HEX(0000), HEX(9E00), HEX(0000) /* 20: 16-bit real mode CS */
 114         .word HEX(FFFF), HEX(0000), HEX(9200), HEX(0000) /* 28: 16-bit real mode DS */
 115         .word HEX(FFFF), HEX(0000), HEX(9B00), HEX(00CF) /* 30: compat mode cs */
 116
 117 /* GDT table pointer */
 118 gdtptr:
 119         .word HEX(37) /* Limit */
 120         .long offset gdt   /* Base Address */
 121
 122
 123 CheckFor64BitSupport:
 124         /* Check if CPU supports CPUID */
 125         pushad
 126         pushfd
 127         pop eax
 128         mov ebx, eax
 129         xor eax, HEX(00200000)
 130         push eax
 131         popfd
 132         pushfd
 133         pop eax
 134         cmp eax,ebx
 135         jnz .CheckForPAE
 136
 137     mov si, offset .Msg_NoCpuidSupport
 138         call writestr
 139     popad
 140     xor al, al
 141     ret
 142
 143 .Msg_NoCpuidSupport:
 144     .ascii "The system doesn't support CPUID.", CR, LF, NUL
 145
 146 .CheckForPAE:
 147         /* CPUID support detected - getting the PAE/PGE */
 148         mov eax,1 // Fn0000_0001 - PAE in EDX[6]
 149         cpuid
 150         and edx, HEX(00a0)
 151         cmp edx, HEX(00a0)
 152         je .CheckForLongMode
 153
 154     mov si, offset .Msg_NoPAE
 155         call writestr
 156     popad
 157     xor al, al
 158     ret
 159
 160 .Msg_NoPAE:
 161     .ascii "PAE or PGE not set.", CR, LF, NUL
 162
 163 .CheckForLongMode:
 164         xor edx, edx
 165         mov eax, HEX(80000001)
 166         cpuid
 167         and edx, HEX(20000000)
 168         test edx,edx
 169         jnz .Success
 170
 171     mov si, offset .Msg_NoLongMode
 172         call writestr
 173     popad
 174     xor al, al
 175     ret
 176
 177 .Msg_NoLongMode:
 178     .ascii "Long mode is not supported.", CR, LF, NUL
 179
 180 .Success:
 181     popad
 182     xor al, al
 183     inc al
 184     ret
 185
 186
 187 BuildPageTables:
 188         pusha
 189         push es
 190
 191         /* Get segment of the PML4 */
 192         mov eax, PML4_ADDRESS / 16
 193         mov es, ax
 194         cld
 195         xor di, di
 196
 197         /* One entry in the PML4 pointing to PDP */
 198         mov eax, PDP_ADDRESS
 199         or eax, HEX(0f)
 200         stosd
 201
 202         /* clear rest */
 203         xor eax, eax
 204         mov cx, 1023
 205         rep stosd
 206
 207         /* One entry in the PDP pointing to PD */
 208         mov eax, PD_ADDRESS
 209         or eax, HEX(0f)
 210         stosd
 211
 212         /* clear rest */
 213         xor eax, eax
 214         mov ecx, 1023
 215         rep stosd
 216
 217         /* 512 entries in the PD, each defining a 2MB page each */
 218         mov ecx, 512
 219         mov eax, HEX(008f)
 220
 221 .Bpt2:
 222         mov es: [di], eax
 223         mov dword ptr es: [di + 4], 0
 224         add eax, 512 * 4096 // add 512 4k pages
 225         add di, 8
 226
 227         /* Loop all PDEs */
 228         dec cx
 229         jnz .Bpt2
 230
 231         /* Return */
 232         pop es
 233         popa
 234         ret
 235
 236
 237 /******************************************************************************/
 238
 239 #define MSR_EFER HEX(C0000080)
 240 #define LMODE_CS HEX(10)
 241
 242 /* This is the entry point from long mode */
 243 RealModeEntryPoint:
 244         /* Disable Protected Mode */
 245         mov eax, cr0
 246         and eax, HEX(0fffffffe) // ~0x00000001
 247         mov cr0, eax
 248
 249         /* Clear prefetch queue & correct CS */
 250         ljmp16 0, offset InRealMode
 251
 252 InRealMode:
 253
 254 //    mov ax, HEX(0b800)
 255 //    mov es, ax
 256 //    mov word ptr es:[12], HEX(0e00) + '6'
 257
 258     /* Set real mode segments */
 259     xor ax, ax
 260     mov ds, ax
 261     mov es, ax
 262     mov fs, ax
 263     mov gs, ax
 264     mov ss, ax
 265
 266     /* Clear out the high 16-bits of ESP */
 267     /* This is needed because I have one */
 268     /* machine that hangs when booted to dos if */
 269     /* anything other than 0x0000 is in the high */
 270     /* 16-bits of ESP. Even though real-mode */
 271     /* code should only use SP and not ESP. */
 272     xor esp, esp
 273
 274     /* Restore real mode stack */
 275     mov sp, word ptr ds:[stack16]
 276
 277    // sti /* These are ok now */
 278
 279     /* Do the callback, specified by bx */
 280     shl bx, 1
 281     call word ptr ds:CallbackTable[bx]
 282
 283 ExitToLongMode:
 284     /* Disable interrupts */
 285     cli
 286
 287     /* Set correct segment registers */
 288         xor     ax,ax
 289         mov     ds,ax
 290         mov     es,ax
 291         mov     fs,ax
 292         mov     gs,ax
 293         mov     ss,ax
 294
 295     /* Safe current stack pointer */
 296     mov word ptr ds:[stack16], sp
 297
 298     /* Set PAE and PGE: 10100000b */
 299         mov eax, HEX(00a0)
 300         mov cr4, eax
 301
 302     /* Point cr3 at the PML4 */
 303         mov eax, PML4_ADDRESS
 304         mov cr3, eax
 305
 306     /* Enable long mode */
 307         mov ecx, MSR_EFER
 308         rdmsr
 309         or eax, HEX(00000100)
 310         wrmsr
 311
 312     /* Activate long mode by enabling paging and protection simultaneously,
 313        skipping protected mode entirely */
 314         mov eax, cr0
 315         or eax, HEX(80000001)
 316         mov cr0, eax
 317
 318     /* Clear prefetch queue & correct CS */
 319     ljmp16 LMODE_CS, InLongMode
 320 InLongMode:
 321         //DB 66h, 0B8h, 18h, 00h // mov ax, LMODE_DS
 322         //DB 66h, 8Eh, 0D8h // mov ds, ax
 323         //DB 66h, 66h, 0C7h, 04h, 25h, 00h, 80h, 0Bh, 00h, 31h, 0Eh
 324         //mov word ptr [HEX(b8000)], HEX(0e00) + '1'
 325
 326     .byte HEX(0ff), HEX(25) // opcode of 64bit indirect jump
 327     .long 1 // relative address of LongModeEntryPoint
 328     nop
 329 LongModeEntryPoint:
 330     .long 0, 0
 331
 332     int HEX(16)
 333     jmp Reboot
 334
 335 CallbackTable:
 336     .word Int386
 337     .word Reboot
 338     .word ChainLoadBiosBootSectorCode
 339     .word PxeCallApi
 340     .word PnpBiosGetDeviceNodeCount
 341     .word PnpBiosGetDeviceNode
 342     .word 0 // BootLinuxKernel
 343
 344     /* 16-bit stack pointer */
 345 stack16:
 346     .word STACK16ADDR
 347
 348
 349 #include "int386.inc"
 350 #include "pxe.inc"
 351 #include "pnp.inc"
 352 #include "helpers.inc"
 353
 354 .org (FREELDR_PE_BASE - FREELDR_BASE - 1)
 355 .byte 0
 356 .endcode16
 357
 358 END