boot: Jump back to real mode to load sectors?
This commit is contained in:
K. Lange
parent
6ed0e72278
commit
a9b853d24c
178
boot/boot.S
178
boot/boot.S
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@ -73,16 +73,6 @@ can_long:
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jmp _oh_no
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good_memory:
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/* Print "Loading..." */
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movl $str_Loading, %esi
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call print_string
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/* Use BIOS disk reads to locate the kernel and ramdisk
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* and load them around the 2MB mark (by loading them
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* in smaller chunks and copying those up thanks to
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* our unreal mode %ds) */
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/* Ask for drive params */
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mov $0x48, %ah
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mov boot_disk, %dl
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@ -102,52 +92,7 @@ _oh_no:
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.extern _bss_start
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/* To load from the CD, we have 2048 byte sectors */
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boot_from_cd:
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movl $0x4000000, %ebx
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movl $0x0, dap_lba_low /* Sector 10h generally has our primary boot descriptor */
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movw $_bss_start, dap_buffer /* Load into root_data */
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/* Load one sector */
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load_one:
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mov $0x42, %ah /* Extended read */
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mov boot_disk, %dl /* Using our boot disk */
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mov $dap, %si /* From the DAP below */
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int $0x13
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cmp $0, %ah
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jnz done
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/* Move the sector up */
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movl $_bss_start, %esi
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movl %ebx, %edi
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xor %ecx, %ecx
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movw drive_params_bps, %cx
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addr32 rep movsb
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/* Increment */
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movl dap_lba_low, %ecx
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add $1, %ecx
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movl %ecx, dap_lba_low
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xor %ecx, %ecx
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movw drive_params_bps, %cx
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add %ecx, %ebx
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/* Update spinner */
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movl ind_Spinny, %ecx
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inc %ecx
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and $0x3FF, %ecx
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movl %ecx, ind_Spinny
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shr $8, %ecx
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movb str_Spinny(%ecx), %ah
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mov $0xb8016, %ecx
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movb %ah, (%ecx)
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jmp load_one
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done:
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/* The entire CD is now in memory at 64MiB, hopefully. */
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/* Collect information on lower memory. */
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mov $0x500, %ax
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mov %ax, %es
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@ -240,6 +185,100 @@ print_string.loop:
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print_string.exit:
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ret
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pm_stack:
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.quad 0
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.global do_bios_call
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do_bios_call:
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.code32
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/* Standard function entry point stuff */
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push %ebp
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mov %esp, %ebp
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push %ebx
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push %edi
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push %esi
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/* Save stack because bios might mess it up? */
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movl %esp, %eax
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movl %eax, (pm_stack)
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/* Prepare intermediary mode */
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mov $0x20, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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mov %ax, %ss
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/* Enable intermediary mode */
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ljmp $0x18,$do_bios_call.0
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do_bios_call.0:
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.code16
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/* Disable protected mode */
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mov %cr0, %eax
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and $~1, %eax
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mov %eax, %cr0
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/* Jump to deactivate protected mode */
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ljmp $0x0,$do_bios_call.1
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do_bios_call.1:
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/* Set up real mode segments */
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xor %ax, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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mov %ax, %ss
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/* Enable interrupts while BIOS is active */
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sti
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/* Perform disk read */
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mov $0x42, %ah /* Extended read */
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mov boot_disk, %dl /* Using our boot disk */
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mov $dap, %si /* From the DAP below */
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int $0x13
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/* Disable interrupts again */
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cli
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/* Restore data segment, gdt */
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xor %ax,%ax
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mov %ax, %ds
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lgdtw gdtr
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/* Enable protected mode */
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mov %cr0, %eax
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or $1, %eax
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mov %eax, %cr0
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/* Jump to activate protected mode */
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ljmp $0x08,$do_bios_call.2
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do_bios_call.2:
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.code32
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/* Restore protected mode data segments */
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mov $0x10, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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mov %ax, %ss
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/* Restore stack */
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movl (pm_stack), %eax
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movl %eax, %esp
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/* Pop callee-saved registers we may messed with */
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pop %esi
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pop %edi
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pop %ebx
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pop %ebp
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/* Return */
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ret
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.align 8
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gdtr:
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.word gdt_end - gdt_base - 1
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@ -253,12 +292,27 @@ gdt_base:
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.byte 0x9a
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.byte 0xcf
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.byte 0
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.word 0xffff
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.word 0
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.byte 0
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.byte 0x92
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.byte 0xcf
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.byte 0
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.word 0xffff
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.word 0
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.byte 0
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.byte 0x9e
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.byte 0
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.byte 0
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.word 0xffff
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.word 0
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.byte 0
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.byte 0x92
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.byte 0
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.byte 0
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gdt_end:
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.global boot_disk
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@ -286,8 +340,10 @@ dap_sectors:
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.global dap_buffer
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dap_buffer:
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.long 0x0
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.global dap_lba_low
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dap_lba_low:
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.long 0
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.global dap_lba_high
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dap_lba_high:
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.long 0
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@ -305,13 +361,13 @@ drive_params_bps:
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str_Bad:
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.asciz "The boot disk does not seem to be a CD."
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str_Loading:
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.asciz "Loading... "
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str_Need_long:
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.asciz "ToaruOS 2.0 requires a 64-bit processor."
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str_More_mem:
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.asciz "ToaruOS 2.0 needs at least 128MiB of RAM, and 1GiB is recommended."
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str_Spinny:
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.byte '|','/','-','\\'
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ind_Spinny:
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.long 0
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str_Out_of_modes:
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.asciz "Out of display modes"
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.global disk_space
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disk_space:
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.zero 2048
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@ -589,10 +589,26 @@ static void finish_boot(void) {
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);
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}
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extern int bios_call(char * into, uint32_t sector);
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static int spin_x = 0;
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static void spin(void) {
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static char spinchars[] = "/-\\|";
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static char tmp[] = "x";
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static int spincnt = 0;
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x = spin_x;
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spincnt = (spincnt + 1) & 0x3;
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tmp[0] = spinchars[spincnt];
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print_(tmp);
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}
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void boot(void) {
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clear_();
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print("Looking for ISO9660 filesystem... ");
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for (int i = 0x10; i < 0x15; ++i) {
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bios_call((char*)(DATA_LOAD_BASE + ISO_SECTOR_SIZE * i), i);
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root = (void*)(DATA_LOAD_BASE + ISO_SECTOR_SIZE * i);
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switch (root->type) {
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case 1:
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@ -612,6 +628,14 @@ done:
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kernel_load_start = (char*)(DATA_LOAD_BASE + dir_entry->extent_start_LSB * ISO_SECTOR_SIZE);
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print_("Loading kernel... "); spin_x = x;
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for (int i = 0, j = 0; i < dir_entry->extent_length_LSB; j++) {
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if (!(j & 0x3FF)) spin();
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bios_call(kernel_load_start + i, dir_entry->extent_start_LSB + j);
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i += ISO_SECTOR_SIZE;
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}
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print_("\n");
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print("Looking for ramdisk... ");
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if (!navigate(ramdisk_path)) {
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print_("Failed to locate ramdisk.\n");
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@ -620,6 +644,15 @@ done:
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print("found.\n");
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ramdisk_off = DATA_LOAD_BASE + dir_entry->extent_start_LSB * ISO_SECTOR_SIZE;
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print_("Loading ramdisk... "); spin_x = x;
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for (int i = 0, j = 0; i < dir_entry->extent_length_LSB; j++) {
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if (!(j & 0x3FF)) spin();
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bios_call((char*)(ramdisk_off + i), dir_entry->extent_start_LSB + j);
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i += ISO_SECTOR_SIZE;
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}
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print_("\n");
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ramdisk_len = dir_entry->extent_length_LSB;
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multiboot_header.cmdline = (uintptr_t)cmdline;
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@ -64,13 +64,31 @@ int bios_main(void) {
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return kmain();
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}
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extern void do_bios_call(void);
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extern volatile uint16_t dap_sectors;
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extern volatile uint32_t dap_buffer;
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extern volatile uint32_t dap_lba_low;
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extern volatile uint32_t dap_lba_high;
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extern uint8_t disk_space[];
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int bios_call(char * into, uint32_t sector) {
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dap_buffer = (uint32_t)disk_space;
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dap_lba_low = sector;
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dap_lba_high = 0;
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dap_sectors = 1;
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do_bios_call();
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memcpy(into, disk_space, 2048);
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}
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iso_9660_volume_descriptor_t * root = NULL;
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iso_9660_directory_entry_t * dir_entry = NULL;
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static char * dir_entries = NULL;
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int navigate(char * name) {
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dir_entry = (iso_9660_directory_entry_t*)&root->root;
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dir_entries = (char*)(DATA_LOAD_BASE + dir_entry->extent_start_LSB * ISO_SECTOR_SIZE);
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bios_call(dir_entries, dir_entry->extent_start_LSB);
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long offset = 0;
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while (1) {
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iso_9660_directory_entry_t * dir = (iso_9660_directory_entry_t *)(dir_entries + offset);
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