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Switching VGA mode with GRUB https://forum.osdev.org/viewtopic.php?f=15&t=31521 |
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Author: | readlnh [ Tue Apr 11, 2017 11:31 am ] |
Post subject: | Switching VGA mode with GRUB |
hi everyone I want to switch to the VGA graphic mode. For this I will use GRUB.I switch back to Real Mode for setting the graphic video mode, but I meet a few problems,it just reboots back to GRUB in qemu i use the code from http://www.rohitab.com/discuss/topic/35 ... -mode/,but seems it dosen't work well. here is my code: Code: MBOOT_HEADER_MAGIC equ 0x1BADB002 MBOOT_PAGE_ALIGN equ 1 << 0 MBOOT_MEM_INFO equ 1 << 1 ;MBOOT_GRAPH_MODE equ 1 << 2 MBOOT_HEADER_FLAGS equ MBOOT_PAGE_ALIGN | MBOOT_MEM_INFO ;| MBOOT_GRAPH_MODE MBOOT_CHECKSUM equ -(MBOOT_HEADER_MAGIC + MBOOT_HEADER_FLAGS) ;magic flags checksum (magic + flags + checksum = 0) [BITS 32] section .text dd MBOOT_HEADER_MAGIC dd MBOOT_HEADER_FLAGS dd MBOOT_CHECKSUM ;dd 0 ;dd 0 ;dd 0 ;dd 0 ;dd 0 ;dd 0 ;dd 640 ;dd 480 ;dd 16 [GLOBAL start] [GLOBAL glb_mboot_ptr] [EXTERN kern_entry] start: cli mov esp, STACK_TOP mov ebp, 0 and esp, 0FFFFFFF0H mov [glb_mboot_ptr] , ebx call kern_entry stop: hlt jmp stop section .bss stack: resb 32768 glb_mboot_ptr: resb 4 STACK_TOP equ $ - stack - 1 Code: // define our structure typedef struct __attribute__ ((packed)) { unsigned short di, si, bp, sp, bx, dx, cx, ax; unsigned short gs, fs, es, ds, eflags; } regs16_t; // tell compiler our int32 function is external extern void int32(unsigned char intnum, regs16_t *regs); // int32 test void int32_test() { int y; regs16_t regs; // switch to 320x200x256 graphics mode regs.ax = 0x0013; int32(0x10, ®s); // full screen with blue color (1) //memset((char *)0xA0000, 0xff, (320*200)); // draw horizontal line from 100,80 to 100,240 in multiple colors //for(y = 0; y < 200; y++) // memset((char *)0xA0000 + (y*320+80), y, 160); // wait for key /*regs.ax = 0x0000; int32(0x16, ®s);*/ // switch to 80x25x16 text mode //regs.ax = 0x0003; //int32(0x10, ®s); } int kern_entry() { //regs16_t regs; //regs.ax = 0x0013; //int32(0x10, ®s); int32_test(); char* p; int i; for(i = 0xA0000; i < 0xAFFFF; i++) { p = (char*)i; *p = 0xff; } return 0; } Code: ; ; Protected Mode BIOS Call Functionailty v2.0 - by Napalm ; ------------------------------------------------------- ; ; This is code shows how its POSSIBLE to execute BIOS interrupts ; by switch out to real-mode and then back into protected mode. ; ; If you wish to use all or part of this code you must agree ; to the license at the following URL. ; ; License: http://creativecommons.org/licenses/by-sa/2.0/uk/ ; ; Notes: This file is in NASM syntax. ; Turn off paging before calling these functions. ; int32() resets all selectors. ; ; C Prototype: ; void _cdelc int32(unsigned char intnum, regs16_t *regs); ; ; Example of usage: ; regs.ax = 0x0013; ; int32(0x10, ®s); ; memset((char *)0xA0000, 1, (320*200)); ; memset((char *)0xA0000 + (100*320+80), 14, 80); ; regs.ax = 0x0000; ; int32(0x16, ®s); ; regs.ax = 0x0003; ; int32(0x10, ®s); ; ; [bits 32] global int32, _int32 struc regs16_t .di resw 1 .si resw 1 .bp resw 1 .sp resw 1 .bx resw 1 .dx resw 1 .cx resw 1 .ax resw 1 .gs resw 1 .fs resw 1 .es resw 1 .ds resw 1 .ef resw 1 endstruc %define INT32_BASE 0x7C00 %define REBASE(x) (((x) - reloc) + INT32_BASE) %define GDTENTRY(x) ((x) << 3) %define CODE32 GDTENTRY(1) ; 0x08 %define DATA32 GDTENTRY(2) ; 0x10 %define CODE16 GDTENTRY(3) ; 0x18 %define DATA16 GDTENTRY(4) ; 0x20 %define STACK16 (INT32_BASE - regs16_t_size) section .text int32: use32 ; by Napalm _int32: cli ; disable interrupts pusha ; save register state to 32bit stack mov esi, reloc ; set source to code below mov edi, INT32_BASE ; set destination to new base address mov ecx, (int32_end - reloc) ; set copy size to our codes size cld ; clear direction flag (so we copy forward) rep movsb ; do the actual copy (relocate code to low 16bit space) jmp INT32_BASE ; jump to new code location reloc: use32 ; by Napalm mov [REBASE(stack32_ptr)], esp ; save 32bit stack pointer sidt [REBASE(idt32_ptr)] ; save 32bit idt pointer sgdt [REBASE(gdt32_ptr)] ; save 32bit gdt pointer lgdt [REBASE(gdt16_ptr)] ; load 16bit gdt pointer lea esi, [esp+0x24] ; set position of intnum on 32bit stack lodsd ; read intnum into eax mov [REBASE(ib)], al ; set intrrupt immediate byte from our arguments mov esi, [esi] ; read regs pointer in esi as source mov edi, STACK16 ; set destination to 16bit stack mov ecx, regs16_t_size ; set copy size to our struct size mov esp, edi ; save destination to as 16bit stack offset rep movsb ; do the actual copy (32bit stack to 16bit stack) jmp word CODE16:REBASE(p_mode16) ; switch to 16bit selector (16bit protected mode) p_mode16: use16 mov ax, DATA16 ; get our 16bit data selector mov ds, ax ; set ds to 16bit selector mov es, ax ; set es to 16bit selector mov fs, ax ; set fs to 16bit selector mov gs, ax ; set gs to 16bit selector mov ss, ax ; set ss to 16bit selector mov eax, cr0 ; get cr0 so we can modify it and al, ~0x01 ; mask off PE bit to turn off protected mode mov cr0, eax ; set cr0 to result jmp word 0x0000:REBASE(r_mode16) ; finally set cs:ip to enter real-mode r_mode16: use16 xor ax, ax ; set ax to zero mov ds, ax ; set ds so we can access idt16 mov ss, ax ; set ss so they the stack is valid lidt [REBASE(idt16_ptr)] ; load 16bit idt mov bx, 0x0870 ; master 8 and slave 112 call resetpic ; set pic's the to real-mode settings popa ; load general purpose registers from 16bit stack pop gs ; load gs from 16bit stack pop fs ; load fs from 16bit stack pop es ; load es from 16bit stack pop ds ; load ds from 16bit stack sti ; enable interrupts db 0xCD ; opcode of INT instruction with immediate byte ib: db 0x00 cli ; disable interrupts xor sp, sp ; zero sp so we can reuse it mov ss, sp ; set ss so the stack is valid mov sp, INT32_BASE ; set correct stack position so we can copy back pushf ; save eflags to 16bit stack push ds ; save ds to 16bit stack push es ; save es to 16bit stack push fs ; save fs to 16bit stack push gs ; save gs to 16bit stack pusha ; save general purpose registers to 16bit stack mov bx, 0x2028 ; master 32 and slave 40 call resetpic ; restore the pic's to protected mode settings mov eax, cr0 ; get cr0 so we can modify it inc eax ; set PE bit to turn on protected mode mov cr0, eax ; set cr0 to result jmp dword CODE32:REBASE(p_mode32) ; switch to 32bit selector (32bit protected mode) p_mode32: use32 mov ax, DATA32 ; get our 32bit data selector mov ds, ax ; reset ds selector mov es, ax ; reset es selector mov fs, ax ; reset fs selector mov gs, ax ; reset gs selector mov ss, ax ; reset ss selector lgdt [REBASE(gdt32_ptr)] ; restore 32bit gdt pointer lidt [REBASE(idt32_ptr)] ; restore 32bit idt pointer mov esp, [REBASE(stack32_ptr)] ; restore 32bit stack pointer mov esi, STACK16 ; set copy source to 16bit stack lea edi, [esp+0x28] ; set position of regs pointer on 32bit stack mov edi, [edi] ; use regs pointer in edi as copy destination mov ecx, regs16_t_size ; set copy size to our struct size cld ; clear direction flag (so we copy forward) rep movsb ; do the actual copy (16bit stack to 32bit stack) popa ; restore registers sti ; enable interrupts ret ; return to caller resetpic: ; reset's 8259 master and slave pic vectors push ax ; expects bh = master vector, bl = slave vector mov al, 0x11 ; 0x11 = ICW1_INIT | ICW1_ICW4 out 0x20, al ; send ICW1 to master pic out 0xA0, al ; send ICW1 to slave pic mov al, bh ; get master pic vector param out 0x21, al ; send ICW2 aka vector to master pic mov al, bl ; get slave pic vector param out 0xA1, al ; send ICW2 aka vector to slave pic mov al, 0x04 ; 0x04 = set slave to IRQ2 out 0x21, al ; send ICW3 to master pic shr al, 1 ; 0x02 = tell slave its on IRQ2 of master out 0xA1, al ; send ICW3 to slave pic shr al, 1 ; 0x01 = ICW4_8086 out 0x21, al ; send ICW4 to master pic out 0xA1, al ; send ICW4 to slave pic pop ax ; restore ax from stack ret ; return to caller stack32_ptr: ; address in 32bit stack after we dd 0x00000000 ; save all general purpose registers idt32_ptr: ; IDT table pointer for 32bit access dw 0x0000 ; table limit (size) dd 0x00000000 ; table base address gdt32_ptr: ; GDT table pointer for 32bit access dw 0x0000 ; table limit (size) dd 0x00000000 ; table base address idt16_ptr: ; IDT table pointer for 16bit access dw 0x03FF ; table limit (size) dd 0x00000000 ; table base address gdt16_base: ; GDT descriptor table .null: ; 0x00 - null segment descriptor dd 0x00000000 ; must be left zero'd dd 0x00000000 ; must be left zero'd .code32: ; 0x01 - 32bit code segment descriptor 0xFFFFFFFF dw 0xFFFF ; limit 0:15 dw 0x0000 ; base 0:15 db 0x00 ; base 16:23 db 0x9A ; present, iopl/0, code, execute/read db 0xCF ; 4Kbyte granularity, 32bit selector; limit 16:19 db 0x00 ; base 24:31 .data32: ; 0x02 - 32bit data segment descriptor 0xFFFFFFFF dw 0xFFFF ; limit 0:15 dw 0x0000 ; base 0:15 db 0x00 ; base 16:23 db 0x92 ; present, iopl/0, data, read/write db 0xCF ; 4Kbyte granularity, 32bit selector; limit 16:19 db 0x00 ; base 24:31 .code16: ; 0x03 - 16bit code segment descriptor 0x000FFFFF dw 0xFFFF ; limit 0:15 dw 0x0000 ; base 0:15 db 0x00 ; base 16:23 db 0x9A ; present, iopl/0, code, execute/read db 0x0F ; 1Byte granularity, 16bit selector; limit 16:19 db 0x00 ; base 24:31 .data16: ; 0x04 - 16bit data segment descriptor 0x000FFFFF dw 0xFFFF ; limit 0:15 dw 0x0000 ; base 0:15 db 0x00 ; base 16:23 db 0x92 ; present, iopl/0, data, read/write db 0x0F ; 1Byte granularity, 16bit selector; limit 16:19 db 0x00 ; base 24:31 gdt16_ptr: ; GDT table pointer for 16bit access dw gdt16_ptr - gdt16_base - 1 ; table limit (size) dd gdt16_base ; table base address int32_end: ; end marker (so we can copy the code) can somenoe give me some advice? Sorry for my poor English |
Author: | obiwac [ Tue Apr 11, 2017 1:08 pm ] |
Post subject: | Re: Switching VGA mode with GRUB |
First off, uncomment all the Code: dd lines at the beginning. These are the flags that pass the graphics mode information to grub, so that it can set your graphics mode before putting you into protected mode (more info: https://www.gnu.org/software/grub/manual/multiboot/multiboot.html). Then, just before Code: call kern_entry , push ebx to the stack with Code: push ebx . You don't need to switch back to real mode. Then, to draw on the screen, you need to get the framebuffer pointer (in the grub command line, type the Code: lspci -i , and under VGA, get the last eight digits of the hex string), and you can start modifying the screen straight away!Example: Code: MBOOT_HEADER_MAGIC equ 0x1BADB002 MBOOT_PAGE_ALIGN equ 1 << 0 MBOOT_MEM_INFO equ 1 << 1 ;MBOOT_GRAPH_MODE equ 1 << 2 MBOOT_HEADER_FLAGS equ MBOOT_PAGE_ALIGN | MBOOT_MEM_INFO ;| MBOOT_GRAPH_MODE MBOOT_CHECKSUM equ -(MBOOT_HEADER_MAGIC + MBOOT_HEADER_FLAGS) ;magic flags checksum (magic + flags + checksum = 0) [BITS 32] section .text dd MBOOT_HEADER_MAGIC dd MBOOT_HEADER_FLAGS dd MBOOT_CHECKSUM dd 0 dd 0 dd 0 dd 0 dd 0 dd 0 dd 800 ; width dd 600 ; height dd 32 ; bpp [GLOBAL start] [GLOBAL glb_mboot_ptr] [EXTERN kern_entry] start: cli mov esp, STACK_TOP mov ebp, 0 and esp, 0FFFFFFF0H mov [glb_mboot_ptr] , ebx push ebx call kern_entry stop: hlt jmp stop section .bss stack: resb 32768 glb_mboot_ptr: resb 4 STACK_TOP equ $ - stack - 1 Code: extern void int32(unsigned char intnum, regs16_t *regs); void kern_entry() { unsigned int* buffer = (unsigned int*) 0xE0000000; for (int i = 0; i < 800 * 600; i++) buffer[i] = 0x00FF00FF; while (1) {} } You won't need the other code anymore. Also, further down the line, you won't want to hard code the framebuffer pointer, as it varies from device to device, but grub gives you a vbe information structure, with the pointer for you to use. But that's for another topic. Ask if you need more help, or if it doesn't work. |
Author: | readlnh [ Tue Apr 11, 2017 8:44 pm ] |
Post subject: | Re: Switching VGA mode with GRUB |
obiwac wrote: First off, uncomment all the Code: dd lines at the beginning. These are the flags that pass the graphics mode information to grub, so that it can set your graphics mode before putting you into protected mode (more info: https://www.gnu.org/software/grub/manual/multiboot/multiboot.html). Then, just before Code: call kern_entry , push ebx to the stack with Code: push ebx . You don't need to switch back to real mode. Then, to draw on the screen, you need to get the framebuffer pointer (in the grub command line, type the Code: lspci -i , and under VGA, get the last eight digits of the hex string), and you can start modifying the screen straight away!thank you very much,but it still dosen't work. I'm wanting just a simple 320 x 200 8bit screen.I don't know what's wrong with it |
Author: | SpyderTL [ Wed Apr 12, 2017 2:15 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
8-bits may not be an option. Try something a little more common, like 640x480x32 bits. |
Author: | obiwac [ Wed Apr 12, 2017 11:21 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
If you're just wanting 320x200x8, then you can write a pure protected mode driver, that'll work for all graphics cards. It's in C++, but if you want, I think I have the same code lying around in C, and I could post it here. |
Author: | readlnh [ Wed Apr 12, 2017 7:10 pm ] |
Post subject: | Re: Switching VGA mode with GRUB |
obiwac wrote: If you're just wanting 320x200x8, then you can write a pure protected mode driver, that'll work for all graphics cards. It's in C++, but if you want, I think I have the same code lying around in C, and I could post it here. thank you very much |
Author: | zesterer [ Thu Apr 13, 2017 6:52 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
I might be talking through my arse here, but I had similar problems a few months back. Turns out you need to actually specify what mode you want in your grub.cfg before it'll actually be nice enough to change things. Something like this, I believe: Code: menuentry "MyOS" { multiboot /boot/myos.bin set gfxpayload=1024x768x32 boot } Hopefully that'll get you what you want |
Author: | obiwac [ Thu Apr 13, 2017 8:49 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
zesterer wrote: I might be talking through my arse here, but I had similar problems a few months back. Turns out you need to actually specify what mode you want in your grub.cfg before it'll actually be nice enough to change things. Something like this, I believe: Code: menuentry "MyOS" { multiboot /boot/myos.bin set gfxpayload=1024x768x32 boot } Hopefully that'll get you what you want Actually, that just changes the graphics mode for grub. But before switching to pmode, grub changes to 80x25 text mode. So, you have to tell it what mode you want with the multiboot flags. |
Author: | zesterer [ Thu Apr 13, 2017 9:39 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
obiwac wrote: zesterer wrote: I might be talking through my arse here, but I had similar problems a few months back. Turns out you need to actually specify what mode you want in your grub.cfg before it'll actually be nice enough to change things. Something like this, I believe: Code: menuentry "MyOS" { multiboot /boot/myos.bin set gfxpayload=1024x768x32 boot } Hopefully that'll get you what you want Actually, that just changes the graphics mode for grub. But before switching to pmode, grub changes to 80x25 text mode. So, you have to tell it what mode you want with the multiboot flags. That's not the case. If you wish to change GRUB's graphics mode, you use "gfxmode". However, "gfxpayload" defines the graphics mode that is passed on to the OS before booting. |
Author: | obiwac [ Thu Apr 13, 2017 9:50 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
Hmm... what version of grub are you using? |
Author: | zesterer [ Fri Apr 14, 2017 11:23 am ] |
Post subject: | Re: Switching VGA mode with GRUB |
obiwac wrote: Hmm... what version of grub are you using? GRUB 2.02~rc1. This was the primary problem I had when requesting graphics modes, and gfxpayload changes this. |
Author: | readlnh [ Sun Apr 16, 2017 11:33 pm ] |
Post subject: | Re: Switching VGA mode with GRUB |
Thank you all for your attention, i have sloved the problem as i do this viewtopic.php?f=1&t=31524 |
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