Bootloader: Implement VESA video mode query and pass it to kernel

Kernel now gets framebuffer from bootloader. Framebuffer dimensions
and bpp are hardcoded in bootloader, but will probably be read from
config file at some point.
This commit is contained in:
Bananymous 2023-11-17 22:45:35 +02:00
parent a554bd0fd8
commit a312d75bb2
6 changed files with 187 additions and 8 deletions

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@ -8,6 +8,7 @@ set(BOOTLOADER_SOURCES
disk.S
elf.S
ext2.S
framebuffer.S
memory_map.S
utils.S
)

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@ -60,6 +60,8 @@ stage2_main:
call get_memory_map
call read_user_command_line
call vesa_find_video_mode
call print_newline
movw $start_kernel_load_msg, %si
@ -82,12 +84,7 @@ stage2_main:
call elf_read_kernel_to_memory
# re-enter 80x25 text mode to clear screen
pushw %ax
movb $0x03, %al
movb $0x00, %ah
int $0x10
popw %ax
call vesa_set_target_mode
cli
@ -167,5 +164,7 @@ gdtr:
banan_boot_info:
boot_command_line:
.long command_line
boot_framebuffer:
.long framebuffer
boot_memory_map:
.long memory_map

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@ -79,5 +79,5 @@ command_line_enter_msg:
command_line:
# 100 character command line
command_line_buffer:
.ascii "root=/dev/sda2 console=ttyS0"
.ascii "root=/dev/sda2"
.skip 100 - 28

156
bootloader/framebuffer.S Normal file
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@ -0,0 +1,156 @@
.set TARGET_WIDTH, 800
.set TARGET_HEIGHT, 600
.set TARGET_BPP, 32
.code16
.section .stage2
# Find suitable video mode
# return:
# ax: video mode number if found, 0 otherwise
.global vesa_find_video_mode
vesa_find_video_mode:
pushw %ax
pushw %cx
pushw %di
pushl %esi
# clear target mode and frame buffer
movw $0, (vesa_target_mode)
movl $0, (framebuffer + 0)
movl $0, (framebuffer + 4)
movl $0, (framebuffer + 8)
movl $0, (framebuffer + 12)
movw $0, (framebuffer + 16)
# get vesa information
movw $0x4F00, %ax
movw $vesa_info_buffer, %di
int $0x10
cmpb $0x4F, %al; jne .vesa_unsupported
cmpb $0x00, %ah; jne .vesa_error
# confirm that response starts with 'VESA'
cmpl $0x41534556, (vesa_info_buffer)
jne .vesa_error
# confirm that version is atleast 2.0
cmpw $0x0200, (vesa_info_buffer + 0x04)
jb .vesa_unsupported_version
movl $(vesa_info_buffer + 0x0E), %esi
movl (%esi), %esi
.vesa_find_video_mode_loop_modes:
cmpw $0xFFFF, (%esi)
je .vesa_find_video_mode_loop_modes_done
# get info of next mode
movw $0x4F01, %ax
movw (%esi), %cx
movw $vesa_mode_info_buffer, %di
int $0x10
cmpb $0x4F, %al; jne .vesa_unsupported
cmpb $0x00, %ah; jne .vesa_error
# check whether in graphics mode
testb $0x10, (vesa_mode_info_buffer + 0)
jz .vesa_find_video_mode_next_mode
# compare mode's dimensions
cmpw $TARGET_WIDTH, (vesa_mode_info_buffer + 0x12)
jne .vesa_find_video_mode_next_mode
cmpw $TARGET_HEIGHT, (vesa_mode_info_buffer + 0x14)
jne .vesa_find_video_mode_next_mode
cmpb $TARGET_BPP, (vesa_mode_info_buffer + 0x19)
jne .vesa_find_video_mode_next_mode
movl (vesa_mode_info_buffer + 0x28), %esi
movl %esi, (framebuffer + 0)
movw (vesa_mode_info_buffer + 0x10), %ax
movw %ax, (framebuffer + 4)
movl $TARGET_WIDTH, (framebuffer + 8)
movl $TARGET_HEIGHT, (framebuffer + 12)
movb $TARGET_BPP, (framebuffer + 16)
movb $1, (framebuffer + 17)
movw %cx, (vesa_target_mode)
jmp .vesa_find_video_mode_loop_modes_done
.vesa_find_video_mode_next_mode:
addl $2, %esi
jmp .vesa_find_video_mode_loop_modes
.vesa_find_video_mode_loop_modes_done:
popl %esi
popw %di
popw %cx
popw %ax
ret
.vesa_unsupported:
movw $vesa_unsupported_msg, %si
jmp print_and_halt
.vesa_unsupported_version:
movw $vesa_unsupported_version_msg, %si
jmp print_and_halt
.vesa_error:
movw $vesa_error_msg, %si
jmp print_and_halt
# set mode found from vesa_find_video_mode. if no mode
# was found, set it to 80x25 text mode to clear the screen.
.global vesa_set_target_mode
vesa_set_target_mode:
pushw %ax
pushw %bx
movw (vesa_target_mode), %bx
testw %bx, %bx
jz .vesa_set_target_mode_generic
movw $0x4F02, %ax
orw $0x4000, %bx
int $0x10
jmp .set_video_done
.vesa_set_target_mode_generic:
movb $0x03, %al
movb $0x00, %ah
int $0x10
.set_video_done:
popw %bx
popw %ax
ret
vesa_error_msg:
.asciz "VESA error"
vesa_unsupported_msg:
.asciz "VESA unsupported"
vesa_unsupported_version_msg:
.asciz "VESA unsupported version"
vesa_success_msg:
.asciz "VESA success"
.section .bss
vesa_info_buffer:
.skip 512
vesa_mode_info_buffer:
.skip 256
vesa_target_mode:
.skip 2
.global framebuffer
framebuffer:
.skip 4 # address
.skip 4 # pitch
.skip 4 # width
.skip 4 # height
.skip 1 # bpp
.skip 1 # type

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@ -2,7 +2,18 @@
#include <stdint.h>
#define BANAN_BOOTLOADER_MAGIC 0xD3C60CFF
#define BANAN_BOOTLOADER_MAGIC 0xD3C60CFF
#define BANAN_BOOTLOADER_FB_RGB 1
struct BananBootFramebufferInfo
{
uint32_t address;
uint32_t pitch;
uint32_t width;
uint32_t height;
uint8_t bpp;
uint8_t type;
};
struct BananBootloaderMemoryMapEntry
{
@ -20,5 +31,6 @@ struct BananBootloaderMemoryMapInfo
struct BananBootloaderInfo
{
uint32_t command_line_addr;
uint32_t framebuffer_addr;
uint32_t memory_map_addr;
} __attribute__((packed));

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@ -71,6 +71,17 @@ namespace Kernel
const char* command_line = reinterpret_cast<const char*>(banan_bootloader_info.command_line_addr);
MUST(g_boot_info.command_line.append(command_line));
const auto& framebuffer = *reinterpret_cast<BananBootFramebufferInfo*>(banan_bootloader_info.framebuffer_addr);
if (framebuffer.type == BANAN_BOOTLOADER_FB_RGB)
{
g_boot_info.framebuffer.address = framebuffer.address;
g_boot_info.framebuffer.width = framebuffer.width;
g_boot_info.framebuffer.height = framebuffer.height;
g_boot_info.framebuffer.pitch = framebuffer.pitch;
g_boot_info.framebuffer.bpp = framebuffer.bpp;
g_boot_info.framebuffer.type = FramebufferType::RGB;
}
const auto& memory_map = *reinterpret_cast<BananBootloaderMemoryMapInfo*>(banan_bootloader_info.memory_map_addr);
MUST(g_boot_info.memory_map_entries.resize(memory_map.entry_count));
for (size_t i = 0; i < memory_map.entry_count; i++)