banan-os/bootloader/memory_map.S

130 lines
2.1 KiB
ArmAsm

.code16
.section .stage2
# fills memory map data structure
# doesn't return on error
# NO REGISTERS SAVED
.global get_memory_map
get_memory_map:
movl $0, (memory_map_entry_count)
movl $0x0000E820, %eax
movl $0x534D4150, %edx
xorl %ebx, %ebx
movl $20, %ecx
movw $memory_map_entries, %di
clc
int $0x15
# If first call returs with CF set, the call failed
jc .get_memory_map_error
.get_memory_map_rest:
cmpl $0x534D4150, %eax
jne .get_memory_map_error
# FIXME: don't assume BIOS to always return 20 bytes
cmpl $20, %ecx
jne .get_memory_map_error
# increment entry count
incl (memory_map_entry_count)
# increment entry pointer
addw %cx, %di
# BIOS can indicate end of list by 0 in ebx
testl %ebx, %ebx
jz .get_memory_map_done
movl $0x0000E820, %eax
movl $0x534D4150, %edx
clc
int $0x15
# BIOS can indicate end of list by setting CF
jnc .get_memory_map_rest
.get_memory_map_done:
ret
.get_memory_map_error:
movw $memory_map_error_msg, %si
jmp print_and_halt
# print memory map from memory_map_entries
# NO REGISTERS SAVED
.global print_memory_map
print_memory_map:
movw $memory_map_msg, %si
call puts
call print_newline
movl (memory_map_entry_count), %edx
movw $memory_map_entries, %si
movw $16, %bx
movw $4, %cx
.loop_memory_map:
movb $' ', %al
call putc; call putc; call putc; call putc
movw 0x06(%si), %ax
call print_number
movw 0x04(%si), %ax
call print_number
movw 0x02(%si), %ax
call print_number
movw 0x00(%si), %ax
call print_number
movb $',', %al
call putc
movb $' ', %al
call putc
movw 0x0E(%si), %ax
call print_number
movw 0x0C(%si), %ax
call print_number
movw 0x0A(%si), %ax
call print_number
movw 0x08(%si), %ax
call print_number
movb $',', %al
call putc
movb $' ', %al
call putc
movw 0x12(%si), %ax
call print_number
movw 0x10(%si), %ax
call print_number
call print_newline
addw $20, %si
decl %edx
jnz .loop_memory_map
ret
memory_map_msg:
.asciz "memmap:"
memory_map_error_msg:
.asciz "Failed to get memory map"
.section .bss
memory_map_entry_count:
.skip 4
# 100 entries should be enough...
memory_map_entries:
.skip 20 * 100