# this is the second-stage boot loader
.code16
- .section .boot2,"a"
+ .section .boot2,"ax"
.set main_load_addr, 0x100000
# enable A20 address line
call enable_a20
+ # detect available memory
+ call detect_memory
+
# load the whole program into memory starting at 1MB
call load_main
- mov $0x13, %ax
- int $0x10
+ #mov $0x13, %ax
+ #int $0x10
# load initial GDT
lgdt (gdt_lim)
push %ecx
call read_track
- mov buffer, %eax
- call print_num
- mov $10, %al
- call putchar
+ # debug: print the first 32bits of the track
+ #mov buffer, %eax
+ #call print_num
+ #mov $10, %al
+ #call putchar
# copy to high memory
mov $buffer, %esi
mov $10, %ax
call putchar
- # DBG
- hlt
-
ret
rdtrk_msg: .asciz "Reading track: "
rdcyl_msg: .asciz " - cyl: "
rdhead_msg: .asciz " head: "
rdsect_msg: .asciz " start sect: "
+rdlast_msg: .asciz " ... "
+rdok_msg: .asciz "OK\n"
+rdfail_msg: .asciz "failed\n"
read_retries: .short 0
call putstr
mov trk_sect, %eax
call print_num
- mov $10, %al
- call putchar
+ mov $rdlast_msg, %esi
+ call putstr
# start sector (1-based) in cl[0, 5]
mov trk_sect, %al
jmp read_try
read_fail:
+ mov $rdfail_msg, %esi
+ call putstr
jmp abort_read
read_ok:
- mov $35, %ax
- call putchar
+ mov $rdok_msg, %esi
+ call putstr
# reset es to 0 before returning
xor %ax, %ax
jmp 0b
-
# better print routines, since we're not constrainted by the 512b of
# the boot sector.
+ .global cursor_x
+ .global cursor_y
cursor_x: .long 0
cursor_y: .long 0
putchar:
- pusha
+ pushal
call ser_putchar
cmp $10, %al
jnz 1f
call video_newline
-1: popa
+1: popal
ret
# expects string pointer in esi
# expects number in eax
print_num:
# save registers
- pusha
+ pushal
mov $numbuf + 16, %esi
movb $0, (%esi)
call putstr
# restore regs
- popa
+ popal
ret
0: ret
scrollup:
- pusha
+ pushal
# move 80 * 24 lines from b80a0 -> b8000
mov $0xb8000, %edi
mov $0xb80a0, %esi
xor %eax, %eax
mov $40, %ecx
addr32 rep stosl
- popa
+ popal
ret
clearscr:
numbuf: .space 16
+
+ # sets the carry flag on failure
+detect_memory:
+ mov $buffer, %edi
+ xor %ebx, %ebx
+ mov $0x534d4150, %edx
+
+memdet_looptop:
+ mov $0xe820, %eax
+ mov $24, %ecx
+ int $0x15
+ jc memdet_fail
+ cmp $0x534d4150, %eax
+ jnz memdet_fail
+
+ mov buffer, %eax
+ mov $boot_mem_map, %esi
+ mov boot_mem_map_size, %ebp
+ # again, that's [ebp * 8 + esi]
+ mov %eax, (%esi,%ebp,8)
+
+ # only care for type 1 (usable ram), otherwise ignore
+ cmpl $1, 16(%edi)
+ jnz memdet_skip
+
+ # skip areas with 0 size (also clamp size to 4gb)
+ # test high 32bits
+ cmpl $0, 12(%edi)
+ jz memdet_highzero
+ # high part is non-zero, make low part ffffffff
+ xor %eax, %eax
+ not %eax
+ jmp 0f
+
+memdet_highzero:
+ # if both high and low parts are zero, ignore
+ mov 8(%edi), %eax
+ cmpl $0, %eax
+ jz memdet_skip
+
+0: mov %eax, 4(%esi,%ebp,8)
+ incl boot_mem_map_size
+
+memdet_skip:
+ # terminate the loop if ebx was reset to 0
+ cmp $0, %ebx
+ jz memdet_done
+ jmp memdet_looptop
+
+memdet_done:
+ ret
+
+memdet_fail:
+ # if size > 0, then it's not a failure, just the end
+ cmpl $0, boot_mem_map_size
+ jnz memdet_done
+
+ # just panic...
+ mov $memdet_fail_msg, %esi
+ call putstr
+0: hlt
+ jmp 0b
+
+memdet_fail_msg: .asciz "Failed to detect available memory!\n"
+
+ .global boot_mem_map_size
+boot_mem_map_size: .long 0
+ .global boot_mem_map
+boot_mem_map: .space 128
+
+
+# this is not boot loader code. It's called later on by the main kernel
+# code in 32bit protected mode. It's placed here because it needs to be
+# located in base memory as it returns and runs in real mode.
+ .code32
+ .align 4
+ # place to save the protected mode IDTR pseudo-descriptor
+ # with sidt, so that it can be restored before returning
+ .short 0
+saved_idtr:
+idtlim: .short 0
+idtaddr:.long 0
+ # real mode IDTR pseudo-descriptor pointing to the IVT at addr 0
+ .short 0
+rmidt: .short 0x3ff
+ .long 0
+
+saved_esp: .long 0
+saved_ebp: .long 0
+
+ # drop back to unreal mode to call 16bit interrupt
+ .global int86
+int86:
+ push %ebp
+ mov %esp, %ebp
+ pushal
+ cli
+ # save protected mode IDTR and replace it with the real mode vectors
+ sidt (saved_idtr)
+ lidt (rmidt)
+
+ # modify the int instruction do this here before the
+ # cs-load jumps, to let them flush the instruction cache
+ mov $int_op, %ebx
+ movb 8(%ebp), %al
+ movb %al, 1(%ebx)
+
+ # long jump to load code selector for 16bit code (6)
+ ljmp $0x30,$0f
+0:
+ .code16
+ # disable protection
+ mov %cr0, %eax
+ and $0xfffe, %ax
+ mov %eax, %cr0
+ # load cs <- 0
+ ljmp $0,$0f
+0: # zero data segments
+ xor %ax, %ax
+ mov %ax, %ds
+ mov %ax, %es
+ mov %ax, %ss
+ nop
+
+ # load registers from the int86regs struct
+ mov %esp, saved_esp
+ mov %ebp, saved_ebp
+ mov 12(%ebp), %esp
+ popal
+ mov saved_esp, %esp
+
+ # call 16bit interrupt
+int_op: int $0
+
+ mov saved_ebp, %ebp
+ mov 12(%ebp), %esp
+ add $34, %esp
+ pushfw
+ pushal
+ mov saved_esp, %esp
+
+ # re-enable protection
+ mov %cr0, %eax
+ or $1, %ax
+ mov %eax, %cr0
+ # long jump to load code selector for 32bit code (1)
+ ljmp $0x8,$0f
+0:
+ .code32
+ # set data selector (2) to all segment regs
+ mov $0x10, %ax
+ mov %ax, %ds
+ mov %ax, %es
+ mov %ax, %ss
+ nop
+
+ # restore 32bit interrupt descriptor table
+ lidt (saved_idtr)
+ sti
+ popal
+ pop %ebp
+ ret
+
+
+ # buffer used by the track loader ... to load tracks.
.align 16
buffer:
projects / bootcensus / blobdiff