# this is the second-stage boot loader
.code16
- .section .boot2,"a"
+ .section .boot2,"ax"
- .set drive_number, 0x7bec
- # reset floppy drive
- xor %ax, %ax
- movb drive_number, %dl
- int $0x13
+ .set main_load_addr, 0x100000
+
+ # make sure any BIOS call didn't re-enable interrupts
+ cli
+
+ # enter unreal mode
+ call unreal
+
+ movb $10, %al
+ call ser_putchar
+
+ call clearscr
+
+ # 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
- # load initial GDT/IDT
+ # load initial GDT
lgdt (gdt_lim)
+ # load initial IDT
lidt (idt_lim)
- # enable protection
+
+ # enter protected mode for the first time
mov %cr0, %eax
or $1, %eax
mov %eax, %cr0
mov %ax, %gs
mov %ax, %fs
- mov $0x18, %ax
- ltr %ax
-
- #movb $10, %al
- #call ser_putchar
-
- call clearscr
-
- mov $hello, %esi
- call putstr
-
- # enable A20 line
- call enable_a20
+ jmp main_load_addr
cli
- hlt
+0: hlt
+ jmp 0b
+
-hello: .asciz "Switched to 32bit\n"
.align 4
-gdt_lim: .word 31
+gdt_lim: .word 23
gdt_base:.long gdt
.align 4
# 2: data - base:0, lim:4g, G:4k, 32bit, avl, pres|app, dpl:0, type:data/rw
.long 0x0000ffff
.long 0x00cf9200
- # 3: dummy TSS - base:tss, lim:103, type avail 32bit TSS, byte-granular
- .short 103
- .short tss
- .short 0x8900
- .short 0
.align 8
.short 0x8f00
.short 0
- .align 4
-tss: .space 104
-
-gpf_msg: .asciz "GPF "
+gpf_msg: .asciz "GP fault "
prot_fault:
mov (%esp), %eax
call putchar
hlt
-ena20_msg: .asciz "A20 line enabled\n"
-foo_msg: .asciz "Foo\n"
+ .code16
+unreal:
+ # use the same GDT above, will use data segment: 2
+ lgdt (gdt_lim)
-enable_a20:
- mov $foo_msg, %esi
+ mov %cr0, %eax
+ or $1, %ax
+ mov %eax, %cr0
+ jmp 0f
+
+0: mov $0x10, %ax
+ mov %ax, %ds
+ mov %ax, %es
+ mov %ax, %fs
+ mov %ax, %gs
+ mov %ax, %ss
+
+ mov %cr0, %eax
+ and $0xfffe, %ax
+ mov %eax, %cr0
+
+ xor %ax, %ax
+ mov %ax, %ds
+ mov %ax, %es
+ mov %ax, %fs
+ mov %ax, %gs
+ mov %ax, %ss
+ ret
+
+mainsz_msg: .asciz "Main program size: "
+mainsz_msg2: .asciz " ("
+mainsz_msg3: .asciz " sectors)\n"
+
+first_sect: .long 0
+sect_left: .long 0
+cur_track: .long 0
+trk_sect: .long 0
+dest_ptr: .long 0
+
+load_main:
+ movl $main_load_addr, dest_ptr
+
+ # calculate first sector
+ mov $_boot2_size, %eax
+ add $511, %eax
+ shr $9, %eax
+ # add 1 to account for the boot sector
+ inc %eax
+ mov %eax, first_sect
+
+ # calculate the first track (first_sect / sect_per_track)
+ movzxw sect_per_track, %ecx
+ xor %edx, %edx
+ div %ecx
+ mov %eax, cur_track
+ # remainder is sector within track
+ mov %edx, trk_sect
+
+ mov $mainsz_msg, %esi
call putstr
- jmp .La20done
+ mov $_main_size, %eax
+ mov %eax, %ecx
+ call print_num
- call test_a20
- jnc .La20done
- call enable_a20_kbd
- call test_a20
- jnc .La20done
- call enable_a20_fast
- call test_a20
- jnc .La20done
- # keep trying ... we can't do anything useful without A20 anyway
- jmp enable_a20
-.La20done:
- mov $ena20_msg, %esi
+ mov $mainsz_msg2, %esi
call putstr
- ret
- # CF = 1 if A20 test fails (not enabled)
-test_a20:
- mov $0x07c000, %ebx
- mov $0x17c000, %edx
- movl $0xbaadf00d, (%ebx)
- movl $0xaabbcc42, (%edx)
- subl $0xbaadf00d, (%ebx)
+ # calculate sector count
+ add $511, %eax
+ shr $9, %eax
+ mov %eax, sect_left
+
+ call print_num
+ mov $mainsz_msg3, %esi
+ call putstr
+
+ # read a whole track into the buffer (or partial first track)
+ldloop:
+ movzxw sect_per_track, %ecx
+ sub trk_sect, %ecx
+ push %ecx
+ call read_track
+
+ # 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 dest_ptr, %edi
+ mov (%esp), %ecx
+ shl $9, %ecx
+ add %ecx, dest_ptr
+ shr $2, %ecx
+ addr32 rep movsl
+
+ incl cur_track
+ # other than the first track which might be partial, all the rest start from 0
+ movl $0, trk_sect
+
+ pop %ecx
+ sub %ecx, sect_left
+ ja ldloop
+
+ # the BIOS might have enabled interrupts
+ cli
+
+ # just in case we were loaded from floppy, turn all floppy motors off
+ mov $0x3f2, %dx
+ in %dx, %al
+ and $0xf0, %al
+ out %al, %dx
+
+ mov $10, %ax
+ call putchar
+
ret
-ena20_fast_msg: .asciz "Attempting fast A20 enable\n"
+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"
-enable_a20_fast:
- mov $ena20_fast_msg, %esi
+read_retries: .short 0
+
+ .set drive_number, 0x7bec
+read_track:
+ # set es to the start of the destination buffer to allow reading in
+ # full 64k chunks if necessary
+ mov $buffer, %bx
+ shr $4, %bx
+ mov %bx, %es
+ xor %ebx, %ebx
+
+ movw $3, read_retries
+
+read_try:
+ # print track
+ mov $rdtrk_msg, %esi
+ call putstr
+ mov cur_track, %eax
+ call print_num
+ mov $rdcyl_msg, %esi
call putstr
- in $0x92, %al
- or $2, %al
- out %al, $0x92
- ret
+ # calc cylinder (cur_track / num_heads) and head (cur_track % num_heads)
+ mov cur_track, %eax
+ movzxw num_heads, %ecx
+ xor %edx, %edx
+ div %ecx
- .set KBC_DATA_PORT, 0x60
- .set KBC_CMD_PORT, 0x64
- .set KBC_STATUS_PORT, 0x64
- .set KBC_CMD_RD_OUTPORT, 0xd0
- .set KBC_CMD_WR_OUTPORT, 0xd1
+ # print cylinder
+ push %eax
+ call print_num
+ # print head
+ mov $rdhead_msg, %esi
+ call putstr
+ movzx %dx, %eax
+ call print_num
+ pop %eax
- .set KBC_STAT_OUT_RDY, 0x01
- .set KBC_STAT_IN_FULL, 0x02
+ # head in dh
+ mov %dl, %dh
-ena20_kbd_msg: .asciz "Attempting KBD A20 enable\n"
+ # cylinder low byte at ch and high bits at cl[7, 6]
+ mov %al, %ch
+ mov %ah, %cl
+ and $3, %cl
+ ror $2, %cl
- # enable A20 line through the keyboard controller
-enable_a20_kbd:
- mov $ena20_kbd_msg, %esi
+ # print start sector
+ mov $rdsect_msg, %esi
+ call putstr
+ mov trk_sect, %eax
+ call print_num
+ mov $rdlast_msg, %esi
call putstr
- call kbc_wait_write
- mov $KBC_CMD_WR_OUTPORT, %al
- out %al, $KBC_CMD_PORT
- call kbc_wait_write
- mov $0xdf, %al
- out %al, $KBC_DATA_PORT
- ret
+ # start sector (1-based) in cl[0, 5]
+ mov trk_sect, %al
+ inc %al
+ and $0x3f, %al
+ or %al, %cl
+
+ # number of sectors in al
+ mov 2(%esp), %ax
+ # call number (2) in ah
+ mov $2, %ah
+ # drive number in dl
+ movb drive_number, %dl
+ int $0x13
+ jnc read_ok
- # wait until the keyboard controller is ready to accept another byte
-kbc_wait_write:
- in $KBC_STATUS_PORT, %al
- and $KBC_STAT_IN_FULL, %al
- jnz kbc_wait_write
+ # abort after 3 attempts
+ decw read_retries
+ jz read_fail
+
+ # error, reset controller and retry
+ xor %ah, %ah
+ int $0x13
+ jmp read_try
+
+read_fail:
+ mov $rdfail_msg, %esi
+ call putstr
+ jmp abort_read
+
+read_ok:
+ mov $rdok_msg, %esi
+ call putstr
+
+ # reset es to 0 before returning
+ xor %ax, %ax
+ mov %ax, %es
ret
+str_read_error: .asciz "Read error while reading track: "
+
+abort_read:
+ mov $str_read_error, %esi
+ call putstr
+ mov cur_track, %eax
+ call print_num
+ mov $10, %al
+ call putchar
+
+ cli
+0: hlt
+ 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)
mov $10, %ebx
-.Lconvloop:
+convloop:
xor %edx, %edx
div %ebx
add $48, %dl
dec %esi
mov %dl, (%esi)
cmp $0, %eax
- jnz .Lconvloop
+ jnz convloop
call putstr
# restore regs
- popa
+ popal
ret
0: ret
scrollup:
- pusha
- # move 80 * 24 lines from b8050 -> b8000
+ pushal
+ # move 80 * 24 lines from b80a0 -> b8000
mov $0xb8000, %edi
- mov $0xb8050, %esi
- mov $480, %ecx
- rep movsl
- # clear last line (b8780)
- mov $0xb8780, %edi
+ mov $0xb80a0, %esi
+ mov $960, %ecx
+ addr32 rep movsl
+ # clear last line (b8f00)
+ mov $0xb8f00, %edi
xor %eax, %eax
- mov $20, %ecx
- rep stosl
- popa
+ mov $40, %ecx
+ addr32 rep stosl
+ popal
ret
clearscr:
mov $0xb8000, %edi
xor %eax, %eax
- mov $500, %ecx
- rep stosl
+ mov $1000, %ecx
+ addr32 rep stosl
ret
.set UART_DATA, 0x3f8
0: mov %al, %ah
# wait until the transmit register is empty
mov $UART_LSTAT, %dx
-.Lwait: in %dx, %al
+wait: in %dx, %al
and $LST_TREG_EMPTY, %al
- jz .Lwait
+ jz wait
mov $UART_DATA, %dx
mov %ah, %al
out %al, %dx
ret
- .code16
-logohack:
- mov $0x13, %ax
- int $0x10
-
- # copy palette
- mov $logo_pal, %si
- xor %cl, %cl
-
-0: xor %eax, %eax
- mov $0x3c8, %dx
- movb %cl, %al
- outb %al, %dx
- inc %dx
- # red
- movb (%si), %al
- inc %si
- shr $2, %al
- outb %al, %dx
- # green
- movb (%si), %al
- inc %si
- shr $2, %al
- outb %al, %dx
- # blue
- movb (%si), %al
- inc %si
- shr $2, %al
- outb %al, %dx
- add $1, %cl
- jnc 0b
-
- # copy pixels
- pushw $0xa000
- pop %es
- mov $logo_pix, %eax
- shr $4, %eax
- #mov %ax, %ds
- mov %ax, %gs
- #mov $16000, %ecx
- #rep movsl
- mov $sintab, %eax
- shr $4, %eax
- mov %ax, %fs
+ena20_msg: .asciz "A20 line enabled\n"
-.Lframeloop:
- xor %di, %di
-
- movw $0, yval
-.Lyloop:
- movw $0, xval
-.Lxloop:
- # calc src scanline address -> bx
- mov yval, %bx
- shl $2, %bx
- add frameno, %bx
- xor %bh, %bh
- mov %fs:(%bx), %cl
- xor %ch, %ch
- shr $5, %cx
-
- mov yval, %ax
- add %cx, %ax
- # bounds check
- cmp $200, %ax
- jl 0f
- mov $199, %ax
-
-0: mov %ax, %bx
- shl $8, %ax
- shl $6, %bx
- add %ax, %bx
-
- # calc src x offset -> si
- mov xval, %ax
- shl $2, %ax
- add frameno, %ax
- xor %ah, %ah
- mov %ax, %si
- mov %fs:(%si), %cl
- xor %ch, %ch
- shr $5, %cx
-
- mov xval, %ax
- add %cx, %ax
- # bounds check
- cmp $320, %ax
- jl 0f
- mov $319, %ax
-
-0: mov %ax, %si
-
- mov %gs:(%bx, %si), %al
-
- mov %al, %es:(%di)
- inc %di
-
- incw xval
- cmpw $320, xval
- jnz .Lxloop
-
- incw yval
- cmpw $200, yval
- jnz .Lyloop
-
- incw frameno
-
- # wait vsync
- mov $0x3da, %dx
-0: in %dx, %al
- and $8, %al
- jnz 0b
-0: in %dx, %al
- and $8, %al
- jz 0b
- jmp .Lframeloop
-
-xval: .word 0
-yval: .word 0
-frameno: .word 0
-
- # expects string pointer in ds:si
-ser_print_str:
- pusha
-
-0: mov (%si), %al
- cmp $0, %al
- jz .Lend
- call ser_putchar
- inc %si
- jmp 0b
+enable_a20:
+ call test_a20
+ jnc a20done
+ call enable_a20_kbd
+ call test_a20
+ jnc a20done
+ call enable_a20_fast
+ call test_a20
+ jnc a20done
+ # keep trying ... we can't do anything useful without A20 anyway
+ jmp enable_a20
+a20done:
+ mov $ena20_msg, %esi
+ call putstr
+ ret
+
+ # CF = 1 if A20 test fails (not enabled)
+test_a20:
+ mov $0x07c000, %ebx
+ mov $0x17c000, %edx
+ movl $0xbaadf00d, (%ebx)
+ movl $0xaabbcc42, (%edx)
+ subl $0xbaadf00d, (%ebx)
+ ret
-.Lend: popa
+ # enable A20 line through port 0x92 (fast A20)
+enable_a20_fast:
+ mov $ena20_fast_msg, %esi
+ call putstr
+
+ in $0x92, %al
+ or $2, %al
+ out %al, $0x92
ret
+ena20_fast_msg: .asciz "Attempting fast A20 enable\n"
+
+ # enable A20 line through the keyboard controller
+ .set KBC_DATA_PORT, 0x60
+ .set KBC_CMD_PORT, 0x64
+ .set KBC_STATUS_PORT, 0x64
+ .set KBC_CMD_RD_OUTPORT, 0xd0
+ .set KBC_CMD_WR_OUTPORT, 0xd1
+
+ .set KBC_STAT_OUT_RDY, 0x01
+ .set KBC_STAT_IN_FULL, 0x02
+
+enable_a20_kbd:
+ mov $ena20_kbd_msg, %esi
+ call putstr
+
+ call kbc_wait_write
+ mov $KBC_CMD_WR_OUTPORT, %al
+ out %al, $KBC_CMD_PORT
+ call kbc_wait_write
+ mov $0xdf, %al
+ out %al, $KBC_DATA_PORT
+ ret
+
+ena20_kbd_msg: .asciz "Attempting KBD A20 enable\n"
+
+ # wait until the keyboard controller is ready to accept another byte
+kbc_wait_write:
+ in $KBC_STATUS_PORT, %al
+ and $KBC_STAT_IN_FULL, %al
+ jnz kbc_wait_write
+ ret
numbuf: .space 16
-logo_pal:
- .incbin "logo.pal"
+ # 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
-logo_pix:
- .incbin "logo.raw"
-
-sintab:
- .byte 127
- .byte 130
- .byte 133
- .byte 136
- .byte 139
- .byte 143
- .byte 146
- .byte 149
- .byte 152
- .byte 155
- .byte 158
- .byte 161
- .byte 164
- .byte 167
- .byte 170
- .byte 173
- .byte 176
- .byte 179
- .byte 182
- .byte 184
- .byte 187
- .byte 190
- .byte 193
- .byte 195
- .byte 198
- .byte 200
- .byte 203
- .byte 205
- .byte 208
- .byte 210
- .byte 213
- .byte 215
- .byte 217
- .byte 219
- .byte 221
- .byte 224
- .byte 226
- .byte 228
- .byte 229
- .byte 231
- .byte 233
- .byte 235
- .byte 236
- .byte 238
- .byte 239
- .byte 241
- .byte 242
- .byte 244
- .byte 245
- .byte 246
- .byte 247
- .byte 248
- .byte 249
- .byte 250
- .byte 251
- .byte 251
- .byte 252
- .byte 253
- .byte 253
- .byte 254
- .byte 254
- .byte 254
- .byte 254
- .byte 254
- .byte 255
- .byte 254
- .byte 254
- .byte 254
- .byte 254
- .byte 254
- .byte 253
- .byte 253
- .byte 252
- .byte 251
- .byte 251
- .byte 250
- .byte 249
- .byte 248
- .byte 247
- .byte 246
- .byte 245
- .byte 244
- .byte 242
- .byte 241
- .byte 239
- .byte 238
- .byte 236
- .byte 235
- .byte 233
- .byte 231
- .byte 229
- .byte 228
- .byte 226
- .byte 224
- .byte 221
- .byte 219
- .byte 217
- .byte 215
- .byte 213
- .byte 210
- .byte 208
- .byte 205
- .byte 203
- .byte 200
- .byte 198
- .byte 195
- .byte 193
- .byte 190
- .byte 187
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