diff options
Diffstat (limited to 'baremetal/boot.hex')
| -rw-r--r-- | baremetal/boot.hex | 58 |
1 files changed, 13 insertions, 45 deletions
diff --git a/baremetal/boot.hex b/baremetal/boot.hex index 2f403e97..fda3c287 100644 --- a/baremetal/boot.hex +++ b/baremetal/boot.hex @@ -92,58 +92,22 @@ # Not bothering initializing sp register. Que sera sera. # 11: - # disk read #1: load remaining 62 sectors from first track of disk into addresses [0x7e00, 0xfa00) + # disk read #1: load remaining sectors from first two tracks of disk into addresses [0x7e00, 0x17800) b4 02 # ah <- 2 # read sectors from disk # dl comes conveniently initialized at boot time with the index of the device being booted b5 00 # ch <- 0 # cylinder 0 b6 00 # dh <- 0 # track 0 b1 02 # cl <- 2 # second sector, 1-based - b0 3e # al <- 62 # number of sectors to read + b0 7d # al <- 125 # number of sectors to read # address to write sectors to = es:bx = 0x7e00, contiguous with boot segment bb 00 00 # bx <- 0 8e c3 # es <- bx # 20: bb 00 7e # bx <- 0x7e00 [label] cd 13 # int 13h, BIOS disk service - 0f 82 8a 00 # jump-if-carry disk_error [label] -# 29: - # disk read #2: 3 sectors from (0, 1, 0) to [0xfa00, 0x10000) - # It looks like some BIOSs can't handle sector reads that cross segment - # alignment boundaries. - b4 02 # ah <- 2 # read sectors from disk - b5 00 # ch <- 0 # cylinder 0 - b6 01 # dh <- 1 # track 1 - b1 01 # cl <- 1 # first sector, 1-based - b0 03 # al <- 3 # number of sectors to read - # "Addressing of Buffer should guarantee that the complete buffer is inside - # the given segment, i.e. ( BX + size_of_buffer ) <= 10000h." - # https://en.wikipedia.org/wiki/INT_13H#INT_13h_AH=02h:_Read_Sectors_From_Drive - bb a0 0f # bx <- 0xfa0 - 8e c3 # es <- bx - bb 00 00 # bx <- 0 - cd 13 # int 13h, BIOS disk service - 0f 82 72 00 # jump-if-carry disk_error [label] - # reset es - bb 00 00 # bx <- 0 - 8e c3 # es <- bx -# 46: - # disk read #3: remaining 60 sectors from (0, 1, 3) to [0x10000, 0x17800) - b4 02 # ah <- 2 # read sectors from disk - b5 00 # ch <- 0 # cylinder 0 - b6 01 # dh <- 1 # track 1 - b1 04 # cl <- 4 # sector 3, 1-based - b0 3c # al <- 60 # number of sectors to read -# 50: - bb 00 10 # bx <- 0x1000 - 8e c3 # es <- bx - bb 00 00 # bx <- 0 - cd 13 # int 13h, BIOS disk service - 0f 82 72 00 # jump-if-carry disk_error [label] - # reset es - bb 00 00 # bx <- 0 - 8e c3 # es <- bx + 0f 82 a6 00 # jump-if-carry disk_error [label] -# 63: +# 29: # undo the A20 hack: https://en.wikipedia.org/wiki/A20_line # this is from https://github.com/mit-pdos/xv6-public/blob/master/bootasm.S # seta20.1: @@ -154,7 +118,7 @@ b0 d1 # al <- 0xd1 e6 64 # port 0x64 <- al -# 6d: +# 33: # seta20.2: e4 64 # al <- port 0x64 a8 02 # set zf if bit 1 (second-least significant) is not set @@ -163,7 +127,7 @@ b0 df # al <- 0xdf e6 64 # port 0x64 <- al -# 77: +# 3d: # adjust video mode b4 4f # ah <- 4f (VBE) b0 02 # al <- 02 (set video mode) @@ -172,7 +136,7 @@ # fallback mode: 0x0101 (640x480x256) cd 10 # int 10h, Vesa BIOS extensions -# 90: +# 46: # load information for the (hopefully) current video mode # mostly just for the address to the linear frame buffer b4 4f # ah <- 4f (VBE) @@ -181,7 +145,7 @@ bf 00 7f # di <- 0x7f00 (video mode info) [label] cd 10 -# 9c: +# 52: # switch to 32-bit mode 0f 01 16 # lgdt 00/mod/indirect 010/subop 110/rm/use-disp16 f8 7c # *gdt_descriptor [label] @@ -191,7 +155,11 @@ ea 00 7d 08 00 # far jump to initialize_32bit_mode after setting cs to the record at offset 8 in the gdt (gdt_code) [label] # padding -# b0: +# 66: + 00 00 00 00 00 00 00 00 00 00 +00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |