diff options
| author | Kartik K. Agaram <vc@akkartik.com> | 2021-02-11 01:14:30 -0800 |
|---|---|---|
| committer | Kartik K. Agaram <vc@akkartik.com> | 2021-02-11 01:14:30 -0800 |
| commit | c4bd8edae25844fc437a0c3df435df55540887de (patch) | |
| tree | 2c5a310fc729a8f671a20c369c57a06771f17bcd /baremetal/boot.hex | |
| parent | e396b3a0a354c017c7582124d51a0380a6e5c7de (diff) | |
| download | mu-c4bd8edae25844fc437a0c3df435df55540887de.tar.gz | |
7720 - baremetal: load more sectors again
Diffstat (limited to 'baremetal/boot.hex')
| -rw-r--r-- | baremetal/boot.hex | 36 |
1 files changed, 26 insertions, 10 deletions
diff --git a/baremetal/boot.hex b/baremetal/boot.hex index 7b29e49f..f9735c9c 100644 --- a/baremetal/boot.hex +++ b/baremetal/boot.hex @@ -65,7 +65,7 @@ # offset 1800 (address 9400): entrypoint for applications (don't forget to adjust survey_baremetal if this changes) # Other details of the current memory map: -# code: first two default-sized disk tracks get loaded to [0x00007c00, 0x00017800) +# code: 4 tracks of disk to [0x00007c00, 0x00027400) # stack grows down from 0x00070000 # see below # heap: [0x01000000, 0x02000000) @@ -107,7 +107,7 @@ b5 00 # ch <- 0 # cylinder 0 b6 00 # dh <- 0 # track 0 b1 02 # cl <- 2 # second sector, 1-based - b0 7d # al <- 125 # number of sectors to read + b0 7d # al <- 125 # number of sectors to read = 2*63 - 1 # address to write sectors to = es:bx = 0x7e00, contiguous with boot segment bb 00 00 # bx <- 0 8e c3 # es <- bx @@ -116,6 +116,24 @@ 0f 82 a3 00 # jump-if-carry disk_error [label] # 2c: + # load two more tracks of disk into addresses [0x17800, 0x27400) + 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 02 # dh <- 2 # track 0 + b1 01 # cl <- 1 # first sector, 1-based + b0 7e # al <- 126 # number of sectors to read = 2*63 + # address to write sectors to = es:bx = 0x17800 + bb 80 17 # bx <- 0x1780 [label] + 8e c3 # es <- bx + bb 00 00 # bx <- 0 + cd 13 # int 13h, BIOS disk service + 0f 82 9b 00 # jump-if-carry disk_error [label] + # reset es + bb 00 00 # bx <- 0 + 8e c3 # es <- bx + +# 39: # 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: @@ -126,7 +144,7 @@ b0 d1 # al <- 0xd1 e6 64 # port 0x64 <- al -# 36: +# 43: # seta20.2: e4 64 # al <- port 0x64 a8 02 # set zf if bit 1 (second-least significant) is not set @@ -135,7 +153,7 @@ b0 df # al <- 0xdf e6 64 # port 0x64 <- al -# 40: +# 4d: # adjust video mode b4 4f # ah <- 4f (VBE) b0 02 # al <- 02 (set video mode) @@ -144,7 +162,7 @@ # fallback mode: 0x0101 (640x480x256) cd 10 # int 10h, Vesa BIOS extensions -# 49: +# 56: # load information for the (hopefully) current video mode # mostly just for the address to the linear frame buffer b4 4f # ah <- 4f (VBE) @@ -153,7 +171,7 @@ bf 00 81 # di <- 0x8100 (video mode info) [label] cd 10 -# 55: +# 62: # switch to 32-bit mode 0f 01 16 # lgdt 00/mod/indirect 010/subop 110/rm/use-disp16 f8 7c # *gdt_descriptor [label] @@ -163,10 +181,8 @@ 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 -# 69: - 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 +# 76: + 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 |