diff options
Diffstat (limited to 'baremetal/bos/32bit.hex')
| -rw-r--r-- | baremetal/bos/32bit.hex | 132 |
1 files changed, 0 insertions, 132 deletions
diff --git a/baremetal/bos/32bit.hex b/baremetal/bos/32bit.hex deleted file mode 100644 index 5a85aa36..00000000 --- a/baremetal/bos/32bit.hex +++ /dev/null @@ -1,132 +0,0 @@ -# Bootable image demonstrating printing to screen in 32-bit mode. -# Must have exactly 512 bytes. -# -# To convert to a disk image: -# ./bootstrap run apps/hex < baremetal/bos/32bit.hex > boot.bin -# To run: -# qemu-system-i386 boot.bin -# Or: -# bochs -f baremetal/bos/bochsrc # bochsrc loads boot.bin -# -# Expected output inside emulator: -# H - -## 16-bit entry point - -# Boot image starts executing at address 0x7c00, -# and so occupies [0x7c00, 0x7e00). -# We don't read or write the stack before we get to 32-bit mode. - -# 00: - fa # cli # TODO: don't forget to reenable interrupts at some point - 0f 01 16 # lgdt 00/mod/indirect 010/subop 110/rm32/TODO - 80 7c # *gdt_descriptor - 0f 20 c0 # eax <- cr0 - 66 83 c8 01 # eax <- or 0x1 - 0f 22 c0 # cr0 <- eax - ea c0 7c 08 00 # far jump to initialize_32bit_mode after setting cs to the record at offset 8 in the gdt (gdt_code) - -# padding -# 15: - 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 - -## GDT: 3 records of 8 bytes each - -# 60: -# gdt_start: -# gdt_null: mandatory null descriptor - 00 00 00 00 00 00 00 00 -# gdt_code: (offset 8 from gdt_start) - ff ff # limit[0:16] - 00 00 00 # base[0:24] - 9a # 1/present 00/privilege 1/descriptor type = 1001b - # 1/code 0/conforming 1/readable 0/accessed = 1010b - cf # 1/granularity 1/32-bit 0/64-bit-segment 0/AVL = 1100b - # limit[16:20] = 1111b - 00 # base[24:32] -# gdt_data: (offset 16 from gdt_start) - ff ff # limit[0:16] - 00 00 00 # base[0:24] - 92 # 1/present 00/privilege 1/descriptor type = 1001b - # 0/data 0/conforming 1/readable 0/accessed = 0010b - cf # same as gdt_code - 00 # base[24:32] -# gdt_end: - -# padding -# 78: - 00 00 00 00 00 00 00 00 - -# 80: -# gdt_descriptor: - 17 00 # final index of gdt = gdt_end - gdt_start - 1 - 60 7c 00 00 # start = gdt_start - -# padding -# 85: - 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 - -## 32-bit code from this point (still some instructions not in SubX) - -# c0: -# initialize_32bit_mode: - 66 b8 10 00 # ax <- offset 16 from gdt_start - 8e d8 # ds <- ax - 8e d0 # ss <- ax - 8e c0 # es <- ax - 8e e0 # fs <- ax - 8e e8 # gs <- ax - e9 1d 00 00 00 # jump to 0x7cf0 - -# padding -# d3: - 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 - -## 'application' SubX code: print one character to top-left of screen - -# f0: -# Entry: - # *0xb8000 <- 0x0f48 - c7 # opcode - # modrm - 05 # 00/mod/indirect 000/subop/copy 101/rm32/use-disp32 - # disp32 - 00 80 0b 00 - # imm32 - 48 # 'H' - 0f # white on black - 00 00 - -e9 fb ff ff ff # loop forever - -# padding to 512 bytes - 00 -# 100: -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 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 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 - -55 aa # final 2 bytes: boot sector marker - -# vim:ft=subx |