## Copyright (C) 2016 Jeremiah Orians
## This file is part of stage0.
##
## stage0 is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## stage0 is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with stage0.  If not, see <http://www.gnu.org/licenses/>.

## Self Bootstrapping Hex Assembler written in Hex
## And a shitload of comments
## That can be converted to assembly and compiled

## If you were linked to this file and have come to assume that the elf header
## is indicative of a dependency of on linux, unix or even operating systems you
## would be mistaken, this is not the bootstrap work that is hardware native,
## that work would be located here: http://git.savannah.nongnu.org/cgit/stage0.git
## This repository is for solely providing tools enabling one to arbitrary verify
## All of the steps and the binaries produced for arbitrary hardware platforms on
## Any arbitrary hardware platform they choose.
## This of course being an example of an arbitrary Linux bootstrap for those not
## Comfortable with native hardware bootstraps and need a simple example to follow

## ELF Header
7F 45 4C 46        ## e_ident[EI_MAG0-3] ELF's magic number
02                 ## e_ident[EI_CLASS] Indicating 64 bit
01                 ## e_ident[EI_DATA] Indicating little endianness
01                 ## e_ident[EI_VERSION] Indicating original elf
03                 ## e_ident[EI_OSABI] Set at 3 because FreeBSD is strict
00                 ## e_ident[EI_ABIVERSION] See above
00 00 00 00 00 00 00 ## e_ident[EI_PAD]
02 00              ## e_type Indicating Executable
3E 00              ## e_machine Indicating AMD64
01 00 00 00        ## e_version Indicating original elf
FB 00 60 00 00 00 00 00 ## e_entry Address of the entry point
40 00 00 00 00 00 00 00 ## e_phoff Address of program header table
00 00 00 00 00 00 00 00 ## e_shoff Address of section header table
00 00 00 00        ## e_flags
40 00              ## e_ehsize Indicating our 64 Byte header
38 00              ## e_phentsize size of a program header table
01 00              ## e_phnum number of entries in program table
00 00              ## e_shentsize size of a section header table
00 00              ## e_shnum number of entries in section table
00 00              ## e_shstrndx index of the section names

## Program Header table
01 00 00 00             ## p_type
07 00 00 00             ## ph_flags: PF-X|PF-W|PF-R = 7
00 00 00 00 00 00 00 00 ## p_offset
00 00 60 00 00 00 00 00 ## p_vaddr
00 00 00 00 00 00 00 00 ## Undefined
9B 01 00 00 00 00 00 00 ## p_filesz
9B 01 00 00 00 00 00 00 ## p_memsz
00 00 20 00 00 00 00 00 ## Required alignment

## Hex
48 83 f8 23        # cmp $0x23,%rax
74 26              # je 6000a4 <purge_comment>
48 83 f8 30        # cmp $0x30,%rax
7c 6f              # jl 6000f3 <ascii_other>
48 83 f8 3a        # cmp $0x3a,%rax
7c 5a              # jl 6000e4 <ascii_num>
48 83 f8 41        # cmp $0x41,%rax
7c 63              # jl 6000f3 <ascii_other>
48 83 f8 47        # cmp $0x47,%rax
7c 58              # jl 6000ee <ascii_high>
48 83 f8 61        # cmp $0x61,%rax
7c 57              # jl 6000f3 <ascii_other>
48 83 f8 67        # cmp $0x67,%rax
7c 47              # jl 6000e9 <ascii_low>
eb 4f              # jmp 6000f3 <ascii_other>

## Purge Comment
48 c7 c2 01 00 00 00 # mov $0x1,%rdx
48 c7 c6 99 01 60 00 # mov $0x600199,%rsi
48 c7 c7 00 00 00 00 # mov $0x0,%rdi
48 c7 c0 00 00 00 00 # mov $0x0,%rax
0f 05                # syscall
48 85 c0             # test %rax,%rax
0f 84 be 00 00 00    # je 600189 <Done>
8a 04 25 99 01 60 00 # mov 0x600199,%al
48 0f b6 c0          # movzbq %al,%rax
48 83 f8 0a          # cmp $0xa,%rax
75 c8                # jne 6000a4 <purge_comment>
48 c7 c0 ff ff ff ff # mov $0xffffffffffffffff,%rax
c3                   # retq

## ascii num
48 83 e8 30          # sub $0x30,%rax
c3                   # retq

## ascii low
48 83 e8 57          # sub $0x57,%rax
c3                   # retq

## ascii high
48 83 e8 37          # sub $0x37,%rax
c3                   # retq

## ascii other
48 c7 c0 ff ff ff ff # mov $0xffffffffffffffff,%rax
c3                   # retq

## start
49 c7 c7 ff ff ff ff # mov $0xffffffffffffffff,%r15
49 c7 c6 00 00 00 00 # mov $0x0,%r14

## Loop
48 c7 c2 01 00 00 00 # mov $0x1,%rdx
48 c7 c6 99 01 60 00 # mov $0x600199,%rsi
48 c7 c7 00 00 00 00 # mov $0x0,%rdi
48 c7 c0 00 00 00 00 # mov $0x0,%rax
0f 05                # syscall
48 85 c0             # test %rax,%rax
74 5d                # je 600189 <Done>
8a 04 25 99 01 60 00 # mov 0x600199,%al
48 0f b6 c0          # movzbq %al,%rax
e8 3c ff ff ff       # callq 600078 <hex>
48 83 f8 00          # cmp $0x0,%rax
7c c7                # jl 600109 <loop>
49 83 ff 00          # cmp $0x0,%r15
7d 0c                # jge 600154 <print>
49 89 c6             # mov %rax,%r14
49 c7 c7 00 00 00 00 # mov $0x0,%r15
eb b5                # jmp 600109 <loop>

## print
49 c1 e6 04          # shl $0x4,%r14
4c 01 f0             # add %r14,%rax
88 04 25 9a 01 60 00 # mov %al,0x60019a
49 c7 c7 ff ff ff ff # mov $0xffffffffffffffff,%r15
48 c7 c2 01 00 00 00 # mov $0x1,%rdx
48 c7 c6 9a 01 60 00 # mov $0x60019a,%rsi
48 c7 c7 01 00 00 00 # mov $0x1,%rdi
48 c7 c0 01 00 00 00 # mov $0x1,%rax
0f 05                # syscall
eb 80                # jmp 600109 <loop>

## Done
48 c7 c7 00 00 00 00 # mov $0x0,%rdi
48 c7 c0 3c 00 00 00 # mov $0x3c,%rax
0f 05                # syscall

## Place for input, This actually isn't required but here it is
02 00 00