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Diffstat (limited to 'Readme.md')
| -rw-r--r-- | Readme.md | 34 |
1 files changed, 23 insertions, 11 deletions
@@ -1,15 +1,19 @@ # Motorola 68000 Disassembler -> Disassemble into what `as` can assemble back +> Disassemble some M68000 machine code into what an assembler can assemble again This project aims to be a disassembler that is capable to produce assembly code -that GNU AS will translate into the same original machine code. It's only use -case for now is Sega Mega Drive / Genesis ROM hacking. I failed to find any way -to disassemble SMD ROMs in such a way that it would be possible to assemble it -back with GNU AS. All disassemblers I tried produce either syntactically -incompatible assembly listing, or it is not the same as original binary after -translation into machine code. So I decided to build my own disassembler, that -will do exactly what I need with full control over the process and maybe more. +that an assembler will translate into the same original machine code. It could +be called a *matching disassembling*. GNU AS and Sierra ASM68 assemblers are +currently supported. + +It's only use case for now is Sega Mega Drive / Genesis ROM hacking. I failed to +find any way to disassemble SMD ROMs in such a way that it would be possible to +assemble it back into binary. All disassemblers I tried produce either +syntactically incompatible assembly listing, or it is not the same as original +binary after translation into machine code. So I decided to build my own +disassembler, that will do exactly what I need with full control over the +process and maybe more.  @@ -112,9 +116,10 @@ To get detailed help you can run: Goals of this Motorola 68000 disassembler project in this particular repo: - Support all Motorola 68000 ISA instructions. -- Flawless compatibility with GNU AS syntax. It should always emit the code on - which GNU AS produces absolutely identical binary (with or without linkage) - without errors or warnings, unless some peculiar flags has been specified. +- Flawless compatibility with GNU AS and Sierra ASM68 syntax. It should always + emit the code on which GNU AS produces absolutely identical binary (with or + without linkage) without errors or warnings, unless some peculiar flags has + been specified. - Support PC trace tables. With trace tables it will disassemble traced PC locations only, without attempt to disassemble everything, because not everything is instruction, some code is just data. @@ -148,6 +153,9 @@ What is **not** the goal (at least not in this repo): - It generates GNU AS compatible listing, that may be translated back to machine code using `m68k-none-elf-as` in the way that it matches original binary file, no matter what. +- It generates Sierra ASM68 compatible listing, that may be translated back to + machine code using `ASM68` in DOS environment in the way that it matches + original binary file, no matter what. - It generates labels for all jump instructions (JSR, JMP, BRA, Bcc and DBcc) if jump location is inside the code being disassembled. This feature can be enabled with `-flabels`, `-frel-labels` and `-fabs-labels` options, all at @@ -160,6 +168,10 @@ What is **not** the goal (at least not in this repo): `--pc-trace=file` to disassemble only what is supposed to be instructions and leave all the rest as raw data. Otherwise it will try to disassemble everything. +- Automatic and non-committing code discovery with jump follow with `-fwalk` and + `-ffollow-jumps`. I.e. when PC trace table provided, the disassembler will try + it's best to disassemble non-traced continuous code spans, until unknown + instruction or unconditional branch encountered. ### Limitations |