7cf3ed38da
Most of register fiddling routines (which is now the only thing contained in care.asm) are used by almost all userspace apps, often in inner loops. That makes the penalty of using jump tables for those a bit too high. Moreover, it burdens jump tables needlessly. Because this unit is very small (now that string routines are out), it makes sense to always include it in binaries. |
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|---|---|---|
| .. | ||
| .gitignore | ||
| glue.asm | ||
| Makefile | ||
| README.md | ||
| user-tmpl.h | ||
zasm and ed from ROM
SMS' RAM is much tighter than in the RC2014, which makes the idea of loading apps like zasm and ed in memory before using it a bit wasteful. In this recipe, we'll include zasm and ed code directly in the kernel and expose them as shell commands.
Moreover, we'll carve ourselves a little 1K memory map to put a filesystem in there. This will give us a nice little system that can edit small source files compile them and run them.
Gathering parts
- A SMS that can run Collapse OS.
- A PS/2 keyboard adapter
Build
There's nothing special with building this recipe. Like the base recipe, run
make then copy os.sms to your destination medium.
If you look at the makefile, however, you'll see that we use a new trick here: we embed "apps" binaries directly in our ROM so that we don't have to load them in memory.
Usage
Alright, here's what we'll do: we'll author a source file, assemble it and run it, all on your SMS! Commands:
Collapse OS
> fnew 1 src
> ed src
: 1i
.org 0xc200
: 1a
ld hl, sFoo
: 2a
call 0x3f
: 3a
xor a
: 4a
ret
: 5a
sFoo: .db "foo", 0
: w
> fnew 1 dest
> fopn 0 src
> fopn 1 dest
> zasm 1 2
First pass
Second pass
> dest
foo>
Awesome right? Some precisions:
- Our glue code specifies a
USER_RAMSTARTof0xc200. This is wheredestis loaded by thepgmshell hook. 0x3fis the offset ofprintstrin the jump table of our glue code.xor ais for the command to report as successful to the shell.