As a start a simple loader for Atari ST Gemdos programs.
To install: place this python script inside the loaders directory
of IDA. Tested with IDA Pro 7.2 in macOS, but it should work on any
platform. On macOS/Linux you can simply copy the loaders directory
to ~/.idapro. If the directory already exists, just copy the script into
it.
Open an Atari Gemdos file in IDA, if the file header matches, it will automatically detect it and creates TEXT/DATA/BSS segments, load the data, relocates the application and even applies a symbol table, if it exists within the file.
The GST extended DRI symbol format is also supported, so up to 14 character long symbols do work. Currently only global symbols are supported, not local ones or register based ones.
In the script you can find AtariSTBaseAddress, which is the address
where the program is loaded. It is 0x10000 to avoid any overlap with
low-memory variables.