I’m currently at a point where I need to link in several modules (basically ELF object files) to my main executable due to a limitation of our target (background: kernel, targeting the ARM architecture). On other targets (x86 specifically) these object files would be loaded at runtime and a specific function in them would be called. At shutdown another function would be called. Both of these functions are exposed to the kernel as symbols, and this all works fine.
When the object files are statically linked however there’s no way for the kernel to “detect” their presence so to speak, and therefore I need a way of telling the kernel about the presence of the init/fini functions without hardcoding their presence into the kernel – it needs to be extensible. I thought a solution to this might be to put all the init/fini function pointers into their own section – in much the same way you’d expect from .ctors and .dtors – and call through them at the relevant time.
Note that they can’t actually go into .ctors, as they require specific support to be running by the time they’re called (specifically threads and memory management, if you’re interested).
What’s the best way of going about putting a bunch of arbitrary function pointers into a specific section? Even better – is it possible to inject arbitrary data into a section, so I could also store stuff like module name (a struct rather than a function pointer, basically). Using GCC targeted to arm-elf.
GCC attributes can be used to specify a section: