linux - Executing machine codes attached at the end of an executable

Question

I have a object file which has a main() function inside and just needs to be linked with crt... objects to be an executable . Unfortunately I can only compile and I can not link it to be an executable .

so I decided to create a c program ( on a pc with working GCC and linker ) to attach object(s) at the end of itself and execute the codes attached at run time (simulating a linked object ).

I saw DL API but I do'nt know how to use it for the problem I said .

May sb help me to know , how I can executing a code attached at the end of an executable .

Answer 1

Avoid doing that; it would be a mess .... And it probably won't reliably work, at least if the program is dynamically linked to the ?libc6.so (e.g. because of ASLR)

Just use shared objects and dynamically linked libraries (See dynamic linker wikipage). You need to learn about dlopen(3) etc.

If you really insist, take many weeks to learn a lot more: read Levine's book on Linker and Loaders, read Advanced Linux Programming, read many man pages (including execve(2), mmap(2), elf(5), ld.so(8), ...) study the kernel code for execve and mmap, the GNU libc and MUSL libc source codes (for details about implementations of the dynamic linker), the x86-64 ABI or the ABI for your target processor (is it an ARM?), learn more about the GNU binutils etc, etc, etc.

^{In short, your life is too short doing such messy things, unless you are already an expert, e.g. able to implement your own dynamic linker.}

addenda

Apparently your real issue seems to use tinycc on the ARM (under Android I am guessing). I would then ask on their mailing list (perhaps contribute with some patch), or simply use binutils and make your own GNU ld linker script to make it work. Then the question becomes entirely different and completely unrelated to your original question. There might be some previous attempts to solve that, according to Google searches.