libProg | Java Lib to open and handle files

I am currently learning assembler for x86 with att syntax. Over the past time I have already written exercise programs without dependencies. Now I wanted to try writing a shared shared-library, as this is what I do in C most of the time.

I thought it may be a good idea to write a simple "test" program, which consists of an, in asm written, test-library and a program, that links to this test-library.

I assembled the library with: as -32 prog.s -o prog.o
and the caller with: as -32 startprog.s -o startprog.o

After I assembled both files, I ran the linker on the library with ld -melf_i386 -fPIE -shared prog.o -o libprog.so
and on the caller ld -melf_i386 startprog.o -L./ -lprog -o startprog

Up to this point everything worked fine. But then I tried to run the program ./startprog, which causes a Segment violation. I re-ran with gdb and set _start as a breakpoint. As soon as I entered r into gdb, to actually start the execution, I was greeted with the same SIGSEGV. It seems to occur in the libc write() function. At least that is, what I can make of this.

The complete output looks like this: