Take care of Segments before entering C programmed binaries

Assume that your loader is written by ASM, and your kernel is written by C. When your loader is to jump to kernel start addr, you have to set ds, es, ss to the same value. I think C language has promised that all its data after compiling will be put to the same segment, under protected mode. So, at runtime, you should promise it too. But you should know that C compiler will not set these three segment registers' values to the current segment because it won't figure out you are writing an OS (I think :)).

But there's another issue left, making ds, es, ss unique means that all your data should be put to the same segment where the kernel also exists. So it'll be too complex if you separate your kernel into an individual segment.

So, as the common solution, treat the whole 4G memory as one segment before entering kernel. Don't worry, you have chance to update GDT later:)