My OS kernel in D: some built-in lines do not work

Question

I know this is a rather difficult question to answer, mainly because there are so many things that can be wrong, and it's hard to catch. But I will give as much information as possible; hope this helps.

I started writing my own kernel using the D language and the Digital Mars D compiler, and after many problems figuring out how to create flat binary files that can be moved, I finally came up with the idea of ​​creating a regular PE file for address 0xC0000000 and replacing all its headers byte 0x90 (operation code NOP). This worked perfectly, and I could write things on the screen, set up paging, enter protected mode, etc. Great, of course, with the help of the help of a 16-bit build-based assembly loader.

Everything was fine, that is, I decided to port the D runtime library for use in my kernel. I managed to extract a subset of the library and modify it so that it was compiled into my application. Then I launched my program. (Note: I didn’t use the whole library, my code was the first code executed after loading - the first thing that happened was printing "Kernel" on the screen and the lack of runtime caused the code before.)

The AD array (and therefore the string, since the string is just char[] ), is nothing more than a structure with a pointer and a size member, so on a 32-bit system it will be 8 bytes. The funny thing is that when I ran my program, members of the structure showed that they are equal to zero, that is, both pointers and size are equal to zero. (I checked this by typing the value of the pointer on the screen, as well as the length member - both were zero.) As soon as I deleted the source code for the runtime (which was never executed), they worked fine.

I narrowed this down to two possibilities:

• The stack somehow wasn’t configured correctly: I solved it because everything worked perfectly without a runtime library, and I confirmed that another code was not executed before my code by parsing the file.

• Something is funny with sections of the PE file: I checked and found out that there are two TLS (thread-local) variables in the version in the version. Of course, when I made them shared (not streamed), my code worked! However, my code still showed the same problem when I called the code that I wrote in another file - only kernel.d , which is the launch file, correctly lines up; in other files, the arrays were zero again.

Now, can anyone guess why this could happen?

If you need more information, I will be happy to publish it.

Thanks!

Answer 1

In a year...

Solved !: D

(> '.')> (^ '.' ^) <('.')> (v '.' v) <('.' <)

This was a problem with my bootloader: I read too few sectors in memory. (Namely, 64 sectors instead of 128 125.)

Answer 2

First, disclaimer: I do not know first about D.

Secondly, another expression of disclaimer. Based on the use of the term "PE file", I am going to suggest that you are using Windows. I'm going to give a suggestion on the GNU software chain ...

But ... Assuming the D compiler generates object files just like the others ... Why not do the following (this is what I did when I was working on an OS hobby in C, when I had time for such things ):

• Create an ELF binary for your kernel ... To do this, create all your object files as usual. In the link step, copy the script linker to ld , which will determine things like the start address, section order (text, data, data, etc.) of the binary ...
• Download it with GRUB (easy enough to do ... you need to add some magic words next to the beginning of your binary file. You can do this using db or dw operators of type in the .asm file, provided that the corresponding obj ends with a link near the beginning of the kernel Check this link )

This way you can focus on more interesting things than hacking a PE header or writing a bootloader.

Of course ... It sounds quite possible that there is some kind of problem in the code, not how you link. It may be informative to run it into something that allows you to get through the assembly. The x86 qemu PC emulator has some debugging options that output the build and log status to the log. I used this.