Error 13: Invalid or unsupported executable while booting simple kernel in grub with string literal

Question

I\'ve written a simple kernel that tries to write two characters to the frame buffer.

If I define a string literal in the kernel, I get the following output when it

Answer 1

You have an extra colon at the end of section .text: so that creates a new section named .text:. For some obscure reason that I couldn't find out from a quick glance at the documentation, this section is emitted to the output even though it is not listed in your linker script. When you have no literal data in the C code, you are lucky that it still falls within the first 8kiB of the image, so that the multiboot header is in the required portion. If you do have a string literal, you will get a new section .rodata and that, for yet another obscure reason, gets sorted before your .text: but after the standard .text. Example:

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00000001  00100000  00100000  00001000  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .rodata       00000005  00101000  00101000  00002000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .text:        00000018  00101008  00101008  00002008  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .bss          0000100a  00102000  00102000  00003000  2**2
                  ALLOC

As you can see it's no longer within the first 8kiB of the image, so grub will be very sad.

TL;DR: remove the extra colon after section .text:.