Fixing bugs in sample code

August 26, 2020

In the last day I’ve found bugs in two different kernel code samples I’ve been using as a reference for my own hobby OS. I’ve done by best to correct them.

The first was in this blog post which contains (among other things) an example of how to set up a Global Descriptor Table (GDT) and Task State Segment (TSS), but it mixed up the code and data segments when installing the GDT, and forgot to set the most-significant 16 bits of the TSS address in its GDT descriptor. I’ve emailed the author with details.

Second issue was in bootboot which is the bootloader I’m using to boot my hobby OS. It includes a sample “hello world” c kernel which declares a extern char* environment pointing to a string containing kernel arguments, whose address is specified in a linker script, but treats environment as if its value was the address of the argument string (it should have been a char array). I made a pull request to address this.