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Bran's Kernel Development Tutorial Known Bugs: Difference between revisions
Bran's Kernel Development Tutorial Known Bugs (view source)
Revision as of 19:46, 12 July 2022
, 1 year agoFix typographical error
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Several sources - including this Wiki - point to [http://osdever.net/bkerndev/Docs/basickernel.htm Bran's Kernel Development Tutorial] as a starting point. This is all well, but there are some issues with that tutorial that usually make people appear on the forum and asking all the same questions again. This article is meant to preempt those questions, like a "Bran's FAQ" if you like.
NOTE: osdever.net, the site that contains Bran's tutorial, went down for an extended amount of time recently. You can find it no matter what on the [http://web.archive.org/web/20190306175430/http://osdever.net/bkerndev/Docs/basickernel.htm Internet Archive].
===As soon as I add strings, things go wrong.===
Line 13 ⟶ 15:
code = .;
*(.text)
'''*(.rodata*)'''
. = ALIGN(4096);
}
Line 48 ⟶ 50:
}
}
</syntaxhighlight>
===Does not properly set up PIT===
The tutorial says the PIT setup code snippet it provides is "optional", when in reality it isn't.
===Does not use Cross-Compiler===
Bran's Kernel Tutorial uses DJGPP and NASM (standard install) on windows.<br />
To allow the code to link on a cross-compiler you must first remove all leading underscores from Global and External ASM Labels.
===Divide by zero interrupt does not get raised===
After implementing the IDT and ISRs, the tutorial explains that dividing by zero will now raise the exception 'divide by zero' and consequently execute the fault handler. The tutorial provides the following C code:
<syntaxhighlight lang="c">
int i = 10 / 0;
</syntaxhighlight>
The fault handler on this exception, however, will not be raised and nothing happens. Compilers usually optimize and insert some extra code (so there is actually no divide by zero). The only way to guarantee this exception is raised is to write some in-line assembly like:
<syntaxhighlight lang="c">
__asm__ ("div %0" :: "r"(0));
</syntaxhighlight>
===Compiler error: unknown type name ‘size_t'===
GCC produces the following errors: ''unknown type name 'X'''. The tutorial source code doesn't include any standard definitions for types like ''size_t'' or ''uint32_t''. Including the following headers in each source file:
<syntaxhighlight lang="c">
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
</syntaxhighlight>
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