Major Bugfixing Milestone Unlocks New Development Path for ExectOS

content/news/20250820-bugfixing-milestone.md

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+title = 'Major Bugfixing Milestone Unlocks New Development Path for ExectOS'
+author = 'Aiken Harris'
+date = '2025-08-20T11:13:37+02:00'
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+Over the past month, since the release of XTbuild 3.0.1, development efforts on ExectOS have focused primarily on resolving
+critical bugs that were blocking further progress on the project. While feature development temporarily took a back seat,
+the work done during this period has been substantial - especially considering that it was carried out by a single developer.
+
+These fixes were essential: as new features were being implemented, they frequently triggered unexpected Page Faults in
+regions of the system where memory behavior should have been stable. After extensive debugging, the root causes were traced
+to issues such as incorrect stack alignment and faulty memory mapping. Thankfully, many of these problems have now been
+resolved, paving the way for continued feature development.
+
+## Key Fixes and Improvements
+Among the most important technical fixes completed in the past month:
+* **Removed compiler library dependencies**, particularly the reliance on memset(), ensuring full control over runtime behavior.
+* **Corrected stack initialization**, taking into account that the stack grows downward and should be initialized to its logical
+  end.
+* **Proper stack alignment**, preventing subtle memory access issues.
+* **Enhanced COM port support**, improving serial communication stability.
+  * Resolved a race condition in HlComPortReadLsr by making RingIndicator part of the CPPORT structure instead of using a
+    shared static variable.
+* **Fixed TSS descriptor limit** to comply with the Intel architecture specification.
+* **Improved XTLDR behavior**:
+  * Automatic booting of the default system after a timeout now works reliably.
+  * Proper highlighting of the default boot menu entry.
+  * Refined volume handling in XTLDR, allowing for correct detection of CD/DVD drives.
+  * Fixed bootloader logic in XTOS_O and CHAINLDR modules to ensure the system is booted from the correct volume instead of
+    always defaulting to the ESP partition.
+* **Improved build pipeline**:
+  * Automated builds for both i686 and AMD64.
+  * Separate outputs for debug and release builds.
+* **Explicit paging activation on AMD64**.
+* **Correct initialization of memory-related structures** through zero-filling before usage.
+* **Improved CPUID handling**.
+* **Replaced XTSTATUS with EFI_STATUS** in the bootloader, aligning with EFI standards.
+* **Memory mapping and PML handling fixes**:
+  * Fixed a PDE conflict on i686 systems without PAE when mapping last 4MB
+
+## Additional Enhancements
+In parallel with the bugfixes, several usability and maintainability improvements were introduced:
+* Added a build configuration script for compiling the project on Windows.
+* Replaced hardcoded values with constants and definitions for better maintainability.
+* Implemented menu scrolling support in the XTLDR bootloader.
+* Changed build output directories to allow separate debug and release folders.
+* Implemented kernel parameter support in the bootloader.
+* Full support for PML2 and PML3 in the bootloader, enabling system boot with or without PAE support.
+* Introduced the *NOXPA* parameter to disable PAE (i686) and LA57 (AMD64) as needed.
+* Automatic PML level detection:
+  * The bootloader now queries CPUID for PAE or LA57 support depending on architecture.
+  * If the user hasn't explicitly disabled XPA, the bootloader enables PAE when available.
+  * LA57 remains unsupported for now, but groundwork has been laid.
+
+## One Month, One Developer, One Giant Leap
+Given the size and complexity of the fixes, this is a remarkable milestone for just one month of development. More
+importantly, resolving these core issues has unblocked the project’s forward momentum. With stability greatly improved,
+the path is now clear to resume development of advanced features without being derailed by low-level system bugs.
+
+Stay tuned - the next phase of ExectOS development promises to be an exciting one.