arch/x86_64: Reimplement the NuttX32 multiboot1 wrapper.

[Fix-Point]

In the previous implementation, we had to copy the entire NuttX to ensure that the executable runs at the correct address. Additionally, we were not loading the .realmode section, which led to issues with SMP booting.

Summary

This commit reimplemented the NuttX32 multiboot1 wrapper:

1. Fixed the issue of SMP AP booting.
2. Reduced memory copy overhead. We only need to copy .realmode section now.
3. Move the multiboot1 header to intel64_head.S.

Impact

x86_64 boot.

Testing

Tested on x86_64 qemu.

[nuttxpr]

[Experimental Bot, please feedback here]

The PR description doesn't fully meet the NuttX requirements. Here's a breakdown:

Strengths:

• Summary: Clearly states the problem, solution, and affected code area.
• Testing: Mentions the testing environment (x86_64 qemu).

Weaknesses:

• Impact:
  • Lacks specificity. "x86_64 boot" is too broad. Mention specific boards or configurations affected.
  • Doesn't address all impact categories:
    • User Impact: Will users need to reconfigure anything?
    • Build Impact: Any changes to build process, tools, dependencies?
    • Hardware Impact: Specific architectures, boards, drivers affected?
    • Documentation: Does anything need updating? Is documentation included?
    • Security: Any implications on security?
    • Compatibility: Any backward/forward compatibility concerns?
• Testing:
  • No logs provided: Include relevant logs from before and after the change.
  • Limited testing detail: Specify the exact steps taken for testing.

Recommendations:

1. Expand the Impact section: Address all impact categories with specific details.
2. Provide testing logs: Include relevant logs showcasing the issue before and the fix after.
3. Detail testing steps: Describe the exact steps taken to test the changes.

Example for Improvement:

Impact:

• Is new feature added? Is existing feature changed?: Existing feature (multiboot1 wrapper) fixed and improved.
• Impact on user: Users with custom multiboot1 configurations might need to adjust their configurations due to the .realmode section changes.
• Impact on build: No changes to the build process itself.
• Impact on hardware: Specifically affects x86_64 systems booting NuttX using the multiboot1 specification. This impacts boards like the QEMU x86_64 virtual machine.
• Impact on documentation: The x86_64 boot process documentation should be updated to reflect the changes to the multiboot1 implementation.
• Impact on security: No known security implications.
• Impact on compatibility: This change improves compatibility with SMP systems booting via multiboot1. No backward compatibility issues anticipated.

By addressing these points, you can create a more complete and informative PR that aligns with the NuttX requirements.