Rewrite build system?

[phil-opp]

Currently the build process is a bit strange:

• First, we build the kernel
• Then we convert the ELF file to a binary
• Then we append a 512 byte sized structure that contains the kernel length
• Finally we append the kernel

We could change it in the following way:

• We could create a build script that reads an BOOTLOADER_KERNEL_PATH environment variable, converts it to a binary blob and then back to an object file (e.g. cargo objcopy -- -I binary -O elf64-x86-64 target/x86_64-blog_os/debug/blog_os blog_os_bin.o --binary-architecture=i386:x86-64)
• Rename the default .data section to .kernel
• The build script then passes the object file to the linker
• This means that we can directly access the kernel blob in the linker script and directly access start/end/size of the kernel

The new build process would be:

• Build the kernel
• Build the bootloader (with an environment variable set to the kernel path)
• Convert the bootloader ELF file to a binary

The big disadvantage of this is that we need to rebuild the bootloader for each kernel change, so maybe it is better to keep the current build system.

[meteor-lsw]

I think rebuild the bootloader for each kernel change is not a good idea

[phil-opp]

It wouldn't really recompile the bootloader, but it would rerun the build script and the linker. I think this shouldn't add much overhead, but I'm not 100% sure.