SMP boot code mapping got broken on Hermit

[cagatay-y]

It seems like 0c51a72 broke SMP on Hermit. When I start Hermit with

  cargo xtask ci rs --arch x86_64 --profile dev  --package thread_test --smp 4 qemu --accel --sudo

it fails at

kernel/src/arch/x86_64/kernel/apic.rs

Lines 767 to 776 in dd4c82a

	// Identity-map the boot code page and copy over the code.
	debug!("Mapping SMP boot code to physical and virtual address {SMP_BOOT_CODE_ADDRESS:p}");
	let mut flags = PageTableEntryFlags::empty();
	flags.normal().writable();
	paging::map::<BasePageSize>(
	SMP_BOOT_CODE_ADDRESS,
	PhysAddr::new(SMP_BOOT_CODE_ADDRESS.as_u64()),
	1,
	flags,
	);

. I do not know if it is the loader that should not map the way it does or the kernel should not assume that the mapping does not exist / is 4 KiB-sized.

[mkroening]

This is a kernel issue, not a loader issue. The kernel should handle this gracefully.