- Make the secondary entry point be logically separate function, though
declared in the same file.
- Add a trick where the kernel base + 4 is the secondary entry point.
Not really useful except makes it easy to compute the offset
elsewhere.
- Changed the entry point to arm64_reset and move _start to the linker
script, which is what most other arches do.
- While was in the linker script, make sure the text segment is aligned
on MAXPAGESIZE, though doesn't make any real difference currently.
- Generally clean up the assembly in start.S with newer macros from
Fuchsia, and avoid using ldr X, =value as much as possible.
- Fix and make sure arm64 can build and run with WITH_SMP set to false.
Add a new no-smp project to test this.
Note this will likely break systems where all of the cpus enter the
kernel simultaneously, which we can fix if that becomes an issue.
Secondary code now completely assumes the cpu number is passed in x0.
This can be emulated with platform specific trampoline code if it needs
to that then just directs into the the secondary entry point, instead of
trying to make the arch code have to deal with all cases.
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