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config(1): TODO about kernel linkage

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uebayasi 2014-11-07 16:41:17 +00:00
parent 74d147444a
commit 701e371cb2
1 changed files with 46 additions and 0 deletions
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usr.bin/config/TODO
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@ -183,3 +183,49 @@ o Shared kernel objects.
While leaving optimizations as options (CPU specific optimizations, inlined
bus_space(9) operations, etc.) for users, the official binaries build
provided by TNF should be as portable as possible.
o Control ELF sections using linker script.
Now kernel is linked and built directly from object files (*.o). Each port
has an MD linker script, which does everything needed to be done at link
time. As a result, they do from MI alignment restriction (read_mostly,
cacheline_aligned) to load address specification for external boot loaders.
Make this into multiple stages to make linkage more structural. Especially,
reserve the final link for purely MD purpose.
Monolithic build:
*.o ---> netbsd.ko Generic MI linkage
netbsd.ko ---> netbsd.ro Kernel MI linkage
netbsd.ro ---> netbsd Kernel MD linkage
Modular build (kernel):
*.o ---> *.ko Generic + Per-module MI linkage
*.ko ---> netbsd.ro Kernel MI linkage
netbsd.ro ---> netbsd Kernel MD linkage
Modular build (module):
*.o ---> *.ko Generic + Per-module MI linkage
*.ko ---> *.ro Modular MI linkage
*.ro ---> *.kmod Modular MD linkage
Genric MI linkage is for processing MI linkage that can be applied generally.
Data section alignment (.data.read_mostly and .data.cacheline_aligned) is
processed here.
Per-module MI linkage is for modules that want some ordering. For example,
machdep.ko wants to put entry code at the top of .text and .data.
Kernel MI linkage is for collecting kernel global section data, that is what
link-set is used for now. Once they are collected and symbols to the ranges
are assigned, those sections are merged into the pre-existing sections
(.rodata) because link-set sections in "netbsd" will never be interpreted by
external loaders.
Kernel MD linkage is used purely for MD purposes, that is, how kernels are
loaded by external loaders. It might be possible that one kernel relocatable
(netbsd.ro) is linked into multiple final kernel image (netbsd) for diferent
load addresses.
XXX Modular MI linkage
XXX Modular MD linkage