Sync the ld scripts:

* Force a PAGE_SIZE alignment of .bss on i386. Normally that's not
required since the bootloader ensures page alignment, but let's be
safe. Same on Xen-i386.

* Fill the .text section padding with int3 instructions on Xen kernels,
to prevent FALLTHROUGHs if a pointer goes crazy, same as native.

branches: 1.21.2;
Implement a real hotpatch feature.

Define a HOTPATCH() macro, that puts a label and additional information
in the new .rodata.hotpatch kernel section. In patch.c, scan the section
and patch what needs to be. Now it is possible to hotpatch the content of
a macro.

SMAP is switched to use this new system; this saves a call+ret in each
kernel entry/exit point.

Many other operating systems do the same.

Fill the .text padding with 0xcc (int3), in such a way that any jump into
this area will automatically fault. The alignment within the section is
necessary, in order to fill strictly all of the padding (took me a while
to figure this out); but it does not change the kernel size.

Greatly inspired from FreeBSD, but for some reason they decided not to
apply the alignment.

branches: 1.19.10;
Align the segments on i386. We're going to map them independently.

Define __kernel_end.

Split the {text+rodata} chunk in two separate chunks on x86. The
rodata segment now loses the large page optimization, gets mapped inside
the data segment, and therefore becomes RWX. It may break the build on
Xen.

KNF

Replace a constant in ldscript.

Don't need to specify OUTPUT_FORMAT/OUTPUT_ARCH in linker scripts.

Simplify these by doing AT () relocation once.

Indent with 2 spaces.

branches: 1.11.2;
Revert previous per joerg@'s request.

According to him, exposing .data.{read_mostly,cacheline_aligned} is
intentional so that people can easily see which variables are optimized.

amd64, i386: Don't expose .data.{read_mostly,cacheline_aligned} sections

sync ldscripts; add cacheline_aligned and read_mostly handling
to the non-default ones.

branches: 1.8.8; 1.8.14; 1.8.18;
Add __cacheline_aligned and __read_mostly annotations.

These annotations help to mitigate false sharing on multiprocessor
systems.

Variables annotated with __cacheline_aligned are placed into the
.data.cacheline_aligned section in the kernel. Each item in this
section is aligned on a cachline boundary - this avoids false
sharing. Highly contended global locks are a good candidate for
__cacheline_aligned annotation.

Variables annotated with __read_mostly are packed together tightly
into a .data.read_mostly section in the kernel. The idea here is that
we can pack infrequently modified data items into a cacheline and
avoid having to purge the cache, which would happen if read mostly
data and write mostly data shared a cachline. Initialisation variables
are a prime candiate for __read_mostly annotations.

branches: 1.7.20; 1.7.34; 1.7.40; 1.7.42;
merge yamt-x86pmap branch.

- reduce differences between amd64 and i386. notably, share pmap.c
between them. it makes several i386 pmap improvements available to
amd64, including tlb shootdown reduction and bug fixes from Stephan Uphoff.
- implement deferred pmap switching for amd64.
- remove LARGEPAGES option. always use large pages if available.
also, make it work on amd64.

branches: 1.6.6; 1.6.22; 1.6.24; 1.6.26; 1.6.28;
keep the note section

branches: 1.5.6; 1.5.8;
New linker scripts for the i386 kernel. The main improvement is setting the
physical load address correctly. (Before, it was set to the same very high
value as the virtual address.)

Provided by Jason Thorpe in
http://mail-index.netbsd.org/port-i386/2006/02/10/0008.html
with some modifications by me, mainly to make the output more similar to
the current one, and to not hardwire the physical and virtual addresses.

See also:
http://mail-index.netbsd.org/port-i386/2006/05/19/0001.html

Now an unpatched grub can load a NetBSD Multiboot kernel.

branches: 1.4.4; 1.4.6; 1.4.8; 1.4.14;
merge ktrace-lwp.

branches: 1.3.12;
put back SIZEOF_HEADERS now that bfd is fixed; you will need to recompile
libbfd...

Use 1024 instead of SIZEOF_HEADERS, so that we can include a note section.

branches: 1.1.2; 1.1.4; 1.1.28;
Add a linker script for the kernel, which places _etext after
all of the read-only data. Move _etext after all the read-only
data in the LARGEPAGES script, as well.

This will cause const data to actually be const on i386 kernels now
(it was, by sheer luck, on LARGEPAGES kernels simply because of the
section rounding that the LARGEPAGES script performed).