Turns out there's two hidden a.out dependencies. pxeldr.S assumes it has
access to the a.out header from /boot/loader and cdboot.S assumes that
/boot/loader is also a.out and doesn't use boot2.
So, go back to making a.out files for these and adjust the size checks
to use ls, but we only need to check loader.bin. Trim the size we check
against by 2,000. The difference in size between loader and loader.bin
is about 3000 bytes, but clang15 produces binaries that are a smidge
bigger so we need to relax the check just a little and accept some
additional risk for the moment.
Add some comments to loader's Makefile about this.
Sponsored by: Netflix
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D36142
It's sometimes desirable to override the size limit: It's a soft limit
and there are times we exceed the limit by just a little bit and don't
want the build to fail (or we are hitting runtime failures below the
510,000 byte limit).
Sponsored by: Netflix
The BIOS method of booting imposes an absolute limit of 640k for the
size of the program being run due to btx. In practice, this means that
programs larger than about 500kiB will fail in odd ways as the stack /
heap will overflow.
Pick 510,000 as the cutoff line semi-arbitrarily. loader_lua is now
almost too big and we want to break the build when it crosses this
threshold. In my experience, below 500,000 always works, above 520,000
always seems to fail with things getting bad somewhere between 512,000
to 515,000. 510,000 is as close to the line as I think we can go, though
experience may dictate we need to lower this in the future.
This is at-best a stop-breakage until we have a better way to subset the
boot loader for BIOS booting to allow better, more fined-tuned
/boot/loaders for the many different environments they have to run
in. This likely means we'll have a graphical loader than understands a
few filesystmes for installation, and a non-graphical loader that
understands the most filesystems possible for everything else in the
future. Our build infrastructure needs some work before we can do that,
however.
At this late date, it likely isn't worth the efforts to move parts of
the loader into high memory. There's a number of assumptions about where
the stack is, where buffers reside, etc that are fulfilled when it lives
in the first 640k that would need bounce buffers and/or other counter
measures if we were to split it up. All BIOS calls are done in 16-bit
mode with SEG:OFF addresses, requiring them to be in the first 640k of
RAM. And nearly all machines in the last decade can boot with UEFI
(though there's some exceptions, so it isn't worth killing outright
yet).
Sponsored by: Netflix
Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D36129
The first level boot blocks have understood how to load ELF code since
1999. Switch /boot/loader and /boot/pxeldr over to being ELF format so
that in-tree tools can examine them more closely. In addition, one
could, in theory, now have a 'lo-mem' and a 'hi-mem' segment (though a
lot of work would need to be done with bounce buffers, btx, code segment
marking, etc for an arrangement like that to work).
As far as I can tell, this is the last a.out binary in the tree. There
are several raw binaries left, but everything else is ELF.
Reviewed by: emaste, kevans
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D36130
While I was there:
- Fix some typos
- Fix an excessive argument "indent" reported by mandoc -Tlint
- Replace a dead link with the one suggested by
https://www.uefi.org/uefi
Submitted by: linimon (in part)
Reviewed by: bcr
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D27774
The same thing can be achieved using the bs=$SIZE and conv=sync options.
Unlike conv=osync, conv=sync is support on both Linux and macOS.
Reviewed By: imp, jhb (earlier version)
Obtained from: CheriBSD
Differential Revision: https://reviews.freebsd.org/D24788
Many components under stand/ had CLANG_NO_IAS added when Clang's
Integrated Assembler (IAS) did not handle .codeNN directives. Clang
gained support quite some time ago, and we can now build stand/ with
IAS. In most cases IAS- and GNU as-assembled boot components were
identical, and CLANG_NO_IAS was already removed from other components.
Clang IAS produces different output for some components, including
pxeldr, so CLANG_NO_IAS was not previously removed for those.
In the case of pxeldr the difference is that IAS adds a size override
prefix (67h) to three instructions to specify a 32-bit address, even
though the two high bytes are zero and the address fits in 16 bits.
this wastes three bytes per instruction and causes some additional nop
npadding to be required elsewhere in the object, but pxeboot is not
size-constrained so it doesn't matter.
Sponsored by: The FreeBSD Foundation
Create loader_{4th,lua,simp}{,.efi}. All of these are installed by
default. Create LOADER_DEFAULT_INTERP to specify the default
interpreter when no other is specified. LOADER_INTERP is the current
interpreter language building. Turn building of lua on by default to
match 4th. simploader is a simplified loader build w/o any interpreter
language (but with a simple loader). This is the historic behavir you
got with WITHOUT_FORTH. Make a hard link to the default loader. This
has to be a hard link rather than the more desirable soft link because
older zfsboot blocks don't support symlinks.
RelNotes: Yes
Differential Revision: https://reviews.freebsd.org/D16705
