LLD 10.0.0 changed the behavior of the -Ttext option, so that using
-Ttext=0x0 now causes linking of the loaders to fail with:
ld: error: output file too large: 18446744073707016908 bytes
I reported this in https://bugs.llvm.org/show_bug.cgi?id=44715, and
initially reverted the upstream change in r357259 to work around it.
However, after some discussion with Fangrui Song in the upstream ticket,
I think we can classify this as an unfortunate interaction between using
-Ttext=0 in combination with --no-rosegment. (We added the latter
in r332090, because btxld does not correctly handle input with more
than 2 PT_LOAD segments.)
Fangrui suggested to use a linker script instead, and Warner was already
attempting this in r305353, but had to revert it due to "crypto-using
boot problems" (not sure what those were :).
This review updates the stand/i386/boot.ldscript to handle more
sections, inserts some symbols like _edata and such that we use in
libsa, and also discards any .interp section.
It uses ORG which is defined on the linker command line using
--defsym ORG=value to set the start of all the sections.
Reviewed by: imp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D23952
This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo". That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.
Updating the vendor area to match this layout is next.
ufsread.c grows a dependency on __ashldi3 with llvm90. Grab ashldi3.c out of
compiler-rt rather than trying to link against libsa (for now).
-Wno-missing-prototypes is necessary to compile ashldi3.c standalone.
Reviewed by: imp
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D21291
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
boot2, so CLANG_NO_IAS was not previously removed for those.
In the case of boot2 the difference is that IAS produces a larger
encoding for one instruction (the testb at the beginning of read).
GNU as produces:
2e f6 06 b0 08 80
while IAS includes an address size override prefix (67) and produces:
2e 67 f6 05 b3 08 00 00 80
This results in three fewer NOPs elsewhere in boot2 but no functional
change, so switch to IAS for boot2.
(We can separately pursue improved 16-bit IAS support with the LLVM
developers.)
Sponsored by: The FreeBSD Foundation
Curiously, changing whitespace seems to cause the md5 of the .o files to differ
these days hence the following testing strategy:
Tested by: objdump -d | md5 (both in-tree clang and lang/gcc6)
