Do not use parallelForEach to call maybeCompress().
Currently LLVM's paralellForEach has a problem with reentracy.
That caused https://bugs.llvm.org/show_bug.cgi?id=35788 (lld somtimes
hangs while linking Ruby 2.4) because maybeCompress calls writeTo
which uses paralellForEach.
This patch is to avoid using paralellForEach to call maybeCompress to
workaround the issue.
This should fix potential hangs when linking parts of ruby24.
[ELF] Compress debug sections after assignAddresses and support
custom layout
Previously, in r320472, I moved the calculation of section offsets
and sizes for compressed debug sections into maybeCompress, which
happens before assignAddresses, so that the compression had the
required information. However, I failed to take account of
relocations that patch such sections. This had two effects:
1. A race condition existed when a debug section referred to a
different debug section (see PR35788).
2. References to symbols in non-debug sections would be patched
incorrectly. This is because the addresses of such symbols are not
calculated until after assignAddresses (this was a partial
regression caused by r320472, but they could still have been
broken before, in the event that a custom layout was used in a
linker script).
assignAddresses does not need to know about the output section size
of non-allocatable sections, because they do not affect the value of
Dot. This means that there is no longer a reason not to support
custom layout of compressed debug sections, as far as I'm aware.
These two points allow for delaying when maybeCompress can be called,
removing the need for the loop I previously added to calculate the
section size, and therefore the race condition. Furthermore, by
delaying, we fix the issues of relocations getting incorrect symbol
values, because they have now all been finalized.
This should fix thread race conditions when linking parts of ruby24.
We normally want to ignore SHT_NOBITS sections when computing
offsets. The sh_offset of section itself seems to be irrelevant and
* If the section is in the middle of a PT_LOAD, it will make no
difference on the computed offset of the followup section.
* If it is in the end of a PT_LOAD, we want to avoid its alignment
changing the offset of the followup sections.
The issue is if it is at the start of the PT_LOAD. In that case we do
have to align it so that the following sections have congruent
address and offset module the page size. We were not handling this
case.
This should fix freebsd kernel link.
In particular, this fixes ctfmerge and/or objcopy throwing "Layout
constraint violation" errors when processing an lld-linked kernel.
Don't create a dummy __tls_get_addr.
We just don't need one with the current setup.
We only error on undefined references that are used by some
relocation.
If we managed to relax all uses of __tls_get_addr, no relocation uses
it and we don't produce an error.
This is less code and fixes the case were we fail to relax. Before we
would produce a broken output, but now we produce an error.
Pull in r320390 from upstream lld trunk (by Rafael Espindola):
Create reserved symbols early so they can be versioned.
This fixes pr35570.
We were creating these symbols after parsing version scripts, so they
could not be versioned.
We cannot move the version script parsing later because we need it for
lto.
One option is to move both addReservedSymbols and
createSyntheticSections earlier. The disadvantage is that some
sections created by createSyntheticSections replace other input
sections. For example, gdb index replaces .debug_gnu_pubnames, so it
wants to run after gc sections so that it can set S->Live to false.
What this patch does instead is to move just the ElfHeader creation
early.
Pull in r320412 from upstream lld trunk (by Rafael Espindola):
Handle symbols pointing to output sections.
Now that gc sections runs after linker defined symbols are added it
can see symbols that point to an OutputSection.
Should fix a bot failure.
Pull in r320431 from upstream lld trunk (by Peter Collingbourne):
ELF: Do not follow relocation edges to output sections during GC.
This fixes an assertion error introduced by r320390.
Differential Revision: https://reviews.llvm.org/D41095
Together these fix handling of reserved symbols, in particular _end,
which is needed to make brk(2) and sbrk(2) work correctly. This
unbreaks the emacs ports on amd64, and also appears to unbreak most of
world on i386.
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D13466
Script commands are processed before unused synthetic sections are
removed. Therefore, if a linker script matches one of these sections
it'll get emitted as an empty output section because the logic for
removing unused synthetic sections ignores script commands which
could have already matched and captured one of these sections. This
patch fixes that by also removing the unused synthetic sections from
the script commands.
Discussed with: dim
Obtained from: LLVM r307037
Sponsored by: The FreeBSD Foundation
The change was made to support glibc and believed to be a no-op on
FreeBSD, but that is not the case for architectures with multiple page
sizes, such as arm64. The relro p_memsz header was rounded up to the
default maximum page size (64K). When 4K pages are in use, multiple
pages beyond the final PT_LOAD segment had their permissions changed to
read-only after application of relocations and copy relocations, which
led to a segfault in certain cases.
This reverts upstream r290986. I have started a discussion about the
upstream fix on the LLVM mailing list.
Reported by: andrew
Sponsored by: The FreeBSD Foundation
