Unlike gold, bfd, gas or MC we were putting exidx sections first since
they are ro.
The spec doesn't explicitly say that they must come after, but it is
definitely more convenient for the consumer, matches other producers
and matches other areas in ELF (like SHT_GROUP) where sections are
ordered in a natural way.
llvm-svn: 286659
We would create a MergeInputSection for the synthetic .comment and
crash trying to add it to a regular output section.
With this we just don't add the synthetic section with -r. That is
consistent with gold that doesn't create .note.gnu.gold-version with
-r.
llvm-svn: 286635
Summary:
This patch adds a ".comment" section to an output. The comment
section contains the linker's version string. You can now
find out whether a binary is created by LLD or not using objdump
command like this.
$ objdump -s -j .comment foo
foo: file format elf64-x86-64
Contents of section .comment:
0000 00474343 3a202855 62756e74 7520342e .GCC: (Ubuntu 4.
0010 382e342d 32756275 6e747531 7e31342e 8.4-2ubuntu1~14.
...
00c0 766d2f74 72756e6b 20323835 38343629 vm/trunk 285846)
00d0 004c696e 6b65723a 204c4c44 20342e30 .Linker: LLD 4.0
00e0 2e302028 7472756e 6b203238 36343036 .0 (trunk 286406
00f0 2900 ).
Compilers emits .comment section as well, so the output contains
both compiler and linker information.
Alternative considered:
I first tried to add a SHT_NOTE section because GNU gold does that.
A NOTE section starts with a header which contains content type.
It turned out that ld.gold sets type NT_GNU_GOLD_VERSION to their
NOTE section. So the NOTE type is only for GNU gold (surprise!)
Next, I tried to create ".linker-version" section. However, it seems
that reusing the existing ".comment" section is better because 1)
other tools already know about .comment section and is able to strip
it and 2) the result contans not only linker info but also compiler
info.
Differential Revision: https://reviews.llvm.org/D26487
llvm-svn: 286496
In a non-LTO build is a nop. In a LTO build, we deallocate/destroy
managed static and this allows us to get the output of, e.g.,
-time-passes without performing a full shutdown.
Differential Revision: https://reviews.llvm.org/D26517
llvm-svn: 286493
Relocations are the last thing that we wore storing a raw section
pointer to and parsing on demand.
With this patch we parse it only once and store a pointer to the
actual data.
The patch also changes where we store it. It is now in
InputSectionBase. Not all sections have relocations, but most do and
this simplifies the logic. It also means that we now only support one
relocation section per section. Given that that constraint is
maintained even with -r with gold bfd and lld, I think it is OK.
llvm-svn: 286459
Patch allows to pass a symbols file to linker.
LLD will map symbols to sections and sort sections
in output according to symbol ordering file.
That can help to reduce the startup time and/or
amount of pagefaults during startup.
Also, interesting benchmark result was produced by Rafael Espíndola.
After applying the symbols file for clang he timed compiling
X86MCTargetDesc.ii to an object file.
The page faults went from just
56,988 to 56,946 since most faults are not in the binary.
Running time went from 4.403053515 to 4.178112244.
The speedup seems to be because of better cache
locality.
Differential revision: https://reviews.llvm.org/D26130
llvm-svn: 286440
Previously, we have both input and output section for .MIPS.abiflags.
Now we have only one class for .MIPS.abiflags, which is MipsAbiFlagsSection.
This class is a synthetic input section.
.MIPS.abiflags sections are handled as regular sections until
the control reaches Writer. Writer then aggregates all sections
whose type is SHT_MIPS_ABIFLAGS to create a single synthesized
input section. The synthesized section is then processed normally
as if it came from an input file.
llvm-svn: 286398
Previously, we have both input and output sections for .reginfo and
.MIPS.options. Now for each such sections we have one synthetic input
sections: MipsReginfoSection and MipsOptionsSection respectively.
Both sections are handled as regular sections until the control reaches
Writer. Writer then aggregates all sections whose type is SHT_MIPS_REGINFO
or SHT_MIPS_OPTIONS to create a single synthesized input section. In that
moment Writer also save GP0 value to the MipsGp0 field of the corresponding
ObjectFile. This value required for R_MIPS_GPREL16 and R_MIPS_GPREL32
relocations calculation.
Differential revision: https://reviews.llvm.org/D26444
llvm-svn: 286397
The ARM 32 and 64-bit ABI does not use 0 for undefined weak references
that are used in PC relative relocations. In particular:
- A branch relocation to an undefined weak resolves to the next
instruction. Effectively making the branch a no-op
- In all other cases the symbol resolves to the place so that S + A - P
resolves to A.
Differential Revision: https://reviews.llvm.org/D26240
llvm-svn: 286353
Patch switches computing of --build-id hash to tree.
This is the way when input data is splitted by chunks,
hash is computed for each one in threaded/non-threaded way.
At the end hash is conputed for result tree.
With or without -threads the result hash is the same.
Differential revision: https://reviews.llvm.org/D26199
llvm-svn: 286061
A CommonInputSection is a section containing all common symbols.
That was an input section but was abstracted in a different way
than the synthetic input sections because it was written before
the synthetic input section was invented.
This patch rewrites CommonInputSection as a synthetic input section
so that it behaves better with other sections.
llvm-svn: 286053
In short the patch introduces support for linking object file conform
MIPS N32 ABI [1]. This ABI is similar to N64 ABI but uses 32-bit
pointer size.
The most non-trivial requirement of this ABI is one more relocation
packing format. N64 ABI puts multiple relocation type into the single
relocation record. The N32 ABI uses series of successive relocations
with the same offset for this purpose. In this patch, new function
`mergeMipsN32RelTypes` handle this case and "convert" N32 relocation to
the N64 relocation so the rest of the code keep unchanged.
For now, linker does not support series of relocations applied to sections
without SHF_ALLOC bit. Probably later I will add the support or insert
some sort of assert into the `relocateNonAlloc` routine to catch this
case.
[1] ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/MIPS-N32-ABI-Handbook.pdf
Differential revision: https://reviews.llvm.org/D26298
llvm-svn: 286052
This change fixes a bug that was introduced by r285851.
r285851 converted .interp section as an output section to an input
section. But I forgot to make it a "Live" section, so if -gc-section
is given, it was garbage collected.
llvm-svn: 286025
An undefined weak reference is given an address of 0 this will
incorrectly trigger the creation of a Thumb to ARM interworking Thunk
if there is a Thumb branch instruction to the symbol. This results in
an error as Thunks only make sense to defined or shared symbols.
We prevent this by detecting an undefined symbol and not creating a thunk
for it.
Differential Revision: https://reviews.llvm.org/D26239
llvm-svn: 285896
When we have SHT_GNU_versym section, it is should be associated with symbol table
section. Usually (and in out implementation) it is .dynsym.
In case when .dynsym is absent (due to broken object for example),
lld crashes in parseVerdefs() when accesses null pointer:
Versym = reinterpret_cast<const Elf_Versym *>(this->ELFObj.base() +
VersymSec->sh_offset) +
this->Symtab->sh_info;
DIfferential revision: https://reviews.llvm.org/D25553
llvm-svn: 285796
Previously, we added strings from DynamicSection::finalize().
It was a bit tricky because finalize() is supposed to fix the final
size of the section, but adding new strings would change the size of
.dynstr section. So there was a dependency between finalize functions
of .dynamic and .dynstr.
However, I noticed that we can elimiante the dependency by simply
add strings early; we don't have to do that in finalize() but can do
from DynamicSection's ctor.
This patch defines a new function, DynamicSection::addEntries, to
add .dynamic entries that doesn't depend on other sections.
llvm-svn: 285784
The example reported in PR30793 shows a case where gc reclaims
a SHF_TLS section, but it doesn't reclaim the section containing
the debug info for it.
This is expected, as we do not reclaim non-alloc sections
during the garbage collection phase (and this is not going to
change anytime soon, at least this is what I gathered last I
talked with Rafael about it).
So, we end up with a pending reference, thinking that the input
was invalid (which is not true, as it's GC that removed the
SHT_TLS section, and therefore didn't create the PT_TLS *segment*
for it). In cases like this, just assign a VA of zero at relocation
time instead of error'ing out (this is what gold does as well, FWIW).
Differential Revision: https://reviews.llvm.org/D26201
llvm-svn: 285735
With this patch we keep track of the fact that . is a position in the
file and therefore not absolute. This allow us to compute relative
relocations that involve symbol that are defined in linker scripts
with '.'.
This fixes https://llvm.org/bugs/show_bug.cgi?id=30406
There is still more work to track absoluteness over the various
expressions, but this should unblock linking the EFI bootloader.
llvm-svn: 285641
We parse linker scripts very early, but whether an expression is
absolute or not can depend on a symbol defined in a .o. Given that, we
have to delay the computation of IsAbsolute. We can do that by storing
an AST when parsing or by also making IsAbsolute a function like we do
for the expression value. This patch implements the second option.
llvm-svn: 285628
And as a token of the new feature, make ALIGNOF always absolute.
This is a step in making it possible to have non absolute symbols out
of output sections.
llvm-svn: 285608
This fixes pr30803 by not relaxing that particular access. We could
also let adjustRelaxExpr know that the target is absolute so that it
uses R_RELAX_GOT_PC_NOPIC, but it is not clear if it is worth it.
llvm-svn: 285317
Rafael Espindola