Differential revision: https://reviews.llvm.org/D26792

llvm-svn: 287322

MergeOutputSection class was a bit hard to use because it provdes
a series of finalize functions that have to be called in a right way
at a right time. It also intereacted with MergeInputSection, and the
logic was somewhat entangled between the two classes.

This patch simplifies it by providing only one finalize function.
Now, all you have to do is to call MergeOutputSection::finalize
when you have added all sections to the output section. Then, it
internally merges strings and initliazes StringPiece objects.
I think this is much easier to understand.

This patch also adds comments.

llvm-svn: 287314

I hit an internal linker script that was defining _DYNAMIC instead of
letting the linker do it. It turns out that both bfd and gold allow
that.

This is pretty easy to implement, just make the linker defined symbol
weak. This should have no impact in the case where there is no user
defined symbol: The visibility is hidden, which causes the output to
still be local.

llvm-svn: 287260

llvm-svn: 287231

Differential revision: https://reviews.llvm.org/D26740

llvm-svn: 287216

MIPS GOT handling is very different from other targets so it is better
to keep the code in the separatre section class MipsGotSection. This
patch introduces the new section and moves all MIPS specific code from
GotSection to the new class. I did not rename fields and methods in the
MipsGotSection class to reduce the diff and plan to do that by the
separate commit.

Differential revision: https://reviews.llvm.org/D26733

llvm-svn: 287150

Differential revision: https://reviews.llvm.org/D26669

llvm-svn: 287092

llvm-svn: 286955

This patch introduces the following changes:
- DynamicSection now inherits InputSection<ELFT> and was moved
  to SyntheticSections.h/.cpp.
- Link and Entsize fields of DynamicSection are propagated to 
  its output section
- In<ELFT>::SyntheticSections was removed.
- Finalization of synthetic sections was removed from 
  OutputSection<ELFT>::finalize. Now finalizeSyntheticSections is
  used instead.

Differential revision: https://reviews.llvm.org/D26603

llvm-svn: 286950

This patch stops creating symbols like __ehdr_start, 
_end/_etext_edata,__tls_get_addr when using -r.

This fixes PR30984.

Differential revision: https://reviews.llvm.org/D26600

llvm-svn: 286941

Patch adds a filename to that error message.

I faced next error when debugged one of FreeBSD port:
error: relocation R_X86_64_PLT32 cannot refer to absolute symbol __tls_get_addr

error message was poor and this patch improves it to show the locations 
of symbol declaration and using.

Differential revision: https://reviews.llvm.org/D26508

llvm-svn: 286940

Propagate program headers by walking the commands, not the
sections. This allows us to propagate program headers even from
sections that don't end up in the output.

Fixes pr30997.

llvm-svn: 286837

llvm-svn: 286805

Differential revision: https://reviews.llvm.org/D26549

llvm-svn: 286799

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

Differential revision: https://reviews.llvm.org/D26498

llvm-svn: 286580

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

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

Differential revision: https://reviews.llvm.org/D26349

llvm-svn: 286443

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

The disadvantage is that we use uint64_t instad of uint32_t for some
value in 32 bit files. The advantage is a substantially simpler code,
faster builds and less code duplication.

llvm-svn: 286414

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

This is similar to what was done for InputSection.

With this the various fields are stored in host order and only
converted to target order when writing.

llvm-svn: 286327

Avoids having to skip them multiple times.

llvm-svn: 286261

We can just use a regular InputSection.

llvm-svn: 286237

With the current infrastructure it can be just an ordinary
InputSection like the real .bss sections.

llvm-svn: 286234

Differential revision: https://reviews.llvm.org/D25325

llvm-svn: 286225

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

Previously, we do this piece of code to iterate over all input sections.

  for (elf::ObjectFile<ELFT> *F : Symtab.getObjectFiles())
    for (InputSectionBase<ELFT> *S : F->getSections())

It turned out that this mechanisms doesn't work well with synthetic
input sections because synthetic input sections don't belong to any
input file.

This patch defines a vector that contains all input sections including
synthetic ones.

llvm-svn: 286051

llvm-svn: 285996

Differential Revision: https://reviews.llvm.org/D26225

llvm-svn: 285851

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

llvm-svn: 285767

This is now doable because this code doesn't have to be in the
dynamic scope of Writer::run().

llvm-svn: 285766

llvm-svn: 285764

llvm-svn: 285763

We are going to have many more classes for linker-synthesized
input sections, so it's worth to be added to a separate file
than to the file for regular input sections.

llvm-svn: 285740

Differential revision: https://reviews.llvm.org/D25627

llvm-svn: 285682