The entries are added if there are "_init" or "_fini" entries in
the symbol table respectively. According to the behavior of ld,
entries are inserted even for undefined symbols.
Symbol names can be overridden by using -init and -fini command
line switches. If used, these switches neither add new symbol table
entries nor require those symbols to be resolved.
Differential Revision: http://reviews.llvm.org/D13385
llvm-svn: 249297
Add symbol specified with -u as undefined which may cause additional
object files from archives to be linked into the resulting binary.
Differential Revision: http://reviews.llvm.org/D13345
llvm-svn: 249295
Using the "raw" Elf64_Dyn or Elf32_Dyn structures in
DynamicSection<ELFT>::writeTo does not correctly handle mixed-Endian
situations. Instead, use the corresponding llvm::object::* structures which
have Endian-converting members (like the rest of the code).
This fixes all currently-failing elf2 tests when running on big-Endian
PPC64/Linux (I've added a big-Endian test case which should fail on
little-Endian machines in the same way that test/elf2/shared.s failed on
big-Endian machines prior to this change).
llvm-svn: 249150
Sort by:
ALLOC
ALLOC && NOBITS
ALLOC & EXEC
ALLOC & EXEC && NOBITS
ALLOC & WRITE
ALLOC & WRITE && NOBITS
<nothing> (ignoring NOBITS)
The dynamic section is finalized early because it adds strings to the dynamic string table, which comes before the dynamic table.
llvm-svn: 249071
Summary:
If --whole-archive is used, all symbols from the following archives are added to the output. --no-whole-archive restores default behavior. These switches can be used multiple times.
NB. We have to keep an ArchiveFile instance within SymbolTable even if --whole-archive mode is active since it can be a thin archive which contains just names of external files. In that case actual memory buffers for the archive members will be stored within the File member of ArchiveFile class.
Reviewers: rafael, ruiu
Subscribers: grimar, llvm-commits
Projects: #lld
Differential Revision: http://reviews.llvm.org/D13286
llvm-svn: 249045
Summary:
These switches affect library searching for '-l' which follow them. Synonym forms are also supported:
* -dy and -call_shared for -Bdynamic switch
* -dn, -non_shared and -static for -Bstatic switch
Reviewers: rafael, ruiu
Subscribers: emaste, llvm-commits
Projects: #lld
Differential Revision: http://reviews.llvm.org/D13238
llvm-svn: 249029
If a shared library has a DT_SONAME entry, that is what should be included
in the DT_NEEDED of a program using it.
We don't implement -soname yet, so check in a .so for now.
llvm-svn: 249025
This linker script parser and evaluator is powerful enough to read
Linux's libc.so, which is (despite its name) a linker script that
contains OUTPUT_FORMAT, GROUP and AS_NEEDED directives.
The parser implemented in this patch is a recursive-descendent one.
It does *not* construct an AST but consumes directives in place and
sets the results to Symtab object, like what Driver is doing.
This should be very fast since less objects are allocated, and
this is also more readable.
http://reviews.llvm.org/D13232
llvm-svn: 248918
Sort by:
ALLOC
ALLOC && NOBITS
ALLOC & EXEC
ALLOC & EXEC && NOBITS
ALLOC & WRITE
ALLOC & WRITE && NOBITS
<nothing> (ignoring NOBITS)
The dynamic section is finalized early because it adds strings to the dynamic string table, which comes before the dynamic table.
llvm-svn: 248845
The code in driver is about to change so that the invalid files would no
longer be seen as ELF.
This makes sure that the error path will remain tested.
llvm-svn: 248820
Besides a trivial MIPS support the patch introduces new TargetInfo class
member getDefaultEntry() to override default name of the entry symbol.
MIPS uses __start for that.
Differential Revision: http://reviews.llvm.org/D13227
llvm-svn: 248779
This is a basic initial implementation of the -flat_namespace and
-undefined options for LLD-darwin. It ignores several subtlties,
but the result is close enough that we can now link LLVM (but not
clang) on Darwin and pass all regression tests.
llvm-svn: 248732
There's actually a room to improve this patch. Instead of not merging
sections that have different alignements, we can choose the section that
has the largest alignment requirement among all sections that are otherwise
considered the same. Then all section alignments are satisfied, so we can
merge them.
I don't know if that improvement could make any difference for real-world
input, so I'll leave it alone. Would be interesting to revisit later.
llvm-svn: 248581
Since FreeBSD 4.1, the kernel expects binaries to be marked with
ELFOSABI_FREEBSD in the ELF header to exec() them. LLD unconditionally
sets OSABI to ELF_OSABINONE, and everything linked with it won't run
on FreeBSD (unless explicitly rebranded).
Example:
% ./aarch64-hello
ELF binary type "0" not known.
zsh: exec format error: ./aarch64-hello
FreeBSD could be modified to accept ELF_OSABINONE, but that would break all
existing binaries, so the kernel needs to support both ABINONE and ABIFREEBSD.
I plan to push this change in FreeBSD one day, which, unfortunately, is
not today. This code patches lld so it sets the header field correctly.
For completeness, the rationale of this change is explained in the FreeBSD
commit message, and it's apparently to pleasee binutils maintainers at the time.
https://svnweb.freebsd.org/base?view=revision&revision=59342
Differential Revision: http://reviews.llvm.org/D13140
llvm-svn: 248554
This is just enough to get PLT working on 32 bit x86.
The idea behind using a virtual interface is that it should be easy to
convert any of the functions to template parameters if any turns out to be
performance critical.
llvm-svn: 248308
This is an LLD extension to MSVC link.exe command line. MSVC linker
does not write symbol tables for executables. We do unless no /debug
option is given.
There's a situation that we want to enable debug info but don't want
to emit the symbol table. One example is when we are comparing output
file size. With this patch, you can tell the linker to not create
a symbol table by just specifying /nosymtab.
llvm-svn: 248225
This patch fixes a regression introduced by r247964. Relocations that
are referring the same symbol should be considered equal, but they
were not if they were pointing to non-section chunks.
llvm-svn: 248132
The offset of the .rela.dyn section isn't the same between hosts because a path comes before it. This test doesn't care what the offset is.
llvm-svn: 247946
We used to sort the symbols at the very end, but we need to know the order
earlier so that we can create reference to them in the dynamic relocations.
Thanks to Igor Kudrin for pointing out the problem.
llvm-svn: 247911
Only live symbols are written to the symbol table. Because isLive()
returned false if dead-stripping was disabled entirely, only
non-COMDAT sections were written to the symbol table. This patch fixes
the issue.
llvm-svn: 247856
Symbol table is now populated correctly, but some fields are missing,
they'll be added in the future. This patch also adds --discard-all
flag, which was the default behavior until now.
Differential Revision: http://reviews.llvm.org/D12874
llvm-svn: 247849
This is a patch to make LLD to be on par with MSVC in terms of ICF
effectiveness. MSVC produces a 27.14MB executable when linking LLD.
LLD previously produced a 27.61MB when self-linking. Now the size
is reduced to 27.11MB. Note that without ICF the size is 29.63MB.
In r247387, I implemented an algorithm that handles section graphs
as cyclic graphs and merge them using SCC. The algorithm did not
always work as intended as I demonstrated in r247721. The new
algortihm implemented in this patch is different from the previous
one. If you are interested the details, you want to read the file
comment of ICF.cpp.
llvm-svn: 247770
In this test, we have two functions, foo and bar. MSVC linker can
choose one and discard the other using ICF. LLD cannot. I add this
test as a TODO.
foo and bar are conceptually equivalent to the following:
void foo() { foo(); }
void bar() { foo(); }
foo and bar are effectively the same function. If foo and bar are
compiled to the same instructions, both their contents (foo and bar)
and relocation targets (foo) become the same, so from the ICF point
of view, they are reducible. But their graphs are not isomorphic!
LLD's ICF algorithm cannot handle this case yet.
llvm-svn: 247721
The first test (call) is now the only test to use .text, which makes it
resistant to more tests being added.
llvm-objdump -d already prints the addresses of symbols. We can use that in the
tests.
llvm-svn: 247685
They are not fully functional yet, but this implements enough support for lld
itself to read them.
With that, delete the .so binary we were using for tests and start eating our
own dog food.
llvm-svn: 247487
Previously, LLD's ICF couldn't merge cyclic graphs. That was unfortunate
because, in COFF, cyclic graphs are not exceptional at all. That is
pretty common.
In this patch, sections are grouped by Tarjan's strongly connected
component algorithm to get acyclic graphs. And then we try to merge
SCCs whose outdegree is zero, and remove them from the graph. This
makes other SCCs to have outdegree zero, so we can repeat the
process until all SCCs are removed. When comparing two SCCs, we handle
cycles properly.
This algorithm works better than previous one. Previously, self-linking
produced a 29.0MB executable. It now produces a 27.7MB. There's still some
gap compared to MSVC linker which produces a 27.1MB executable for the
same input. So the gap is narrowed, but still LLD is not on par with MSVC.
I'll investigate that later.
llvm-svn: 247387
For now it includes every symbol in the regular table. Since we don't
create dynamic relocations yet, we don't have a good way of knowing which
symbols are actually needed.
llvm-svn: 247365
With this patch we create a dynamic string table (it is allocated, unlike
the regular one) and the dynamic section has a DT_STRTAB pointing to it.
llvm-svn: 247155
I don't understand why the previous code is pretty flaky and
the new code is at least less flaky, but the original test
occasionally failed on the second run of lib.exe.
My guess was that lib.exe was failing because the output of
the echo command executed immediately before lib.exe was not
flushed to a file, but as far as I can say, the file
descriptor is properly closed in TestRunner.py, so this's
probably not correct. Other theory is that, on Windows, file
output is not guaranteed to be visible to other processes even
if a process flushes file descriptors, but I'd think that's
unlikely. So honestly I don't know the cause yet.
llvm-svn: 246621
This patch fixes a subtle incompatibility with MSVC linker.
MSVC linker preserves the original spelling of a DLL in the
import descriptor table. LLD previously converted all
characters to lowercase. Usually this difference is benign,
but if a program explicitly checks for DLL file names, the
program could fail.
llvm-svn: 246620
The ELF spec says:
... if any reference to or definition of a name is a symbol with a
non-default visibility attribute, the visibility attribute must be
propagated to the resolving symbol in the linked object. If different
visibility attributes are specified for distinct references to or
definitions of a symbol, the most constraining visibility attribute
must be propagated to the resolving symbol in the linked object. The
attributes, ordered from least to most constraining, are:
STV_PROTECTED, STV_HIDDEN and STV_INTERNAL.
llvm-svn: 246603
In r246424, I made a change that disables non-DLL to export
symbols. It turned out that the change was not correct. Both
DLLs and executables are able to export symbols (although the
latter is relatively rare). This change restores the feature.
llvm-svn: 246537
I have totally no idea why, but MSVC linker is sensitive about
file names of archive members. If we do not make import library
file names to the same as the DLL name, MSVC link *crashes*
when it is processing the library file. This patch is to set
the same name.
llvm-svn: 246535
The rules for dllexported symbols are overly complicated due to
x86 name decoration, fuzzy symbol resolution, and the fact that
one symbol can be resolved by so many different names. The rules
are probably intended to be "intuitive", so that users don't have
to understand the name mangling schemes, but it seems that it can
lead to unintended symbol exports.
To make it clear what I'm trying to do with this patch, let me
write how the export rules are subtle and complicated.
- x86 name decoration: If machine type is i386 and export name
is given by a command line option, like /export:foo, the
real symbol name the linker has to search for is _foo because
all symbols are decorated with "_" prefixes. This doesn't happen
on non-x86 machines. This automatic name decoration happens only
when the name is not C++ mangled.
However, the symbol name exported from DLLs are ones without "_"
on all platforms.
Moreover, if the option is given via .drectve section, no
symbol decoration is done (the reason being that the .drectve
section is created by a compiler and the compiler should always
know the exact name of the symbol, I guess).
- Fuzzy symbol resolution: In addition to x86 name decoration,
the linker has to look for cdecl or C++ mangled symbols
for a given /export. For example, it searches for not only
_foo but also _foo@<number> or ??foo@... for /export:foo.
Previous implementation didn't get it right. I'm trying to make
it as compatible with MSVC linker as possible with this patch
however the rules are. The new code looks a bit messy to me, but
I don't think it can be simpler due to the ad-hoc-ness of the rules.
llvm-svn: 246424
Now that we print a symbol table and all symbol kinds are at least declared,
we can test all combinations that don't produce an error.
This also includes a few fixes to keep the test passing:
* Keep the strong symbol in a weak X strong pair
* Handle common symbols.
The common X common case will be finished in a followup patch.
llvm-svn: 246401
This is exposed via a new flag /opt:lldltojobs=N, where N is the number of
code generation threads.
Differential Revision: http://reviews.llvm.org/D12309
llvm-svn: 246342
This is a basic implementation that allows lld to emit binaries
consumable by the HSA runtime.
Differential Revision: http://reviews.llvm.org/D11267
llvm-svn: 246155
ICF is a feature to merge sections not by name (which is the regular
COMDAT merging) but by contents. If two or more sections have the
identical contents and relocations, ICF merges them to save space.
Accessors or templated functions tend to have the same contents, and
ICF can hold them.
If we consider sections as vertices and relocations as edges, the
problem is to find as many isomorphic graphs as possile from input
graphs. MSVC linker is smart enough to identify isomorphic graphs
even if they contain circles (GNU gold cannot handle circles
according to http://research.google.com/pubs/pub36912.html, so this
is impressive).
Circular references are not uncommon in COFF object files.
One example is .pdata. .pdata sections contain exception handler info
for functions, so they naturally have relocations for the functions.
The functions in turn have references to the .pdata sections so that
the functions and their .pdata are linked together. As a result, they
form circles.
This is a test case for circular graphs. LLD is not able to handle
this test case yet. I'll add code soon.
llvm-svn: 245827
The old test files were just compiler outputs, so it was hard to
debug if something goes wrong. The new test file is carefully
hand-crafted to trigger ICF to avoid that.
llvm-svn: 245826
Previously, weak external symbols could reference only symbols that
appeared before them. Although that covers almost all use cases
of weak externals, there are object files out there which contains
weak externals that have forward references.
This patch supports such weak externals.
llvm-svn: 245258
Rafael Espindola