Now 'writer' creates an instance of `RuntimeFile` in the constructor, then
populates the file in the virtual function `addDefaultAtoms`, then pass
owning of this file to the caller of virtual function `createImplicitFiles`.
First, we do not need to keep an instance of `RuntimeFile` so long. It is
enough to create the file, right after that populate it and pass the owning.
Second, relationship between `createImplicitFiles` and `addDefaultAtoms`
is complicated. The `createImplicitFiles` might call `addDefaultAtoms`,
overridden version of `addDefaultAtoms` might call base class `addDefaultAtoms`,
and overridden version of `createImplicitFiles` might call base class
`createImplicitFiles` as well as `addDefaultAtoms`.
The patch solves both problems above. It creates and populates runtime files
right in the createImplicitFiles(), removes `addDefaultAtoms` at all and
does not keep references to runtime files in class fields.
llvm-svn: 234347
This matches other linkers behaviour. Moreover, there's really
no need to keep them around.
Reported by: Rafael Avila de Espindola
PR: 22890
llvm-svn: 234130
In r233772, I removed an empty class, DefaultTargetHandler, from
the class hierarchy by merging the class with TargetHandler. I then
found that TargetHandler and its base class, TargetHandlerBase,
are also almost the same.
We need to go deeper.
In this patch, I merged TargetHandlerBase with TargetHandler.
The only difference between them is the existence (or absense)
of a pure virtual function registerRelocationName(). I added that
function to the (new) TargetHandler.
One more thing is that TargetHandler was templated for no reason.
I made it non-templated class.
llvm-svn: 233773
All calls of findAbsoluteAtoms seem a bit awkward because of the type
of the function. It semantically returns a pointer to an AtomLayout or
nothing, so I made the function return AtomLayout*.
In this patch, I also expanded some "auto"s because their actual type
were not obvious in their contexts.
llvm-svn: 233769
This changes improves performance of lld, when self-hosting lld, when compared
with the bfd linker. BFD linker on average takes 8 seconds in elapsed time.
lld takes 3 seconds elapased time average. Without this change, lld takes ~5
seconds average. The runtime comparisons were done on a release build and
measured by running linking thrice.
lld self-host without the change
----------------------------------
real 0m3.196s
user 0m4.580s
sys 0m0.832s
lld self-host with lld
-----------------------
user 0m3.024s
user 0m3.252s
sys 0m0.796s
time taken to build lld with bfd
--------------------------------
real 0m8.419s
user 0m7.748s
sys 0m0.632s
llvm-svn: 232460
Puts symbols defined in linker script expressions in a runtime file that is
added as input to the resolver, making the input object files see symbols
defined in linker scripts.
http://reviews.llvm.org/D8263
llvm-svn: 232409
Handle resolution of symbols coming from linked object files lazily.
Add implementation of handling _GLOBAL_OFFSET_TABLE_ and __exidx_start/_end symbols for ARM platform.
Differential Revision: http://reviews.llvm.org/D8159
llvm-svn: 232261
SHF_GROUP: Group Member Sections
----------------------------------
A section which is part of a group, and is to be retained or discarded with the
group as a whole, is identified by a new section header attribute: SHF_GROUP
This section is a member (perhaps the only one) of a group of sections, and the
linker should retain or discard all or none of the members. This section must be
referenced in a SHT_GROUP section. This attribute flag may be set in any section
header, and no other modification or indication is made in the grouped sections.
All additional information is contained in the associated SHT_GROUP section.
SHT_GROUP: Section Group Definition
-------------------------------------
Represents a group section.
The section group's sh_link field identifies a symbol table section, and its
sh_info field the index of a symbol in that section. The name of that symbol is
treated as the identifier of the section group.
More information: https://mentorembedded.github.io/cxx-abi/abi/prop-72-comdat.html
Added a lot of extensive tests, that tests functionality.
llvm-svn: 230195
Before this patch there was a cyclic dependency between lldCore and
lldReaderWriter. Only lldConfig could be built as a shared library.
* Moved Reader and Writer base classes into lldCore.
* The following shared libraries can now be built:
lldCore
lldYAML
lldNative
lldPasses
lldReaderWriter
Differential Revision: http://reviews.llvm.org/D7105
From: Greg Fitzgerald <garious@gmail.com>
llvm-svn: 226732
The previous default behavior of LLD is --as-needed. LLD linked
against a DSO only if the DSO file was actually used to link an
executable (i.e. at least one symbol was resolved using the shared
library file.)
In this patch I added a boolean flag to FileNode for --as-needed.
I also added an accessor to DSO name to shared library file class.
llvm-svn: 226274
To find an AtomLayout object for the given symbol I replace the
`Layout::findAtomAddrByName` method by `Layout::findAtomLayoutByName` method.
llvm-svn: 223359
This reverts commit r222310.
Not sure which commit is the cause of the failure on the darwin bot. Will need
to revert my changes and commit one change at a time.
llvm-svn: 222330
MIPS ELF symbols might contain some additional MIPS-specific flags
in the st_other field besides visibility ones. These flags indicate
code properties like microMIPS / MIPS16 encoding, position independent
code etc. We need to transfer the flags from input objects to the
output linked file to write them into the symbol table, adjust symbols
addresses etc.
I add new attribute CodeModel to the DefinedAtom class to hold target
specific flag and to get over YAML/Native format conversion barrier.
Other architectures/targets can extend CodeModel enumeration by their
own flags.
MIPS specific part of this patch adds support for STO_MIPS_MICROMIPS
flag. This flag marks microMIPS symbols. Such symbol should:
a) Has STO_MIPS_MICROMIPS in the corresponding .symtab record.
b) Has adjusted (odd) address in the corresponding .symtab
and .dynsym records.
llvm-svn: 221864
ELFLinkingContext had these two functions, which is really not needed since
the Writer uses a llvm::object template composed of Endianness, Alignment,
Is32bit/64bit. We could just use that and not duplicate functionality.
No Change In Functionality.
llvm-svn: 221523
The ELF writer creates a invalid binary for few cases with large filesize and
memory size for segments. This patch addresses the functionality and updates the
test. This patch also cleans up parts of the ELF writer for future enhancements
to support Linker scripts.
llvm-svn: 221233
This would permit the ELF reader to check the architecture that is being
selected by the linking process.
This patch also sorts the include files according to LLVM conventions.
llvm-svn: 220129
When committed in r219353, this patch originally caused problems because it was
not tested in debug build. In such scenarios, Driver.cpp adds two additional
passes. These passes serialize all atoms via YAML and reads it back. Since the
patch changed ObjectAtom to hold a new reference, the serialization was removing
the extra data.
This commit implements r219853 in another way, similar to the original MIPS way,
by using a StringSet that holds the names of all copied atoms instead of
directly holding a reference to the copied atom. In this way, this commit is
simpler and eliminate the necessity of changing the DefinedAtom hierarchy to
hold a new data.
Reviewers: shankarke
http://reviews.llvm.org/D5713
llvm-svn: 219449
Enhances the creation of an ELF dynamic executable by avoiding recording
unnecessary shared libraries as NEEDED to load a program.
To do this, we must keep track of not only symbols that were referenced but
also of COPY relocations, which steal the symbol from a shared library but does
not store from which lib this symbol came from. To fix this, this commit changes
ObjectSymbol to store the original library from which this symbol came. With
this information, we are able to build a list of the exact shared libraries that
must be marked as DT_NEEDED, instead of blindly marking all shared libraries as
needed.
This logic originally came from the MIPS backend with some adaptation.
Reviewers: atanasyan, shankar.easwaran
http://reviews.llvm.org/D5574
llvm-svn: 219353
When creating a dynamic executable and receiving the -E flag, the linker should
export all globally visible symbols in its dynamic symbol table.
This commit also moves the logic that exports symbols in the dynamic symbol
table from OutputELFWriter to the ExecutableWriter class. It is not correct to
leave this at OutputELFWriter because DynamicLibraryWriter, another subclass of
OutputELFWriter, already exports all symbols, meaning we can potentially end up
with duplicated symbols in the dynamic symbol table when creating shared libs.
Reviewers: shankarke
http://reviews.llvm.org/D5585
llvm-svn: 219334
This patch adds logic to avoid putting the dynamic linker library (ld.so) as a
DT_NEEDED entry in the dynamic table. It should only appear in PT_INTERP.
This patch fixes SPEC programs 433, 445, 450, 453, 456, 462 when running on
Ubuntu Linux x86_64 and when linking SPEC programs with LLD and glibc 2.19.
http://reviews.llvm.org/D5573
llvm-svn: 218847
Summary:
This patch adds support for the general dynamic TLS access model for X86_64 (see www.akkadia.org/drepper/tls.pdf).
To properly support TLS, the patch also changes the __tls_get_addr atom to be a shared library atom instead of a regularly defined atom (the previous lld approach). This closely models the reality of a function that will be resolved at runtime by the dynamic linker and loader itself (ld.so). I was tempted to force LLD to link against ld.so itself to resolve these symbols, but since GNU ld does not need the ld.so library to resolve this symbol, I decided to mimic its behavior and keep hardwired a definition of __tls_get_addr in the lld code.
This patch also moves some important logic that previously was only available to the MIPS lld backend to be used to all ELF backends. This logic, which now lives in the DefaultLayout class, will monitor which external (shared lib) symbols are really imported by the current module and will only populate the dynamic symbol table with used symbols, as opposed to the previous approach of dumping all shared lib symbols in the dynamic symbol table. This is important to this patch to avoid __tls_get_addr from getting injected into all dynamic symbol tables.
By solving the previous problem of always adding __tls_get_addr, now the produced symbol tables are slightly smaller. But this impacted several tests that relied on hardwired/predefined sizes of the symbol table, requiring this patch to update such tests.
Test Plan: Added a LIT test case that exercises a simple use case of TLS variable in a shared library.
Reviewers: ruiu, rafael, Bigcheese, shankarke
Reviewed By: Bigcheese, shankarke
Subscribers: emaste, shankarke, joerg, kledzik, mcrosier, llvm-commits
Projects: #lld
Differential Revision: http://reviews.llvm.org/D5505
llvm-svn: 218633
Patch from Rafael Auler!
When a shared lib has an undefined symbol that is defined in a regular object
(the program), the final executable must export this symbol in the dynamic
symbol table. However, in the current logic, lld only puts the symbol in the
dynamic symbol table if the symbol is weak. This patch fixes lld to put the
symbol in the dynamic symbol table regardless if it is weak or not.
This caused a problem in FreeBSD10, whose programs link against a crt1.o
that defines the symbol __progname, which is, in turn, undefined in libc.so.7
and will only be resolved in runtime.
http://reviews.llvm.org/D5424
llvm-svn: 218259
defined in a shared library.
Now LLD does not export a strong defined symbol if it coalesces away a
weak symbol defined in a shared library. This bug affects all ELF
architectures and leads to segfault:
% cat foo.c
extern int __attribute__((weak)) flag;
int foo() { return flag; }
% cat main.c
int flag = 1;
int foo();
int main() { return foo() == 1 ? 0 : -1; }
% clang -c -fPIC foo.c main.c
% lld -flavor gnu -target x86_64 -shared -o libfoo.so ... foo.o
% lld -flavor gnu -target x86_64 -o a.out ... main.o libfoo.so
% ./a.out
Segmentation fault
The problem is caused by the fact that we lose all information about
coalesced symbols after the `Resolver::resolve()` method is finished.
The patch solves the problem by overriding the
`LinkingContext::notifySymbolTableCoalesce()` method and saving names
of coalesced symbols. Later in the `buildDynamicSymbolTable()` routine
we use this information to export these symbols.
llvm-svn: 217363
dynamic symbol table populating and DT_NEEDED tag creation.
The `isDynSymEntryRequired` function returns true if the specified shared
library atom requires a dynamic symbol table entry. The `isNeededTagRequired`
function returns true if we need to create DT_NEEDED tag for the shared
library defined specified shared atom.
By default the both functions return true. So there is no functional changes
for all targets except MIPS. Probably we need to spread the same modifications
on other ELF targets but I want to implement and fully tested complete set of
changes for MIPS target first.
For MIPS we create a dynamic symbol table entry for a shared library atom iif
this atom is referenced by a regular defined atom. For example, if library L1
defines symbol T1, library L2 defines symbol T2 and uses symbol T1
and executable file E1 uses symbol T2 but does not use symbol T1 we create
an entry in the E1 dynamic symbol table for symbol T2 and do not create
an entry for T1.
The patch creates DT_NEEDED tags for shared libraries contain shared library
atoms which a) referenced by regular defined atoms; b) have corresponding
copy dynamic relocations (R_MIPS_COPY).
Now the patch does not take in account --as-needed / --no-as-needed command
line options. So it is too restrictive and create DT_NEEDED tags for really
needed shared libraries only. I plan to fix that by subsequent patches.
llvm-svn: 211674
Denis Protivensky