This patch implements --hash-style command line switch.
* By default, or with "sysv" or "both" parameters, the linker generates
a standard ELF hash section.
* With "gnu" or "both", it produces a GNU-style hash section.
That section requires the symbols in the dynamic symbol table section, which
are referenced in the GNU hash section, to be placed after not hashed ones and
to be sorted to correspond the order of hash buckets in the GNU Hash section.
The division function, as well as estimations for the section's parameters,
are just the first rough attempt and the subjects for further adjustments.
Differential Revision: http://reviews.llvm.org/D13815
llvm-svn: 251000
* Move the responsibility to call SymbolBody::setDynamicSymbolTableIndex()
from the hash table to the dynamic symbol table.
* Hash table is not longer responsible for filling the dynamic symbol table.
* The final order of symbols of both symbol tables is set before writing
phase starts.
* Remove repeaded scan of the symbol table during writting SymbolTableSection.
Differential Revision: http://reviews.llvm.org/D13911
llvm-svn: 250864
The section header table index of the entry that is associated with the section name string table.
Differential Revision: http://reviews.llvm.org/D13904
llvm-svn: 250836
Target has supportsLazyRelocations() method which can switch lazy relocations on/off (currently all targets are OFF except x64 which is ON). So no any other targets are affected now.
Differential Revision: http://reviews.llvm.org/D13856?id=37726
llvm-svn: 250808
If one file is MIPS64EL, all files are MIPS64EL, and vice versa.
We do not have to look up MIPS-ness for each file. Currently we
do not support 64-bit MIPS, so the config value is always false.
llvm-svn: 250566
This patch is to use ELFT instead of Is64Bits to template OutputSection
and its subclasses. This increases code size slightly because it creates
two identical functions for some classes, but that's only 20 KB out of
33 MB, so it's negligible.
This is as per discussion with Rafael. He's not fan of the idea but OK
with this. We'll revisit later to this topic.
llvm-svn: 250466
String table is added to end of the file so that all the other sections
are finalized before string table. But we can just add section names to
the string table before calling finalize() on any section instead.
llvm-svn: 250463
If a section name is valid as a C identifier (which is rare because of
the leading '.'), linkers are expected to define __start_<secname> and
__stop_<secname> symbols. They are at beginning and end of the section,
respectively. This is not requested by the ELF standard, but GNU ld and
gold provide this feature.
llvm-svn: 250432
After some additional post-commit (post-revert) discussion and research, this
reverts, in part, r250205, so the ABI-recommended starting address can be used
on PPC64 (as is done by other linkers).
Also, this addresses the FIXME in ELF/Writer.cpp by making VAStart a
target-dependent property.
llvm-svn: 250378
If an argument for --entry is a number, that's not a symbol name but
an absolute address. If that's the case, the address is directly set
to ELF header's e_entry.
llvm-svn: 250334
Previously, we used input section names as output section names.
That resulted that we created lots of sections for comdat
or -f{function,data}-section sections.
This patch reduces the number of sections by dropping suffix from
all section names which start with ".text.", ".rodata.", ".data."
or ".bss.". GNU linker does this using the internal linker script,
but for LLD I chose to do that directly.
Interestingly, this makes the linker faster. Time to link Clang
is this.
Before:
real 0m0.537s
user 0m0.433s
sys 0m0.104s
After:
real 0m0.390s
user 0m0.268s
sys 0m0.120s
It make sense because previously we created 57659 sections now only 27.
llvm-svn: 250315
Suggested by Rafael in his review of r250100. As Rafael points out, this may
grow into a switch in the future, but regardless, calling this on files for
other architectures is unnecessary.
llvm-svn: 250209
This has turned out to be unnecessary, and while some ability to set VAStart
will be needed at some point, this is not clearly the right direction.
llvm-svn: 250205
The fix in r250109 to ensure a strict weak ordering in the section sorting was
a bit overzealous. We only use the NOBITS comparison if either A or B is a
NOBITS section. Otherwise, we fall through to the target-specific ranking
function. Failure to do this causes the sorting to fail in cases where, for
example, a .dynamic section happens to end up in between .got and .toc, etc. in
the initial ordering (.dynamic has a type SHT_DYNAMIC, compared to SHT_PROGBITS
or SHT_NOBITS).
llvm-svn: 250190
What was done:
1) .got.plt section is created for functions that requires PLT. .got.plt has 3 predefined empty entries now that are required for dynamic linker.
Also other new items created are configured to have correct jump to PLT[N].
2) PLT section now has PLT[0] entry, also others ones are configured to support PLT->GOT(.got.plt) calls.
3) Implemented .rel[a].plt sections (based on patch http://reviews.llvm.org/D13569).
4) Fixed plt relocations types (based on patch http://reviews.llvm.org/D13589).
NOTES:
The .plt.got zero entry is still empty now. According to ELF specification it should hold the address of the dynamic structure, referenced with the symbol
_DYNAMIC. The _DYNAMIC entry points to the .dynamic section which contains information used by the ELF interpreter to setup the binary.
Differential Revision: http://reviews.llvm.org/D13651
llvm-svn: 250169
Under PPC64 ELF v1 ABI, the symbols associated with each function name don't
point directly to the code in the .text section (or similar), but rather to a
function descriptor structure in a special data section named .opd. The
elements in the .opd structure include a pointer to the actual code, and a the
relevant TOC base value. Both of these are themselves set by relocations.
When we have a local call, we need the relevant relocation to refer directly to
the target code, not to the function-descriptor in the .opd section. Only when
we have a .plt stub do we care about the address of the .opd function
descriptor itself.
So we make a few changes here:
1. Always write .opd first, so that its relocated data values are available
for later use when writing the text sections. Record a pointer to the .opd
structure, and its corresponding buffer.
2. When processing a relative branch relocation under ppc64, if the
destination points into the .opd section, read the code pointer out of the
function descriptor structure and use that instead.
This this, I can link, and run, a dynamically-compiled "hello world"
application on big-Endian PPC64/Linux (ELF v1 ABI) using lld.
llvm-svn: 250122
As pointed out by Rui (post-commit review), we need to always return based on
the section type when the types differ to ensure a strict weak ordering.
llvm-svn: 250109
PPC64 has several special sections that are intended to be accessed from the
TOC base pointer. When a .got is present, the TOC base pointer is .got + 0x8000
(as specified by the ABI). Furthermore, the glibc startup code contains an
assumption that a 16-bit relocation can hold the offset from the TOC base value
to the beginning of the .toc section. Thus, we need to make sure that .toc
appears after .got. This much, at least, is required in practice. The other
PPC64 special sections (.toc, .toc1, .opd, etc.) should also be close by to
optimize access by smaller TOC-base-pointer offsets.
llvm-svn: 250100
This patch adds AsNeeded and IsUsed bool fields to SharedFile. AsNeeded bit
is set if the DSO is enclosed with --as-needed and --no-as-needed. IsUsed
bit is off by default. When we adds a symbol to the symbol table for dynamic
linking, we set its SharedFile's IsUsed bit.
If AsNeeded is set but IsUsed is not set, we don't want to write that
file's SO name to DT_NEEDED field.
http://reviews.llvm.org/D13579
llvm-svn: 249998
Previously, we reserved the first page for the program header, so no
sections would be written to very beginning of the output file.
FreeBSD requires .interp section be exist on the first page, so that
was not good.
This patch calculates the size of the program header and then assign
addresses to the sections. Now the first section is located next to
the program header. Because the first section is .interp, it's very
likely to be on the first page.
llvm-svn: 249957
SymbolTable was not a right place for initialization. We had to do that
because Driver didn't know what type of ELF objects are being handled.
We taught Driver that, so we can now move this code to Driver.
llvm-svn: 249904
SymbolTable was not a template class. Instead we had switch-case-based
type dispatch to call desired functions. We had to do that because
SymbolTable was created before we know what ELF type objects had been
passed.
Every time I tried to add a new function to the symbol table, I had to
define a dispatcher which consist of a single switch statement.
It also brought an restriction what the driver can do. For example,
we cannot add undefined symbols before any files are added to the symbol
table. That's because no symbols can be added until the symbol table
knows the ELF type, but when it knows about that, it's too late.
In this patch, the driver makes a decision on what ELF type objects
are being handled. Then the driver creates a SymbolTable object for
an appropriate ELF type.
http://reviews.llvm.org/D13544
llvm-svn: 249902
This reverts commit r249816.
It broke building llvm with lld:
$ ./bin/FileCheck
./bin/FileCheck: error while loading shared libraries: unexpected PLT reloc type 0x06
I think the only thing that is wrong with this patch is that it is too soon.
The plt we create (and its relocs) don't support lazy loading, so they have
to be relocated as ordinary dynamic relocations.
llvm-svn: 249835
.rela.plt contains list of elements in the PLT, which are liable to the relocation during the dynamic linking.
Differential Revision: http://reviews.llvm.org/D13569
llvm-svn: 249816
The required page alignment is different on different targets. On PowerPC, for
example, we need 64K pages (the loader won't set different permissions on a
finer granularity than that). I've set the existing targets to what I believe
to be the correct values, and have updated the regression tests accordingly.
llvm-svn: 249760
Reapply r249726 (and r249723), hopefully with the correct test fixups this time.
Original commit message:
Address a FIXME in ELF/Writer.cpp: Make VAStart a target-dependent property.
I've set the values for the existing targets to what I believe to be the
correct values, and updated the regression tests accordingly.
llvm-svn: 249752
Address a FIXME in ELF/Writer.cpp: Make VAStart a target-dependent property.
I've set the values for the existing targets to what I believe to be the
correct values, and updated the regression tests accordingly.
llvm-svn: 249723
Previously, output sections that are handled specially by the linker
(e.g. PLT or GOT) were created by Writer and passed to other classes
that need them. The problem was that because these special sections
are required by so many classes, the plumbing work became too much
burden.
This patch is to simply make them accessible from anywhere in the
linker to eliminate the plumbing work once and for all.
http://reviews.llvm.org/D13486
llvm-svn: 249590
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
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
The new name starts with a verb, and it does not imply that it errors
out and exit (it acutally can just emit a warning depending on settings.)
llvm-svn: 249016
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
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 more consistent with OutputSection. This is also part of removing
the "Chunk" term from the ELF linker, since we just have input/output sections
and program headers.
llvm-svn: 248183
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
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
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
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
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
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
With this patch only the name is set. I will set the other fields shortly.
For now the table doesn't include local symbols. This is equivalent to using
--discard-all with gnu ld. This is OK for now since the symbols are not
needed for execution and for testing symbol resolution we only need the
global symbols.
llvm-svn: 245044
With OutputSection being a virtual interface, each concrete OutputSection
handles only one type of chunk and we don't need a base Chunk class.
So for we have a class that handles input sections and one that handles
the string table, but this extends naturally for other outputs (symbol table,
merging of SHF_MERGE sections, etc.).
llvm-svn: 244972
We were creating the string table in a completely ad hoc way. Now the
string table is an output section and gets its output offset set just like
any other section.
This opens the way for other linker created sections like the symbol table.
llvm-svn: 244969
This is a bit more c++ code, but:
* It is less machine code: lld's text is 44688 bytes smaller.
* It should be a bit more efficient in the non native endian case.
* It should be a bit more efficient on architectures with slow unaligned access.
llvm-svn: 244934
Various parameters are passed implicitly using Config global variable
already. Output file path is no different from others, so there was no
special reason to handle that differnetly.
This patch changes the signature of writeResult(SymbolTable *, StringRef)
to writeResult(SymbolTable *).
llvm-svn: 244180
We are using Writer more like a function instead of a class.
This patch makes it a function to simplify the interface.
All details of Writer class is now hidden from other parts of the linker.
llvm-svn: 244169
The others we have in sight are
* common symbols.
* entries in SHF_MERGE sections.
They will have a substantially different treatment. It is not clear if it is
worth it putting them all in a single list just to dispatch based on the kind on
the other side.
I hope to implement common symbols soon, and then we will be in a position
to have a concrete discussion. For now this is simpler for the the implemented
features.
llvm-svn: 244042
When we were using a std::sort over all the chunks we needed to put them in a
single storage.
Now that we just iterate over them and use a map to find the output section,
we can avoid allocating the temporary storage.
llvm-svn: 243980
This is a direct port of the new PE/COFF linker to ELF.
It can take a single object file and generate a valid executable that executes at the first byte in the text section.
llvm-svn: 242088
Igor Kudrin