The assembly at the top of this file contained more relocations than
the YAML. I regenerated it so that we'd have complete relocation testing.
Also added detailed explanations of the relocations in the file so that
future people don't have to try decode them when something goes wrong.
llvm-svn: 256064
@indntpoff is similar to @gotntpoff, but for use in position dependent code. While @gotntpoff resolves to GOT slot address relative to the
start of the GOT in the movl or addl instructions, @indntpoff resolves to the
absolute GOT slot address. ("ELF Handling For Thread-Local Storage", Ulrich Drepper).
Differential revision: http://reviews.llvm.org/D15494
llvm-svn: 255884
negDelta32 is only ever implicitly generated as the FDE->CIE reference.
We therefore don't emit a relocation for it in the object file in -r mode.
The value we write in to the FDE location therefore needs to point to the
final target address of the CIE, and not the inAtomAddress as it was currently
doing.
llvm-svn: 255835
The `_gp_disp` is a magic symbol designates offset between start of
function and gp pointer into GOT. Only `R_MIPS_HI16` and `R_MIPS_LO16`
relocations are permitted with `_gp_disp`. The patch adds the `_gp_disp`
as an ignored symbol and adjusts symbol value before call the `relocateOne`
for `R_MIPS_HI16/LO16` relocations.
Differential Revision: http://reviews.llvm.org/D15480
llvm-svn: 255768
The `R_MIPS_JALR` is a relocation generated by gcc and gas. This
relocation points to the `jalr` instruction which might be optimized and
converted to the `b` instruction under some conditions.
Now we just ignore this relocation and keep instructions unchanged.
llvm-svn: 255453
If we don't filter these out we can end up, generating bogus paths, for example:
/home/user/lld/build/bin -> /home/user/home/user/lld/build/bin/lld/build/bin.
llvm-svn: 255378
It is reasonable to specify an entry point for shared objects - for
example, for the FreeBSD rtld ld-elf.so.1.
Unlike GNU ld we leave the entry address as 0 if -shared is specified
without -e.
Differential Revision: http://reviews.llvm.org/D15454
llvm-svn: 255349
R_X86_64_SIZE64/R_X86_64_SIZE32 relocations were introduced in 0.98v of "System V Application Binary Interface x86-64" (http://www.x86-64.org/documentation/abi.pdf).
Calculation for them is Z + A, where:
Z - Represents the size of the symbol whose index resides in the relocation entry.
A - Represents the addend used to compute the value of the relocatable field.
Differential revision: http://reviews.llvm.org/D15335
llvm-svn: 255332
When llvm-lit prints a failure, you'll see something like 'lld *command*' However, you can't then take this, paste it in to a terminal and run it, because it's not got the absolute path of lld.
llvm and clang's lit.cfg files contain lists of commands to look for which are substituted by their full paths. So now you'd see something like '*build dir*/bin/lld *command*'.
This patch adds the same capability to lld's lit.cfg
Reviewed by Rafael Espíndola
llvm-svn: 255283
The delta64 relocation is represented as the pair ARM64_RELOC_SUBTRACTOR and ARM64_RELOC_UNSIGNED.
Those should always have the same offset, so this adds a check and tests to ensure this is the case.
Also updated the error printing in this case to shows both relocs when erroring on pair.
llvm-svn: 255274
List all sections removed by garbage collection. This option is only effective if garbage collection has been enabled via the `--gc-sections' option.
Differential revision: http://reviews.llvm.org/D15327
llvm-svn: 255235
If R_386_PLT32 relocation is applied against symbol that can not be preempted then it can be resolved statically.
Patch implements it for x86 target.
Differential revision: http://reviews.llvm.org/D15376
llvm-svn: 255233
Implement the TLS relocation optimization for 32-bit x86 that is described in
"ELF Handling For Thread-Local Storage" by Ulrich Drepper, chapter 5,
"IA-32 Linker Optimizations". Specifically, this patch implements these
optimizations: LD->LE, GD->IE, GD->LD, and IE->LE.
Differential revision: http://reviews.llvm.org/D15292
llvm-svn: 255103
The gcc_except_tab was generating these references to point to the typeinfo in the data section.
gcc_except_tab also had the DW_EH_PE_indirect flag set which means that at runtime we are going
to dereference this entry as if it is in the GOT.
Reviewed by Nick Kledzik in http://reviews.llvm.org/D15360.
llvm-svn: 255085
All relocations, which cannot be handled by the dynamic linker,
cause a linking error "rebuild with -fPIC".
Differential revision: http://reviews.llvm.org/D15193
llvm-svn: 254840
"Ulrich Drepper, ELF Handling For Thread-Local Storage" (5.5 x86-x64 linker optimizations, http://www.akkadia.org/drepper/tls.pdf) shows how GD can be optimized to IE.
This patch implements the optimization.
Differential revision: http://reviews.llvm.org/D15000
llvm-svn: 254713
If a section symbol is not external, that COMDAT section should never
be merge with other sections in other compilation unit. Previously,
we didn't take visibility into account.
Note that COMDAT sections with non-external visibility makes sense
because they can be removed by dead-stripping.
Fixes https://llvm.org/bugs/show_bug.cgi?id=25686
llvm-svn: 254578
Main aim of the patch to introduce basic support for TLS access models for x86 target.
Models using @tlsgd, @tlsldm and @gotntpoff are implemented.
Differential revision: http://reviews.llvm.org/D15060
llvm-svn: 254500
Some MIPS relocations including `R_MIPS_HI16/R_MIPS_LO16` use combined
addends. Such addend is calculated using addends of both paired relocations.
Each `R_MIPS_HI16` relocation is paired with the next `R_MIPS_LO16`
relocation. ABI requires to compute such combined addend in case of REL
relocation record format only.
For details see p. 4-17 at
ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
This patch implements lookup of the next paired relocation suing new
`InputSectionBase::findPairedRelocLocation` method. The primary
disadvantage of this approach is that we put MIPS specific logic into
the common code. The next disadvantage is that we lookup `R_MIPS_LO16`
for each `R_MIPS_HI16` relocation, while in fact multiple `R_MIPS_HI16`
might be paired with the single `R_MIPS_LO16`. From the other side
this way allows us to keep `MipsTargetInfo` class stateless and implement
later relocation handling in parallel.
This patch does not support `R_MIPS_HI16/R_MIPS_LO16` relocations against
`_gp_disp` symbol. In that case the relocations use a special formula for
the calculation. That will be implemented later.
Differential Revision: http://reviews.llvm.org/D15112
llvm-svn: 254461
Combination of @tlsgd and @gottpoff at the same time leads to miss of R_X86_64_TPOFF64 dynamic relocation. Patch fixes that.
@tlsgd(%rip) - Allocate two contiguous entries in the GOT to hold a tls index
structure (for passing to tls get addr).
@gottpoff(%rip) - Allocate one GOT entry to hold a variable offset in initial TLS
block (relative to TLS block end, %fs:0).
The same situation can be observed for x86 (probably others too, not sure) with corresponding for that target relocations: @tlsgd, @gotntpoff.
Differential revision: http://reviews.llvm.org/D15105
llvm-svn: 254443
ABI specifies the allowed range for these relocations as 2^(n-1) <= X < 2^n.
The patch fixes checks and introduces precise tests for these relocations.
Differential revision: http://reviews.llvm.org/D14957
llvm-svn: 254146
In case a sysroot prefix is configured, and the filename starts with
the '/' character, and the script being processed was located inside
the sysroot prefix, the file's name will be looked for in the sysroot
prefix. Otherwise, the linker falls to the common lookup scheme.
It is slightly modified version of the commit r254031. The problem of
the initial commit was in the `is_absolute` call. On Windows 'C:\' is
absolute path but we do not need to find it under sysroot. In this patch
linker looks up a path under sysroot only if the paths starts with '/'
character.
llvm-svn: 254135
Implements @tlsld (LD to LE) and @tlsgd (GD to LE) optimizations.
Patch does not implement the GD->IE case for @tlsgd.
Differential revision: http://reviews.llvm.org/D14870
llvm-svn: 254101
Patch implements lazy relocations for x86.
One of features of x86 is that executable files and shared object files have separate procedure linkage tables. So patch implements both cases.
Detailed information about instructions used can be found in http://docs.oracle.com/cd/E19620-01/805-3050/chapter6-1235/index.html (search: x86: Procedure Linkage Table).
Differential revision: http://reviews.llvm.org/D14955
llvm-svn: 254098
R_MIPS_CALL16 relocation provides the same result as R_MIPS_GOT16
relocation but does not need to check the result on overflow.
Differential Revision: http://reviews.llvm.org/D14916
llvm-svn: 254092
This patch implements next relocations:
R_386_TLS_LE - Negative offset relative to static TLS (GNU version).
R_386_TLS_LE_32 - Offset relative to static TLS block.
These ones are created when using next code sequences:
* @tpoff - The operator must be used to compute an immediate value. The linker will report
an error if the referenced variable is not defined or it is not code for the executable
itself. No GOT entry is created in this case.
* @ntpoff Calculate the negative offset of the variable it is added to relative to the static TLS block.
The operator must be used to compute an immediate value. The linker will report
an error if the referenced variable is not defined or it is not code for the executable
itself. No GOT entry is created in this case.
Information was found in Ulrich Drepper, ELF Handling For Thread-Local Storage, http://www.akkadia.org/drepper/tls.pdf, (6.2, p76)
Differential revision: http://reviews.llvm.org/D14930
llvm-svn: 254090
In the previous patch (r254003), I made the linker emit PT_GNU_STACK
unconditionally. But sometimes you want to have a control over the
presence of the segment. With this patch, you can omit the segment
by passing -z execstack option.
llvm-svn: 254039
In case a sysroot prefix is configured, and the filename starts with the
'/' character, and the script being processed was located inside the
sysroot prefix, the file's name will be looked for in the sysroot
prefix. Otherwise, the linker falls to the common lookup scheme.
https://www.sourceware.org/binutils/docs-2.24/ld/File-Commands.html
Differential Revision: http://reviews.llvm.org/D14916
llvm-svn: 254031
Partial (-z relro) and full (-z relro, -z now) relro cases are implemented.
Partial relro:
The ELF sections are reordered so that the ELF internal data sections (.got, .dtors, etc.) precede the program's data sections (.data and .bss).
.got is readonly, .got.plt is still writeable.
Full relro:
Supports all the features of partial RELRO, .got.plt is also readonly.
Differential revision: http://reviews.llvm.org/D14218
llvm-svn: 253967
R_X86_64_GOTTPOFF is not always requires GOT entries. Some relocations can be converted to local ones.
Differential revision: http://reviews.llvm.org/D14713
llvm-svn: 253966
With these relocations, it is now possible to build a simple "hello world"
program for AArch64 Debian.
Differential revision: http://reviews.llvm.org/D14917
llvm-svn: 253957
With this patch, lld creates PT_GNU_STACK segments only when all input
files have .note.GNU-stack sections. This is in line with other linkers
with a minor difference (we don't care about .note.GNU-stack rwx bits as
you can always remove .note.GNU-stack sections instead of setting x bit.)
At least, NetBSD loader does not understand PT_GNU_STACK segments and
reject any executables that have the section. This patch makes lld
compatible with such operating systems.
llvm-svn: 253797
This option is passed by clang driver if the target triple
is "aarch64-unknown-linux".
Differential Revision: http://reviews.llvm.org/D14831
llvm-svn: 253639
PT_GNU_STACK is a entry in the elf file format which contains the access rights (read, write, execute) of the stack,
it is always generated now. By default stack is not executable in this implementation.
-z execstack can be used to make executable.
Differential revision: http://reviews.llvm.org/D14571
llvm-svn: 253145
This sections can be protected with relro after resolving relocations by dynamic linker.
Differential revision: http://reviews.llvm.org/D14567
llvm-svn: 253018
The MIPS target requires specific dynamic section entries to be defined.
* DT_MIPS_RLD_VERSION and DT_MIPS_FLAGS store predefined values.
* DT_MIPS_BASE_ADDRESS holds base VA.
* DT_MIPS_LOCAL_GOTNO holds the number of local GOT entries.
* DT_MIPS_SYMTABNO holds the number of .dynsym entries.
* DT_MIPS_GOTSYM holds the index of the .dynsym entry
which corresponds to the first entry of the global part of GOT.
* DT_MIPS_RLD_MAP holds the address of the reserved space in the data segment.
* DT_MIPS_PLTGOT points to the .got.plt section if it exists.
* DT_PLTGOT holds the address of the GOT section.
See "Dynamic Section" in Chapter 5 in the following document for detailed
description: ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
Differential revision: http://reviews.llvm.org/D14450
llvm-svn: 252857
The MIPS ABI has requirements to sort the entries in the .dyn.sym section.
Symbols which are not in the GOT have to precede the symbols which are added to
the GOT. The latter must have the same order as the corresponding GOT entries.
Since these sorting requirements contradict those of the GNU hash section,
they cannot be used together.
Differential revision: http://reviews.llvm.org/D14281
llvm-svn: 252854
This adds support for:
* Uniquing CIEs
* Dropping FDEs that point to dropped sections
It drops 657 488 bytes from the .eh_frame of a Release+Asserts clang.
The link time impact is smallish. Linking clang with a Release+Asserts
lld goes from 0.488064805 seconds to 0.504763060 seconds (1.034 X slower).
llvm-svn: 252790
GNU as can give it type SHT_PROGBITS or SHT_X86_64_UNWIND depending on
teh construct.
MC gives it type SHT_X86_64_UNWIND.
The linker has to canonicalize to one or the other so that there is only
one .eh_frame in the end.
llvm-svn: 252757
leaq symbol@tlsld(%rip), %rdi
call __tls_get_addr@plt
symbol@tlsld (R_X86_64_TLSLD) instructs the linker to generate a tls_index entry (two GOT slots) in the GOT for the entire module (shared object or executable) with an offset of 0. The symbol for this GOT entry doesn't matter (as long as it's either local to the module or null), and gold doesn't put a symbol in the dynamic R_X86_64_DTPMOD64 relocation for the GOT entry.
All other platforms defined in http://www.akkadia.org/drepper/tls.pdf except for Itanium use a similar model where global and local dynamic GOT entries take up 2 contiguous GOT slots, so we can handle this in a unified manner if we don't care about Itanium.
While scanning relocations we need to identify local dynamic relocations and generate a single tls_index entry in the GOT for the module and store the address of it somewhere so we can later statically resolve the offset for R_X86_64_TLSLD relocations. We also need to generate a R_X86_64_DTPMOD64 relocation in the RelaDyn relocation section.
This implementation is a bit hacky. It side steps the issue of GotSection and RelocationSection only handling SymbolBody entries by relying on a specific relocation type. The alternative to this seemed to be completely rewriting how GotSection and RelocationSection work, or using a different hacky signaling method.
llvm-svn: 252682
This is cleaner than computing relocations as if we had done it.
While at it, keep a single Phdr variable instead of multiple fields of it.
llvm-svn: 252352
This patch implements R_MIPS_GOT16 relocation for global symbols in order to
generate some entries in GOT. Only reserved and global entries are supported
for now. For the detailed description about GOT in MIPS, see "Global Offset
Table" in Chapter 5 in the followin document:
ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
In addition, the platform specific symbol "_gp" is added, see "Global Data
Symbols" in Chapter 6 in the aforementioned document.
Differential revision: http://reviews.llvm.org/D14211
llvm-svn: 252275
For x86-64 the initial executable TLS block is placed directly before the
thread specific data register so compilers can directly access it via
R_X86_64_TPOFF32. Generate the correct (negative) offset for this case.
llvm-svn: 252131
This does not support TPOFF32 relocations to local symbols as the address calculations are separate. Support for this will be a separate patch.
llvm-svn: 251998
This is a case where there is inconsistency among ELF linkers:
* The spec says nothing special about empty sections.
* BFD ld removes them.
* Gold handles them like regular sections.
We were outputting them but sometimes ignoring them. This would create
odd looking outputs where a rw section could be in a ro segment for example.
The bfd way of doing things is also strange for the case where a symbol
points to the empty section.
Now we match gold and what seems to be the intention of the spec.
llvm-svn: 251988
GNU linkers accept both variants and at least for MIPS target gcc passes
joined variant of the '-m' option.
Differential Revision: http://reviews.llvm.org/D14133
llvm-svn: 251497
This matches ld.bfd and ld.gold behavior. The change is simple enough
and avoid trouble to consumers (they don't have to change their Makefiles).
Side note: found while trying to build FreeBSD base system with lld.
llvm-svn: 251408
.eh_frame sections need to be preserved if they refer to live sections.
So the liveness relation is reverse for eh_frame sections. For now,
we simply preserve all .eh_frame sections. Thanks Rafael for pointing
this out. .jcr are kept for the same reason.
llvm-svn: 251068
Section garbage collection is a feature to remove unused sections
from outputs. Unused sections are sections that cannot be reachable
from known GC-root symbols or sections. Naturally the feature is
implemented as a mark-sweep garbage collector.
In this patch, I added Live bit to InputSectionBase. If and only
if Live bit is on, the section will be written to the output.
Starting from GC-root symbols or sections, a new function, markLive(),
visits all reachable sections and sets their Live bits. Writer then
ignores sections whose Live bit is off, so that such sections are
excluded from the output.
This change has small negative impact on performance if you use
the feature because making sections means more work. The time to
link Clang changes from 0.356s to 0.386s, or +8%.
It reduces Clang size from 57,764,984 bytes to 55,296,600 bytes.
That is 4.3% reduction.
http://reviews.llvm.org/D13950
llvm-svn: 251043
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
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
The option now just sets NOW bit in DT_FLAGS_1 but some loaders
seem to require also BIND_NOW bit to be set in DT_FLAGS. This is,
also, what ld.bfd and gold do.
Differential Revision: http://reviews.llvm.org/D13883
llvm-svn: 250799
The two names are similar enough that they might lead to confusion.
The output of readobj clarifies but I missed it when I originally
committed this. Found while linking FreeBSD userland with lld.
llvm-svn: 250739
The reason of collecting all undefines in vector is that during reading files we already need to have Symtab created. Or like was done in that patch - to put undefines from scripts somewhere to delay Symtab.addUndefinedOpt() call.
Differential Revision: http://reviews.llvm.org/D13870
llvm-svn: 250711
Instead of specifically creating .plt entries for weak undef symbols, mirror
the logic in r250584, and use canBePreempted to determine is a REL24 relocation
needs a .plt entry. This might cause relocateOne to be called for a weak undef
symbol, with a REL24 relocation, but ignore this as a special case (this will
cause SA == 0, which won't happen under any other circumstance).
llvm-svn: 250597
There is sometimes no need to generate relocation via PLT.
Example - when symbol is not undefined and we are not creating shared library. Then we can create relative relocation instead of referencing and creating PLT records.
Differential Revision: http://reviews.llvm.org/D13835
llvm-svn: 250584
When we have a R_PPC64_ADDR64 for a weak undef symbol, which thus resolves to
0, and we're creating a shared library, we need to make sure that it stays 0
(because code that conditionally calls the weak function tests for this).
Unfortunately, we were creating a R_PPC64_RELATIVE for these relocation
targets, making the address of the undefined weak symbol equal to the base
address of the shared library (which is non-zero). In general, we should not be
creating RelativeReloc relocs for undef weak symbols.
llvm-svn: 250558
R_PPC64_TOC does not have an associated symbol, but does have a non-zero VA
that target-specific code must compute using some non-trivial rule. We
handled this as a special case in PPC64TargetInfo::relocateOne, where
we knew to write this special address, but that did not work when creating shared
libraries. The special TOC address needs to be the subject of a
R_PPC64_RELATIVE relocation, and so we also need to know how to encode this
special address in the addend of that relocation.
Thus, some target-specific logic is necessary when creating R_PPC64_RELATIVE as
well. To solve this problem, we teach getLocalRelTarget to handle R_PPC64_TOC
as a special case. This allows us to remove the special case in
PPC64TargetInfo::relocateOne (simplifying code there), and naturally allows the
existing logic to do the right thing when creating associated R_PPC64_RELATIVE
relocations for shared libraries.
llvm-svn: 250555
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
Unfortunately, the check was not as dead as I had thought, and adjusting the
starting VA again exposed the problem. We end up trying to relocate the bl
(using a 24-bit relative offset) to a symbol address of zero, and in general,
that does not fit.
Thus, reverting for now, and adding a test case.
llvm-svn: 250423
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
- Make the `MipsTargetInfo` template class with `ELFType` argument. Use
the argument to select an appropriate relocation type and read/write
routines.
- Add template function `add32` to add-and-write relocation value in
both big and little endian cases. Keep the `add32le` to reduce code
changes.
Differential Revision: http://reviews.llvm.org/D13723
llvm-svn: 250297
The documentation says: "You may separate commands using semicolons",
so they seem to be optional.
Differential Revision: http://reviews.llvm.org/D13703
llvm-svn: 250223
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
BSD's DSO files have undefined symbol "__progname" which is defined
in crt1.o. On that system, both user programs and system shared
libraries depend on each other.
In general, we need to put symbols defined by user programs which are
referenced by shared libraries to user program's .dynsym.
http://reviews.llvm.org/D13637
llvm-svn: 250176
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
Under the PPC64 ELF ABI, functions that might call into other modules (and,
thus, need to load a different TOC base value into %r2), need to restore the
old value after the call. The old value is saved by the .plt code, and the
caller only needs to include a nop instruction after the call, which the linker
will transform into a TOC restore if necessary.
In order to do this the relocation handler needs two things:
1. It needs to know whether the call instruction it is modifying is targeting
a .plt stub that will load a new TOC base value (necessitating a restore after
the call).
2. It needs to know where the buffer ends, so that it does not accidentally
run off the end of the buffer when looking for the 'nop' instruction after the
call.
Given these two pieces of information, we can insert the restore instruction in
place of the following nop when necessary.
llvm-svn: 250110
This is mostly an adaptation of the code in LLVM's
lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp, and handles a sufficient
number of relocations to link a 'hello world' program on big-Endian PPC64/Linux
(ELF v1 ABI).
llvm-svn: 250101
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
In order to actually verify the condition, we have to use a weak symbol.
If an undefined symbol is not used at all, it is naturally ignored not by
the code for --as-needed but by the code for something else.
llvm-svn: 250062
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
In the linker script, -l and = have the same meaning as in the command line.
In addition to that, if a path is not absolute, the path needs to be searched
from the search paths. This patch implements them.
llvm-svn: 249967
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 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
`not` command on Windows is not able to find an executable from PATH
if a given command already has an extension even if the extension is
not ".exe".
llvm-svn: 249630
When generating an executable or shared library, mark it to tell the dynamic linker to resolve all symbols when the program is started, or when the shared library is linked to using dlopen, instead of deferring function call resolution to the point when the function is first called.
Differential Revision: http://reviews.llvm.org/D13468
llvm-svn: 249551
Parse and apply emulation given with -m option.
Check input files to match ELF type and machine architecture provided with -m.
Differential Revision: http://reviews.llvm.org/D13055
llvm-svn: 249529
I am about to change lld to avoid creating unnecessary got entries for locally
defined symbols when creating executables.
Update tests that were depending on the current behavior.
llvm-svn: 249474
We were still fetching them when the archive was seen first.
We should experiment with just letting lazy symbols get to compare, it
might be cleaner for ELF.
llvm-svn: 249417
This is a case that requires --start-group --end-group with regular ELF
linkers. Fortunately it is still possible to handle it with lazy symbols without
taking a second look at archives.
Thanks to Michael Spencer for the bug report.
llvm-svn: 249406
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
Pete Cooper