These relocations apply to 16-bit Thumb instructions, so reading 16 bits
rather than 32 bits ensures the correct bits are masked and written
back. This fixes the incorrect masking and aligns the relocation logic
with the instruction encoding.
Before this patch, 32 bits were read from the ELF object. This did not
align with the instruction size of 16 bits, but the masking incidentally
made it all work nonetheless. However, this was the case only in little
endian.
In big endian mode, the read 32-bit word had to have its bytes reversed.
With this byte reordering, the masking would be applied to the wrong
bits, hence causing the incorrect encoding to be produced as a result of
the relocation resolution.
The added test checks the result for both little and big endian modes.
--export-dynamic should be a no-op when ctx.hasDynsym is false.
* Drop unneeded ctx.hasDynsym checks.
* Static linking with --export-dynamic does not prevent devirtualization.
ICF runs before BPSectionOrderer. When a section is ICF'ed, it seems
that the original sections are marked as not live, but are still kept
around. Prior to this patch, those ICF'ed sections would be passed to BP
and ordered before being skipped when writing the output. Now, these
sections are no longer passed to BP, saving runtime and possibly
improving BP's output.
In a large binary, I found that the number of sections ordered using BP
decreased, while the number of duplicate sections drastically decreased
as expected.
```
Functions for startup: 50755 -> 50520
Functions for compression: 165734 -> 105328
Duplicate functions: 1827231 -> 55230
```
(This application-specific option is probably not appropriate as a
linker option (.o file offers more flexibility and decouples JSON
verification from linkers). However, the option has gained some traction
in Linux distributions, with support in GNU ld, gold, and mold.)
GNU ld has supported percent-encoded bytes and extensions like
`%[comma]` since November 2024. mold supports just percent-encoded
bytes. To prepare for potential adoption by Ubuntu, let's support
percent-encoded bytes.
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=32003
Link: https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/2071468
Pull Request: https://github.com/llvm/llvm-project/pull/126396
Reland 994cea3f0a2d0caf4d66321ad5a06ab330144d89 after bolt tests no
longer rely on -pie --unresolved-symbols=ignore-all with no input DSO
generating PLT entries.
---
Commit f10441ad003236ef3b9e5415a571d2be0c0ce5ce , while dropping a
special case for isUndefWeak and --no-dynamic-linking, made
--export-dynamic ineffective when -pie is used without any input DSO.
This change restores --export-dynamic and unifies -pie and -pie
--no-dynamic-linker when there is no input DSO.
* -pie with no input DSO suppresses undefined symbols in .dynsym.
Previously this only appied to -pie --no-dynamic-linker.
* As a side effect, -pie with no input DSO suppresses PLT.
LLVM has started to emit AArch64 build attributes sections called
.ARM.attributes. LLD does not yet have support for these so they are
accumulating in the ELF output. As the first part of that support
discard all the .ARM.attributes sections. This can be built upon by the
full implementation in LLD.
The build attributes specification only defines build attributes for
relocatable objects. The intention for LLD is that files of type ET_EXEC
and ET_SHARED will not have a build attributes in the output. A
relocatable link with -r will need a merged build attributes, but until
the merge is implemented it is better to discard.
Reland #120514 after 2f6e3df08a8b7cd29273980e47310cf09c6fdbd8 fixed
iteration order issue and libstdc++/libc++ differences.
---
Both options instruct the linker to optimize section layout with the
following goals:
* `--bp-compression-sort=[data|function|both]`: Improve Lempel-Ziv
compression by grouping similar sections together, resulting in a
smaller compressed app size.
* `--bp-startup-sort=function --irpgo-profile=<file>`: Utilize a
temporal profile file to reduce page faults during program startup.
The linker determines the section order by considering three groups:
* Function sections ordered according to the temporal profile
(`--irpgo-profile=`), prioritizing early-accessed and frequently
accessed functions.
* Function sections. Sections containing similar functions are placed
together, maximizing compression opportunities.
* Data sections. Similar data sections are placed together.
Within each group, the sections are ordered using the Balanced
Partitioning algorithm.
The linker constructs a bipartite graph with two sets of vertices:
sections and utility vertices.
* For profile-guided function sections:
+ The number of utility vertices is determined by the symbol order
within the profile file.
+ If `--bp-compression-sort-startup-functions` is specified, extra
utility vertices are allocated to prioritize nearby function similarity.
* For sections ordered for compression: Utility vertices are determined
by analyzing k-mers of the section content and relocations.
The call graph profile is disabled during this optimization.
When `--symbol-ordering-file=` is specified, sections described in that
file are placed earlier.
Co-authored-by: Pengying Xu <xpy66swsry@gmail.com>
The ELF/bp-section-orderer.s test is failing on some buildbots due to
what seems like non-determinism issues, see comments on the original PR
and #125450
Reverting to green the build.
This reverts commit 0154dce8d39d2688b09f4e073fe601099a399365 and
follow-up commits 046dd4b28b9c1a75a96cf63465021ffa9fe1a979 and
c92f20416e6dbbde9790067b80e75ef1ef5d0fa4.
Add new ELF linker options for profile-guided section ordering
optimizations:
- `--irpgo-profile=<file>`: Read IRPGO profile data for use with startup
and compression optimizations
- `--bp-startup-sort={none,function}`: Order sections based on profile
data to improve star tup time
- `--bp-compression-sort={none,function,data,both}`: Order sections
using balanced partitioning to improve compressed size
- `--bp-compression-sort-startup-functions`: Additionally optimize
startup functions for compression
- `--verbose-bp-section-orderer`: Print statistics about balanced
partitioning section ordering
Thanks to the @ellishg, @thevinster, and their team's work.
---------
Co-authored-by: Fangrui Song <i@maskray.me>
Commit f10441ad003236ef3b9e5415a571d2be0c0ce5ce dropped a special case
for isUndefWeak and --no-dynamic-linking but also made --export-dynamic
ineffective for static PIE.
This change restores the --export-dynamic behavior and entirely drops
special handling of --no-dynamic-linker:
* -pie with no input DSO, similar to --no-dynamic-linker, suppresses
undefined symbols in .dynsym
The new behaviors resemble GNU ld more.
Commit 3733ed6f1c6b0eef1e13e175ac81ad309fc0b080 introduced isExported to
cache includeInDynsym. If we don't unnecessarily set isExported for
undefined symbols, exportDynamic/includeInDynsym can be replaced with
isExported.
Similar to the change to MarkLive.cpp when isExported was introduced.
includeInDynsym might return true even when isExported is false for
statically linked executables.
Commit 2a26292388fcab0c857c91b2d08074c33abd37e8 made `isExported`
accurate except a few linker-synthesized symbols in finalizeSections.
We can collect these linker-synthesized symbols into a vector
and avoid recomputation for other symbols.
This is reland of 1a4d6de1b532149b10522eae5dabce39e5f7c687 after
`isExported` has been made accurate by f10441ad003236ef3b9e5415a571d2be0c0ce5ce
`includeInDynsym` has a special case for isUndefWeak and
--no-dynamic-linker, which can be removed if we simplify disallow
dynamic symbols for static-pie.
The partition feature reports errors only when a symbol `isExported`.
We need to link in a DSO to trigger the mips error.
This reverts commit 048f35037779763963c4b4478a0884e828ea9538.
This reverts commit f7bbc40b0736cc417f57cd039b098b504cf6a71f.
Related to #95949. A developer with no prior lld contribution and very
little AMD contribution sneaked in these application-specific section
order rules we discourage.
Commit 2a26292388fcab0c857c91b2d08074c33abd37e8 made `isExported`
accurate except a few linker-synthesized symbols in finalizeSections.
We can collect these linker-synthesized symbols into a vector
and avoid recomputation for other symbols.
LTO compilation might define symbols not in the symbol table (e.g.
__emutls_v.x in test/ELF/lto/wrap-unreferenced-before-codegen.test).
These symbols have a false `isExported` until
`demoteSymbolsAndComputeIsPreemptible`. This is usually benign as we do
not reference `isExported` that early.
Ensure that `isExported` is correct early. This helps remove a redundant
`isExported` computation in `demoteSymbolsAndComputeIsPreemptible`.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change the Fatal to
ErrAlways (not-recoverable) as subsequent code assumes SHF_LINK_ORDER
sh_link is correct.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change a few Fatal to
recoverable Err.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change a few Fatal to
recoverable Err.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change a few Fatal to
recoverable Err.
These diagnostics are mostly reported by a thread during writeSections.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1.
.note.GNU-stack with the SHF_EXECINSTR flag requires an executable
stack. This is exceedingly rare. We report an error to force
the user to explicitly request an executable stack.
Close#121234
Pull Request: https://github.com/llvm/llvm-project/pull/124068
Depends on #120010
Support `R_AARCH64_AUTH_TLSDESC_ADR_PAGE21`, `R_AARCH64_AUTH_TLSDESC_LD64_LO12`
and `R_AARCH64_AUTH_TLSDESC_LD64_LO12` static relocations and
`R_AARCH64_AUTH_TLSDESC` dynamic relocation. IE/LE optimization is not
currently supported for AUTH TLSDESC.
According to the binutils spec:
https://sourceware.org/binutils/docs/ld/Input-Section-Basics.html
You should be able to specify all files in an archive using this syntax
`archivename:` , however, lld currently will only accept `archivename:*`
to match all files within an archive.
This patch will, only when necessary, create a copy of the file
specification and add an implicit wildcard `*` to the end. It also
updates the filename-spec linkerscript test to check for this behavior.
---------
Co-authored-by: Peter Smith <peter.smith@arm.com>
Port https://reviews.llvm.org/D117354 from the MachO port.
If both --symbol-ordering-file and call graph profile are present, the
--symbol-ordering-file takes precedence, but the call graph profile is
still used for symbols that don't appear in the order file.
In addition, call graph profile described sections are now ordered
before other sections.
cg_profile in object is from CGProfilePass and it is often inaccurate.
While call-graph-ordering-file is provided by user. It is weird to
aggregate them together especially when call-graph-ordering-file is
accurate enough.
`InputSectionBase::relsOrRelas` make at most one array-ref non-empty. One-off counter (as debugging log) shows the number of empty member containers is 2 or 3 in a real build.
Fix the typo.
Depends on #114525
Support `R_AARCH64_AUTH_GOT_ADR_PREL_LO21` and `R_AARCH64_AUTH_GOT_LD_PREL19`
GOT-generating relocations. A corresponding `RE_AARCH64_AUTH_GOT_PC` member
of `RelExpr` is added, which is an AUTH-specific variant of `R_GOT_PC`.
Depends on #113811
Support `R_AARCH64_AUTH_ADR_GOT_PAGE`, `R_AARCH64_AUTH_GOT_LO12_NC` and
`R_AARCH64_AUTH_GOT_ADD_LO12_NC` GOT-generating relocations. For preemptible
symbols, dynamic relocation `R_AARCH64_AUTH_GLOB_DAT` is emitted. Otherwise,
we unconditionally emit `R_AARCH64_AUTH_RELATIVE` dynamic relocation since
pointers in signed GOT needs to be signed during dynamic link time.
