I think D79300 has fixed the D51892 (`__i686.get_pc_thunk.bx`) issue, so
we can bring back rL330869.
D79300 says `would error undefined symbol instead of the more relevant discarded section`
but it doesn't reproduce now.
This avoids a quirk in `isUndefWeak()`.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D111365
Currenlty PseudoProbeInserter is a pass conditioned on a target switch. It works well with a single clang invocation. It doesn't work so well when the backend is called separately (i.e, through the linker or llc), where user has always to pass -pseudo-probe-for-profiling explictly. I'm making the pass a default pass that requires no command line arg to trigger, but will be actually run depending on whether the CU comes with `llvm.pseudo_probe_desc` metadata.
Reviewed By: wenlei
Differential Revision: https://reviews.llvm.org/D110209
Similar to D69607 but for archive member extraction unrelated to GC. This patch adds --why-extract=.
Prior art:
GNU ld -M prints
```
Archive member included to satisfy reference by file (symbol)
a.a(a.o) main.o (a)
b.a(b.o) (b())
```
-M is mainly for input section/symbol assignment <-> output section mapping
(often huge output) and the information may appear ad-hoc.
Apple ld64
```
__Z1bv forced load of b.a(b.o)
_a forced load of a.a(a.o)
```
It doesn't say the reference file.
Arm's proprietary linker
```
Selecting member vsnprintf.o(c_wfu.l) to define vsnprintf.
...
Loading member vsnprintf.o from c_wfu.l.
definition: vsnprintf
reference : _printf_a
```
---
--why-extract= gives the user the full data (which is much shorter than GNU ld
-Map). It is easy to track a chain of references to one archive member with a
one-liner, e.g.
```
% ld.lld main.o a_b.a b_c.a c.a -o /dev/null --why-extract=- | tee stdout
reference extracted symbol
main.o a_b.a(a_b.o) a
a_b.a(a_b.o) b_c.a(b_c.o) b()
b_c.a(b_c.o) c.a(c.o) c()
% ruby -ane 'BEGIN{p={}}; p[$F[1]]=[$F[0],$F[2]] if $.>1; END{x="c.a(c.o)"; while y=p[x]; puts "#{y[0]} extracts #{x} to resolve #{y[1]}"; x=y[0] end}' stdout
b_c.a(b_c.o) extracts c.a(c.o) to resolve c()
a_b.a(a_b.o) extracts b_c.a(b_c.o) to resolve b()
main.o extracts a_b.a(a_b.o) to resolve a
```
Archive member extraction happens before --gc-sections, so this may not be a live path
under --gc-sections, but I think it is a good approximation in practice.
* Specifying a file avoids output interleaving with --verbose.
* Required `=` prevents accidental overwrite of an input if the user forgets `=`. (Most of compiler drivers' long options accept `=` but not ` `)
Differential Revision: https://reviews.llvm.org/D109572
When enable CSPGO for ThinLTO, there are profile cfg mismatch warnings that will cause lld-link errors (with /WX)
due to source changes (e.g. `#if` code runs for profile generation but not for profile use)
To disable it we have to use an internal "/mllvm:-no-pgo-warn-mismatch" option.
In contrast clang uses option ”-Wno-backend-plugin“ to avoid such warnings and gcc has an explicit "-Wno-coverage-mismatch" option.
Add "lto-pgo-warn-mismatch" option to lld COFF/ELF to help turn on/off the profile mismatch warnings explicitly when build with ThinLTO and CSPGO.
Differential Revision: https://reviews.llvm.org/D104431
When enable CSPGO for ThinLTO, there are profile cfg mismatch warnings that will cause lld-link errors (with /WX).
To disable it we have to use an internal "/mllvm:-no-pgo-warn-mismatch" option.
In contrast clang uses option ”-Wno-backend-plugin“ to avoid such warnings and gcc has an explicit "-Wno-coverage-mismatch" option.
Add this "lto-pgo-warn-mismatch" option to lld to help turn on/off the profile mismatch warnings explicitly when build with ThinLTO and CSPGO.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D104431
Currently version script patterns are ignored for .symver produced
non-default version (single @) symbols. This makes such symbols
not localizable by `local:`, e.g.
```
.symver foo3_v1,foo3@v1
.globl foo_v1
foo3_v1:
ld.lld --version-script=a.ver -shared a.o
```
This patch adds the support:
* Move `config->versionDefinitions[VER_NDX_LOCAL].patterns` to `config->versionDefinitions[versionId].localPatterns`
* Rename `config->versionDefinitions[versionId].patterns` to `config->versionDefinitions[versionId].nonLocalPatterns`
* Allow `findAllByVersion` to find non-default version symbols when `includeNonDefault` is true. (Note: `symtab` keys do not have `@@`)
* Make each pattern check both the unversioned `pat.name` and the versioned `${pat.name}@${v.name}`
* `localPatterns` can localize `${pat.name}@${v.name}`. `nonLocalPatterns` can prevent localization by assigning `verdefIndex` (before `parseSymbolVersion`).
---
If a user notices new `undefined symbol` errors with a version script containing
`local: *;`, the issue is likely due to a missing `global:` pattern.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D107234
Due to an assembler design flaw (IMO), `.symver foo,foo@v1` produces two symbols `foo` and `foo@v1` if `foo` is defined.
* `v1 {};` produces both `foo` and `foo@v1`, but GNU ld only produces `foo@v1`
* `v1 { foo; };` produces both `foo@@v1` and `foo@v1`, but GNU ld only produces `foo@v1`
* `v2 { foo; };` produces both `foo@@v2` and `foo@v1`, matching GNU ld. (Tested by symver.s)
This patch implements the GNU ld behavior by reusing the symbol redirection mechanism
in D92259. The new test symver-non-default.s checks the first two cases.
Without the patch, the second case will produce `foo@v1` and `foo@@v1` which
looks weird and makes foo unnecessarily default versioned.
Note: `.symver foo,foo@v1,remove` exists but the unfortunate `foo` will not go
away anytime soon.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D107235
Currently version script patterns are ignored for .symver produced
non-default version (single @) symbols. This makes such symbols
not localizable by `local:`, e.g.
```
.symver foo3_v1,foo3@v1
.globl foo_v1
foo3_v1:
ld.lld --version-script=a.ver -shared a.o
# In a.out, foo3@v1 is incorrectly exported.
```
This patch adds the support:
* Move `config->versionDefinitions[VER_NDX_LOCAL].patterns` to `config->versionDefinitions[versionId].localPatterns`
* Rename `config->versionDefinitions[versionId].patterns` to `config->versionDefinitions[versionId].nonLocalPatterns`
* Allow `findAllByVersion` to find non-default version symbols when `includeNonDefault` is true. (Note: `symtab` keys do not have `@@`)
* Make each pattern check both the unversioned `pat.name` and the versioned `${pat.name}@${v.name}`
* `localPatterns` can localize `${pat.name}@${v.name}`. `nonLocalPatterns` can prevent localization by assigning `verdefIndex` (before `parseSymbolVersion`).
---
If a user notices new `undefined symbol` errors with a version script containing
`local: *;`, the issue is likely due to a missing `global:` pattern.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D107234
This is available in GNU ld 2.35 and can be seen as a shortcut for multiple
--export-dynamic-symbol, or a --dynamic-list variant without the symbolic intention.
In the long term, this option probably should be preferred over --dynamic-list.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D107317
This option is a subset of -Bsymbolic-functions. It applies to STB_GLOBAL
STT_FUNC definitions.
The address of a vague linkage function (STB_WEAK STT_FUNC, e.g. an inline
function, a template instantiation) seen by a -Bsymbolic-functions linked
shared object may be different from the address seen from outside the shared
object. Such cases are uncommon. (ELF/Mach-O programs may use
`-fvisibility-inlines-hidden` to break such pointer equality. On Windows,
correct dllexport and dllimport are needed to make pointer equality work.
Windows link.exe enables /OPT:ICF by default so different inline functions may
have the same address.)
```
// a.cc -> a.o -> a.so (-Bsymbolic-functions)
inline void f() {}
void *g() { return (void *)&f; }
// b.cc -> b.o -> exe
// The address is different!
inline void f() {}
```
-Bsymbolic-non-weak-functions is a safer (C++ conforming) subset of
-Bsymbolic-functions, which can make such programs work.
Implementations usually emit a vague linkage definition in a COMDAT group. We
could detect the group (with more code) but I feel that we should just check
STB_WEAK for simplicity. A weak definition will thus serve as an escape hatch
for rare cases when users want interposition on definitions.
GNU ld feature request: https://sourceware.org/bugzilla/show_bug.cgi?id=27871
Longer write-up: https://maskray.me/blog/2021-05-16-elf-interposition-and-bsymbolic
If Linux distributions migrate to protected non-vague-linkage external linkage
functions by default, the linker option can still be handy because it allows
rapid experiment without recompilation. Protected function addresses currently
have deep issues in GNU ld.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D102570
This is a follow up to https://reviews.llvm.org/D104080, and ca3bdb57fa (diff-e64a48fabe31db213a631fdc5f2acb51bdddf3f16a8fb2928784f4c579229585). The implementation of call graph profile was changed from a black box section to relocation approach. This was done to be compatible with post processing tools like strip/objcopy, and llvm equivalent. When they are invoked on object file before the final linking step with this new approach the symbol indices correctness is preserved.
The GNU binutils tools change the REL section to RELA section, unlike llvm tools. For example when strip -S is run on the ELF object files, as an intermediate step before linking. To preserve compatibility this patch extends implementation in LLD and ELFDumper to support both REL and RELA sections for call graph profile.
Reviewed By: MaskRay, jhenderson
Differential Revision: https://reviews.llvm.org/D105217
There used to be many cases where addends for Elf_Rel were not emitted in
the final object file (mostly when building for MIPS64 since the input .o
files use RELA but the output uses REL). These cases have been fixed since,
but this patch adds a check to ensure that the written values are correct.
It is based on a previous patch that I added to the CHERI fork of LLD since
we were using MIPS64 as a baseline. The work has now almost entirely
shifted to RISC-V and Arm Morello (which use Elf_Rela), but I thought
it would be useful to upstream our local changes anyway.
This patch adds a (hidden) command line flag --check-dynamic-relocations
that can be used to enable these checks. It is also on by default in
assertions builds for targets that handle all dynamic relocations kinds
that LLD can emit in Target::getImplicitAddend(). Currently this is
enabled for ARM, MIPS, and I386.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D101450
... even on targets preferring RELA. The section is only consumed by ld.lld
which can handle REL.
Follow-up to D104080 as I explained in the review. There are two advantages:
* The D104080 code only handles RELA, so arm/i386/mips32 etc may warn for -fprofile-use=/-fprofile-sample-use= usage.
* Decrease object file size for RELA targets
While here, change the relocation to relocate weights, instead of 0,1,2,3,..
I failed to catch the issue during review.
Currently when .llvm.call-graph-profile is created by llvm it explicitly encodes the symbol indices. This section is basically a black box for post processing tools. For example, if we run strip -s on the object files the symbol table changes, but indices in that section do not. In non-visible behavior indices point to wrong symbols. The visible behavior indices point outside of Symbol table: "invalid symbol index".
This patch changes the format by using R_*_NONE relocations to indicate the from/to symbols. The Frequency (Weight) will still be in the .llvm.call-graph-profile, but symbol information will be in relocation section. In LLD information from both sections is used to reconstruct call graph profile. Relocations themselves will never be applied.
With this approach post processing tools that handle relocations correctly work for this section also. Tools can add/remove symbols and as long as they handle relocation sections with this approach information stays correct.
Doing a quick experiment with clang-13.
The size went up from 107KB to 322KB, aggregate of all the input sections. Size of clang-13 binary is ~118MB. For users of -fprofile-use/-fprofile-sample-use the size of object files will go up slightly, it will not impact final binary size.
Reviewed By: jhenderson, MaskRay
Differential Revision: https://reviews.llvm.org/D104080
This option will be available in GNU ld 2.27 (https://sourceware.org/bugzilla/show_bug.cgi?id=27834).
This option can cancel previously specified -Bsymbolic and
-Bsymbolic-functions. This is useful for excluding some links when the
default uses -Bsymbolic-functions.
Reviewed By: jhenderson, peter.smith
Differential Revision: https://reviews.llvm.org/D102383
Stop using the compatibility spellings of `OF_{None,Text,Append}`
left behind by 1f67a3cba9. A follow-up
will remove them.
Differential Revision: https://reviews.llvm.org/D101650
Fix PR49897: if `__real_foo` has the isUsedInRegularObj bit set, we need to
retain `foo` in .symtab, even if `foo` is undefined. The new behavior will match
GNU ld.
Before the patch, we produced an R_X86_64_JUMP_SLOT relocation referencing the
index 0 undefined symbol, which would be erroed by glibc
(see f96ff3c0f8).
While here, fix another bug: if `__wrap_foo` does not exist, its initial binding
should be `foo`'s.
Change the default to facilitate GC for metadata section usage, so that they
don't need SHF_LINK_ORDER or SHF_GROUP just to drop the unhelpful rule (if they
want to be unconditionally retained, use SHF_GNU_RETAIN
(`__attribute__((retain))`) or linker script `KEEP`).
The dropped SHF_GROUP special case makes the behavior of -z start-stop-gc and -z
nostart-stop-gc closer to GNU ld>=2.37 (https://sourceware.org/PR27451).
However, we default to -z start-stop-gc (which actually matches more closely to
GNU ld before 2015-10 https://sourceware.org/PR19167), which is different from
modern GNU ld (which has the unhelpful rule to work around glibc). As a
compensation, we special case `__libc_` sections as a workaround for glibc<2.34
(https://sourceware.org/PR27492).
Since -z start-stop-gc as the default actually matches the traditional GNU ld
behavior, there isn't much to be aware of. There was a systemd usage which has
been fixed by https://github.com/systemd/systemd/pull/19144
`--shuffle-sections=<seed>` applies to all sections. The new
`--shuffle-sections=<section-glob>=<seed>` makes shuffling selective. To the
best of my knowledge, the option is only used as debugging, so just drop the
original form.
`--shuffle-sections '.init_array*=-1'` `--shuffle-sections '.fini_array*=-1'`.
reverses static constructors/destructors of the same priority.
Useful to detect some static initialization order fiasco.
`--shuffle-sections '.data*=-1'`
reverses `.data*` sections. Useful to detect unfunded pointer comparison results
of two unrelated objects.
If certain sections have an intrinsic order, the old form cannot be used.
Differential Revision: https://reviews.llvm.org/D98679
Implemented the option to omit Power10 instructions from save stubs via the
option --no-power10-stubs or --power10-stubs=no on lld. --power10-stubs= will
override the other option. --power10-stubs=auto also exists to use the default
behaviour (ie allow Power10 instructions in stubs).
Differential Revision: https://reviews.llvm.org/D94627
For one metadata section usage, each text section references a metadata section.
The metadata sections have a C identifier name to allow the runtime to collect them via `__start_/__stop_` symbols.
Since `__start_`/`__stop_` references are always present from live sections, the
C identifier name sections appear like GC roots, which means they cannot be
discarded by `ld --gc-sections`.
To make such sections GCable, either SHF_LINK_ORDER or a section group is needed.
SHF_LINK_ORDER is not suitable for the references can be inlined into other functions
(See D97430:
Function A (in the section .text.A) references its `__sancov_guard` section.
Function B inlines A (so now .text.B references `__sancov_guard` - this is invalid with the semantics of SHF_LINK_ORDER).
In the linking stage,
if `.text.A` gets discarded, and `__sancov_guard` is retained via the reference from `.text.B`,
the output will be invalid because `__sancov_guard` references the discarded `.text.A`.
LLD errors "sh_link points to discarded section".
)
A section group have size overhead, and is cumbersome when there is just one metadata section.
Add `-z start-stop-gc` to drop the "__start_/__stop_ references retain
non-SHF_LINK_ORDER non-SHF_GROUP C identifier name sections" rule.
We reserve the rights to switch the default in the future.
Reviewed By: phosek, jrtc27
Differential Revision: https://reviews.llvm.org/D96914
`extern const bfd_target aarch64_elf64_le_vec;` is a variable in BFD.
It was somehow misused as an emulation by Android.
```
% aarch64-linux-gnu-ld -m aarch64_elf64_le_vec a.o
aarch64-linux-gnu-ld: unrecognised emulation mode: aarch64_elf64_le_vec
Supported emulations: aarch64linux aarch64elf aarch64elf32 aarch64elf32b aarch64elfb armelf armelfb aarch64linuxb aarch64linux32 aarch64linux32b armelfb_linux_eabi armelf_linux_eabi
```
Acked by Stephen Hines, who removed the flag from Android a while back.
The option catches incompatibility between `R_*_IRELATIVE` and DT_TEXTREL/DF_TEXTREL
before glibc 2.29. Newer glibc versions are more common nowadays and I don't
think this option has ever been used. Diagnosing this problem is also
straightforward by reading the stack trace.
If foo is referenced in any object file, bitcode file or shared object,
`__wrap_foo` should be retained as the redirection target of sym
(f96ff3c0f8).
If the object file defining foo has foo references, we cannot easily distinguish
the case from cases where foo is not referenced (we haven't scanned
relocations). Retain `__wrap_foo` because we choose to wrap sym references
regardless of whether sym is defined to keep non-LTO/LTO/relocatable links' behaviors similar
https://sourceware.org/bugzilla/show_bug.cgi?id=26358 .
If foo is defined in a shared object, `__wrap_foo` can still be omitted
(`wrap-dynamic-undef.s`).
Reviewed By: andrewng
Differential Revision: https://reviews.llvm.org/D95152
```
// a.s
jmp fcntl
// b.s
.globl fcntl
fcntl:
ret
```
`ld.lld -shared --wrap=fcntl a.o b.o` has an `R_X86_64_JUMP_SLOT` referencing
the index 0 undefined symbol, which will cause a glibc `symbol lookup error` at
runtime. This is because `__wrap_fcntl` is not in .dynsym
We use an approximation `!wrap->isUndefined()`, which doesn't set
`isUsedInRegularObj` of `__wrap_fcntl` when `fcntl` is referenced and
`__wrap_fcntl` is undefined.
Fix this by using `sym->referenced`.
Fixes PR48681: after LTO, lto.tmp may reference a libcall symbol not in an IR
symbol table of any bitcode file. If such a symbol is defined in an archive
matched by a --exclude-libs, we don't correctly localize the symbol.
Add another `excludeLibs` after `compileBitcodeFiles` to localize such libcall
symbols. Unfortunately we have keep the existing one for D43126.
Using VER_NDX_LOCAL is an implementation detail of `--exclude-libs`, it does not
necessarily tie to the "localize" behavior. `local:` patterns in a version
script can be omitted.
The `symbol ... has undefined version ...` error should not be exempted.
Ideally we should error as GNU ld does. https://issuetracker.google.com/issues/73020933
Reviewed By: psmith
Differential Revision: https://reviews.llvm.org/D94280
Add support for linking powerpcle code in LLD.
Rewrite lld/test/ELF/emulation-ppc.s to use a shared check block and add powerpcle tests.
Update tests.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D93917
Libraries linked to the lld elf library exposes a function named main.
When debugging code linked to such libraries and intending to set a
breakpoint at main, the debugger also sets breakpoint at the main
function at lld elf driver. The possible choice was to rename it to
link but that would again clash with lld::*::link. This patch tries
to consistently rename them to linkerMain.
Differential Revision: https://reviews.llvm.org/D91418
Follow the naming set by TI's own GCC-based toolchain.
Also, force the `osabi` field to `ELFOSABI_STANDALONE`, this matches GNU LD's output (the patching is done in `elf32_msp430_post_process_headers`).
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D92931
Normally we should not delete options. However, the Clang driver passes
`-plugin-opt={new,legacy}-pass-manager` instead of
`--[no-]lto-legacy-pass-manager` (`-plugin-opt=new-pass-manager` has been used
since 7.0), and it is unlikely anyone will use the `--lto-*` style options directly.
So let's rename them to be consistent with the Clang driver option names.
Reviewed By: aeubanks
Differential Revision: https://reviews.llvm.org/D92988
This patch changes the archive handling to enable the semantics needed
for legacy FORTRAN common blocks and block data. When we have a COMMON
definition of a symbol and are including an archive, LLD will now
search the members for global/weak defintions to override the COMMON
symbol. The previous LLD behavior (where a member would only be included
if it satisifed some other needed symbol definition) can be re-enabled with the
option '-no-fortran-common'.
Differential Revision: https://reviews.llvm.org/D86142
The symbol resolution rules for versioned symbols are:
* foo@@v1 (default version) resolves both undefined foo and foo@v1
* foo@v1 (non-default version) resolves undefined foo@v1
Note, foo@@v1 must be defined (the assembler errors if attempting to
create an undefined foo@@v1).
For defined foo@@v1 in a shared object, we call `SymbolTable::addSymbol` twice,
one for foo and the other for foo@v1. We don't do the same for object files, so
foo@@v1 defined in one object file incorrectly does not resolve a foo@v1
reference in another object file.
This patch fixes the issue by reusing the --wrap code to redirect symbols in
object files. This has to be done after processing input files because
foo and foo@v1 are two separate symbols if we haven't seen foo@@v1.
Add a helper `Symbol::getVersionSuffix` to retrieve the optional trailing
`@...` or `@@...` from the possibly truncated symbol name.
Depends on D92258
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D92259
