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We have an issue with -wrap that the option doesn't work well when
renamed symbols get PLT entries. I'll explain what is the issue and
how this patch solves it.
For one -wrap option, we have three symbols: foo, wrap_foo and real_foo.
Currently, we use memcpy to overwrite wrapped symbols so that they get
the same contents. This works in most cases but doesn't when the relocation
processor sets some flags in the symbol. memcpy'ed symbols are just
aliases, so they always have to have the same contents, but the
relocation processor breaks that assumption.
r336609 is an attempt to fix the issue by memcpy'ing again after
processing relocations, so that symbols that are out of sync get the
same contents again. That works in most cases as well, but it breaks
ASan build in a mysterious way.
We could probably fix the issue by choosing symbol attributes that need
to be copied after they are updated. But it feels too complicated to me.
So, in this patch, I fixed it once and for all. With this patch, we no
longer memcpy symbols. All references to renamed symbols point to new
symbols after wrapSymbols() is done.
Differential Revision: https://reviews.llvm.org/D50569
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This reverts commit r336609 as it doesn't seem to work with AArch64
thunk creation when used with ASan.
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Patch by Matthew Koontz!
Before, direct calls to __wrap_sym would not map to valid PLT entries,
so they would crash at runtime. This change maps such calls to the same
PLT entry as calls to sym that are then wrapped.
Differential Revision: https://reviews.llvm.org/D48502
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Previously, fetchIfLazy did more than the name says. Now, setting
to UsedInRegularObj is moved to another function.
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Patch removes Lazy class which
is just an excessive layer.
Differential revision: https://reviews.llvm.org/D45083
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This should resolve the issue that lld build fails in some hosts
that uses case-insensitive file system.
Differential Revision: https://reviews.llvm.org/D43788
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With the recent fixes these symbols have more in common than not with
regular undefined symbols.
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There seems to be no reason to collect this list of symbols.
Also fix a bug where --exclude-libs would apply to all symbols that
appear in an archive's symbol table, even if the relevant archive
member was not added to the link.
Differential Revision: https://reviews.llvm.org/D43369
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We normally avoid "switch (Config->EKind)", but in this case I think
it is worth it.
It is only executed when there is an error and it allows detemplating
a lot of code.
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Every shared symbol has a file, so we can use a reference.
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By using an index instead of a pointer for verdef we can put the index
next to the alignment field. This uses the otherwise wasted area and
reduces the shared symbol size.
By itself the performance change of this is in the noise, but I have a
followup patch to remove another 8 bytes that improves performance
when combined with this.
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They were not used in InputFiles.h and it was getting too easy to add
circular includes.
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This is also consistent with SymVector that exists in COFF port
and soon to be added to the wasm port.
Split off as part of https://reviews.llvm.org/D40371
Differential Revision: https://reviews.llvm.org/D40525
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Since we always have Binding in the current symbol design IsLocal is
redundant.
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copyFrom doesn't copy the Binding, so this was a nop.
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The Traced flag is unnecessary because we only need to set the index
to -1 to mark a symbol for tracing.
Differential Revision: https://reviews.llvm.org/D39672
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Now that DefinedRegular is the only remaining derived class of
Defined, we can merge the two classes.
Differential Revision: https://reviews.llvm.org/D39667
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r317396 changed the way how we handle the -defsym option. The option is
now handled using the infrastructure for the linker script.
We used to handle both -defsym and -wrap using the same set of functions
in the symbol table. Now, we don't need to do that.
This patch rewrites the functions so that they become more straightforward.
The new functions directly handle -wrap rather than abstract it.
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Now that we have only SymbolBody as the symbol class. So, "SymbolBody"
is a bit strange name now. This is a mechanical change generated by
perl -i -pe s/SymbolBody/Symbol/g $(git grep -l SymbolBody lld/ELF lld/COFF)
nd clang-format-diff.
Differential Revision: https://reviews.llvm.org/D39459
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SymbolBody and Symbol were separated classes due to a historical reason.
Symbol used to be a pointer to a SymbolBody, and the relationship
between Symbol and SymbolBody was n:1.
r2681780 changed that. Since that patch, SymbolBody and Symbol are
allocated next to each other to improve memory locality, and they have
1:1 relationship now. So, the separation of Symbol and SymbolBody no
longer makes sense.
This patch merges them into one class. In order to avoid updating too
many places, I chose SymbolBody as a unified name. I'll rename it Symbol
in a follow-up patch.
Differential Revision: https://reviews.llvm.org/D39406
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This change allows us to use less templates for Shared symbol and
the functions that deals with shared symbols.
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It causes MSVC 2015 to emit "C4307: '-': integral constant overflow" warning
Differential Revision: https://reviews.llvm.org/D38955
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Before this patch we would copy foo into real_foo and wrap_foo into
foo. The net result is that __wrap_foo shows up twice in the symbol
table.
With this patch we:
* save a copy of __real_foo before copying foo.
* drop one of the __wrap_foo from the symbol table.
* if __real_foo was not undefined, add a *new* symbol with that content to
the symbol table.
The net result is that
Anything using foo now uses __wrap_foo
Anything using __real_foo now uses foo.
Anything using __wrap_foo still does.
And the symbol table has foo, __wrap_foo and __real_foo (if defined).
Which I think is the desired behavior.
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Without this patch, lld emits "error: undefined symbol: _start"
if it encountered only weak references to that symbol.
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In order to keep track of symbol renaming, we used to have
Config->SymbolRenaming, and whether a symbol is in the map or not
affects its symbol attribute (i.e. "LinkeRedefined" bit).
This patch adds "CanInline" bit to Symbol to aggreagate symbol
information in one place and removed the member from Config since
no one except SymbolTable now uses the table.
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This allows combining --dynamic-list and version scripts too. The
version script controls which symbols are visible, and
--dynamic-list controls which of those are preemptible.
Unlike previous versions, undefined symbols are still considered
preemptible, which was the issue breaking the cfi tests.
This fixes pr34053.
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symbols are preemptible""
This reverts commit r312757.
Evgenii Stepanov reports that it broke some tests.
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preemptible"
If --dynamic-list is given, only those symbols are preemptible.
This allows combining --dynamic-list and version scripts too. The
version script controls which symbols are visible, and --dynamic-list
controls which of those are preemptible.
This fixes pr34053.
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This reverts commit r311468 because it broke some CFI bots.
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Patch by Rafael Espíndola.
This is PR34053.
The implementation is a bit of a hack, given the precise location where
IsPreemtible is set, it cannot be used from
SymbolTable::handleAnonymousVersion.
I could add another method to SymbolTable if you think that would be
better.
Differential Revision: https://reviews.llvm.org/D36499
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This function doesn't seem to add value to the symbol table as
it is easy to write code without it.
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Rename it because it was too easy to conflict with llvm::object::ObjectFile
which broke buildbots several times.
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NFC, just makes it easier to access from non templated code.
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Differential Revision: https://reviews.llvm.org/D34852
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The --exclude-libs option is not a popular option, but at least some
programs in Android depend on it, so it's worth to support it.
Differential Revision: https://reviews.llvm.org/D34422
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procedural optimizations to prevent dropping symbols and allow the linker
to process re-directs.
PR33145: --wrap doesn't work with lto.
Differential Revision: https://reviews.llvm.org/D33621
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CachedHashStringRef."
This reverts commit r303787.
It caused a slowdown in fast links. That is, links with no debug info
or optimizations.
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A variable `ComdatGroup` is not supposed to contain a large number of
items. Even when linking clang, it ends up having only 300K strings.
It doesn't make sense to use CachedHashStringRef for this hash table.
This patch has neutral or slightly positive impact on performance while
reducing code complexity.
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gnu ld description of option is:
--defsym=symbol=expression
Create a global symbol in the output file, containing the absolute address given
by expression. You may use this option as many times as necessary to define multiple
symbols in the command line. A limited form of arithmetic is supported for the
expression in this context: you may give a hexadecimal constant or the name of an
existing symbol, or use "+" and "-" to add or subtract hexadecimal constants or
symbols. If you need more elaborate expressions, consider using the linker command
language from a script. Note: there should be no white space between symbol,
the equals sign ("="), and expression.
In compare with D32082, this patch does not support math expressions and absolute
symbols. It implemented via code similar to --wrap. That covers 1 of 3 possible
--defsym cases.
Differential revision: https://reviews.llvm.org/D32171
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With this we have a single section hierarchy. It is a bit less code,
but the main advantage will be in a future patch being able to handle
foo = symbol_in_obj;
in a linker script. Currently that fails since we try to find the
output section of symbol_in_obj. With this we should be able to just
return an InputSection from the expression.
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