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Enumeration of relocation types is not always sequential, e.g. on
AArch64 the first real relocation type is 0x101. As such, the existing
code in `Relocation::print()` was crashing while printing AArch64
relocations. Fix it by using `llvm::object::getELFRelocationTypeName()`.
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R_AARCH64_TLSDESC_CALL is a relocation emitted as a hint for a linker to
replace `blr r` instruction with nop. BOLT does not currently require
any special handling for it.
Note that previously existing extraction of the relocated value was
incorrect.
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This change is necessary to build BOLT with MSVC on Windows.
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This patch adds code generation for RISCV64 instrumentation.The work
involved includes the following three points:
a) Implements support for instrumenting direct function call and jump
on RISC-V which relies on , Atomic instructions
(used to increment counters) are only available on RISC-V when the A
extension is used.
b) Implements support for instrumenting direct function inderect call
by implementing the createInstrumentedIndCallHandlerEntryBB and
createInstrumentedIndCallHandlerExitBB interfaces. In this process, we
need to accurately record the target address and IndCallID to ensure
the correct recording of the indirect call counters.
c)Implemented the RISCV64 Bolt runtime library, implemented some system
call interfaces through embedded assembly. Get the difference between
runtime addrress of .text section andstatic address in section header
table, which in turn can be used to search for indirect call
description.
However, the community code currently has problems with relocation in
some scenarios, but this has nothing to do with instrumentation. We
may continue to submit patches to fix the related bugs.
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To handle relative vftable, which is enabled with clang option
`-fexperimental-relative-c++-abi-vtables`, we look for PC relative
relocations whose fixup locations fall in vtable address ranges.
For such relocations, actual target is just virtual function itself,
and the addend is to record the distance between vtable slot for
target virtual function and the first virtual function slot in vtable,
which is to match generated code that calls virtual function. So
we can skip the logic of handling "function + offset" and directly
save such relocations for future fixup after new layout is known.
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When a pending relocation is created it is also marked whether it is
optional or not. It can be optional when such relocation is added as
part of an optimization (i.e., `scanExternalRefs`).
When bolt tries to `flushPendingRelocations`, it safely skips any
optional relocations that cannot be encoded due to being out of
range. A pre-requisite to that is the usage of the `-force-patch`
flag. Alternatrively, BOLT will bail out with a relevant message.
Background:
BOLT, as part of scanExternalRefs, identifies external references from
calls and creates some pending relocations for them. Those when
flushed will update references to point to the optimized functions.
This optimization can be disabled using `--no-scan`.
BOLT can assert if any of these pending relocations cannot be encoded.
This patch does not disable this optimization but instead selectively
applies it given that a pending relocation is optional and `-force-patch`
was enabled.
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Instead of filtering and modifying relocations in readRelocations(),
preserve the relocation info and use it in the symbolizing disassembler.
This change mostly affects AArch64, where we need to look at original
linker relocations in order to properly symbolize instruction operands.
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We used to filter out relocations corresponding to NOP+ADR instruction
pairs that were a result of linker "relaxation" optimization. However,
these relocations will be useful for reversing the linker optimization.
Keep the relocations and ignore them while symbolizing ADR instruction
operands.
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Co-authored-by: yavtuk <yavtuk@ya.ru>
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Some refactoring.
* Make the arrays themselves const -- not just the strings being pointed to.
* Move each relocation array to the case using it.
* Add a suitable assert, to make sure there's no out-of-bounds indexing.
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Convert the relocation routines to switch on architecture and have an explicit unreachable default.
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Add R_AARCH64_JUMP26 implementation for createRelocation, which
could significantly reduce the number of failed scan-refs cases if we
perform bolt on a selective range of functions.
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Closes https://github.com/llvm/llvm-project/issues/63097
Before merging please make sure the change to
bolt/include/bolt/Passes/StokeInfo.h is correct.
bolt/include/bolt/Passes/StokeInfo.h
```diff
// This Pass solves the two major problems to use the Stoke program without
- // proting its code:
+ // probing its code:
```
I'm still not happy about the awkward wording in this comment.
bolt/include/bolt/Passes/FixRelaxationPass.h
```
$ ed -s bolt/include/bolt/Passes/FixRelaxationPass.h <<<'9,12p'
// This file declares the FixRelaxations class, which locates instructions with
// wrong targets and fixes them. Such problems usually occures when linker
// relaxes (changes) instructions, but doesn't fix relocations types properly
// for them.
$
```
bolt/docs/doxygen.cfg.in
bolt/include/bolt/Core/BinaryContext.h
bolt/include/bolt/Core/BinaryFunction.h
bolt/include/bolt/Core/BinarySection.h
bolt/include/bolt/Core/DebugData.h
bolt/include/bolt/Core/DynoStats.h
bolt/include/bolt/Core/Exceptions.h
bolt/include/bolt/Core/MCPlusBuilder.h
bolt/include/bolt/Core/Relocation.h
bolt/include/bolt/Passes/FixRelaxationPass.h
bolt/include/bolt/Passes/InstrumentationSummary.h
bolt/include/bolt/Passes/ReorderAlgorithm.h
bolt/include/bolt/Passes/StackReachingUses.h
bolt/include/bolt/Passes/StokeInfo.h
bolt/include/bolt/Passes/TailDuplication.h
bolt/include/bolt/Profile/DataAggregator.h
bolt/include/bolt/Profile/DataReader.h
bolt/lib/Core/BinaryContext.cpp
bolt/lib/Core/BinarySection.cpp
bolt/lib/Core/DebugData.cpp
bolt/lib/Core/DynoStats.cpp
bolt/lib/Core/Relocation.cpp
bolt/lib/Passes/Instrumentation.cpp
bolt/lib/Passes/JTFootprintReduction.cpp
bolt/lib/Passes/ReorderData.cpp
bolt/lib/Passes/RetpolineInsertion.cpp
bolt/lib/Passes/ShrinkWrapping.cpp
bolt/lib/Passes/TailDuplication.cpp
bolt/lib/Rewrite/BoltDiff.cpp
bolt/lib/Rewrite/DWARFRewriter.cpp
bolt/lib/Rewrite/RewriteInstance.cpp
bolt/lib/Utils/CommandLineOpts.cpp
bolt/runtime/instr.cpp
bolt/test/AArch64/got-ld64-relaxation.test
bolt/test/AArch64/unmarked-data.test
bolt/test/X86/Inputs/dwarf5-cu-no-debug-addr-helper.s
bolt/test/X86/Inputs/linenumber.cpp
bolt/test/X86/double-jump.test
bolt/test/X86/dwarf5-call-pc-function-null-check.test
bolt/test/X86/dwarf5-split-dwarf4-monolithic.test
bolt/test/X86/dynrelocs.s
bolt/test/X86/fallthrough-to-noop.test
bolt/test/X86/tail-duplication-cache.s
bolt/test/runtime/X86/instrumentation-ind-calls.s
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BOLT currently hooks its its instrumentation finalization function via
`DT_FINI`. However, this method of calling finalization routines is not
supported anymore on newer ABIs like RISC-V. `DT_FINI_ARRAY` is
preferred there.
This patch adds support for hooking into `DT_FINI_ARRAY` instead if the
binary does not have a `DT_FINI` entry. If it does, `DT_FINI` takes
precedence so this patch should not change how the currently supported
instrumentation targets behave.
`DT_FINI_ARRAY` points to an array in memory of `DT_FINI_ARRAYSZ` bytes.
It consists of pointer-length entries that contain the addresses of
finalization functions. However, the addresses are only filled-in by the
dynamic linker at load time using relative relocations. This makes
hooking via `DT_FINI_ARRAY` a bit more complicated than via `DT_FINI`.
The implementation works as follows:
- While scanning the binary: find the section where `DT_FINI_ARRAY`
points to, read its first dynamic relocation and use its addend to find
the address of the fini function we will use to hook;
- While writing the output file: overwrite the addend of the dynamic
relocation with the address of the runtime library's fini function.
Updating the dynamic relocation required a bit of boiler plate: since
dynamic relocations are stored in a `std::multiset` which doesn't
support getting mutable references to its items, functions were added to
`BinarySection` to take an existing relocation and insert a new one.
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On RISC-V, there are certain relocations that target a specific
instruction instead of a more abstract location like a function or basic
block. Take the following example that loads a value from symbol `foo`:
```
nop
1: auipc t0, %pcrel_hi(foo)
ld t0, %pcrel_lo(1b)(t0)
```
This results in two relocation:
- auipc: `R_RISCV_PCREL_HI20` referencing `foo`;
- ld: `R_RISCV_PCREL_LO12_I` referencing to local label `1` which points
to the auipc instruction.
It is of utmost importance that the `R_RISCV_PCREL_LO12_I` keeps
referring to the auipc instruction; if not, the program will fail to
assemble. However, BOLT currently does not guarantee this.
BOLT currently assumes that all local symbols are jump targets and
always starts a new basic block at symbol locations. The example above
results in a CFG the looks like this:
```
.BB0:
nop
.BB1:
auipc t0, %pcrel_hi(foo)
ld t0, %pcrel_lo(.BB1)(t0)
```
While this currently works (i.e., the `R_RISCV_PCREL_LO12_I` relocation
points to the correct instruction), it has two downsides:
- Too many basic blocks are created (the example above is logically only
one yet two are created);
- If instructions are inserted in `.BB1` (e.g., by instrumentation),
things will break since the label will not point to the auipc anymore.
This patch proposes to fix this issue by teaching BOLT to track labels
that should always point to a specific instruction. This is implemented
as follows:
- Add a new annotation type (`kLabel`) that allows us to annotate
instructions with an `MCSymbol *`;
- Whenever we encounter a relocation type that is used to refer to a
specific instruction (`Relocation::isInstructionReference`), we
register it without a symbol;
- During disassembly, whenever we encounter an instruction with such a
relocation, create a symbol for its target and store it in an offset
to symbol map (to ensure multiple relocations referencing the same
instruction use the same label);
- After disassembly, iterate this map to attach labels to instructions
via the new annotation type;
- During emission, emit these labels right before the instruction.
I believe the use of annotations works quite well for this use case as
it allows us to reliably track instruction labels. If we were to store
them as offsets in basic blocks, it would be error prone to keep them
updated whenever instructions are inserted or removed.
I have chosen to add labels as first-class annotations (as opposed to a
generic one) because the documentation of `MCAnnotation` suggests that
generic annotations are to be used for optional metadata that can be
discarded without affecting correctness. As this is not the case for
labels, a first-class annotation seemed more appropriate.
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Handle the following relocations related to TLS local-exec and
initial-exec:
- R_RISCV_TLS_GOT_HI20
- R_RISCV_TPREL_HI20
- R_RISCV_TPREL_ADD
- R_RISCV_TPREL_LO12_I
- R_RISCV_TPREL_LO12_S
In addition, GNU ld has a quirk where after TLS le relaxation, two
unofficial relocation types may be emitted:
- R_RISCV_TPREL_I
- R_RISCV_TPREL_S
Since they are unofficial (defined in the reserved range of relocation
types), LLVM does not define them. Hence, I've defined them locally in
BOLT in a private namespace.
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In large code model, the address of GOT is calculated by the
static linker via R_X86_GOTPC64 reloc applied against a MOVABSQ
instruction. In the final binary, it can be disassembled as a regular
immediate, but because such immediate is the result of PC-relative
pointer arithmetic, we need to parse this relocation and update this
calculation whenever we move code, otherwise we break the code trying
to read GOT.
A test case showing how GOT is accessed was provided.
Reviewed By: #bolt, maksfb
Differential Revision: https://reviews.llvm.org/D158911
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Relocation for 64-bit absolute values.
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Implement the following relocations used by the medlow code model and
non-PIE binaries:
- R_RISCV_HI20
- R_RISCV_LO12_I
- R_RISCV_LO12_S
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If the R_AARCH64_CALL26 against a symbol that has a lower address, then
encodeValueAArch64 will return a wrong value.
Reviewed By: Kepontry, yota9
Differential Revision: https://reviews.llvm.org/D159513
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Relocation used for store instructions.
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The implementation is based on the X86 version, with the same code
of symbol and addend extraction. The differences include the
support for RelType `R_AARCH64_CALL26` and the deletion of 8-bit
relocation.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D156018
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Thispatch implements the R_RISCV_ADD32 and R_RISCV_SUB32 relocations for
RISC-V.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D146554
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BOLT currently assumes (and asserts) that no two relocations can share
the same offset. Although this is true in most cases, ELF has a feature
called (not sure if this is an official term) composed relocations [1]
where multiple relocations at the same offset are combined to produce a
single value.
For example, to support label subtraction (a - b) on RISC-V, two
relocations are emitted at the same offset:
- R_RISCV_ADD32 a + 0
- R_RISCV_SUB32 b + 0
which, when combined, will produce the value of (a - b).
To support this in BOLT, first, RelocationSetType in BinarySection is
changed to be a multiset in order to allow it to store multiple
relocations at the same offset.
Next, Relocation::emit() is changed to receive an iterator pair of
relocations. In most cases, these will point to a single relocation in
which case its behavior is unaltered by this patch. For composed
relocations, they should point to all relocations at the same offset and
the following happens:
- A new method Relocation::createExpr() is called for every relocation.
This method is essentially the same as the original emit() except that
it returns the MCExpr without emitting it.
- The MCExprs of relocations i and i+1 are combined using the opcode
returned by the new method Relocation::getComposeOpcodeFor().
- After combining all MCExprs, the last one is emitted.
Note that in the current patch, getComposeOpcodeFor() simply calls
llvm_unreachable() since none of the current targets use composed
relocations. This will change once the RISC-V target lands.
Finally, BinarySection::emitAsData() is updated to group relocations by
offset and emit them all at once.
Note that this means composed relocations are only supported in data
sections. Since this is the only place they seem to be used in RISC-V, I
believe it's reasonable to only support them there for now to avoid
further code complexity.
[1]: https://www.sco.com/developers/gabi/latest/ch4.reloc.html
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D146546
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Just enough features are implemented to process a simple "hello world"
executable and produce something that still runs (including libc calls).
This was mainly a matter of implementing support for various
relocations. Currently, the following are handled:
- R_RISCV_JAL
- R_RISCV_CALL
- R_RISCV_CALL_PLT
- R_RISCV_BRANCH
- R_RISCV_RVC_BRANCH
- R_RISCV_RVC_JUMP
- R_RISCV_GOT_HI20
- R_RISCV_PCREL_HI20
- R_RISCV_PCREL_LO12_I
- R_RISCV_RELAX
- R_RISCV_NONE
Executables linked with linker relaxation will probably fail to be
processed. BOLT relocates .text to a high address while leaving .plt at
its original (low) address. This causes PC-relative PLT calls that were
relaxed to a JAL to not fit their offset in an I-immediate anymore. This
is something that will be addressed in a later patch.
Changes to the BOLT core are relatively minor. Two things were tricky to
implement and needed slightly larger changes. I'll explain those below.
The R_RISCV_CALL(_PLT) relocation is put on the first instruction of a
AUIPC/JALR pair, the second does not get any relocation (unlike other
PCREL pairs). This causes issues with the combinations of the way BOLT
processes binaries and the RISC-V MC-layer handles relocations:
- BOLT reassembles instructions one by one and since the JALR doesn't
have a relocation, it simply gets copied without modification;
- Even though the MC-layer handles R_RISCV_CALL properly (adjusts both
the AUIPC and the JALR), it assumes the immediates of both
instructions are 0 (to be able to or-in a new value). This will most
likely not be the case for the JALR that got copied over.
To handle this difficulty without resorting to RISC-V-specific hacks in
the BOLT core, a new binary pass was added that searches for
AUIPC/JALR pairs and zeroes-out the immediate of the JALR.
A second difficulty was supporting ABS symbols. As far as I can tell,
ABS symbols were not handled at all, causing __global_pointer$ to break.
RewriteInstance::analyzeRelocation was updated to handle these
generically.
Tests are provided for all supported relocations. Note that in order to
test the correct handling of PLT entries, an ELF file produced by GCC
had to be used. While I tried to strip the YAML representation, it's
still quite large. Any suggestions on how to improve this would be
appreciated.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D145687
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https://github.com/facebookincubator/BOLT/pull/255 accidentally
omitted a relocation type when refactoring the code. Add this type back
and change function name so its intent is more clear.
Reviewed By: #bolt, Amir
Differential Revision: https://reviews.llvm.org/D150335
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Vladislav Khmelevsky,
Advanced Software Technology Lab, Huawei
Differential Revision: https://reviews.llvm.org/D146085
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Use proper relocation for aarch64
Differential Revision: https://reviews.llvm.org/D144095
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Follow LLVM Coding Standards guideline on using anonymous namespaces
(https://llvm.org/docs/CodingStandards.html#anonymous-namespaces)
and use `static` modifier for function definitions.
Reviewed By: #bolt, maksfb
Differential Revision: https://reviews.llvm.org/D143124
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Linker might relax adrp + ldr got address loading to adrp + add for
local non-preemptible symbols (e.g. hidden/protected symbols in
executable). As usually linker doesn't change relocations properly after
relaxation, so we have to handle such cases by ourselves. To do that
during relocations reading we change LD64 reloc to ADD if instruction
mismatch found and introduce FixRelaxationPass that searches for ADRP+ADD
pairs and after performing some checks we're replacing ADRP target symbol
to already fixed ADDs one.
Vladislav Khmelevsky,
Advanced Software Technology Lab, Huawei
Differential Revision: https://reviews.llvm.org/D138097
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section relocations""
This reverts commit 76029cc53e838e6d86b13b0c39152f474fb09263.
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relocations"
Summary:
This reverts commit 729d29e167a553ee1190c310b6a510db8d8731ac.
Needed as a workaround for T112872562.
Manual rebase conflict history:
https://phabricator.intern.facebook.com/D35230076
https://phabricator.intern.facebook.com/D35681740
Test Plan: sandcastle
Reviewers: #llvm-bolt
Subscribers: spupyrev
Differential Revision: https://phabricator.intern.facebook.com/D37098481
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Supress failed to analyze relocations warning for R_AARCH64_LD_PREL_LO19
relocation. This relocation is mostly used to get value stored in CI and
we don't process it since we are caluclating target address using the
instruction value in evaluateMemOperandTarget().
Differential Revision: https://reviews.llvm.org/D127413
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The linker can convert instructions with GOTPCRELX relocations into a
form that uses an absolute addressing with an immediate. BOLT needs to
recognize such conversions and symbolize the immediates.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D126747
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Reviewed By: yota9, rafauler
Differential Revision: https://reviews.llvm.org/D122294
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The ld might relax ADRP+ADD or ADRP+LDR sequences to the ADR+NOP, add
the new case to the skipRelocation for aarch64.
Vladislav Khmelevsky,
Advanced Software Technology Lab, Huawei
Differential Revision: https://reviews.llvm.org/D123334
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PC-relative memory operand could reference a different object from
the one located at the target address, e.g. when a negative offset
is used. Check relocations for the real referenced object.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D120379
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This patch changes patchELFAllocatableRelaSections from going through
old relocations sections and update the relocation offsets to emitting
the relocations stored in binary sections. This is needed in case we
would like to remove and add dynamic relocations during BOLT work and it
is used by golang support pass. Note: Currently we emit relocations in
the old sections, so the total number of them should be equal or less
of old number.
Testing: No special tests are neeeded, since this patch does not fix
anything or add new functionality (it only prepares to add). Every
PIC-compiled test binary will use this code and thus become a test.
But just in case the aarch64 dynamic relocations tests were added.
Vladislav Khmelevsky,
Advanced Software Technology Lab, Huawei
Reviewed By: maksfb
Differential Revision: https://reviews.llvm.org/D117612
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Changes needed after ef736a1c39f27ef4 that removes some implicit
dependencies from MrCV headers.
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Summary: Fix comments at the start of source files.
(cherry picked from FBD33274597)
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Summary:
This patch adds AArch64 relocations handling in case updating of
debug sections is enabled
Elvina Yakubova,
Advanced Software Technology Lab, Huawei
(cherry picked from FBD33077609)
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Summary: Selectively apply clang-format to BOLT code base.
(cherry picked from FBD33119052)
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Summary: Print the relocation name instead of just the number.
(cherry picked from FBD32704832)
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Summary:
Add R_AARCH64_ABS32 and R_AARCH64_ABS16 relocations support
Vladislav Khmelevsky,
Advanced Software Technology Lab, Huawei
(cherry picked from FBD31875254)
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Summary:
Moves source files into separate components, and make explicit
component dependency on each other, so LLVM build system knows how to
build BOLT in BUILD_SHARED_LIBS=ON.
Please use the -c merge.renamelimit=230 git option when rebasing your
work on top of this change.
To achieve this, we create a new library to hold core IR files (most
classes beginning with Binary in their names), a new library to hold
Utils, some command line options shared across both RewriteInstance
and core IR files, a new library called Rewrite to hold most classes
concerned with running top-level functions coordinating the binary
rewriting process, and a new library called Profile to hold classes
dealing with profile reading and writing.
To remove the dependency from BinaryContext into X86-specific classes,
we do some refactoring on the BinaryContext constructor to receive a
reference to the specific backend directly from RewriteInstance. Then,
the dependency on X86 or AArch64-specific classes is transfered to the
Rewrite library. We can't have the Core library depend on targets
because targets depend on Core (which would create a cycle).
Files implementing the entry point of a tool are transferred to the
tools/ folder. All header files are transferred to the include/
folder. The src/ folder was renamed to lib/.
(cherry picked from FBD32746834)
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