The find-dynamic-unwind-info callback registration APIs in libunwind
limit the number of callbacks that can be registered. If we use multiple
UnwindInfoManager instances, each with their own own callback function
(as was the case prior to this patch) we can quickly exceed this limit
(see https://github.com/llvm/llvm-project/issues/126611).
This patch updates the UnwindInfoManager class to use a singleton
pattern, with the single instance shared between all LLVM JITs in the
process.
This change does _not_ apply to compact unwind info registered through
the ORC runtime (which currently installs its own callbacks).
As a bonus this change eliminates the need to load an IR "bouncer"
module to supply the unique callback for each instance, so support for
compact-unwind can be extended to the llvm-jitlink tools (which does not
support adding IR).
The system libunwind on older Darwins does not support JIT registration of
compact-unwind. Since the CompactUnwindManager utility discards redundant
eh-frame FDEs by default we need to remove the compact-unwind section first
when targeting older libunwinds in order to preserve eh-frames.
While LLJIT was already doing this as of eae6d6d18bd, MachOPlatform was not.
This was causing buildbot failures in the ORC runtime (e.g. in
https://green.lab.llvm.org/job/llvm.org/job/clang-stage1-RA/3479/).
This patch updates both LLJIT and MachOPlatform to check a bootstrap value,
"darwin-use-ehframes-only", to determine whether to forcibly preserve
eh-frame sections. If this value is present and set to true then compact-unwind
sections will be discarded, causing eh-frames to be preserved. If the value is
absent or set to false then compact-unwind will be used and redundant FDEs in
eh-frames discarded (FDEs that are needed by the compact-unwind section are
always preserved).
rdar://143895614
Compact-unwind encodings are more limited than DWARF frame descriptions. For
functions whose frame layout cannot be described by a compact unwind encoding,
the encoding for the function will specify "use DWARF", and the corresponding
unwind-info record will use the low bits of the encoding to point to the FDE
for the function.
We test this with a frame-pointer=none function, since these frame layouts
always triger a fall-back to DWARF on arm64.
SecondLevelPageOffset should be incremented by SecondLevelPageSize bytes, not
one byte.
Failure to calculate the offset correctly leads to corrupted unwind-info (and
consequently broken exceptions / unwinding) when more than one second level
page is needed. Since JITLink's unwind support only produces
UNWIND_SECOND_LEVEL_REGULAR-style pages this would trigger for any file
containing more than 511 functions with unwind info. The included test-case
contains 1022 functions (sufficient for both the current format and any
future implementation that supports UNWIND_SECOND_LEVEL_COMPRESSED pages).
Thanks to @edoardo on discord for spotting this bug!
Re-enables compact-unwind support in JITLink, which was reverted in b04847b427d
due to buildbot failures.
The underlying cause for the failures on the buildbots was the lack of
compact-unwind registration support on older Darwin OSes. Since the
CompactUnwindManager pass now removes eh-frames by default we were left with
unwind-info that could not be registered. On x86-64, where eh-frame info is
produced by default the solution is to fall back to using eh-frames. On arm64
we simply can't support exceptions on older OSes.
This patch updates the EHFrameRegistrationPlugin to remove the compact-unwind
section (__LD,__compact_unwind) when installed, forcing use of eh-frames when
the EHFrameRegistrationPlugin is used. In LLJIT, the EHFrameRegistrationPlugin
continues to be used for all non-Darwin platform, and will be added on Darwin
platforms when the a CompactUnwindRegistrationPlugin instance can't be created
(e.g. due to missing support for compact-unwind info registration).
The lit.cfg.py script is updated to check whether the host OSes default unwind
info supports JIT registration, allowing tests to be disabled for older Darwin
OSes on arm64.
Some eh-frame records are CIEs, which don't point to functions. We need to skip
these records. This patch reuses EHFrameCFIBlockInspector to identify function
targets, rather than a custom loop. Any performance impact will be minimal, and
essentially irrelevant once compact-unwind support re-lands (since at that
point we'll discard most eh-frame records).
For unwind-info sections: don't assume one block per record: the unwind-info
section packs all records into a single block.
Unwind-info records only have one keep-alive edge to their target function, but
eh-frame records may have multiple edges (to the CIE, function, personality, and
lsda). We need to identify the target-function edge differently for each section
type.
a1ff2d18466 should have disambiguated MachOCompactUnwindInfoSectionName to
MachOUnwindInfoSectionName, given how it's used in MachOPlatform and its
value.
A MachOCompactUnwindSectionName variable with an appropriate value will be
added in an upcoming patch to re-enable compact-unwind support in JITLink.
Rename MachOCompactUnwindInfoSectionName to MachOCompactUnwindSectionName.
Background:
There are two related sections used for compact-unwind info processing:
__LD,__compact_unwind -- the input table stored in relocatable object formats,
and __TEXT,__unwind_info -- the compressed table produced by the linker and
consumed by libunwind. To keep the distinction clear we'll use *CompactUnwind*
for names that refer to the __LD,__compact_unwind input tables and *UnwindInfo*
for names that refer to the __TEXT,__unwind_info output tables. Dropping 'Info'
from the variable above clarifies which section it refers to.
This reverts commit d6524c8dfa37634257050ca71d16e117b802181c. This
reverts commit b1bd73700a1fb6f450e0f6f9c405a9c8bde2cae7.
This was causing bot failures on Darwin
https://green.lab.llvm.org/job/llvm.org/job/clang-stage1-cmake-RA-incremental/7315/
Clang.Interpreter.simple-exception.cpp
Clang-Unit.Interpreter/ExceptionTests/_/ClangReplInterpreterExceptionTests/0.1
LLVM.ExecutionEngine/OrcLazy.minimal-throw-catch.ll
https://green.lab.llvm.org/job/llvm.org/job/clang-stage1-RA/3415/
ORC-x86_64-darwin.TestCases/Darwin/Generic.exceptions.cpp
ORC-x86_64-darwin.TestCases/Darwin/x86-64.lljit-ehframe.cpp
This reapplies 4f0325873fa (and follow up patches 26fc07d5d88, a001cc0e6cdc,
c9bc242e387, and fd174f0ff3e), which were reverted in 212cdc9a377 to
investigate bot failures (e.g.
https://lab.llvm.org/buildbot/#/builders/108/builds/8502)
The fix to address the bot failures was landed in d0052ebbe2e. This patch also
restricts construction of the UnwindInfoManager object to Apple platforms (as
it won't be used on other platforms).
Attempt to install the EHFrameRegistrationPlugin during GenericLLVMIRPlatform
setup, rather than object linking layer creation time.
Platform classes are responsible for exception handling: installing the plugin
unconditionally during linking-layer construction could result in frames being
registered more than once when native platform classes are used.
This is a precursor to re-landing compact unwind support (4f0325873fa).
Transform Pointer64Authenticated edges into KeepAlive edges, rather than
removing them, in order to preserve symbol dependence information.
The lowerPointer64AuthEdgesToSigningFunction pass is responsible for
transforming Pointer64Authenticated edges to a signing function that can be run
in the executing process to initialize global PAC pointers. Removing the edges
entirely in this pass results in loss of dependence tracking, which can in turn
cause ORC to report PAC pointers as ready before the pointers targets have
completed materialization (resulting in a use-before-finalize error, often
manifesting as access to uninitialized / unprotected memory).
This commit addresses the issue by leaving the edges in the graph and simply
changing their kind to KeepAlive, a no-op for fixup purposes but followed for
dependence tracking purposes.
No testcase: this change just allows edge names to be correctly reported in
debug dumps of LinkGraphs. (Previously Pointer64Authenticated edges were
reported as "<Unrecognized edge kind>").
This reverts 4f0325873faccfbe171bae4babceb65975ca892e and follow-up patches
(see below) while I investigate some ongoing failures on the buildbots.
---
Revert "[clang-repl] Try to XFAIL testcase on arm32 without affecting arm64
darwin."
This reverts commit fd174f0ff3e793fe96a6663b1488ed159cfe042f.
Revert "[clang-repl] The simple-exception test now passes on arm64-darwin."
This reverts commit c9bc242e387f4a4a3dfcd86561f3ec0ca8a72d62.
Revert "[ORC] Destroy defunct MaterializationUnits outside the session lock."
This reverts commit a001cc0e6cdcfa672b8aff9ce6d14782bb96356a.
Revert "[ORC] Add explicit narrowing casts to fix build errors."
This reverts commit 26fc07d5d88760ad659599184fd10181287d2d9e.
Revert "[ORC] Enable JIT support for the compact-unwind frame info format on
Darwin."
This reverts commit 4f0325873faccfbe171bae4babceb65975ca892e.
Linker relaxation is not implemented for jitlink now. But if
relaxation is enabled by clang, R_LARCH_RELAX and
R_LARCH_ALIGN relocations will be emitted.
This commit adapts lld's algorithm to jitlink. Currently, only
relaxing R_LARCH_ALIGN is implemented. Other relaxable
relocs can be implemented in the future.
Without this, interpreting C++ code using clang-repl or running
ir using lli when relaxation is enabled will occur error: `JIT
session error: Unsupported loongarch relocation:102: R_LARCH_ALIGN`.
Similar to 310473c536 but only implement align.
MaterializationUnits may contain arbitrary resources that need cleanup. We want
to do this outside the JIT's session lock.
This should fix a lock-order-inversion warning in clang-repl (for details see
https://github.com/llvm/llvm-project/issues/124215).
For Darwin/arm64 (including Apple Silicon Macs) this will enable exception
handling and stack unwinding in JIT'd code.
Darwin supports two unwind-info formats: DWARF eh-frames and compact-unwind. On
Darwin/x86-64 compilers usually produce both by default, and ORC supported
exceptions and unwinding via eh-frames (same as on Linux), discarding the
redundant compact-unwind info. On Darwin/arm64 compilers typically default to
producing compact-unwind only, with DWARF eh-frames as a fallback for functions
that can't be described in compact-unwind. Since ORC did not previously support
the compact-unwind format and eh-frames were not present ORC was unable to
handle exceptions or unwinding by default in Darwin/arm64 JIT'd code.
This patch enables support for the compact-unwind-info format, and contains
three major moving parts:
(1) The JITLink CompactUnwindManager class is responsible for transforming the
__compact_unwind records produced by the linker into the __unwind_info
tables that libunwind parses during unwinding. To enable this the
CompactUnwindManager class provides three JITLink passes: The
prepareForPrune pass that splits the __compact_unwind section into
single-record blocks, allowing unused records to be dead-stripped; the
processAndReserveUnwindInfo pass that reserves space for the final
__unwind_info section, and the writeUnwindInfo pass that writes the
__unwind_info section.
(2) The OrcTargetProcess UnwindInfoManager class maintains a table of
registered JIT'd __unwind_info and __eh_frame sections, and handles
requests from libunwind for unwind info sections (by registering a callback
with libunwind's __unw_add_find_dynamic_unwind_sections function).
(3) The Orc UnwindInfoRegistrationPlugin, which scans LinkGraphs for
__unwind_info and __eh_frame sections to register with the
UnwindInfoManager.
This commit adds the CompactUnwindManager passes to the default JITLink
pipelines for Darwin/arm64 and Darwin/x86-64, and UnwindInfoManager intances to
the SelfExecutorProcessControl class (when built for apple platforms) and the
llvm-jitlink-executor tool.
The LLJIT class will now create an UnwindInfoRegistrationPlugin when targeting
a process running on Darwin if it detects that an UnwindInfoManager is
available to handle the registrations.
The ORC runtime macho_platform class already supported libunwind callbacks, so
out-of-process execution and unwinding support will work when loading the ORC
runtime.
The llvm-jitlink tool will only support compact-unwind when the orc-runtime is
loaded, as the UnwindInfoRegistrationPlugin requires access to an IR compiler
to load a helper module and llvm-jitlink does not provide an IR compiler.
The MachOPlatform::MachOPlatformPlugin class will now inject a
"__jitlink$libunwind_dso_base" symbol into each LinkGraph pointing to the Mach
header for the containing JITDylib. The compact-unwind support plugin will use
this symbol as the dso-base for the __unwind_info sections. (Failure to inject
this symbol would result in the compact-unwind support plugin creating a new
header for every graph).
This function can be called on a LinkGraph to get an anonymous symbol pointing
to the start of a mach_header / mach_header_64 block with suitable cputype and
cpusubtype values for the LinkGraph, and with filetype = MachO::MH_OBJECT.
This functionality will be used in the upcoming compact-unwind support patch:
For graphs that do not have a suitable existing header to use (indicated by the
presence of a "__jitlink$libunwind_dso_base" symbol) the compact-unwind support
plugin will create a local header to use as the dso-base to report to
libunwind.
Enable ELFNixPlatform support for loongarch64. These are few simple
changes, but it allows us to use the orc runtime in ELF/LoongArch64
backend.
This change adds test cases targeting the LoongArch64 Linux platform to
the ORC runtime integration test suite. Since jitlink for loongarch64 is
ready for general use, and ELF-based platforms support defining multiple
static initializer table sections with differing priorities, some
relevant test cases in compiler-rt for ELFNixPlatform support can be
enabled.
x86_64::GOTTableManager and x86_64::PLTTableManager will now look for existing
GOT and PLT sections and re-use existing entries if they're present.
This will be used for an upcoming MachO patch to enable compact unwind support.
This patch is the x86-64 counterpart 42595bdaefb, which added the same
functionality to the GOT and PLT managers for aarch64.
These are unneeded even on AIX, PURE_WINDOWS, and ZOS (per #104706)
* HAVE_ERRNO_H: introduced by 1a93330ffa2ae2aa0b49461f05e6f0d51e8443f8 (2009) but unneeded.
The guarded ABI is unconditionally used by lldb.
* HAVE_FCNTL_H
* HAVE_FENV_H
* HAVE_SYS_STAT_H
Pull Request: https://github.com/llvm/llvm-project/pull/123087
On platfarms where some relocations for eh-frame sections are implicit (e.g.
MachO/x86-64) EHFrameEdgeFixer is responsible for adding edges for the
implicit relocations.
Adds new convenience methods findDefinedSymbolByName, findExternalSymbolByName
and findAbsoluteSymbolByName to the LinkGraph class. These should be used to
find symbols of the given types by name.
COFFLinkGraphBuilder and MachOPlatform are updated to take advantage of the
new methods.
