This patch is the initial support, it implements translation from object file to JIT link graph, and very few relocations were supported. Currently, the test file ELF_pc_indirect.s is passed, the HelloWorld program(compiled with mno-relax flag) can be linked correctly and run on instruction emulator correctly.
In the downstream implementation, I have implemented the GOT, PLT function, and EHFrame and some optimization will be implement soon. I will organize the code in to patches, then gradually send it to upstream.
Differential Revision: https://reviews.llvm.org/D105429
LinkGraph::transferBlock can be used to move a block and all associated symbols
from one section to another.
LinkGraph::mergeSections moves all blocks and sections from a source section to
a destination section.
Adds support for MachO static initializers/deinitializers and eh-frame
registration via the ORC runtime.
This commit introduces cooperative support code into the ORC runtime and ORC
LLVM libraries (especially the MachOPlatform class) to support macho runtime
features for JIT'd code. This commit introduces support for static
initializers, static destructors (via cxa_atexit interposition), and eh-frame
registration. Near-future commits will add support for MachO native
thread-local variables, and language runtime registration (e.g. for Objective-C
and Swift).
The llvm-jitlink tool is updated to use the ORC runtime where available, and
regression tests for the new MachOPlatform support are added to compiler-rt.
Notable changes on the ORC runtime side:
1. The new macho_platform.h / macho_platform.cpp files contain the bulk of the
runtime-side support. This includes eh-frame registration; jit versions of
dlopen, dlsym, and dlclose; a cxa_atexit interpose to record static destructors,
and an '__orc_rt_macho_run_program' function that defines running a JIT'd MachO
program in terms of the jit- dlopen/dlsym/dlclose functions.
2. Replaces JITTargetAddress (and casting operations) with ExecutorAddress
(copied from LLVM) to improve type-safety of address management.
3. Adds serialization support for ExecutorAddress and unordered_map types to
the runtime-side Simple Packed Serialization code.
4. Adds orc-runtime regression tests to ensure that static initializers and
cxa-atexit interposes work as expected.
Notable changes on the LLVM side:
1. The MachOPlatform class is updated to:
1.1. Load the ORC runtime into the ExecutionSession.
1.2. Set up standard aliases for macho-specific runtime functions. E.g.
___cxa_atexit -> ___orc_rt_macho_cxa_atexit.
1.3. Install the MachOPlatformPlugin to scrape LinkGraphs for information
needed to support MachO features (e.g. eh-frames, mod-inits), and
communicate this information to the runtime.
1.4. Provide entry-points that the runtime can call to request initializers,
perform symbol lookup, and request deinitialiers (the latter is
implemented as an empty placeholder as macho object deinits are rarely
used).
1.5. Create a MachO header object for each JITDylib (defining the __mh_header
and __dso_handle symbols).
2. The llvm-jitlink tool (and llvm-jitlink-executor) are updated to use the
runtime when available.
3. A `lookupInitSymbolsAsync` method is added to the Platform base class. This
can be used to issue an async lookup for initializer symbols. The existing
`lookupInitSymbols` method is retained (the GenericIRPlatform code is still
using it), but is deprecated and will be removed soon.
4. JIT-dispatch support code is added to ExecutorProcessControl.
The JIT-dispatch system allows handlers in the JIT process to be associated with
'tag' symbols in the executor, and allows the executor to make remote procedure
calls back to the JIT process (via __orc_rt_jit_dispatch) using those tags.
The primary use case is ORC runtime code that needs to call bakc to handlers in
orc::Platform subclasses. E.g. __orc_rt_macho_jit_dlopen calling back to
MachOPlatform::rt_getInitializers using __orc_rt_macho_get_initializers_tag.
(The system is generic however, and could be used by non-runtime code).
The new ExecutorProcessControl::JITDispatchInfo struct provides the address
(in the executor) of the jit-dispatch function and a jit-dispatch context
object, and implementations of the dispatch function are added to
SelfExecutorProcessControl and OrcRPCExecutorProcessControl.
5. OrcRPCTPCServer is updated to support JIT-dispatch calls over ORC-RPC.
6. Serialization support for StringMap is added to the LLVM-side Simple Packed
Serialization code.
7. A JITLink::allocateBuffer operation is introduced to allocate writable memory
attached to the graph. This is used by the MachO header synthesis code, and will
be generically useful for other clients who want to create new graph content
from scratch.
This patch introduces new operations on jitlink::Blocks: setMutableContent,
getMutableContent and getAlreadyMutableContent. The setMutableContent method
will set the block content data and size members and flag the content as
mutable. The getMutableContent method will return a mutable copy of the existing
content value, auto-allocating and populating a new mutable copy if the existing
content is marked immutable. The getAlreadyMutableMethod asserts that the
existing content is already mutable and returns it.
setMutableContent should be used when updating the block with totally new
content backed by mutable memory. It can be used to change the size of the
block. The argument value should *not* be shared with any other block.
getMutableContent should be used when clients want to modify the existing
content and are unsure whether it is mutable yet.
getAlreadyMutableContent should be used when clients want to modify the existing
content and know from context that it must already be immutable.
These operations reduce copy-modify-update boilerplate and unnecessary copies
introduced when clients couldn't me sure whether the existing content was
mutable or not.
Keeping these bitfields from Block to Addressable allows them to be packed with
the bitfields at the end of Addressable, reducing the size of Block by eight
bytes.
The transferDefinedSymbol operation updates a Symbol's target block, offset,
and size. This can be convenient when you want to redefine the content of some
symbol(s) pointing at a block, while retaining the original block in the graph.
These can be used to create eh-frame section fixing passes outside the usual
linker pipeline, which can be useful for tests and tools that just want to
verify or dump graphs.
Adds utilities for creating anonymous pointers and jump stubs to x86_64.h. These
are used by the GOT and Stubs builder, but may also be used by pass writers who
want to create pointer stubs for indirection.
This patch also switches the underlying type for LinkGraph content from
StringRef to ArrayRef<char>. This avoids any confusion when working with buffers
that contain null bytes in the middle like, for example, a newly added null
pointer content array. ;)
This allows clients to modify the memory protection settings on sections via
jitlink passes. This can be used to, for example, override the default settings
on text pages and make them Read/Write/Executable under the JIT.
Introduces DefineExternalSectionStartAndEndSymbols.h, which defines a template
for a JITLink pass that transforms external symbols meeting a user-supplied
predicate into defined symbols pointing at the start and end of a Section
identified by the predicate. JITLink.h is updated with a new makeAbsolute
function to support this pass.
Also renames BasicGOTAndStubsBuilder to PerGraphGOTAndPLTStubsBuilder -- the new
name better describes the intent of this GOT and PLT stubs builder, and will
help to distinguish it from future GOT and PLT stub builders that build entries
that may be shared between multiple graphs.
This patch introduces generic x86-64 edge kinds, and refactors the MachO/x86-64
backend to use these edge kinds. This simplifies the implementation of the
MachO/x86-64 backend and makes it possible to write generic x86-64 passes and
utilities.
The new edge kinds are different from the original set used in the MachO/x86-64
backend. Several edge kinds that were not meaningfully distinguished in that
backend (e.g. the PCRelMinusN edges) have been merged into single edge kinds in
the new scheme (these edge kinds can be reintroduced later if we find a use for
them). At the same time, new edge kinds have been introduced to convey extra
information about the state of the graph. E.g. The Request*AndTransformTo**
edges represent GOT/TLVP relocations prior to synthesis of the GOT/TLVP
entries, and the 'Relaxable' suffix distinguishes edges that are candidates for
optimization from edges which should be left as-is (e.g. to enable runtime
redirection).
ELF/x86-64 will be refactored to use these generic edges at some point in the
future, and I anticipate a similar refactor to create a generic arm64 support
header too.
Differential Revision: https://reviews.llvm.org/D98305
This makes the target triple, graph name, and full graph content available
when making decisions about how to populate the linker pass pipeline.
Also updates the LLJITWithObjectLinkingLayerPlugin example to show more
API use, including use of the API changes in this patch.
The new assertions check that Addressables removed when removing
external or absolute symbols are not referenced by another symbol.
A comment on post-fixup passes is updated: vmaddrs have all been
set up by the time the pre-fixup passes are run, post-fixup passes
run after fixups have been applied to content.
Passes in the new PostAllocationPasses list will run immediately after memory
allocation and address assignment for defined symbols, and before
JITLinkContext::notifyResolved is called. These passes can set up state
associated with the addresses of defined symbols before any query for these
addresses completes.
PreFixupPasses better reflects when these passes will run.
A future patch will (re)introduce a PostAllocationPasses list that will run
after allocation, but before JITLinkContext::notifyResolved is called to notify
the rest of the JIT about the resolved symbol addresses.
Separates link graph creation from linking. This allows raw LinkGraphs to be
created and passed to a link. ObjectLinkingLayer is updated to support emission
of raw LinkGraphs in addition to object buffers.
Raw LinkGraphs can be created by in-memory compilers to bypass object encoding /
decoding (though this prevents caching, as LinkGraphs have do not have an
on-disk representation), and by utility code to add programatically generated
data structures to the JIT target process.
JITLinkDylib represents a target dylib for a JITLink link. By representing this
explicitly we can:
- Enable JITLinkMemoryManagers to manage allocations on a per-dylib basis
(e.g by maintaining a seperate allocation pool for each JITLinkDylib).
- Enable new features and diagnostics that require information about the
target dylib (not implemented in this patch).
implementation.
This patch aims to improve support for out-of-process JITing using OrcV2. It
introduces two new class templates, OrcRPCTargetProcessControlBase and
OrcRPCTPCServer, which together implement the TargetProcessControl API by
forwarding operations to an execution process via an Orc-RPC Endpoint. These
utilities are used to implement out-of-process JITing from llvm-jitlink to
a new llvm-jitlink-executor tool.
This patch also breaks the OrcJIT library into three parts:
-- OrcTargetProcess: Contains code needed by the JIT execution process.
-- OrcShared: Contains code needed by the JIT execution and compiler
processes
-- OrcJIT: Everything else.
This break-up allows JIT executor processes to link against OrcTargetProcess
and OrcShared only, without having to link in all of OrcJIT. Clients executing
JIT'd code in-process should start linking against OrcTargetProcess as well as
OrcJIT.
In the near future these changes will enable:
-- Removal of the OrcRemoteTargetClient/OrcRemoteTargetServer class templates
which provided similar functionality in OrcV1.
-- Restoration of Chapter 5 of the Building-A-JIT tutorial series, which will
serve as a simple usage example for these APIs.
-- Implementation of lazy, cross-target compilation in lli's -jit-kind=orc-lazy
mode.
The -harness option enables new testing use-cases for llvm-jitlink. It takes a
list of objects to treat as a test harness for any regular objects passed to
llvm-jitlink.
If any files are passed using the -harness option then the following
transformations are applied to all other files:
(1) Symbols definitions that are referenced by the harness files are promoted
to default scope. (This enables access to statics from test harness).
(2) Symbols definitions that clash with definitions in the harness files are
deleted. (This enables interposition by test harness).
(3) All other definitions in regular files are demoted to local scope.
(This causes untested code to be dead stripped, reducing memory cost and
eliminating spurious unresolved symbol errors from untested code).
These transformations allow the harness files to reference and interpose
symbols in the regular object files, which can be used to support execution
tests (including fuzz tests) of functions in relocatable objects produced by a
build.
This allows clients to detect invalid transformations applied by JITLink passes
(e.g. inserting or removing symbols in unexpected ways) and terminate linking
with an error.
This change is used to simplify the error propagation logic in
ObjectLinkingLayer.
Summary: This adds the basic support for GOT in elf x86.
Was able to just get away using the macho code by generalising the edges.
There will be a follow up patch to turn that into a generic utility for both of the x86 and Mach-O code.
This patch also lands support for relocations relative to symbol.
Reviewers: lhames
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D83748
This will be used by upcoming patches that implement indirection utils
(reentry, reentry trampolines, and stubs) on top of
JITLinkMemoryManager to unify in-process and cross-process lazy
compilation support.
This relaxes an assertion that required symbols to start before the end
of a block. Instead, symbols are now required to end on or before the
end of a block. This fixes two important corner cases: Symbols at the
start of empty blocks/sections, and block/section end symbols.
Summary:
Adding in our first relocation type, and all the required plumbing to support the rest in following patches
Differential Revision: https://reviews.llvm.org/D80613
Reviewer: lhames
This initial implementation supports section and symbol parsing, but no
relocation support. It enables JITLink to link and execute ELF relocatable
objects that do not require relocations.
Patch by Jared Wyles. Thanks Jared!
Differential Revision: https://reviews.llvm.org/D79832
This patch changes Block::removeEdge to return a valid iterator to the new next
element, and uses this to update the edge removal algorithm in
LinkGraph::splitBlock.
This optimization bypasses GOT loads and calls/branches through stubs when the
ultimate target of the access/branch is found to be within range of the
reference.
Extra debugging output is also added to the generic JITLink algorithm and
basic GOT and Stubs builder utility to aid debugging.
Initializers and deinitializers are used to implement C++ static constructors
and destructors, runtime registration for some languages (e.g. with the
Objective-C runtime for Objective-C/C++ code) and other tasks that would
typically be performed when a shared-object/dylib is loaded or unloaded by a
statically compiled program.
MCJIT and ORC have historically provided limited support for discovering and
running initializers/deinitializers by scanning the llvm.global_ctors and
llvm.global_dtors variables and recording the functions to be run. This approach
suffers from several drawbacks: (1) It only works for IR inputs, not for object
files (including cached JIT'd objects). (2) It only works for initializers
described by llvm.global_ctors and llvm.global_dtors, however not all
initializers are described in this way (Objective-C, for example, describes
initializers via specially named metadata sections). (3) To make the
initializer/deinitializer functions described by llvm.global_ctors and
llvm.global_dtors searchable they must be promoted to extern linkage, polluting
the JIT symbol table (extra care must be taken to ensure this promotion does
not result in symbol name clashes).
This patch introduces several interdependent changes to ORCv2 to support the
construction of new initialization schemes, and includes an implementation of a
backwards-compatible llvm.global_ctor/llvm.global_dtor scanning scheme, and a
MachO specific scheme that handles Objective-C runtime registration (if the
Objective-C runtime is available) enabling execution of LLVM IR compiled from
Objective-C and Swift.
The major changes included in this patch are:
(1) The MaterializationUnit and MaterializationResponsibility classes are
extended to describe an optional "initializer" symbol for the module (see the
getInitializerSymbol method on each class). The presence or absence of this
symbol indicates whether the module contains any initializers or
deinitializers. The initializer symbol otherwise behaves like any other:
searching for it triggers materialization.
(2) A new Platform interface is introduced in llvm/ExecutionEngine/Orc/Core.h
which provides the following callback interface:
- Error setupJITDylib(JITDylib &JD): Can be used to install standard symbols
in JITDylibs upon creation. E.g. __dso_handle.
- Error notifyAdding(JITDylib &JD, const MaterializationUnit &MU): Generally
used to record initializer symbols.
- Error notifyRemoving(JITDylib &JD, VModuleKey K): Used to notify a platform
that a module is being removed.
Platform implementations can use these callbacks to track outstanding
initializers and implement a platform-specific approach for executing them. For
example, the MachOPlatform installs a plugin in the JIT linker to scan for both
__mod_inits sections (for C++ static constructors) and ObjC metadata sections.
If discovered, these are processed in the usual platform order: Objective-C
registration is carried out first, then static initializers are executed,
ensuring that calls to Objective-C from static initializers will be safe.
This patch updates LLJIT to use the new scheme for initialization. Two
LLJIT::PlatformSupport classes are implemented: A GenericIR platform and a MachO
platform. The GenericIR platform implements a modified version of the previous
llvm.global-ctor scraping scheme to provide support for Windows and
Linux. LLJIT's MachO platform uses the MachOPlatform class to provide MachO
specific initialization as described above.
Reviewers: sgraenitz, dblaikie
Subscribers: mgorny, hiraditya, mgrang, ributzka, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74300
