ef2389235c
Add a new ObjectLinkingLayer plugin `DebugObjectManagerPlugin` and infrastructure to handle creation of `DebugObject`s as well as their registration in OrcTargetProcess. The current implementation only covers ELF on x86-64, but the infrastructure is not limited to that. The journey starts with a new `LinkGraph` / `JITLinkContext` pair being created for a `MaterializationResponsibility` in ORC's `ObjectLinkingLayer`. It sends a `notifyMaterializing()` notification, which is forwarded to all registered plugins. The `DebugObjectManagerPlugin` aims to create a `DebugObject` form the provided target triple and object buffer. (Future implementations might create `DebugObject`s from a `LinkGraph` in other ways.) On success it will track it as the pending `DebugObject` for the `MaterializationResponsibility`. This patch only implements the `ELFDebugObject` for `x86-64` targets. It follows the RuntimeDyld approach for debug object setup: it captures a copy of the input object, parses all section headers and prepares to patch their load-address fields with their final addresses in target memory. It instructs the plugin to report the section load-addresses once they are available. The plugin overrides `modifyPassConfig()` and installs a JITLink post-allocation pass to capture them. Once JITLink emitted the finalized executable, the plugin emits and registers the `DebugObject`. For emission it requests a new `JITLinkMemoryManager::Allocation` with a single read-only segment, copies the object with patched section load-addresses over to working memory and triggers finalization to target memory. For registration, it notifies the `DebugObjectRegistrar` provided in the constructor and stores the previously pending`DebugObject` as registered for the corresponding MaterializationResponsibility. The `DebugObjectRegistrar` registers the `DebugObject` with the target process. `llvm-jitlink` uses the `TPCDebugObjectRegistrar`, which calls `llvm_orc_registerJITLoaderGDBWrapper()` in the target process via `TargetProcessControl` to emit a `jit_code_entry` compatible with the GDB JIT interface [1]. So far the implementation only supports registration and no removal. It appears to me that it wouldn't raise any new design questions, so I left this as an addition for the near future. [1] https://sourceware.org/gdb/current/onlinedocs/gdb/JIT-Interface.html Reviewed By: lhames Differential Revision: https://reviews.llvm.org/D97335
111 lines
3.5 KiB
C++
111 lines
3.5 KiB
C++
//===- JITLoaderGDB.h - Register objects via GDB JIT interface -*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.h"
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#include "llvm/ExecutionEngine/JITSymbol.h"
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#include "llvm/Support/BinaryStreamReader.h"
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#include "llvm/Support/ManagedStatic.h"
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#include <cstdint>
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#include <mutex>
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#include <utility>
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#define DEBUG_TYPE "orc"
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// First version as landed in August 2009
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static constexpr uint32_t JitDescriptorVersion = 1;
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// Keep in sync with gdb/gdb/jit.h
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extern "C" {
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typedef enum {
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JIT_NOACTION = 0,
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JIT_REGISTER_FN,
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JIT_UNREGISTER_FN
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} jit_actions_t;
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struct jit_code_entry {
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struct jit_code_entry *next_entry;
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struct jit_code_entry *prev_entry;
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const char *symfile_addr;
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uint64_t symfile_size;
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};
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struct jit_descriptor {
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uint32_t version;
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// This should be jit_actions_t, but we want to be specific about the
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// bit-width.
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uint32_t action_flag;
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struct jit_code_entry *relevant_entry;
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struct jit_code_entry *first_entry;
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};
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// We put information about the JITed function in this global, which the
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// debugger reads. Make sure to specify the version statically, because the
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// debugger checks the version before we can set it during runtime.
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struct jit_descriptor __jit_debug_descriptor = {JitDescriptorVersion, 0,
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nullptr, nullptr};
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// Debuggers that implement the GDB JIT interface put a special breakpoint in
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// this function.
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LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
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// The noinline and the asm prevent calls to this function from being
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// optimized out.
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#if !defined(_MSC_VER)
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asm volatile("" ::: "memory");
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#endif
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}
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}
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using namespace llvm;
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// Serialize rendezvous with the debugger as well as access to shared data.
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ManagedStatic<std::mutex> JITDebugLock;
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static std::pair<const char *, uint64_t> readDebugObjectInfo(uint8_t *ArgData,
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uint64_t ArgSize) {
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BinaryStreamReader ArgReader(ArrayRef<uint8_t>(ArgData, ArgSize),
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support::endianness::big);
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uint64_t Addr, Size;
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cantFail(ArgReader.readInteger(Addr));
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cantFail(ArgReader.readInteger(Size));
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return std::make_pair(jitTargetAddressToPointer<const char *>(Addr), Size);
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}
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extern "C" orc::tpctypes::CWrapperFunctionResult
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llvm_orc_registerJITLoaderGDBWrapper(uint8_t *Data, uint64_t Size) {
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if (Size != sizeof(uint64_t) + sizeof(uint64_t))
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return orc::tpctypes::WrapperFunctionResult::from(
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"Invalid arguments to llvm_orc_registerJITLoaderGDBWrapper")
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.release();
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jit_code_entry *E = new jit_code_entry;
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std::tie(E->symfile_addr, E->symfile_size) = readDebugObjectInfo(Data, Size);
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E->prev_entry = nullptr;
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std::lock_guard<std::mutex> Lock(*JITDebugLock);
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// Insert this entry at the head of the list.
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jit_code_entry *NextEntry = __jit_debug_descriptor.first_entry;
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E->next_entry = NextEntry;
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if (NextEntry) {
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NextEntry->prev_entry = E;
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}
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__jit_debug_descriptor.first_entry = E;
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__jit_debug_descriptor.relevant_entry = E;
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// Run into the rendezvous breakpoint.
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__jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
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__jit_debug_register_code();
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return orc::tpctypes::WrapperFunctionResult().release();
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}
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