JITLoaderGDB.cpp

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//===- JITLoaderGDB.h - Register objects via GDB JIT interface -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "llvm/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.h"
 
#include "llvm/ExecutionEngine/JITSymbol.h"
#include "llvm/Support/BinaryStreamReader.h"
#include "llvm/Support/FormatVariadic.h"
 
#include <cstdint>
#include <mutex>
#include <utility>
 
#define DEBUG_TYPE "orc"
 
// First version as landed in August 2009
static constexpr uint32_t JitDescriptorVersion = 1;
 
// Keep in sync with gdb/gdb/jit.h
extern "C" {
 
typedef enum {
  JIT_NOACTION = 0,
  JIT_REGISTER_FN,
  JIT_UNREGISTER_FN
} jit_actions_t;
 
struct jit_code_entry {
  struct jit_code_entry *next_entry;
  struct jit_code_entry *prev_entry;
  const char *symfile_addr;
  uint64_t symfile_size;
};
 
struct jit_descriptor {
  uint32_t version;
  // This should be jit_actions_t, but we want to be specific about the
  // bit-width.
  uint32_t action_flag;
  struct jit_code_entry *relevant_entry;
  struct jit_code_entry *first_entry;
};
 
// We put information about the JITed function in this global, which the
// debugger reads.  Make sure to specify the version statically, because the
// debugger checks the version before we can set it during runtime.
struct jit_descriptor __jit_debug_descriptor = {JitDescriptorVersion, 0,
                                                nullptr, nullptr};
 
// Debuggers that implement the GDB JIT interface put a special breakpoint in
// this function.
LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
  // The noinline and the asm prevent calls to this function from being
  // optimized out.
#if !defined(_MSC_VER)
  asm volatile("" ::: "memory");
#endif
}
}
 
using namespace llvm;
using namespace llvm::orc;
 
// Register debug object, return error message or null for success.
static void appendJITDebugDescriptor(const char *ObjAddr, size_t Size) {
  LLVM_DEBUG({
    dbgs() << "Adding debug object to GDB JIT interface "
           << formatv("([{0:x16} -- {1:x16}])",
                      reinterpret_cast<uintptr_t>(ObjAddr),
                      reinterpret_cast<uintptr_t>(ObjAddr + Size))
           << "\n";
  });
 
  jit_code_entry *E = new jit_code_entry;
  E->symfile_addr = ObjAddr;
  E->symfile_size = Size;
  E->prev_entry = nullptr;
 
  // Serialize rendezvous with the debugger as well as access to shared data.
  static std::mutex JITDebugLock;
  std::lock_guard<std::mutex> Lock(JITDebugLock);
 
  // Insert this entry at the head of the list.
  jit_code_entry *NextEntry = __jit_debug_descriptor.first_entry;
  E->next_entry = NextEntry;
  if (NextEntry) {
    NextEntry->prev_entry = E;
  }
 
  __jit_debug_descriptor.first_entry = E;
  __jit_debug_descriptor.relevant_entry = E;
  __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
}
 
extern "C" orc::shared::CWrapperFunctionResult
llvm_orc_registerJITLoaderGDBAllocAction(const char *Data, size_t Size) {
  using namespace orc::shared;
  return WrapperFunction<SPSError(SPSExecutorAddrRange, bool)>::handle(
             Data, Size,
             [](ExecutorAddrRange R, bool AutoRegisterCode) {
               appendJITDebugDescriptor(R.Start.toPtr<const char *>(),
                                        R.size());
               // Run into the rendezvous breakpoint.
               if (AutoRegisterCode)
                 __jit_debug_register_code();
               return Error::success();
             })
      .release();
}
 
extern "C" orc::shared::CWrapperFunctionResult
llvm_orc_registerJITLoaderGDBWrapper(const char *Data, uint64_t Size) {
  using namespace orc::shared;
  return WrapperFunction<SPSError(SPSExecutorAddrRange, bool)>::handle(
             Data, Size,
             [](ExecutorAddrRange R, bool AutoRegisterCode) {
               appendJITDebugDescriptor(R.Start.toPtr<const char *>(),
                                        R.size());
               // Run into the rendezvous breakpoint.
               if (AutoRegisterCode)
                 __jit_debug_register_code();
               return Error::success();
             })
      .release();
}