llvm-project/lldb/tools/lldb-dap/Handler/DisassembleRequestHandler.cpp

//===-- DisassembleRequestHandler.cpp -------------------------------------===//
//
// 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 "DAP.h"
#include "EventHelper.h"
#include "JSONUtils.h"
#include "RequestHandler.h"
#include "lldb/API/SBInstruction.h"
#include "llvm/ADT/StringExtras.h"

namespace lldb_dap {

// "DisassembleRequest": {
//   "allOf": [ { "$ref": "#/definitions/Request" }, {
//     "type": "object",
//     "description": "Disassembles code stored at the provided
//     location.\nClients should only call this request if the corresponding
//     capability `supportsDisassembleRequest` is true.", "properties": {
//       "command": {
//         "type": "string",
//         "enum": [ "disassemble" ]
//       },
//       "arguments": {
//         "$ref": "#/definitions/DisassembleArguments"
//       }
//     },
//     "required": [ "command", "arguments" ]
//   }]
// },
// "DisassembleArguments": {
//   "type": "object",
//   "description": "Arguments for `disassemble` request.",
//   "properties": {
//     "memoryReference": {
//       "type": "string",
//       "description": "Memory reference to the base location containing the
//       instructions to disassemble."
//     },
//     "offset": {
//       "type": "integer",
//       "description": "Offset (in bytes) to be applied to the reference
//       location before disassembling. Can be negative."
//     },
//     "instructionOffset": {
//       "type": "integer",
//       "description": "Offset (in instructions) to be applied after the byte
//       offset (if any) before disassembling. Can be negative."
//     },
//     "instructionCount": {
//       "type": "integer",
//       "description": "Number of instructions to disassemble starting at the
//       specified location and offset.\nAn adapter must return exactly this
//       number of instructions - any unavailable instructions should be
//       replaced with an implementation-defined 'invalid instruction' value."
//     },
//     "resolveSymbols": {
//       "type": "boolean",
//       "description": "If true, the adapter should attempt to resolve memory
//       addresses and other values to symbolic names."
//     }
//   },
//   "required": [ "memoryReference", "instructionCount" ]
// },
// "DisassembleResponse": {
//   "allOf": [ { "$ref": "#/definitions/Response" }, {
//     "type": "object",
//     "description": "Response to `disassemble` request.",
//     "properties": {
//       "body": {
//         "type": "object",
//         "properties": {
//           "instructions": {
//             "type": "array",
//             "items": {
//               "$ref": "#/definitions/DisassembledInstruction"
//             },
//             "description": "The list of disassembled instructions."
//           }
//         },
//         "required": [ "instructions" ]
//       }
//     }
//   }]
// }
void DisassembleRequestHandler::operator()(
    const llvm::json::Object &request) const {
  llvm::json::Object response;
  FillResponse(request, response);
  auto *arguments = request.getObject("arguments");

  llvm::StringRef memoryReference =
      GetString(arguments, "memoryReference").value_or("");
  auto addr_opt = DecodeMemoryReference(memoryReference);
  if (!addr_opt.has_value()) {
    response["success"] = false;
    response["message"] =
        "Malformed memory reference: " + memoryReference.str();
    dap.SendJSON(llvm::json::Value(std::move(response)));
    return;
  }
  lldb::addr_t addr_ptr = *addr_opt;

  addr_ptr += GetInteger<int64_t>(arguments, "instructionOffset").value_or(0);
  lldb::SBAddress addr(addr_ptr, dap.target);
  if (!addr.IsValid()) {
    response["success"] = false;
    response["message"] = "Memory reference not found in the current binary.";
    dap.SendJSON(llvm::json::Value(std::move(response)));
    return;
  }

  const auto inst_count =
      GetInteger<int64_t>(arguments, "instructionCount").value_or(0);
  lldb::SBInstructionList insts = dap.target.ReadInstructions(addr, inst_count);

  if (!insts.IsValid()) {
    response["success"] = false;
    response["message"] = "Failed to find instructions for memory address.";
    dap.SendJSON(llvm::json::Value(std::move(response)));
    return;
  }

  const bool resolveSymbols =
      GetBoolean(arguments, "resolveSymbols").value_or(false);
  llvm::json::Array instructions;
  const auto num_insts = insts.GetSize();
  for (size_t i = 0; i < num_insts; ++i) {
    lldb::SBInstruction inst = insts.GetInstructionAtIndex(i);
    auto addr = inst.GetAddress();
    const auto inst_addr = addr.GetLoadAddress(dap.target);
    const char *m = inst.GetMnemonic(dap.target);
    const char *o = inst.GetOperands(dap.target);
    const char *c = inst.GetComment(dap.target);
    auto d = inst.GetData(dap.target);

    std::string bytes;
    llvm::raw_string_ostream sb(bytes);
    for (unsigned i = 0; i < inst.GetByteSize(); i++) {
      lldb::SBError error;
      uint8_t b = d.GetUnsignedInt8(error, i);
      if (error.Success()) {
        sb << llvm::format("%2.2x ", b);
      }
    }

    llvm::json::Object disassembled_inst{
        {"address", "0x" + llvm::utohexstr(inst_addr)},
        {"instructionBytes",
         bytes.size() > 0 ? bytes.substr(0, bytes.size() - 1) : ""},
    };

    std::string instruction;
    llvm::raw_string_ostream si(instruction);

    lldb::SBSymbol symbol = addr.GetSymbol();
    // Only add the symbol on the first line of the function.
    if (symbol.IsValid() && symbol.GetStartAddress() == addr) {
      // If we have a valid symbol, append it as a label prefix for the first
      // instruction. This is so you can see the start of a function/callsite
      // in the assembly, at the moment VS Code (1.80) does not visualize the
      // symbol associated with the assembly instruction.
      si << (symbol.GetMangledName() != nullptr ? symbol.GetMangledName()
                                                : symbol.GetName())
         << ": ";

      if (resolveSymbols) {
        disassembled_inst.try_emplace("symbol", symbol.GetDisplayName());
      }
    }

    si << llvm::formatv("{0,7} {1,12}", m, o);
    if (c && c[0]) {
      si << " ; " << c;
    }

    disassembled_inst.try_emplace("instruction", instruction);

    auto line_entry = addr.GetLineEntry();
    // If the line number is 0 then the entry represents a compiler generated
    // location.
    if (line_entry.GetStartAddress() == addr && line_entry.IsValid() &&
        line_entry.GetFileSpec().IsValid() && line_entry.GetLine() != 0) {
      auto source = CreateSource(line_entry);
      disassembled_inst.try_emplace("location", source);

      const auto line = line_entry.GetLine();
      if (line && line != LLDB_INVALID_LINE_NUMBER) {
        disassembled_inst.try_emplace("line", line);
      }
      const auto column = line_entry.GetColumn();
      if (column && column != LLDB_INVALID_COLUMN_NUMBER) {
        disassembled_inst.try_emplace("column", column);
      }

      auto end_line_entry = line_entry.GetEndAddress().GetLineEntry();
      if (end_line_entry.IsValid() &&
          end_line_entry.GetFileSpec() == line_entry.GetFileSpec()) {
        const auto end_line = end_line_entry.GetLine();
        if (end_line && end_line != LLDB_INVALID_LINE_NUMBER &&
            end_line != line) {
          disassembled_inst.try_emplace("endLine", end_line);

          const auto end_column = end_line_entry.GetColumn();
          if (end_column && end_column != LLDB_INVALID_COLUMN_NUMBER &&
              end_column != column) {
            disassembled_inst.try_emplace("endColumn", end_column - 1);
          }
        }
      }
    }

    instructions.emplace_back(std::move(disassembled_inst));
  }

  llvm::json::Object body;
  body.try_emplace("instructions", std::move(instructions));
  response.try_emplace("body", std::move(body));
  dap.SendJSON(llvm::json::Value(std::move(response)));
}

} // namespace lldb_dap