src/developer/debug/unwinder/dwarf_expr.cc

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/developer/debug/unwinder/dwarf_expr.h"

#include <cstdint>

#include "src/developer/debug/unwinder/error.h"
#include "src/developer/debug/unwinder/memory.h"

namespace unwinder {

namespace {

enum : uint8_t {
  DW_OP_addr = 0x03,
  DW_OP_deref = 0x06,
  DW_OP_const1u = 0x08,
  DW_OP_const1s = 0x09,
  DW_OP_const2u = 0x0a,
  DW_OP_const2s = 0x0b,
  DW_OP_const4u = 0x0c,
  DW_OP_const4s = 0x0d,
  DW_OP_const8u = 0x0e,
  DW_OP_const8s = 0x0f,
  DW_OP_constu = 0x10,
  DW_OP_consts = 0x11,
  DW_OP_dup = 0x12,
  DW_OP_drop = 0x13,
  DW_OP_over = 0x14,
  DW_OP_pick = 0x15,
  DW_OP_swap = 0x16,
  DW_OP_rot = 0x17,
  DW_OP_xderef = 0x18,
  DW_OP_abs = 0x19,
  DW_OP_and = 0x1a,
  DW_OP_div = 0x1b,
  DW_OP_minus = 0x1c,
  DW_OP_mod = 0x1d,
  DW_OP_mul = 0x1e,
  DW_OP_neg = 0x1f,
  DW_OP_not = 0x20,
  DW_OP_or = 0x21,
  DW_OP_plus = 0x22,
  DW_OP_plus_uconst = 0x23,
  DW_OP_shl = 0x24,
  DW_OP_shr = 0x25,
  DW_OP_shra = 0x26,
  DW_OP_xor = 0x27,
  DW_OP_bra = 0x28,
  DW_OP_eq = 0x29,
  DW_OP_ge = 0x2a,
  DW_OP_gt = 0x2b,
  DW_OP_le = 0x2c,
  DW_OP_lt = 0x2d,
  DW_OP_ne = 0x2e,
  DW_OP_skip = 0x2f,
  DW_OP_lit0 = 0x30,
  DW_OP_lit1 = 0x31,
  DW_OP_lit2 = 0x32,
  DW_OP_lit3 = 0x33,
  DW_OP_lit4 = 0x34,
  DW_OP_lit5 = 0x35,
  DW_OP_lit6 = 0x36,
  DW_OP_lit7 = 0x37,
  DW_OP_lit8 = 0x38,
  DW_OP_lit9 = 0x39,
  DW_OP_lit10 = 0x3a,
  DW_OP_lit11 = 0x3b,
  DW_OP_lit12 = 0x3c,
  DW_OP_lit13 = 0x3d,
  DW_OP_lit14 = 0x3e,
  DW_OP_lit15 = 0x3f,
  DW_OP_lit16 = 0x40,
  DW_OP_lit17 = 0x41,
  DW_OP_lit18 = 0x42,
  DW_OP_lit19 = 0x43,
  DW_OP_lit20 = 0x44,
  DW_OP_lit21 = 0x45,
  DW_OP_lit22 = 0x46,
  DW_OP_lit23 = 0x47,
  DW_OP_lit24 = 0x48,
  DW_OP_lit25 = 0x49,
  DW_OP_lit26 = 0x4a,
  DW_OP_lit27 = 0x4b,
  DW_OP_lit28 = 0x4c,
  DW_OP_lit29 = 0x4d,
  DW_OP_lit30 = 0x4e,
  DW_OP_lit31 = 0x4f,
  DW_OP_reg0 = 0x50,
  DW_OP_reg1 = 0x51,
  DW_OP_reg2 = 0x52,
  DW_OP_reg3 = 0x53,
  DW_OP_reg4 = 0x54,
  DW_OP_reg5 = 0x55,
  DW_OP_reg6 = 0x56,
  DW_OP_reg7 = 0x57,
  DW_OP_reg8 = 0x58,
  DW_OP_reg9 = 0x59,
  DW_OP_reg10 = 0x5a,
  DW_OP_reg11 = 0x5b,
  DW_OP_reg12 = 0x5c,
  DW_OP_reg13 = 0x5d,
  DW_OP_reg14 = 0x5e,
  DW_OP_reg15 = 0x5f,
  DW_OP_reg16 = 0x60,
  DW_OP_reg17 = 0x61,
  DW_OP_reg18 = 0x62,
  DW_OP_reg19 = 0x63,
  DW_OP_reg20 = 0x64,
  DW_OP_reg21 = 0x65,
  DW_OP_reg22 = 0x66,
  DW_OP_reg23 = 0x67,
  DW_OP_reg24 = 0x68,
  DW_OP_reg25 = 0x69,
  DW_OP_reg26 = 0x6a,
  DW_OP_reg27 = 0x6b,
  DW_OP_reg28 = 0x6c,
  DW_OP_reg29 = 0x6d,
  DW_OP_reg30 = 0x6e,
  DW_OP_reg31 = 0x6f,
  DW_OP_breg0 = 0x70,
  DW_OP_breg1 = 0x71,
  DW_OP_breg2 = 0x72,
  DW_OP_breg3 = 0x73,
  DW_OP_breg4 = 0x74,
  DW_OP_breg5 = 0x75,
  DW_OP_breg6 = 0x76,
  DW_OP_breg7 = 0x77,
  DW_OP_breg8 = 0x78,
  DW_OP_breg9 = 0x79,
  DW_OP_breg10 = 0x7a,
  DW_OP_breg11 = 0x7b,
  DW_OP_breg12 = 0x7c,
  DW_OP_breg13 = 0x7d,
  DW_OP_breg14 = 0x7e,
  DW_OP_breg15 = 0x7f,
  DW_OP_breg16 = 0x80,
  DW_OP_breg17 = 0x81,
  DW_OP_breg18 = 0x82,
  DW_OP_breg19 = 0x83,
  DW_OP_breg20 = 0x84,
  DW_OP_breg21 = 0x85,
  DW_OP_breg22 = 0x86,
  DW_OP_breg23 = 0x87,
  DW_OP_breg24 = 0x88,
  DW_OP_breg25 = 0x89,
  DW_OP_breg26 = 0x8a,
  DW_OP_breg27 = 0x8b,
  DW_OP_breg28 = 0x8c,
  DW_OP_breg29 = 0x8d,
  DW_OP_breg30 = 0x8e,
  DW_OP_breg31 = 0x8f,
  DW_OP_regx = 0x90,
  DW_OP_fbreg = 0x91,
  DW_OP_bregx = 0x92,
  DW_OP_piece = 0x93,
  DW_OP_deref_size = 0x94,
  DW_OP_xderef_size = 0x95,
  DW_OP_nop = 0x96,
};

}  // namespace

Error DwarfExpr::Eval(Memory* mem, const Registers& regs, uint64_t initial_value,
                      uint64_t& result) {
  if (!expr_) {
    return Error("No DWARF expression to evaluate");
  }
  std::vector<uint64_t> stack;  // the evaluation stack
  stack.push_back(initial_value);

  uint64_t p = expr_begin_;
  while (p < expr_end_) {
    uint8_t op;
    if (auto err = expr_->Read(p, op); err.has_err()) {
      return err;
    }
    if (op >= DW_OP_breg0 && op <= DW_OP_breg31) {
      int64_t offset;
      if (auto err = expr_->ReadSLEB128(p, offset); err.has_err()) {
        return err;
      }
      uint64_t val;
      if (auto err = regs.Get(static_cast<RegisterID>(op - DW_OP_breg0), val); err.has_err()) {
        return err;
      }
      stack.push_back(val + offset);
      continue;
    }
    return Error("unsupported DWARF expression op: %hhu", op);
  }

  if (p != expr_end_) {
    return Error("invalid DWARF expression");
  }

  result = stack.back();
  return Success();
}

}  // namespace unwinder