src/mc/inspect/DwarfExpression.cpp

   1 /* Copyright (c) 2014-2020. The SimGrid Team. All rights reserved.          */
   2
   3 /* This program is free software; you can redistribute it and/or modify it
   4  * under the terms of the license (GNU LGPL) which comes with this package. */
   5
   6 #include <cstddef>
   7 #include <cstdint>
   8 #include <unordered_set>
   9
  10 #include "src/mc/AddressSpace.hpp"
  11 #include "src/mc/inspect/DwarfExpression.hpp"
  12 #include "src/mc/inspect/Frame.hpp"
  13 #include "src/mc/inspect/LocationList.hpp"
  14 #include "src/mc/inspect/ObjectInformation.hpp"
  15 #include "src/mc/inspect/mc_dwarf.hpp"
  16 #include "src/mc/mc_private.hpp"
  17
  18 using simgrid::mc::remote;
  19
  20 namespace simgrid {
  21 namespace dwarf {
  22
  23 void execute(const Dwarf_Op* ops, std::size_t n, const ExpressionContext& context, ExpressionStack& stack)
  24 {
  25   for (size_t i = 0; i != n; ++i) {
  26     const Dwarf_Op* op = ops + i;
  27     std::uint8_t atom  = op->atom;
  28     intptr_t first;
  29     intptr_t second;
  30
  31     switch (atom) {
  32
  33         // Push the CFA (Canonical Frame Address):
  34       case DW_OP_call_frame_cfa: {
  35         /* See 6.4 of DWARF4 (http://dwarfstd.org/doc/DWARF4.pdf#page=140):
  36          *
  37          * > Typically, the CFA is defined to be the value of the stack
  38          * > pointer at the call site in the previous frame (which may be
  39          * > different from its value on entry to the current frame).
  40          *
  41          * We need to unwind the frame in order to get the SP of the parent
  42          * frame.
  43          *
  44          * Warning: the CFA returned by libunwind (UNW_X86_64_RSP, etc.)
  45          * is the SP of the *current* frame. */
  46
  47         if (not context.cursor)
  48           throw evaluation_error("Missint cursor");
  49
  50         // Get frame:
  51         unw_cursor_t cursor = *(context.cursor);
  52         unw_step(&cursor);
  53
  54         unw_word_t res;
  55         unw_get_reg(&cursor, UNW_REG_SP, &res);
  56         stack.push(res);
  57         break;
  58       }
  59
  60         // Frame base:
  61       case DW_OP_fbreg:
  62         stack.push((std::uintptr_t)context.frame_base + op->number);
  63         break;
  64
  65         // Address from the base address of this ELF object.
  66         // Push the address on the stack (base_address + argument).
  67       case DW_OP_addr: {
  68         if (not context.object_info)
  69           throw evaluation_error("No base address");
  70         Dwarf_Off addr = (Dwarf_Off)(std::uintptr_t)context.object_info->base_address() + op->number;
  71         stack.push(addr);
  72         break;
  73       }
  74
  75
  76         // ***** Stack manipulation:
  77
  78         // Push another copy/duplicate the value at the top of the stack:
  79       case DW_OP_dup:
  80         stack.dup();
  81         break;
  82
  83         // Pop/drop the top of the stack:
  84       case DW_OP_drop:
  85         stack.pop();
  86         break;
  87
  88       case DW_OP_swap:
  89         stack.swap();
  90         break;
  91
  92         // Duplicate the value under the top of the stack:
  93       case DW_OP_over:
  94         stack.push(stack.top(1));
  95         break;
  96
  97         // ***** Operations:
  98         // Those usually take the top of the stack and the next value as argument
  99         // and replace the top of the stack with the computed value
 100         // (stack.top() += stack.before_top()).
 101
 102       case DW_OP_plus:
 103         first  = stack.pop();
 104         second = stack.pop();
 105         stack.push(first + second);
 106         break;
 107
 108       case DW_OP_mul:
 109         first  = stack.pop();
 110         second = stack.pop();
 111         stack.push(first * second);
 112         break;
 113
 114       case DW_OP_plus_uconst:
 115         stack.top() += op->number;
 116         break;
 117
 118       case DW_OP_not:
 119         stack.top() = ~stack.top();
 120         break;
 121
 122       case DW_OP_neg:
 123         stack.top() = -(intptr_t)stack.top();
 124         break;
 125
 126       case DW_OP_minus:
 127         first  = stack.pop();
 128         second = stack.pop();
 129         stack.push(second - first);
 130         break;
 131
 132       case DW_OP_and:
 133         first  = stack.pop();
 134         second = stack.pop();
 135         stack.push(first & second);
 136         break;
 137
 138       case DW_OP_or:
 139         first  = stack.pop();
 140         second = stack.pop();
 141         stack.push(first | second);
 142         break;
 143
 144       case DW_OP_xor:
 145         first  = stack.pop();
 146         second = stack.pop();
 147         stack.push(first ^ second);
 148         break;
 149
 150       case DW_OP_nop:
 151         break;
 152
 153         // ***** Deference (memory fetch)
 154
 155       case DW_OP_deref_size:
 156         throw evaluation_error("Unsupported operation");
 157
 158       case DW_OP_deref:
 159         // Computed address:
 160         if (not context.address_space)
 161           throw evaluation_error("Missing address space");
 162         context.address_space->read_bytes(&stack.top(), sizeof(uintptr_t), remote(stack.top()));
 163         break;
 164
 165       default:
 166
 167         // Registers:
 168         static const std::unordered_set<uint8_t> registers = {
 169             DW_OP_breg0,  DW_OP_breg1,  DW_OP_breg2,  DW_OP_breg3,  DW_OP_breg4,  DW_OP_breg5,  DW_OP_breg6,
 170             DW_OP_breg7,  DW_OP_breg8,  DW_OP_breg9,  DW_OP_breg10, DW_OP_breg11, DW_OP_breg12, DW_OP_breg13,
 171             DW_OP_breg14, DW_OP_breg15, DW_OP_breg16, DW_OP_breg17, DW_OP_breg18, DW_OP_breg19, DW_OP_breg20,
 172             DW_OP_breg21, DW_OP_breg22, DW_OP_breg23, DW_OP_breg24, DW_OP_breg25, DW_OP_breg26, DW_OP_breg27,
 173             DW_OP_breg28, DW_OP_breg29, DW_OP_breg30, DW_OP_breg31};
 174         if (registers.count(atom) > 0) {
 175           // Push register + constant:
 176           int register_id = simgrid::dwarf::dwarf_register_to_libunwind(op->atom - DW_OP_breg0);
 177           unw_word_t res;
 178           if (not context.cursor)
 179             throw evaluation_error("Missing stack context");
 180           unw_get_reg(context.cursor, register_id, &res);
 181           stack.push(res + op->number);
 182           break;
 183         }
 184
 185         // ***** Constants:
 186
 187         // Short constant literals:
 188         static const std::unordered_set<uint8_t> literals = {
 189             DW_OP_lit0,  DW_OP_lit1,  DW_OP_lit2,  DW_OP_lit3,  DW_OP_lit4,  DW_OP_lit5,  DW_OP_lit6,  DW_OP_lit7,
 190             DW_OP_lit8,  DW_OP_lit9,  DW_OP_lit10, DW_OP_lit11, DW_OP_lit12, DW_OP_lit13, DW_OP_lit14, DW_OP_lit15,
 191             DW_OP_lit16, DW_OP_lit17, DW_OP_lit18, DW_OP_lit19, DW_OP_lit20, DW_OP_lit21, DW_OP_lit22, DW_OP_lit23,
 192             DW_OP_lit24, DW_OP_lit25, DW_OP_lit26, DW_OP_lit27, DW_OP_lit28, DW_OP_lit29, DW_OP_lit30, DW_OP_lit31};
 193         if (literals.count(atom) > 0) {
 194           // Push a literal/constant on the stack:
 195           stack.push(atom - DW_OP_lit0);
 196           break;
 197         }
 198
 199         // General constants:
 200         static const std::unordered_set<uint8_t> constants = {
 201             DW_OP_const1u, DW_OP_const2u, DW_OP_const4u, DW_OP_const8u, DW_OP_const1s,
 202             DW_OP_const2s, DW_OP_const4s, DW_OP_const8s, DW_OP_constu,  DW_OP_consts};
 203         if (constants.count(atom) > 0) {
 204           // Push the constant argument on the stack.
 205           stack.push(op->number);
 206           break;
 207         }
 208
 209         // Not handled:
 210         throw evaluation_error("Unsupported operation");
 211     }
 212   }
 213 }
 214
 215 } // namespace dwarf
 216 } // namespace simgrid