src/mc/inspect/DwarfExpression.cpp

   1 /* Copyright (c) 2014-2022. 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 namespace simgrid {
  19 namespace dwarf {
  20
  21 void execute(const Dwarf_Op* ops, std::size_t n, const ExpressionContext& context, ExpressionStack& stack)
  22 {
  23   for (size_t i = 0; i != n; ++i) {
  24     const Dwarf_Op* op = ops + i;
  25     std::uint8_t atom  = op->atom;
  26     intptr_t first;
  27     intptr_t second;
  28
  29     switch (atom) {
  30         // Push the CFA (Canonical Frame Address):
  31       case DW_OP_call_frame_cfa:
  32         /* See 6.4 of DWARF4 (http://dwarfstd.org/doc/DWARF4.pdf#page=140):
  33          *
  34          * > Typically, the CFA is defined to be the value of the stack
  35          * > pointer at the call site in the previous frame (which may be
  36          * > different from its value on entry to the current frame).
  37          *
  38          * We need to unwind the frame in order to get the SP of the parent
  39          * frame.
  40          *
  41          * Warning: the CFA returned by libunwind (UNW_X86_64_RSP, etc.)
  42          * is the SP of the *current* frame. */
  43         if (context.cursor) {
  44           // Get frame:
  45           unw_cursor_t cursor = *(context.cursor);
  46           unw_step(&cursor);
  47
  48           unw_word_t res;
  49           unw_get_reg(&cursor, UNW_REG_SP, &res);
  50           stack.push(res);
  51           break;
  52         }
  53         throw evaluation_error("Missing cursor");
  54
  55         // Frame base:
  56       case DW_OP_fbreg:
  57         stack.push((std::uintptr_t)context.frame_base + op->number);
  58         break;
  59
  60         // Address from the base address of this ELF object.
  61         // Push the address on the stack (base_address + argument).
  62       case DW_OP_addr:
  63         if (context.object_info) {
  64           Dwarf_Off addr = (Dwarf_Off)(std::uintptr_t)context.object_info->base_address() + op->number;
  65           stack.push(addr);
  66           break;
  67         }
  68         throw evaluation_error("No base address");
  69
  70         // ***** Stack manipulation:
  71
  72         // Push another copy/duplicate the value at the top of the stack:
  73       case DW_OP_dup:
  74         stack.dup();
  75         break;
  76
  77         // Pop/drop the top of the stack:
  78       case DW_OP_drop:
  79         (void)stack.pop();
  80         break;
  81
  82       case DW_OP_swap:
  83         stack.swap();
  84         break;
  85
  86         // Duplicate the value under the top of the stack:
  87       case DW_OP_over:
  88         stack.push(stack.top(1));
  89         break;
  90
  91         // ***** Operations:
  92         // Those usually take the top of the stack and the next value as argument
  93         // and replace the top of the stack with the computed value
  94         // (stack.top() += stack.before_top()).
  95
  96       case DW_OP_plus:
  97         first  = stack.pop();
  98         second = stack.pop();
  99         stack.push(first + second);
 100         break;
 101
 102       case DW_OP_mul:
 103         first  = stack.pop();
 104         second = stack.pop();
 105         stack.push(first * second);
 106         break;
 107
 108       case DW_OP_plus_uconst:
 109         stack.top() += op->number;
 110         break;
 111
 112       case DW_OP_not:
 113         stack.top() = ~stack.top();
 114         break;
 115
 116       case DW_OP_neg:
 117         stack.top() = -(intptr_t)stack.top();
 118         break;
 119
 120       case DW_OP_minus:
 121         first  = stack.pop();
 122         second = stack.pop();
 123         stack.push(second - first);
 124         break;
 125
 126       case DW_OP_and:
 127         first  = stack.pop();
 128         second = stack.pop();
 129         stack.push(first & second);
 130         break;
 131
 132       case DW_OP_or:
 133         first  = stack.pop();
 134         second = stack.pop();
 135         stack.push(first | second);
 136         break;
 137
 138       case DW_OP_xor:
 139         first  = stack.pop();
 140         second = stack.pop();
 141         stack.push(first ^ second);
 142         break;
 143
 144       case DW_OP_nop:
 145         break;
 146
 147         // ***** Deference (memory fetch)
 148
 149       case DW_OP_deref_size:
 150         throw evaluation_error("Unsupported operation");
 151
 152       case DW_OP_deref:
 153         // Computed address:
 154         if (not context.address_space)
 155           throw evaluation_error("Missing address space");
 156         context.address_space->read_bytes(&stack.top(), sizeof(uintptr_t), mc::remote(stack.top()));
 157         break;
 158
 159       default:
 160
 161         // Registers:
 162         if (static const std::unordered_set<uint8_t> registers =
 163                 {DW_OP_breg0,  DW_OP_breg1,  DW_OP_breg2,  DW_OP_breg3,  DW_OP_breg4,  DW_OP_breg5,  DW_OP_breg6,
 164                  DW_OP_breg7,  DW_OP_breg8,  DW_OP_breg9,  DW_OP_breg10, DW_OP_breg11, DW_OP_breg12, DW_OP_breg13,
 165                  DW_OP_breg14, DW_OP_breg15, DW_OP_breg16, DW_OP_breg17, DW_OP_breg18, DW_OP_breg19, DW_OP_breg20,
 166                  DW_OP_breg21, DW_OP_breg22, DW_OP_breg23, DW_OP_breg24, DW_OP_breg25, DW_OP_breg26, DW_OP_breg27,
 167                  DW_OP_breg28, DW_OP_breg29, DW_OP_breg30, DW_OP_breg31};
 168             registers.count(atom) > 0) {
 169           // Push register + constant:
 170           int register_id = dwarf_register_to_libunwind(op->atom - DW_OP_breg0);
 171           unw_word_t res;
 172           if (not context.cursor)
 173             throw evaluation_error("Missing stack context");
 174           unw_get_reg(context.cursor, register_id, &res);
 175           stack.push(res + op->number);
 176           break;
 177         }
 178
 179         // ***** Constants:
 180
 181         // Short constant literals:
 182         if (static const std::unordered_set<uint8_t> literals = {DW_OP_lit0,  DW_OP_lit1,  DW_OP_lit2,  DW_OP_lit3,
 183                                                                  DW_OP_lit4,  DW_OP_lit5,  DW_OP_lit6,  DW_OP_lit7,
 184                                                                  DW_OP_lit8,  DW_OP_lit9,  DW_OP_lit10, DW_OP_lit11,
 185                                                                  DW_OP_lit12, DW_OP_lit13, DW_OP_lit14, DW_OP_lit15,
 186                                                                  DW_OP_lit16, DW_OP_lit17, DW_OP_lit18, DW_OP_lit19,
 187                                                                  DW_OP_lit20, DW_OP_lit21, DW_OP_lit22, DW_OP_lit23,
 188                                                                  DW_OP_lit24, DW_OP_lit25, DW_OP_lit26, DW_OP_lit27,
 189                                                                  DW_OP_lit28, DW_OP_lit29, DW_OP_lit30, DW_OP_lit31};
 190             literals.count(atom) > 0) {
 191           // Push a literal/constant on the stack:
 192           stack.push(atom - DW_OP_lit0);
 193           break;
 194         }
 195
 196         // General constants:
 197         if (static const std::unordered_set<uint8_t> constants = {DW_OP_const1u, DW_OP_const2u, DW_OP_const4u,
 198                                                                   DW_OP_const8u, DW_OP_const1s, DW_OP_const2s,
 199                                                                   DW_OP_const4s, DW_OP_const8s, DW_OP_constu,
 200                                                                   DW_OP_consts};
 201             constants.count(atom) > 0) {
 202           // Push the constant argument on the stack.
 203           stack.push(op->number);
 204           break;
 205         }
 206
 207         // Not handled:
 208         throw evaluation_error("Unsupported operation");
 209     }
 210   }
 211 }
 212
 213 } // namespace dwarf
 214 } // namespace simgrid