src/mc/inspect/LocationList.cpp

   1 /* Copyright (c) 2004-2022. 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 "src/mc/inspect/LocationList.hpp"
   7 #include "src/mc/inspect/ObjectInformation.hpp"
   8 #include "src/mc/inspect/mc_dwarf.hpp"
   9
  10 #include "xbt/asserts.h"
  11 #include "xbt/log.h"
  12 #include "xbt/sysdep.h"
  13
  14 #include <cstddef>
  15 #include <cstdint>
  16 #include <libunwind.h>
  17 #include <utility>
  18
  19 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(mc_dwarf);
  20
  21 namespace simgrid::dwarf {
  22
  23 /** Resolve a location expression */
  24 Location resolve(simgrid::dwarf::DwarfExpression const& expression, simgrid::mc::ObjectInformation* object_info,
  25                  unw_cursor_t* c, void* frame_pointer_address, const simgrid::mc::AddressSpace* address_space)
  26 {
  27   simgrid::dwarf::ExpressionContext context;
  28   context.frame_base    = frame_pointer_address;
  29   context.cursor        = c;
  30   context.address_space = address_space;
  31   context.object_info   = object_info;
  32
  33   if (not expression.empty() && expression[0].atom >= DW_OP_reg0 && expression[0].atom <= DW_OP_reg31) {
  34     int dwarf_register = expression[0].atom - DW_OP_reg0;
  35     xbt_assert(c, "Missing frame context for register operation DW_OP_reg%i", dwarf_register);
  36     return Location(dwarf_register_to_libunwind(dwarf_register));
  37   }
  38
  39   simgrid::dwarf::ExpressionStack stack;
  40   simgrid::dwarf::execute(expression, context, stack);
  41   return Location((void*)stack.top());
  42 }
  43
  44 // TODO, move this in a method of LocationList
  45 static simgrid::dwarf::DwarfExpression const* find_expression(simgrid::dwarf::LocationList const& locations,
  46                                                               unw_word_t ip)
  47 {
  48   for (simgrid::dwarf::LocationListEntry const& entry : locations)
  49     if (entry.valid_for_ip(ip))
  50       return &entry.expression();
  51   return nullptr;
  52 }
  53
  54 Location resolve(simgrid::dwarf::LocationList const& locations, simgrid::mc::ObjectInformation* object_info,
  55                  unw_cursor_t* c, void* frame_pointer_address, const simgrid::mc::AddressSpace* address_space)
  56 {
  57   unw_word_t ip = 0;
  58   if (c)
  59     xbt_assert(unw_get_reg(c, UNW_REG_IP, &ip) == 0, "Could not resolve IP");
  60   simgrid::dwarf::DwarfExpression const* expression = find_expression(locations, ip);
  61   xbt_assert(expression != nullptr, "Could not resolve location");
  62   return simgrid::dwarf::resolve(*expression, object_info, c, frame_pointer_address, address_space);
  63 }
  64
  65 LocationList location_list(const simgrid::mc::ObjectInformation& info, Dwarf_Attribute& attr)
  66 {
  67   LocationList locations;
  68   std::ptrdiff_t offset = 0;
  69   while (true) {
  70     Dwarf_Addr base;
  71     Dwarf_Addr start;
  72     Dwarf_Addr end;
  73     Dwarf_Op* ops;
  74     std::size_t len;
  75
  76     offset = dwarf_getlocations(&attr, offset, &base, &start, &end, &ops, &len);
  77
  78     if (offset == -1)
  79       XBT_WARN("Error while loading location list: %s", dwarf_errmsg(-1));
  80     if (offset <= 0)
  81       break;
  82
  83     auto base_address = reinterpret_cast<std::uint64_t>(info.base_address());
  84
  85     LocationListEntry::range_type range;
  86     if (start == 0)
  87       // If start == 0, this is not a location list:
  88       range = {0, UINT64_MAX};
  89     else
  90       range = {base_address + start, base_address + end};
  91
  92     locations.emplace_back(DwarfExpression(ops, ops + len), range);
  93   }
  94
  95   return locations;
  96 }
  97 } // namespace simgrid::dwarf