X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/1610a3a014ca193868cd6ed987728201c15b423c..4bcfd40036f842e976d329cd0cee7349b8e0f4d6:/src/mc/inspect/DwarfExpression.hpp

diff --git a/src/mc/inspect/DwarfExpression.hpp b/src/mc/inspect/DwarfExpression.hpp
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+/* Copyright (c) 2015-2019. The SimGrid Team. All rights reserved.          */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+#ifndef SIMGRID_MC_DWARF_EXPRESSION_HPP
+#define SIMGRID_MC_DWARF_EXPRESSION_HPP
+
+#include <cstdint>
+#include <cstdlib>
+
+#include <stdexcept> // runtime_error
+#include <utility>
+#include <vector>
+
+#include <elfutils/libdw.h>
+#include <libunwind.h>
+
+#include "src/mc/AddressSpace.hpp"
+#include "src/mc/inspect/mc_dwarf.hpp"
+#include "src/mc/mc_forward.hpp"
+
+/** @file DwarfExpression.hpp
+ *
+ *  Evaluation of DWARF location expressions.
+ */
+
+namespace simgrid {
+namespace dwarf {
+
+/** A DWARF expression
+ *
+ *  DWARF defines a simple stack-based VM for evaluating expressions
+ *  (such as locations of variables, etc.): a DWARF expression is
+ *  just a sequence of dwarf instructions. We currently directly use
+ *  `Dwarf_Op` from `dwarf.h` for dwarf instructions.
+ */
+typedef std::vector<Dwarf_Op> DwarfExpression;
+
+/** Context of evaluation of a DWARF expression
+ *
+ *  Some DWARF instructions need to read the CPU registers,
+ *  the process memory, etc. All those informations are gathered in
+ *  the evaluation context.
+ */
+class ExpressionContext {
+public:
+  ExpressionContext()
+      : cursor(nullptr)
+      , frame_base(nullptr)
+      , address_space(nullptr)
+      , object_info(nullptr)
+      , process_index(simgrid::mc::ProcessIndexMissing)
+  {
+  }
+  /** CPU state (registers) */
+  unw_cursor_t* cursor;
+  void* frame_base;
+  /** Address space used to read memory */
+  simgrid::mc::AddressSpace* address_space;
+  simgrid::mc::ObjectInformation* object_info;
+  int process_index;
+};
+
+/** When an error happens in the execution of a DWARF expression */
+class evaluation_error : public std::runtime_error {
+public:
+  explicit evaluation_error(const char* what) : std::runtime_error(what) {}
+};
+
+/** A stack for evaluating a DWARF expression
+ *
+ *  DWARF expressions work by manipulating a stack of integer values.
+ */
+class ExpressionStack {
+public:
+  typedef std::uintptr_t value_type;
+  static const std::size_t max_size = 64;
+
+private:
+  // Values of the stack (the top is stack_[size_ - 1]):
+  uintptr_t stack_[max_size]{0};
+  size_t size_;
+
+public:
+  ExpressionStack() : size_(0) {}
+
+  // Access:
+  std::size_t size() const { return size_; }
+  bool empty() const { return size_ == 0; }
+  void clear() { size_ = 0; }
+  uintptr_t& operator[](int i) { return stack_[i]; }
+  uintptr_t const& operator[](int i) const { return stack_[i]; }
+
+  /** Top of the stack */
+  value_type& top()
+  {
+    if (size_ == 0)
+      throw evaluation_error("Empty stack");
+    return stack_[size_ - 1];
+  }
+
+  /** Access the i-th element from the top of the stack */
+  value_type& top(unsigned i)
+  {
+    if (size_ < i)
+      throw evaluation_error("Invalid element");
+    return stack_[size_ - 1 - i];
+  }
+
+  /** Push a value on the top of the stack */
+  void push(value_type value)
+  {
+    if (size_ == max_size)
+      throw evaluation_error("DWARF stack overflow");
+    stack_[size_++] = value;
+  }
+
+  /* Pop a value from the top of the stack */
+  value_type pop()
+  {
+    if (size_ == 0)
+      throw evaluation_error("DWARF stack underflow");
+    return stack_[--size_];
+  }
+
+  // These are DWARF operations (DW_OP_foo):
+
+  /* Push a copy of the top-value (DW_OP_dup) */
+  void dup() { push(top()); }
+
+  /* Swap the two top-most values */
+  void swap() { std::swap(top(), top(1)); }
+};
+
+/** Executes a DWARF expression
+ *
+ *  @param ops     DWARF expression instructions
+ *  @param n       number of instructions
+ *  @param context evaluation context (registers, memory, etc.)
+ *  @param stack   DWARf stack where the operations are executed
+ */
+void execute(const Dwarf_Op* ops, std::size_t n, ExpressionContext const& context, ExpressionStack& stack);
+
+/** Executes/evaluates a DWARF expression
+ *
+ *  @param expression DWARF expression to execute
+ *  @param context    evaluation context (registers, memory, etc.)
+ *  @param stack      DWARf stack where the operations are executed
+ */
+inline void execute(simgrid::dwarf::DwarfExpression const& expression, ExpressionContext const& context,
+                    ExpressionStack& stack)
+{
+  execute(expression.data(), expression.size(), context, stack);
+}
+
+} // namespace dwarf
+} // namespace simgrid
+
+#endif