X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/8f327dfbe1524884e5a1bccaf90a0454c17567dc..debe4e5871c0c3d1c714bbb1bd28ba7147454aa5:/src/mc/DwarfExpression.cpp

diff --git a/src/mc/DwarfExpression.cpp b/src/mc/DwarfExpression.cpp
index 07b5f0d7cd..31852a6719 100644
--- a/src/mc/DwarfExpression.cpp
+++ b/src/mc/DwarfExpression.cpp
@@ -1,31 +1,24 @@
-/* Copyright (c) 2014-2015. The SimGrid Team.
- * All rights reserved.                                                     */
+/* Copyright (c) 2014-2019. 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. */
 
+#include <cstddef>
 #include <cstdint>
-#include <cstdarg>
 
-#include <dwarf.h>
-#include <elfutils/libdw.h>
-
-#include "mc_object_info.h"
-#include "mc_private.h"
-#include "mc/LocationList.hpp"
-#include "mc/AddressSpace.hpp"
-#include "mc/Frame.hpp"
-#include "mc/ObjectInformation.hpp"
-#include "mc/DwarfExpression.hpp"
-#include "mc_dwarf.hpp"
+#include "src/mc/AddressSpace.hpp"
+#include "src/mc/DwarfExpression.hpp"
+#include "src/mc/Frame.hpp"
+#include "src/mc/LocationList.hpp"
+#include "src/mc/ObjectInformation.hpp"
+#include "src/mc/mc_dwarf.hpp"
+#include "src/mc/mc_private.hpp"
 
 using simgrid::mc::remote;
 
 namespace simgrid {
 namespace dwarf {
 
-evaluation_error::~evaluation_error() noexcept(true) {}
-
 void execute(
   const Dwarf_Op* ops, std::size_t n,
   const ExpressionContext& context, ExpressionStack& stack)
@@ -33,6 +26,8 @@ void execute(
   for (size_t i = 0; i != n; ++i) {
     const Dwarf_Op *op = ops + i;
     std::uint8_t atom = op->atom;
+    intptr_t first;
+    intptr_t second;
 
     switch (atom) {
 
@@ -70,24 +65,33 @@ void execute(
     case DW_OP_breg29:
     case DW_OP_breg30:
     case DW_OP_breg31:{
+        // Push register + constant:
         int register_id = simgrid::dwarf::dwarf_register_to_libunwind(
           op->atom - DW_OP_breg0);
         unw_word_t res;
-        if (!context.cursor)
-          throw evaluation_error("Missin stack context");
+        if (not context.cursor)
+          throw evaluation_error("Missing stack context");
         unw_get_reg(context.cursor, register_id, &res);
         stack.push(res + op->number);
         break;
       }
 
-      // Push the CFA (Canonical Frame Addresse):
+      // Push the CFA (Canonical Frame Address):
     case DW_OP_call_frame_cfa:
       {
-        // UNW_X86_64_CFA does not return the CFA DWARF expects
-        // (it is a synonym for UNW_X86_64_RSP) so copy the cursor,
-        // unwind it once in order to find the parent SP:
-
-        if (!context.cursor)
+        /* See 6.4 of DWARF4 (http://dwarfstd.org/doc/DWARF4.pdf#page=140):
+         *
+         * > Typically, the CFA is defined to be the value of the stack
+         * > pointer at the call site in the previous frame (which may be
+         * > different from its value on entry to the current frame).
+         *
+         * We need to unwind the frame in order to get the SP of the parent
+         * frame.
+         *
+         * Warning: the CFA returned by libunwind (UNW_X86_64_RSP, etc.)
+         * is the SP of the *current* frame. */
+
+        if (not context.cursor)
           throw evaluation_error("Missint cursor");
 
         // Get frame:
@@ -109,7 +113,6 @@ void execute(
       // ***** Constants:
 
       // Short constant literals:
-      // DW_OP_lit15 pushed the 15 on the stack.
     case DW_OP_lit0:
     case DW_OP_lit1:
     case DW_OP_lit2:
@@ -142,13 +145,14 @@ void execute(
     case DW_OP_lit29:
     case DW_OP_lit30:
     case DW_OP_lit31:
+      // Push a literal/constant on the stack:
       stack.push(atom - DW_OP_lit0);
       break;
 
       // Address from the base address of this ELF object.
       // Push the address on the stack (base_address + argument).
     case DW_OP_addr: {
-      if (!context.object_info)
+      if (not context.object_info)
         throw evaluation_error("No base address");
       Dwarf_Off addr = (Dwarf_Off) (std::uintptr_t)
         context.object_info->base_address() + op->number;
@@ -183,9 +187,8 @@ void execute(
       stack.pop();
       break;
 
-      // Swap the two top-most value of the stack:
     case DW_OP_swap:
-      std::swap(stack.top(), stack.top(1));
+      stack.swap();
       break;
 
       // Duplicate the value under the top of the stack:
@@ -199,11 +202,15 @@ void execute(
       // (stack.top() += stack.before_top()).
 
     case DW_OP_plus:
-      stack.push(stack.pop() + stack.pop());
+      first  = stack.pop();
+      second = stack.pop();
+      stack.push(first + second);
       break;
 
     case DW_OP_mul:
-      stack.push(stack.pop() * stack.pop());
+      first  = stack.pop();
+      second = stack.pop();
+      stack.push(first * second);
       break;
 
     case DW_OP_plus_uconst:
@@ -219,19 +226,27 @@ void execute(
       break;
 
     case DW_OP_minus:
-      stack.push(stack.pop() - stack.pop());
+      first  = stack.pop();
+      second = stack.pop();
+      stack.push(second - first);
       break;
 
     case DW_OP_and:
-      stack.push(stack.pop() & stack.pop());
+      first  = stack.pop();
+      second = stack.pop();
+      stack.push(first & second);
       break;
 
     case DW_OP_or:
-      stack.push(stack.pop() | stack.pop());
+      first  = stack.pop();
+      second = stack.pop();
+      stack.push(first | second);
       break;
 
     case DW_OP_xor:
-      stack.push(stack.pop() ^ stack.pop());
+      first  = stack.pop();
+      second = stack.pop();
+      stack.push(first ^ second);
       break;
 
     case DW_OP_nop:
@@ -244,7 +259,7 @@ void execute(
 
     case DW_OP_deref:
       // Computed address:
-      if (!context.address_space)
+      if (not context.address_space)
         throw evaluation_error("Missing address space");
       context.address_space->read_bytes(
         &stack.top(), sizeof(uintptr_t), remote(stack.top()),