Add instructions coverage statistics

report/data/instruction_coverage

@@ -0,0 +1,25 @@
+(54666427,
+ (1607, 67587841),
+ (1154, 13869),
+ {'UNDEFINED': 1698,
+  'SAME_VALUE': 0,
+  'OFFSET': 54666405,
+  'VAL_OFFSET': 0,
+  'REGISTER': 22,
+  'EXPRESSION': 12367,
+  'VAL_EXPRESSION': 0,
+  'ARCHITECTURAL': 0},
+ {'seen': 12922916, 'expr': 1502, 'offset': 12921414})
+
+(30038269,
+ (1603, 42959683),
+ (1114, 5977),
+ {'UNDEFINED': 1698,
+  'SAME_VALUE': 0,
+  'OFFSET': 30038255,
+  'VAL_OFFSET': 0,
+  'REGISTER': 14,
+  'EXPRESSION': 4475,
+  'VAL_EXPRESSION': 0,
+  'ARCHITECTURAL': 0},
+ {'seen': 12922916, 'expr': 1502, 'offset': 12921414})

report/report.tex

@@ -342,18 +342,14 @@ quite efficient, most of its optimization comes from fine-tuned code and good
 caching mechanisms. While parsing DWARF, \prog{libunwind} is forced to parse
 the relevant FDE from its start, until it finds the row it was seeking.
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\subsection{General statistics}
-\todo{}
-
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{DWARF semantics}\label{sec:semantics}
 
-We will now define semantics covering most of the operations used for
+We will now define semantics covering most of the operations used for FDEs
-CFI\todo{To be defined elsewhere in the report} described in the DWARF
+described in the DWARF standard~\cite{dwarf5std}, such as seen in
-standard~\cite{dwarf5std}, with the exception of DWARF expressions. These are
+Listing~\ref{lst:ex1_dwraw}, with the exception of DWARF expressions. These are
 not exhaustively treated because they are quite rich and would take a lot of
 time and space to formalize, and in the meantime are only seldom used (see the
 DWARF statistics regarding this).
@@ -634,7 +630,7 @@ a reasonable space loss was to compile directly the \ehframe{} into native
 machine code on the x86\_64 platform.
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\subsection{Compilation: \ehelfs}
+\subsection{Compilation: \ehelfs}\label{ssec:ehelfs}
 
 The rough idea of the compilation is to produce, out of the \ehframe{} section
 of a binary, C code that resembles the code shown in the DWARF semantics from
@@ -1006,7 +1002,116 @@ lot.
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \subsection{Instructions coverage}
-\todo{}
+
+In order to determine which proportion of real-world ELF instructions are
+covered by our compiler and \ehelfs.
+
+The method chosen was to randomly select 4000 ELFs among those present on a
+basic ArchLinux system setup, in the directories \texttt{/bin}, \texttt{/lib},
+\texttt{/usr/bin}, \texttt{/usr/lib} and their subdirectories, making sure
+those files were ELF64 files, then gathering statistics on those files.
+
+\begin{table}[h]
+    \centering
+    \begin{tabular}{r r r r r r r}
+        \toprule
+        \thead{} & \thead{Unsupported \\ register rule}
+            & \thead{Register \\ rules seen}
+            & \thead{\% \\ supp.}
+            & \thead{Unsupported \\ expression}
+            & \thead{Expressions \\ seen}
+            & \thead{\% \\ supp.}
+            \\
+        \midrule
+            \makecell{Only supp. \\ columns} &
+                1603 & 42959683 & 99.996\,\% &
+                1114 & 5977 & 81.4\,\%
+                \\
+            All columns &
+                1607 & 67587841 & 99.998\,\% &
+                1154 & 13869 & 91.7\,\%
+                \\
+        \bottomrule
+    \end{tabular}
+
+    \caption{Instructions coverage statistics}\label{table:instr_cov}
+\end{table}
+
+\begin{table}[h]
+    \centering
+    \begin{tabular}{r r r r r r}
+        \toprule
+        \thead{}
+            & \thead{\texttt{Undefined}}
+            & \thead{\texttt{Same\_value}}
+            & \thead{\texttt{Offset}}
+            & \thead{\texttt{Val\_offset}}
+            & \thead{\texttt{Register}}
+            \\
+        \midrule
+            \makecell{Only supp. \\ columns}
+                & 1698 (0.006\,\%)
+                & 0
+                & 30038255 (99.9\,\%)
+                & 0
+                & 14 (0\,\%)
+                \\
+            All columns
+                & 1698 (0.003\,\%)
+                & 0
+                & 54666405 (99.9\,\%)
+                & 0
+                & 22 (0\,\%)
+                \\
+        \bottomrule
+        \toprule
+        \thead{}
+            & \thead{\texttt{Expression}}
+            & \thead{\texttt{Val\_expression}}
+            & \thead{\texttt{Architectural}}
+            & & \thead{Total}
+            \\
+        \midrule
+            \makecell{Only supp. \\ columns}
+                & 4475 (0.015\,\%)
+                & 0
+                & 0
+                & & 30044442
+                \\
+            All columns
+                & 12367 (0.02\,\%)
+                & 0
+                & 0
+                & & 54680492
+                \\
+
+        \bottomrule
+    \end{tabular}
+
+    \caption{Instruction type statistics}\label{table:instr_types}
+\end{table}
+
+The Table~\ref{table:instr_cov} gives statistics about the proportion of
+instructions encountered that were not supported by \ehelfs. The first row is
+only concerned about the columns CFA, \reg{rip}, \reg{rsp}, \reg{rbp} and
+\reg{rbx} (the supported registers --~see Section~\ref{ssec:ehelfs}). The
+second row analyzes all the columns that were encountered, no matter whether
+supported or not.
+
+The Table~\ref{table:instr_types} analyzes the proportion of each command
+(\ie\ the formal way a register is set) for non-CFA columns in the sampled
+data. For a brief explanation, \texttt{Offset} means stored at offset from CFA,
+\texttt{Register} means the value from a machine register, \texttt{Expression}
+means stored at the value of an expression, and the \texttt{Val\_} prefix means
+that the value must not be dereferenced. Overall, it can be seen that
+supporting \texttt{Offset} already means supporting the vast majority of
+registers. The data gathered (not reproduced here) also suggests that
+supporting a few common expressions is enough to support most of them.
+
+It is also worth noting that of all the 4000 analyzed files, there are only 12
+that contained all the unsupported expressions seen, and only 24 that contained
+some unsupported instruction at all.
+
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%% End main text content %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -1020,8 +1125,8 @@ lot.
 \hfill \begin{minipage}{0.7\textwidth}
     \begin{flushright}
         \itshape{} \small{}
-        Unless otherwise explicitly stated, any image or source code snippet
+        Unless otherwise explicitly stated, any image, source code snippet or
-        from the present document can be reused freely by anyone.
+        table from the present document can be reused freely by anyone.
     \end{flushright}
 \end{minipage}
 

shared/report.bib

@@ -33,7 +33,7 @@
 }
 
 @article{dinechin2000exn,
-    title={C++ exception handling},
+    title={C++ exception handling \qtodo{CHECK}},
     author={De Dinechin, Christophe},
     journal={IEEE Concurrency},
     volume={8},