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parents:
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\documentclass[dvipsnames,14pt,t]{beamer}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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\usepackage{../slides}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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\usepackage{../langs}
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\usepackage{../data}
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\usepackage{../graphics}
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\usepackage{../grammar}
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\usepackage{soul}
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\usepackage{mathpartir}
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% beamer stuff
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\renewcommand{\slidecaption}{CFL 09, King's College London}
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\newcommand{\bl}[1]{\textcolor{blue}{#1}}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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\begin{document}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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\begin{frame}[t]
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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\frametitle{%
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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\begin{tabular}{@ {}c@ {}}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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\\[-3mm]
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\LARGE Compilers and \\[-2mm]
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\LARGE Formal Languages (9)\\[3mm]
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65
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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\end{tabular}}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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\normalsize
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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\begin{center}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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\begin{tabular}{ll}
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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Email: & christian.urban at kcl.ac.uk\\
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Office: & N\liningnums{7.07} (North Wing, Bush House)\\
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Slides: & KEATS (also homework is there)\\
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\end{tabular}
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\end{center}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\begin{frame}[t]
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\frametitle{While Language}
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\begin{center}
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\bl{\begin{tabular}{@{}lcl@{}}
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\\[-12mm]
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\meta{Stmt} & $::=$ & $\texttt{skip}$\\
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& $|$ & \textit{Id}\;\texttt{:=}\;\meta{AExp}\\
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& $|$ & \texttt{if}\; \meta{BExp} \;\texttt{then}\; \meta{Block} \;\texttt{else}\; \meta{Block}\\
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& $|$ & \texttt{while}\; \meta{BExp} \;\texttt{do}\; \meta{Block}\\
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& $|$ & \texttt{read}\;\textit{Id}\\
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& $|$ & \texttt{write}\;\textit{Id}\\
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& $|$ & \texttt{write}\;\textit{String}\medskip\\
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\meta{Stmts} & $::=$ & \meta{Stmt} \;\texttt{;}\; \meta{Stmts} $|$ \meta{Stmt}\medskip\\
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\meta{Block} & $::=$ & \texttt{\{}\,\meta{Stmts}\,\texttt{\}} $|$ \meta{Stmt}\medskip\\
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\meta{AExp} & $::=$ & \ldots\\
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\meta{BExp} & $::=$ & \ldots\\
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\end{tabular}}
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\end{center}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\begin{frame}[c]
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\frametitle{\begin{tabular}{c}Fibonacci Numbers\end{tabular}}
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\mbox{}\\[-18mm]\mbox{}
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{\lstset{language=While}\fontsize{10}{12}\selectfont
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\texttt{\lstinputlisting{../progs/fib.while}}}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\begin{frame}[c,fragile]
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\frametitle{BF***}
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some big array, say \texttt{a}; 7 (8) instructions:
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\begin{itemize}
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\item \texttt{>} move \texttt{ptr++}
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\item \texttt{<} move \texttt{ptr-{}-}
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\item \texttt{+} add \texttt{a[ptr]++}
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\item \texttt{-} subtract \texttt{a[ptr]-{}-}
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\item \texttt{.} print out \texttt{a[ptr]} as ASCII
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\item \texttt{[} if \texttt{a[ptr] == 0} jump just after the corresponding \texttt{]}; otherwise \texttt{ptr++}
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\item \texttt{]} if \texttt{a[ptr] != 0} jump just after the corresponding \texttt{[}; otherwise \texttt{ptr++}
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\end{itemize}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\begin{frame}[c,fragile]
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\frametitle{Arrays in While}
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|
609
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\begin{itemize}
|
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\item \texttt{new arr[15000]}\medskip
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\item \texttt{x := 3 + arr[3 + y]}\medskip
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\item \texttt{arr[42 * n] := ...}
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\end{itemize}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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|
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\begin{frame}[c,fragile]
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\frametitle{New Arrays}
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\begin{lstlisting}[mathescape,numbers=none,language=While]
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new arr[number]
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\end{lstlisting}\bigskip\bigskip
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\begin{lstlisting}[mathescape,numbers=none,language=While]
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ldc number
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newarray int
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astore loc_var
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\end{lstlisting}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\begin{frame}[c,fragile]
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\frametitle{Array Update}
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\begin{lstlisting}[mathescape,numbers=none,language=While]
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arr[...] :=
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\end{lstlisting}\bigskip\bigskip
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132 |
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\begin{lstlisting}[mathescape,numbers=none,language=While]
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aload loc_var
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index_aexp
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value_aexp
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137 |
iastore
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138 |
\end{lstlisting}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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143 |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
145 |
\begin{frame}[c,fragile]
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\frametitle{Array Lookup in AExp}
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147 |
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|
148 |
\begin{lstlisting}[mathescape,numbers=none,language=While]
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149 |
...arr[...]...
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150 |
\end{lstlisting}\bigskip\bigskip
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|
151 |
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|
152 |
\begin{lstlisting}[mathescape,numbers=none,language=While]
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153 |
aload loc_var
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|
154 |
index_aexp
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155 |
iaload
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156 |
\end{lstlisting}
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157 |
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158 |
|
|
159 |
\end{frame}
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|
160 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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610
|
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
163 |
\mode<presentation>{
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164 |
\begin{frame}[c]
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165 |
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\large\bf
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|
167 |
Using a compiler, \\how can you mount the\\ perfect attack against a system?
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\end{frame}}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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171 |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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173 |
\mode<presentation>{
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174 |
\begin{frame}[c]
|
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175 |
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176 |
{\large\bf
|
|
177 |
What is a \alert{perfect} attack?}\bigskip
|
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178 |
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\begin{enumerate}
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180 |
\item you can potentially completely take over a target system
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181 |
\item your attack is (nearly) undetectable
|
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182 |
\item the victim has (almost) no chance to recover
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183 |
\end{enumerate}
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184 |
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185 |
\end{frame}}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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187 |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
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189 |
\mode<presentation>{
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190 |
\begin{frame}[c]
|
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191 |
|
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192 |
|
|
193 |
\begin{center}
|
|
194 |
\begin{tikzpicture}[scale=1]
|
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195 |
|
|
196 |
\onslide<1->{
|
|
197 |
\node (A) at (0,0) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=17mm] {};
|
|
198 |
\node [below right] at (A.north west) {\footnotesize\begin{tabular}{@{}l@{}}
|
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\only<1,2>{clean}\only<3->{\alert{hacked}}\\compiler\end{tabular}};}
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200 |
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201 |
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\onslide<2->{
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\node (B) at (-2,2) [draw=black, rectangle, very thick, minimum height=10mm, minimum width=12mm] {};
|
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\node [below right] at (B.north west) {\footnotesize\begin{tabular}{@{}l@{}}login\\(src)\end{tabular}};
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205 |
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\node (C) at (2,2) [draw=black, rectangle, very thick, minimum height=10mm, minimum width=12mm] {};
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\node [below right] at (C.north west) {\footnotesize\begin{tabular}{@{}l@{}}login\\(bin)\end{tabular}};
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208 |
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\draw[->, line width=2mm] (B) -- (C);
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}
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211 |
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\onslide<3->{\node [above left=-1.5mm] at (C.south east) {\footnotesize \alert{$\blacksquare$}};}
|
|
213 |
|
|
214 |
\end{tikzpicture}
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|
215 |
\end{center}
|
|
216 |
|
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217 |
\end{frame}}
|
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218 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
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219 |
|
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220 |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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222 |
\mode<presentation>{
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223 |
\begin{frame}[c]
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224 |
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225 |
\begin{center}
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226 |
\begin{tikzpicture}[scale=1]
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227 |
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228 |
\onslide<1->{
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|
229 |
\node (A) at (0,0) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
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230 |
\node [below right] at (A.north west) {\small V0.01};
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231 |
\node [below right] (A1) at (A.south west) {\small Scala};
|
|
232 |
\node [below right] (A1) at (A1.south west) {\small\textcolor{gray}{host language}};
|
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233 |
\node [above right] at (A.north west) {my compiler (src)};}
|
|
234 |
|
|
235 |
\onslide<2->{
|
|
236 |
\node (B) at (1.8,0) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
|
237 |
\node [below right] at (B.north west) {\small V0.02};
|
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\node [below right] at (B.south west) {\small Scala};
|
|
239 |
\node at (3,0) {\ldots};
|
|
240 |
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\node (C) at (5,0) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
|
242 |
\node [below right] at (C.north west) {\small V1.00};
|
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243 |
\node [below right] at (C.south west) {\small Scala};}
|
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244 |
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|
245 |
\onslide<3->{
|
|
246 |
\node (D) at (6.8,0) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
|
247 |
\node [below right] at (D.north west) {\small V1.00};
|
|
248 |
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|
249 |
\node (E) at (6.8,2) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
|
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\node [below right] at (E.north west) {\small V1.01};}
|
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251 |
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|
252 |
\onslide<4->{
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|
253 |
\node (F) at (8.6,0) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
|
254 |
\node [below right] at (F.north west) {\small V1.01};
|
|
255 |
|
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256 |
\node (G) at (8.6,2) [draw=black, rectangle, very thick, minimum height=18mm, minimum width=14mm] {};
|
|
257 |
\node [below right] at (G.north west) {\small V1.02};
|
|
258 |
\node at (9.8,0) {\ldots};
|
|
259 |
\node at (9.8,2) {\ldots};
|
|
260 |
\node at (8,-2) {\textcolor{gray}{\begin{tabular}{@{}l@{}}no host language\\needed\end{tabular}}};
|
|
261 |
}
|
|
262 |
|
|
263 |
\end{tikzpicture}
|
|
264 |
\end{center}
|
|
265 |
|
|
266 |
\end{frame}}
|
|
267 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
268 |
|
|
269 |
|
|
270 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
271 |
\mode<presentation>{
|
|
272 |
\begin{frame}<1-3>
|
|
273 |
\frametitle{\LARGE\begin{tabular}{c}Hacking Compilers
|
|
274 |
\end{tabular}}
|
|
275 |
|
|
276 |
%Why is it so paramount to have a small trusted code base (TCB)?
|
|
277 |
\bigskip\bigskip
|
|
278 |
|
|
279 |
\begin{columns}
|
|
280 |
\begin{column}{2.7cm}
|
|
281 |
\begin{minipage}{2.5cm}%
|
|
282 |
\begin{tabular}{c@ {}}
|
|
283 |
\includegraphics[scale=0.2]{../pics/ken-thompson.jpg}\\[-1.8mm]
|
|
284 |
\footnotesize Ken Thompson\\[-1.8mm]
|
|
285 |
\footnotesize Turing Award, 1983\\
|
|
286 |
\end{tabular}
|
|
287 |
\end{minipage}
|
|
288 |
\end{column}
|
|
289 |
\begin{column}{9cm}
|
|
290 |
\begin{tabular}{l@ {\hspace{1mm}}p{8cm}}
|
|
291 |
|
|
292 |
& Ken Thompson showed how to hide a Trojan Horse in a
|
|
293 |
compiler \textcolor{red}{without} leaving any traces in the source code.\\[2mm]
|
|
294 |
|
|
295 |
& No amount of source level verification will protect
|
|
296 |
you from such Thompson-hacks.\\[2mm]
|
|
297 |
|
|
298 |
\end{tabular}
|
|
299 |
\end{column}
|
|
300 |
\end{columns}
|
|
301 |
|
|
302 |
\only<2>{
|
|
303 |
\begin{textblock}{6}(4,2)
|
|
304 |
\begin{tikzpicture}
|
|
305 |
\draw (0,0) node[inner sep=3mm,fill=cream, ultra thick, draw=red, rounded corners=2mm]
|
|
306 |
{\normalsize
|
|
307 |
\begin{minipage}{8cm}
|
|
308 |
\begin{quote}
|
|
309 |
\includegraphics[scale=0.05]{../pics/evil.png}
|
|
310 |
\begin{enumerate}
|
|
311 |
\item[1)] Assume you ship the compiler as binary and also with sources.
|
|
312 |
\item[2)] Make the compiler aware when it compiles itself.
|
|
313 |
\item[3)] Add the Trojan horse.
|
|
314 |
\item[4)] Compile.
|
|
315 |
\item[5)] Delete Trojan horse from the sources of the compiler.
|
|
316 |
\item[6)] Go on holiday for the rest of your life. ;o)\\[-7mm]\mbox{}
|
|
317 |
\end{enumerate}
|
|
318 |
\end{quote}
|
|
319 |
\end{minipage}};
|
|
320 |
\end{tikzpicture}
|
|
321 |
\end{textblock}}
|
|
322 |
|
|
323 |
\end{frame}}
|
|
324 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
325 |
|
|
326 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
327 |
\begin{frame}[c]
|
|
328 |
|
|
329 |
\begin{center}
|
|
330 |
\includegraphics[scale=0.6]{../pics/bridge-limits.png}
|
|
331 |
\end{center}
|
|
332 |
|
|
333 |
\end{frame}
|
|
334 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
335 |
|
|
336 |
|
|
337 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
338 |
\begin{frame}[c]
|
|
339 |
\frametitle{Compilers \& Boeings 777}
|
|
340 |
|
|
341 |
First flight in 1994. They want to achieve triple redundancy in hardware
|
|
342 |
faults.\bigskip
|
|
343 |
|
|
344 |
They compile 1 Ada program to\medskip
|
|
345 |
|
|
346 |
\begin{itemize}
|
|
347 |
\item Intel 80486
|
|
348 |
\item Motorola 68040 (old Macintosh's)
|
|
349 |
\item AMD 29050 (RISC chips used often in laser printers)
|
|
350 |
\end{itemize}\medskip
|
|
351 |
|
|
352 |
using 3 independent compilers.\bigskip\pause
|
|
353 |
|
|
354 |
\small Airbus uses C and static analysers. Recently started using CompCert.
|
|
355 |
|
|
356 |
\end{frame}
|
|
357 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
358 |
|
|
359 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
360 |
\begin{frame}[c]
|
|
361 |
\frametitle{Goal}
|
|
362 |
|
|
363 |
Remember the Bridges example?
|
|
364 |
|
|
365 |
\begin{itemize}
|
|
366 |
\item Can we look at our programs and somehow ensure
|
|
367 |
they are bug free/correct?\pause\bigskip
|
|
368 |
|
|
369 |
\item Very hard: Anything interesting about programs is equivalent
|
|
370 |
to the Halting Problem, which is undecidable.\pause\bigskip
|
|
371 |
|
|
372 |
\item \alert{Solution:} We avoid this ``minor'' obstacle by
|
|
373 |
being as close as possible of deciding the halting
|
|
374 |
problem, without actually deciding the halting problem.
|
|
375 |
\small$\quad\Rightarrow$ yes, no, don't know (static analysis)
|
|
376 |
\end{itemize}
|
|
377 |
|
|
378 |
\end{frame}
|
|
379 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
380 |
|
|
381 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
382 |
\begin{frame}[c]
|
|
383 |
\frametitle{What is Static Analysis?}
|
|
384 |
|
|
385 |
\begin{center}
|
|
386 |
\includegraphics[scale=0.4]{../pics/state.png}
|
|
387 |
\end{center}
|
|
388 |
|
|
389 |
\begin{itemize}
|
|
390 |
\item depending on some initial input, a program
|
|
391 |
(behaviour) will ``develop'' over time.
|
|
392 |
\end{itemize}
|
|
393 |
|
|
394 |
\end{frame}
|
|
395 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
396 |
|
|
397 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
398 |
\begin{frame}[c]
|
|
399 |
\frametitle{What is Static Analysis?}
|
|
400 |
|
|
401 |
\begin{center}
|
|
402 |
\includegraphics[scale=0.4]{../pics/state2.png}
|
|
403 |
\end{center}
|
|
404 |
|
|
405 |
\end{frame}
|
|
406 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
407 |
|
|
408 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
409 |
\begin{frame}[c]
|
|
410 |
\frametitle{What is Static Analysis?}
|
|
411 |
|
|
412 |
\begin{center}
|
|
413 |
\includegraphics[scale=0.4]{../pics/state3.jpg}
|
|
414 |
\end{center}
|
|
415 |
|
|
416 |
\end{frame}
|
|
417 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
418 |
|
|
419 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
420 |
\begin{frame}[c]
|
|
421 |
\frametitle{What is Static Analysis?}
|
|
422 |
|
|
423 |
\begin{center}
|
|
424 |
\includegraphics[scale=0.4]{../pics/state4.jpg}
|
|
425 |
\end{center}
|
|
426 |
|
|
427 |
\begin{itemize}
|
|
428 |
\item to be avoided
|
|
429 |
\end{itemize}
|
|
430 |
|
|
431 |
\end{frame}
|
|
432 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
433 |
|
|
434 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
435 |
\begin{frame}[c]
|
|
436 |
\frametitle{What is Static Analysis?}
|
|
437 |
|
|
438 |
\begin{center}
|
|
439 |
\includegraphics[scale=0.4]{../pics/state5.png}
|
|
440 |
\end{center}
|
|
441 |
|
|
442 |
\begin{itemize}
|
|
443 |
\item this needs more work
|
|
444 |
\end{itemize}
|
|
445 |
|
|
446 |
\end{frame}
|
|
447 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
448 |
|
|
449 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
450 |
\begin{frame}[c]
|
|
451 |
\frametitle{What is Static Analysis?}
|
|
452 |
|
|
453 |
\begin{center}
|
|
454 |
\includegraphics[scale=0.4]{../pics/state6.png}
|
|
455 |
\end{center}
|
|
456 |
|
|
457 |
\end{frame}
|
|
458 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
459 |
|
|
460 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
461 |
\begin{frame}[c,fragile]
|
|
462 |
\frametitle{\Large\begin{tabular}{c}Concrete Example:\\[-1mm]
|
|
463 |
Are Vars Definitely Initialised?\end{tabular}}
|
|
464 |
|
|
465 |
Assuming \texttt{x} is initialised, what about \texttt{y}?\bigskip
|
|
466 |
|
|
467 |
Prog.~1:\\
|
|
468 |
\begin{lstlisting}[numbers=none,
|
|
469 |
basicstyle=\ttfamily,
|
|
470 |
language=While,xleftmargin=3mm]
|
|
471 |
if x < 1 then y := x else y := x + 1;
|
|
472 |
y := y + 1
|
|
473 |
\end{lstlisting}\medskip
|
|
474 |
|
|
475 |
Prog.~2:\\
|
|
476 |
\begin{lstlisting}[numbers=none,
|
|
477 |
basicstyle=\ttfamily,
|
|
478 |
language=While,xleftmargin=3mm]
|
|
479 |
if x < x then y := y + 1 else y := x;
|
|
480 |
y := y + 1
|
|
481 |
\end{lstlisting}
|
|
482 |
|
|
483 |
\end{frame}
|
|
484 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
485 |
|
|
486 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
487 |
\begin{frame}[c,fragile]
|
|
488 |
\frametitle{\Large\begin{tabular}{c}Concrete Example:\\[-1mm]
|
|
489 |
Are Vars Definitely Initialised?\end{tabular}}
|
|
490 |
|
|
491 |
What should the rules be for deciding when a
|
|
492 |
variable is initialised?\bigskip\pause
|
|
493 |
|
|
494 |
\begin{itemize}
|
|
495 |
\item variable \texttt{x} is definitely initialized after
|
|
496 |
\texttt{skip}\\
|
|
497 |
iff \texttt{x} is definitely initialized before \texttt{skip}.
|
|
498 |
\end{itemize}
|
|
499 |
|
|
500 |
\end{frame}
|
|
501 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
502 |
|
|
503 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
504 |
\begin{frame}[c,fragile]
|
|
505 |
% \frametitle{\Large\begin{tabular}{c}Concrete Example:\\[-1mm]
|
|
506 |
% Are Vars Definitely Initialised?\end{tabular}}
|
|
507 |
|
|
508 |
$\bl{A}$ is the set of definitely defined variables:
|
|
509 |
|
|
510 |
\begin{center}
|
|
511 |
\begin{tabular}{c}
|
612
|
512 |
\bl{\infer{\mbox{}}{A\triangleright\texttt{skip}\triangleright{}A}}\qquad
|
|
513 |
\bl{\infer{vars(a) \subseteq A}{A\triangleright
|
|
514 |
(\texttt{x\,:=\,a})\triangleright\{x\}\cup A}}
|
610
|
515 |
\medskip\\\pause
|
|
516 |
|
612
|
517 |
\bl{\infer{A_1\triangleright{}s_1\triangleright{}A_2
|
|
518 |
\quad A_2\triangleright{}s_2\triangleright{}A_3}
|
|
519 |
{A_1\triangleright{}(s_1 ; s_2)\triangleright{}A_3}}
|
610
|
520 |
\medskip\\\pause
|
|
521 |
|
612
|
522 |
\bl{\infer{vars(b)\subseteq A\quad A\triangleright{}s_1\triangleright{}A_1
|
|
523 |
\quad A\triangleright{}s_2\triangleright{}A_2}
|
|
524 |
{A\triangleright(\texttt{if}\;b\;\texttt{then}\;s_1\;\texttt{else}\;s_2)\triangleright{}A_1\cap A_2}}
|
610
|
525 |
\medskip\\\pause
|
|
526 |
|
612
|
527 |
\bl{\infer{vars(b)\subseteq A\quad A\triangleright{}s\triangleright{}A'}
|
|
528 |
{A\triangleright(\texttt{while}\;b\;\texttt{do}\;s)\triangleright{}A}}\pause
|
610
|
529 |
\end{tabular}
|
|
530 |
\end{center}
|
|
531 |
|
|
532 |
\hfill we start with $\bl{A = \{\}}$
|
|
533 |
\end{frame}
|
|
534 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
535 |
|
310
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
536 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
537 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
538 |
\begin{frame}[c]
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
539 |
\frametitle{Dijkstra on Testing}
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
540 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
541 |
\begin{bubble}[10cm]
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
542 |
``Program testing can be a very effective way to show the
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
543 |
presence of bugs, but it is hopelessly inadequate for showing
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
544 |
their absence.''
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
545 |
\end{bubble}\bigskip
|
609
|
546 |
|
|
547 |
\small
|
|
548 |
What is good about compilers: the either seem to work,
|
|
549 |
or go horribly wrong (most of the time).
|
|
550 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
551 |
\end{frame}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
552 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
553 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
554 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
555 |
\begin{frame}[c]
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
556 |
\frametitle{\Large Proving Programs to be Correct}
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
557 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
558 |
\begin{bubble}[10cm]
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
559 |
\small
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
560 |
{\bf Theorem:} There are infinitely many prime
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
561 |
numbers.\medskip\\
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
562 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
563 |
{\bf Proof} \ldots\\
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
564 |
\end{bubble}\bigskip
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
565 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
566 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
567 |
similarly\bigskip
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
568 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
569 |
\begin{bubble}[10cm]
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
570 |
\small
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
571 |
{\bf Theorem:} The program is doing what
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
572 |
it is supposed to be doing.\medskip
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
573 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
574 |
{\bf Long, long proof} \ldots\\
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
575 |
\end{bubble}\bigskip\medskip
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
576 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
577 |
\small This can be a gigantic proof. The only hope is to have
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
578 |
help from the computer. `Program' is here to be understood to be
|
609
|
579 |
quite general (compiler, OS, \ldots).
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
580 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
581 |
\end{frame}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
582 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
583 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
584 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
585 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
586 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
587 |
\begin{frame}[c]
|
609
|
588 |
\frametitle{Can This Be Done?}
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
589 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
590 |
\begin{itemize}
|
609
|
591 |
\item in 2008, verification of a small C-compiler
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
592 |
\begin{itemize}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
593 |
\item ``if my input program has a certain behaviour, then the compiled machine code has the same behaviour''
|
609
|
594 |
\item is as good as \texttt{gcc -O1}, but much, much less buggy
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
595 |
\end{itemize}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
596 |
\end{itemize}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
597 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
598 |
\begin{center}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
599 |
\includegraphics[scale=0.12]{../pics/compcert.png}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
600 |
\end{center}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
601 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
602 |
\end{frame}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
603 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
604 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
605 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
610
|
606 |
\begin{frame}[t]
|
609
|
607 |
\frametitle{Fuzzy Testing C-Compilers}
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
608 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
609 |
\begin{itemize}
|
609
|
610 |
\item tested GCC, LLVM and others by randomly generating
|
|
611 |
C-programs
|
|
612 |
\item found more than 300 bugs in GCC and also
|
|
613 |
many in LLVM (some of them highest-level critical)\bigskip
|
|
614 |
\item about CompCert:
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
615 |
|
610
|
616 |
\begin{bubble}[10.7cm]\small ``The striking thing about our CompCert
|
609
|
617 |
results is that the middle-end bugs we found in all other
|
|
618 |
compilers are absent. As of early 2011, the under-development
|
|
619 |
version of CompCert is the only compiler we have tested for
|
|
620 |
which Csmith cannot find wrong-code errors. This is not for
|
|
621 |
lack of trying: we have devoted about six CPU-years to the
|
|
622 |
task.''
|
|
623 |
\end{bubble}
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
624 |
\end{itemize}
|
206
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
625 |
|
383
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
626 |
\end{frame}
|
609
|
627 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
82
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
628 |
|
612
|
629 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
630 |
|
|
631 |
\begin{frame}[c]
|
|
632 |
\frametitle{Next Week}
|
|
633 |
|
|
634 |
\begin{itemize}
|
|
635 |
\item Revision Lecture\medskip
|
|
636 |
\item How many strings are in $\bl{L(a^*)}$?\pause\medskip
|
|
637 |
\item How many strings are in $\bl{L((a + b)^*)}$?\\ Are there more than
|
|
638 |
in $\bl{L(a^*)}$?
|
|
639 |
\end{itemize}
|
|
640 |
|
|
641 |
|
|
642 |
|
|
643 |
\end{frame}
|
|
644 |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
645 |
|
|
646 |
|
|
647 |
|
65
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
648 |
\end{document}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
649 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
650 |
%%% Local Variables:
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
651 |
%%% mode: latex
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
652 |
%%% TeX-master: t
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
653 |
%%% End:
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
654 |
|