Add a few slides

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Théophile Bastian 2018-08-29 22:14:26 +02:00
parent 2950a42bf4
commit 3a924a3dea
4 changed files with 128 additions and 2 deletions

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shared/imgs/call_stack.png Symbolic link
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../../report/imgs/call_stack/call_stack.png

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\newcommand{\qtodo}[1]{\colorbox{todobg}{\textcolor{todofg}{#1}}} \newcommand{\qtodo}[1]{\colorbox{todobg}{\textcolor{todofg}{#1}}}
\newcommand{\todo}[1]{\qtodo{\textbf{TODO:}\,#1}} \newcommand{\todo}[1]{\qtodo{\textbf{TODO:}\,#1}}
\newcommand{\qnote}[1]{\colorbox{notebg}{\textcolor{notefg}{#1}}} \newcommand{\qnote}[1]{\colorbox{notebg}{\textcolor{notefg}{#1}}}
\newcommand{\note}[1]{\qnote{\textbf{NOTE:}\,#1}} \newcommand{\tnote}[1]{\qnote{\textbf{NOTE:}\,#1}}

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\usepackage{amsmath} \usepackage{amsmath}
\usepackage{amsfonts} \usepackage{amsfonts}
\usepackage{amssymb} \usepackage{amssymb}
\usepackage{my_listings}
\usepackage{../shared/my_listings}
%\usepackage{../shared/my_hyperref}
\usepackage{../shared/specific}
\usepackage{../shared/common}
\usepackage{../shared/todo}
\setbeamertemplate{navigation symbols}{} \setbeamertemplate{navigation symbols}{}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\tableofcontents \tableofcontents
\end{frame} \end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Stack unwinding data}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Introduction}
\begin{frame}[fragile]{We often use stack unwinding!}
\begin{lstlisting}[language=, numbers=none, escapechar=|]
Program received signal SIGSEGV, Segmentation fault.
0x0000555555554625 in fct_b (m=0x5c) at segfault.c:5
5 printf("%l\n", *m);
|\pause|
(gdb) backtrace
#0 0x0000555555554625 in fct_b (m=0x5c) at segfault.c:5
#1 0x0000555555554663 in fct_a (n=42) at segfault.c:10
#2 0x0000555555554674 in main () at segfault.c:14
|\pause|
(gdb) frame 1
#1 0x0000555555554663 in fct_a (n=42) at segfault.c:10
10 fct_b((int*)(some_fct_a_var + 8));
|\pause|
(gdb) print some_fct_a_var
$1 = 84
\end{lstlisting}
\pause{}
\begin{center}
\textbf{\Large How does it work?!}
\end{center}
\vspace{1em}
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Stack frames and unwinding}
\begin{frame}{Call stack and registers}
\begin{columns}[c]
\begin{column}{0.65\textwidth}
\begin{itemize}
\item Programs use a \alert{call stack}
\item Organized in \alert{stack frames}
\begin{itemize}
\item Local variables
\item Function parameters
\item Keep track of nesting, registers and ``return
point''
\end{itemize}
\end{itemize}
Common registers:
\begin{itemize}
\item \reg{rip}: program counter (PC)
\item \reg{rsp}: stack pointer
\item \reg{rbp}: base pointer
\begin{itemize}
\item Saves \reg{rsp}
\item Easy access
\item Wastes a register
\item Not often used (x86\_64)
\end{itemize}
\end{itemize}
\end{column}
\begin{column}{0.35\textwidth}
\includegraphics[width=0.95\linewidth]{../shared/imgs/call_stack}
\end{column}
\end{columns}
\end{frame}
\begin{frame}{Isn't it as trivial as \texttt{pop()}?}
\begin{itemize}
\item This is only a \alert{blob of binary data} without mandatory
structure
\item We ignore \alert{which registers were saved}
\item We ignore \alert{whether \reg{rbp} was used}
\item We ignore \alert{where the return address is stored}
\item We ignore \alert{where the previous frame begins}
\end{itemize}
\medskip
But\ldots{} if we know how to \alert{unwind one}, we can \alert{recurse}!
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{DWARF tables}
\begin{frame}[fragile]{DWARF unwinding data}
\begin{lstlisting}[numbers=none, language=]
00009b30 48 009b34 FDE cie=0000 pc=0084950..0084b37
LOC CFA rbx rbp r12 r13 r14 r15 ra
0084950 rsp+8 u u u u u u c-8
0084952 rsp+16 u u u u u c-16 c-8
0084954 rsp+24 u u u u c-24 c-16 c-8
0084956 rsp+32 u u u c-32 c-24 c-16 c-8
0084958 rsp+40 u u c-40 c-32 c-24 c-16 c-8
0084959 rsp+48 u c-48 c-40 c-32 c-24 c-16 c-8
008495a rsp+56 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084962 rsp+64 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a19 rsp+56 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a1d rsp+48 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a1e rsp+40 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a20 rsp+32 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a22 rsp+24 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a24 rsp+16 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a26 rsp+8 c-56 c-48 c-40 c-32 c-24 c-16 c-8
0084a30 rsp+64 c-56 c-48 c-40 c-32 c-24 c-16 c-8
\end{lstlisting}
\pause{}
\vspace{-4cm}
\hfill\includegraphics[height=3cm, angle=45, origin=c]{img/dwarf_logo}
\hspace{-1cm}
\end{frame}
\end{document} \end{document}