Add a few slides
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4 changed files with 128 additions and 2 deletions
1
shared/imgs/call_stack.png
Symbolic link
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shared/imgs/call_stack.png
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../../report/imgs/call_stack/call_stack.png
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\newcommand{\qtodo}[1]{\colorbox{todobg}{\textcolor{todofg}{#1}}}
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\newcommand{\todo}[1]{\qtodo{\textbf{TODO:}\,#1}}
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\newcommand{\qnote}[1]{\colorbox{notebg}{\textcolor{notefg}{#1}}}
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\newcommand{\note}[1]{\qnote{\textbf{NOTE:}\,#1}}
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\newcommand{\tnote}[1]{\qnote{\textbf{NOTE:}\,#1}}
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BIN
slides/img/dwarf_logo.png
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BIN
slides/img/dwarf_logo.png
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\usepackage{amsmath}
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\usepackage{amsfonts}
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\usepackage{amssymb}
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\usepackage{my_listings}
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\usepackage{../shared/my_listings}
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%\usepackage{../shared/my_hyperref}
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\usepackage{../shared/specific}
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\usepackage{../shared/common}
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\usepackage{../shared/todo}
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\setbeamertemplate{navigation symbols}{}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\tableofcontents
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section{Stack unwinding data}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Introduction}
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\begin{frame}[fragile]{We often use stack unwinding!}
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\begin{lstlisting}[language=, numbers=none, escapechar=|]
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Program received signal SIGSEGV, Segmentation fault.
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0x0000555555554625 in fct_b (m=0x5c) at segfault.c:5
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5 printf("%l\n", *m);
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|\pause|
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(gdb) backtrace
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#0 0x0000555555554625 in fct_b (m=0x5c) at segfault.c:5
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#1 0x0000555555554663 in fct_a (n=42) at segfault.c:10
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#2 0x0000555555554674 in main () at segfault.c:14
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|\pause|
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(gdb) frame 1
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#1 0x0000555555554663 in fct_a (n=42) at segfault.c:10
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10 fct_b((int*)(some_fct_a_var + 8));
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|\pause|
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(gdb) print some_fct_a_var
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$1 = 84
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\end{lstlisting}
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\pause{}
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\begin{center}
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\textbf{\Large How does it work?!}
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\end{center}
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\vspace{1em}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Stack frames and unwinding}
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\begin{frame}{Call stack and registers}
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\begin{columns}[c]
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\begin{column}{0.65\textwidth}
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\begin{itemize}
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\item Programs use a \alert{call stack}
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\item Organized in \alert{stack frames}
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\begin{itemize}
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\item Local variables
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\item Function parameters
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\item Keep track of nesting, registers and ``return
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point''
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\end{itemize}
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\end{itemize}
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Common registers:
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\begin{itemize}
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\item \reg{rip}: program counter (PC)
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\item \reg{rsp}: stack pointer
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\item \reg{rbp}: base pointer
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\begin{itemize}
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\item Saves \reg{rsp}
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\item Easy access
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\item Wastes a register
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\item Not often used (x86\_64)
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\end{itemize}
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\end{itemize}
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\end{column}
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\begin{column}{0.35\textwidth}
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\includegraphics[width=0.95\linewidth]{../shared/imgs/call_stack}
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\end{column}
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\end{columns}
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\end{frame}
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\begin{frame}{Isn't it as trivial as \texttt{pop()}?}
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\begin{itemize}
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\item This is only a \alert{blob of binary data} without mandatory
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structure
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\item We ignore \alert{which registers were saved}
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\item We ignore \alert{whether \reg{rbp} was used}
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\item We ignore \alert{where the return address is stored}
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\item We ignore \alert{where the previous frame begins}
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\end{itemize}
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\medskip
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But\ldots{} if we know how to \alert{unwind one}, we can \alert{recurse}!
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{DWARF tables}
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\begin{frame}[fragile]{DWARF unwinding data}
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\begin{lstlisting}[numbers=none, language=]
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00009b30 48 009b34 FDE cie=0000 pc=0084950..0084b37
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LOC CFA rbx rbp r12 r13 r14 r15 ra
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0084950 rsp+8 u u u u u u c-8
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0084952 rsp+16 u u u u u c-16 c-8
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0084954 rsp+24 u u u u c-24 c-16 c-8
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0084956 rsp+32 u u u c-32 c-24 c-16 c-8
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0084958 rsp+40 u u c-40 c-32 c-24 c-16 c-8
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0084959 rsp+48 u c-48 c-40 c-32 c-24 c-16 c-8
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008495a rsp+56 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084962 rsp+64 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a19 rsp+56 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a1d rsp+48 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a1e rsp+40 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a20 rsp+32 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a22 rsp+24 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a24 rsp+16 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a26 rsp+8 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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0084a30 rsp+64 c-56 c-48 c-40 c-32 c-24 c-16 c-8
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\end{lstlisting}
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\pause{}
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\vspace{-4cm}
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\hfill\includegraphics[height=3cm, angle=45, origin=c]{img/dwarf_logo}
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\hspace{-1cm}
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\end{frame}
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\end{document}
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