Add slides about fixpoint

Different stack frame sizes, no main RA, %rsp -> stack pointer

slides.tex

@@ -1,6 +1,6 @@
 % vim: spell spelllang=en
 
-\documentclass[11pt,xcolor={usenames,dvipsnames}]{beamer}
+\documentclass[12pt,xcolor={usenames,dvipsnames}]{beamer}
 \usetheme{Warsaw}
 \usepackage[utf8]{inputenc}
 \usepackage[english]{babel}
@@ -17,7 +17,7 @@
 \usepackage{multirow}
 \usepackage[many]{tcolorbox}
 \usepackage[absolute,overlay]{textpos}
-\usetikzlibrary{arrows.meta}
+\usetikzlibrary{arrows.meta,shapes}
 
 \usepackage{texlib/my_listings}
 \usepackage{texlib/specific}
@@ -33,15 +33,15 @@
 \setbeamertemplate{navigation symbols}{}
 \setbeamertemplate{headline}{}
 
-\newcommand{\thenalert}[1]{\only<1>{#1}\only<2>{\alert{#1}}}
-\newcommand{\slidecountline}{
-    \ifthenelse{\theframenumber = 0}
-        {}
-        {\insertframenumber/\inserttotalframenumber}}
-
 \newcommand{\cmark}{\color{OliveGreen}\ding{52}}
 \newcommand{\xmark}{\color{BrickRed}\ding{56}}
 
+\let\tempone\itemize
+\let\temptwo\enditemize
+\renewenvironment{itemize}{\tempone\addtolength{\itemsep}{0.5\baselineskip}}{\temptwo}
+
+
+
 \newcommand{\sectiontitleframe}{
     \begin{frame}
         \vfill
@@ -56,6 +56,16 @@
     morekeywords={gdb},
     sensitive=false,
 }
+\lstdefinelanguage{cfiasm}{
+    morekeywords={cfi_startproc,cfi_def_cfa_offset,cfi_offset,cfi_def_cfa_register},
+    sensitive=false,
+}
+
+\newcommand{\thenalert}[1]{\only<1>{#1}\only<2>{\alert{#1}}}
+\newcommand{\slidecountline}{
+    \ifthenelse{\theframenumber = 0}
+        {}
+        {\insertframenumber/\inserttotalframenumber}}
 
 \setbeamertemplate{footline}
 {
@@ -71,6 +81,23 @@
   \vskip0pt%
 }
 
+\setbeamercolor{block title}{use=structure,fg=white,bg=structure.fg!75!black}
+\setbeamercolor{block title alerted}{use=alerted text,fg=white,bg=alerted
+text.fg!75!black}
+\setbeamercolor{block title example}{use=example text,fg=white,bg=example
+text.fg!75!black}
+
+%\setbeamertemplate{frametitle}{
+%  \leavevmode%
+%  \hbox{%
+%  \begin{beamercolorbox}[wd=\paperwidth,ht=2.25ex,dp=1ex,center]{title in head/foot}%
+%    \usebeamerfont{author in head/foot}\insertframetitle
+%  \end{beamercolorbox}%
+%  }
+%  \vskip0pt%
+%    %\color{black}\bfseries\insertframetitle\par\vskip-6pt\hrulefill
+%}
+
 
 \newcolumntype{b}{X}
 \newcolumntype{s}{>{\hsize=.43\hsize}X}
@@ -96,6 +123,7 @@
 
     \vspace{-2em}
 
+
     \begin{columns}
         \begin{column}{0.55\textwidth}
             \begin{tcolorbox}[halign=center, colframe=blue]
@@ -103,7 +131,7 @@
 
                 \smallskip
                 \vspace{0.5em}
-                {\url{https://huit.re/frdwarf}}\\
+                {\small\url{https://huit.re/frdwarf}}\\
                 \vspace{0.5em}
             \end{tcolorbox}
         \end{column}
@@ -119,6 +147,13 @@
             \end{tcolorbox}
         \end{column}
     \end{columns}
+
+    \begin{textblock*}{0.22\textwidth}[0.5,0](0.15\paperwidth,0.38\paperheight)%
+        \includegraphics[width=\linewidth]{img/stephen_circ.jpg}
+    \end{textblock*}
+    \begin{textblock*}{0.22\textwidth}[0.5,0](0.85\paperwidth,0.38\paperheight)%
+        \includegraphics[width=\linewidth]{img/fzn_circ.jpg}
+    \end{textblock*}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -159,7 +194,7 @@ Segmentation fault.
         \begin{column}{0.65\textwidth}
             \begin{center}
                 \large\bf
-                How do we get the RA\@?\\Easy, \reg{rbp}!
+                How do we get the RA\@?
 
                 \vspace{2em}
 
@@ -179,7 +214,6 @@ Segmentation fault.
 \newcolumntype{a}{>{\columncolor{RedOrange}}l}
 
 \begin{frame}{DWARF unwinding data}
-    \vspace{2em}
     \tt \footnotesize
     \begin{center}
         \begin{tabular}{
@@ -201,12 +235,11 @@ Segmentation fault.
 0084a1e & rsp+40 & c-56 & c-48 & c-40 & c-32 & c-24 & c-16 & c-8 \\
         \end{tabular}
     \end{center}
-    \vspace{1em}
 
     \only<1>{\vspace{19mm}}
     \begin{columns}
         \begin{column}{0.50\textwidth}
-            \only<2->{
+            \onslide<2->{
                 \begin{tcolorbox}[enhanced, halign=center, frame hidden, colback=YellowGreen]
                     \textbf{For each instruction\ldots}\\
                     (identified by its program counter)
@@ -214,7 +247,7 @@ Segmentation fault.
             }
         \end{column}
         \begin{column}{0.50\textwidth}
-            \only<3->{
+            \onslide<3->{
                 \begin{tcolorbox}[enhanced, halign=center, frame hidden,
                         interior style={right color=Apricot, left color=Thistle}]
                         \textbf{\ldots{}an expression to compute its return address
@@ -237,29 +270,75 @@ Segmentation fault.
     \end{lstlisting}
 
     \pause{}
+    \vfill
 
     \begin{itemize}
         \item[\textbf{$\longrightarrow$}] \textbf{\alert{constructed} on-demand
             by a \alert{Turing-complete stack machine}!}
     \end{itemize}
+\end{frame}
+
+\begin{frame}{What does this imply?}
+    Your compiler actually generates codes for \alert{two machines}: your
+        processor and the DWARF VM\@.
+
+    \vfill{}
+    \begin{columns}
+        \begin{column}{0.5\textwidth}
+            \begin{center}
+                \begin{tikzpicture}
+                    \begin{scope}[every node/.style={rectangle,thick,draw,scale=0.95}]
+                        \node (cmd) at (0, 2.5) {
+                            \lstbash{\$ gcc -S foo.c}
+                        };
+                        \node (asm) at (0, 0) {
+                            \lstinputlisting[numbers=none, language=cfiasm]{src/main_cfi.s}
+                        };
+                    \end{scope}
+                    \begin{scope}[>={Stealth[black]},
+                        every path/.style={draw=black,very thick}]
+                        \path [->] (cmd) -- (asm);
+                    \end{scope}
+                \end{tikzpicture}
+                \medskip{}
+
+                \textbf{The \lstc{.cfi_*} is inline DWARF!}
+            \end{center}
+        \end{column}
+
+        \begin{column}{0.5\textwidth}
+            \begin{center}
+                \bf
+                $\implies$ if you write inline asm, you must write inline DWARF!
+            \end{center}
+
+            In \prog{glibc}, \prog{lowlevellock.h}:
+            \alert{off by one error in unwinding data}.
+
+            \lstinputlisting[language=gdb,numbers=none]{src/lowlevellock_backtrace}
+        \end{column}
+    \end{columns}
+
 
     \only<2->{
-        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.17\paperheight)%
+        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.10\paperheight)%
             \begin{tcolorbox}[halign=center, colframe=red, colback=Lavender]
-                \bf \huge
+                \bf \LARGE
                 Complex \,\& \,slow
             \end{tcolorbox}
         \end{textblock*}
     }
 
     \only<3->{
-        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.35\paperheight)%
+        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.30\paperheight)%
             \begin{tcolorbox}[halign=center, colframe=red, colback=Lavender]
-                \huge
-                \textbf{Pervasive:}\\ relied upon by debuggers, profilers, C++
-                exceptions \\
-                \medskip{}
-                \textbf{$\leadsto$ not only for debuggers!}
+                \LARGE
+                \textbf{Pervasive:}\\ relied upon by profilers, debuggers,
+                aaand\ldots{}
+                \onslide<4->{
+                    C++ exceptions. \\
+                    \medskip{}
+                \textbf{$\leadsto$ not only for debuggers!}}
             \end{tcolorbox}
         \end{textblock*}
     }
@@ -369,18 +448,17 @@ Segmentation fault.
 \firsttblrows{}%
 \tblrowval{add}{\$0x68,\%rsp}{rsp+160}{c-8}
 \tblrowval{pop}{\%rbx}{rsp+56}{c-8}
-\tblrowval{pop}{\%rbp}{rsp+48}{c-8}
             \end{tabularx}
         \end{table}
         \blknote{
             \centering
-        \begin{overlayarea}{0.9\textwidth}{4.8ex}
+        \begin{overlayarea}{0.9\textwidth}{2.6em}
             \only<4>{Upon function call, \alert{ra = *(\reg{rsp})}}
             \only<5>{\texttt{push} decreases \reg{rsp} by 8: %
                 \alert{ra = *(\reg{rsp} + 8)}}
             \only<6>{and again: %
                 \alert{ra = *(\reg{rsp} + 16)}}
-            \only<7>{This \texttt{mov} leaves \reg{rsp} untouched: %
+            \only<7>{This \texttt{mov} leaves \reg{rsp} untouched: \\%
                 \alert{ra = *(\reg{rsp} + 16)}}
             \only<8>{The unwinding table captures an \alert{abstract execution}
             of the code\ldots}
@@ -410,8 +488,11 @@ Segmentation fault.
         \item The fixpoints are immediate, cf article
     \end{itemize}
 
-    \todo{Mettre en boîte}
-    Implemented on top of CMU's \prog{BAP}
+    \vspace{1em}
+    \begin{tcolorbox}[halign=center, colframe=OliveGreen, colback=YellowGreen]
+        \large
+        Implemented on top of CMU's \prog{BAP}
+    \end{tcolorbox}
 \end{frame}
 
 \begin{frame}{}
@@ -427,6 +508,20 @@ Segmentation fault.
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Unwinding data compilation}
 
+\begin{frame}
+    \begin{center}
+        \Huge
+        Unwinding data is
+        \textsc{slo\pause{}o\pause{}o\pause{}o\pause{}o\pause{}o\pause{}o\pause{}o\pause{}o\pause{}o\pause{}w}.
+    \end{center}
+    \vspace{2em}
+
+    \pause{}
+
+    So much that \prog{perf} doesn't use it by default! You must use
+    \lstbash{perf report --call-graph dwarf} explicitly!
+\end{frame}
+
 \sectiontitleframe{}
 
 \subsection{Compilation ahead-of-time}
@@ -440,7 +535,7 @@ Segmentation fault.
                 \lstinputlisting[basicstyle=\tiny\tt,numbers=none,language=]{src/dw_plt_abbr}
             };
 
-            \only<2->{
+            \onslide<2->{
                 \node (table) at (0.5\textwidth, -0.23\textheight) {
                     \tiny\tt
                     \begin{tabular}{
@@ -456,7 +551,7 @@ Segmentation fault.
                     \end{tabular}
                 };
             }
-            \only<3->{
+            \onslide<3->{
                 \node (csrc) at (0, -0.6\textheight) {
                     \lstinputlisting[basicstyle=\tiny,numbers=none,language=C]{src/fib7/fib7.eh_elf_basic.c}
                 };
@@ -501,16 +596,24 @@ Segmentation fault.
 \subsection{Results}
 
 \begin{frame}{Performances}
-    \begin{itemize}
-        \item \alert{Speedup}: x15 (\prog{gzip}) to x25 (\prog{hackbench}) vs.
-            libunwind
+    \begin{center}
+        \Large\bf Speedup vs. libunwind:
+        \begin{columns}
+            \begin{column}{0.5\textwidth}
+                \alert{x15} on gzip
+            \end{column}
+            \begin{column}{0.5\textwidth}
+                \alert{x25} on hackbench
+            \end{column}
+        \end{columns}
+    \end{center}
 
-            \begin{itemize}
-                \item libunwind: state of the art, aggressive caching.
-            \end{itemize}
+    \vfill
 
-        \item \alert{Space overhead}: x2.6 to x3 vs. DWARF
-    \end{itemize}
+    \begin{center}
+        \Large\bf Space overhead vs. DWARF:\\
+        \alert{x2.6 -- x3}
+    \end{center}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -543,4 +646,89 @@ Segmentation fault.
     \end{center}
 \end{frame}
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\section*{Extra slides}
+
+\begin{frame}[noframenumbering]
+\end{frame}
+
+\begin{frame}[noframenumbering]{Fixpoint upon control flow merge}
+    \begin{columns}
+        \begin{column}{0.3\textwidth}
+            \begin{tikzpicture}
+                \begin{scope}[every node/.style={rectangle,thick,draw,scale=0.95}]
+                    \node (if) at (0, 5) {\lstbash{if cnd}};
+                    \node (then) at (-1, 3) { \lstbash{then A} };
+                    \node (else) at (1, 3) { \lstbash{else B} };
+                    \node (after) at (0, 1) { \lstbash{C} };
+                \end{scope}
+                \node [circle, thick, draw, minimum size=3em, color=red] (circafter) at (0, 1) {};
+                \begin{scope}[>={Stealth[black]}, every path/.style={draw=black,very thick}]
+                    \path [->] (if) -- (then);
+                    \path [->] (if) -- (else);
+                    \path [->] (then) -- (after);
+                    \path [->] (else) -- (after);
+                \end{scope}
+            \end{tikzpicture}
+        \end{column}
+        \begin{column}{0.6\textwidth}
+            \begin{center}
+                If eg.
+                \[
+                    CFA(A) = c-48 \qquad CFA(B) = c-52
+                \]
+                no possible unwinding data for C, \alert{even for the
+                compiler}!
+
+                \vspace{1em}
+                Also, \alert{no possible clean function postlude}!
+
+                \vspace{2em}
+                $\implies$ $CFA(A) = CFA(B)$ and merge is immediate
+            \end{center}
+        \end{column}
+    \end{columns}
+\end{frame}
+
+\begin{frame}[noframenumbering]{Fixpoint upon loop control flow merge}
+    \begin{columns}
+        \begin{column}{0.3\textwidth}
+            \begin{tikzpicture}
+                \begin{scope}[every node/.style={rectangle,thick,draw,scale=0.95}]
+                    \node (inbound) at (0, 7) {\lstbash{A}};
+                    \node (while) at (0, 5) {\lstbash{for i in ...}};
+                    \node (do) at (0, 3) { \lstbash{do a = array[i]; B} };
+                    \node (done) at (0, 1) { \lstbash{C} };
+                \end{scope}
+                \node [ellipse, thick, draw, minimum width=10em, minimum height=3em, color=red] (circafter) at (0, 3) {};
+                \begin{scope}[>={Stealth[black]}, every path/.style={draw=black,very thick}]
+                    \path [->] (inbound) -- (while);
+                    \path [->] (while) edge[bend right] (do);
+                    \path [->] (do) -- (done);
+                    \path [->] (do) edge[bend right] (while);
+                \end{scope}
+            \end{tikzpicture}
+        \end{column}
+        \begin{column}{0.6\textwidth}
+            \begin{center}
+                {\large\alert{Variable stack frame size!}}
+
+                \vspace{1em}
+
+                We cannot hope for an invariant\dots\\
+                but the compiler cannot
+                either.
+
+                \vspace{1em}
+
+                {
+                    \large\alert{$\implies$} the compiler will \alert{fallback to
+                    \reg{rbp}}\\
+                }
+                even with \lstbash{--fomit-frame-pointer}
+            \end{center}
+        \end{column}
+    \end{columns}
+\end{frame}
+
 \end{document}

src/lowlevellock_backtrace

@@ -0,0 +1,5 @@
+(gdb) backtrace
+#0 0x406c2c in _L_lock_19
+#1 0x406c2c in _L_lock_19
+#2 0x4069c6 in abort
+#3 0x401017 in main

src/main_cfi.s

@@ -0,0 +1,8 @@
+main:
+.cfi_startproc
+pushq	%rbp
+.cfi_def_cfa_offset 16
+.cfi_offset 6, -16
+movq	%rsp, %rbp
+.cfi_def_cfa_register 6
+subq	$32, %rsp