From 24f53aa0de31d490ae56ba3d0be481aa43eded73 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Sat, 19 Oct 2019 07:56:54 +0200
Subject: [PATCH] What does this imply: enhance

---
 slides.tex          | 39 +++++++++++++++++++++++++--------------
 src/main_cfi.s      |  2 ++
 src/main_cfi_full.s | 27 +++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 14 deletions(-)
 create mode 100644 src/main_cfi_full.s

diff --git a/slides.tex b/slides.tex
index cb8bb2e..5803df6 100644
--- a/slides.tex
+++ b/slides.tex
@@ -283,16 +283,16 @@ Segmentation fault.
 \end{frame}
 
 \begin{frame}{What does this imply?}
-    Your compiler actually generates codes for \alert{two machines}: your
-        processor and the DWARF VM\@.
+    Your compiler actually generates codes for \alert{two machines}:\\
+    your processor and the DWARF VM\@.
 
     \vfill{}
     \begin{columns}
-        \begin{column}{0.5\textwidth}
+        \begin{column}{0.45\textwidth}
             \begin{center}
                 \begin{tikzpicture}
                     \begin{scope}[every node/.style={rectangle,thick,draw,scale=0.95}]
-                        \node (cmd) at (0, 2.5) {
+                        \node (cmd) at (0, 3.0) {
                             \lstbash{\$ gcc -S foo.c}
                         };
                         \node (asm) at (0, 0) {
@@ -304,25 +304,36 @@ Segmentation fault.
                         \path [->] (cmd) -- (asm);
                     \end{scope}
                 \end{tikzpicture}
-                \medskip{}
+                %\vspace{0.2em}
 
-                \textbf{The \lstc{.cfi_*} is inline DWARF!}
+                \textbf{\lstc{.cfi_*}: \alert{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}
+        \begin{column}{0.55\textwidth}
+            \begin{itemize}
+                \item[$\implies$] \alert{Cumbersome} to generate for the
+                    \alert{compiler}
+                    \begin{itemize}
+                        \item[$\leadsto$] might do it wrong
+                        \item[$\leadsto$] might not do it at all
+                    \end{itemize}
 
-            In \prog{glibc}, \prog{lowlevellock.h}:
-            \alert{off by one error in unwinding data}.
+                \item[$\implies$] If you write \alert{inline asm}, \alert{you} must write
+                    inline DWARF\@!
+            \end{itemize}
 
-            \lstinputlisting[language=gdb,numbers=none]{src/lowlevellock_backtrace}
         \end{column}
     \end{columns}
+\end{frame}
 
+\begin{frame}
+    \todo{Actually add lowlevellock code}
+
+    In \prog{glibc}, \prog{lowlevellock.h}:
+    \alert{off by one error in unwinding data}.
+
+    \lstinputlisting[language=gdb,numbers=none]{src/lowlevellock_backtrace}
 
     \only<2->{
         \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.10\paperheight)%
diff --git a/src/main_cfi.s b/src/main_cfi.s
index 53838b7..dafd463 100644
--- a/src/main_cfi.s
+++ b/src/main_cfi.s
@@ -6,3 +6,5 @@ pushq	%rbp
 movq	%rsp, %rbp
 .cfi_def_cfa_register 6
 subq	$32, %rsp
+movl    %edi, -20(%rbp)
+movq    %rsi, -32(%rbp)
diff --git a/src/main_cfi_full.s b/src/main_cfi_full.s
new file mode 100644
index 0000000..352d89f
--- /dev/null
+++ b/src/main_cfi_full.s
@@ -0,0 +1,27 @@
+main:
+.LFB6:
+        .cfi_startproc
+        pushq   %rbp
+        .cfi_def_cfa_offset 16
+        .cfi_offset 6, -16
+        movq    %rsp, %rbp
+        .cfi_def_cfa_register 6
+        subq    $32, %rsp
+        movl    %edi, -20(%rbp)
+        movq    %rsi, -32(%rbp)
+        movq    -32(%rbp), %rax
+        addq    $8, %rax
+        movq    (%rax), %rax
+        movq    %rax, %rdi
+        call    atoi@PLT
+        movl    %eax, -4(%rbp)
+        movl    -4(%rbp), %eax
+        leave
+        .cfi_def_cfa 7, 8
+        ret
+        .cfi_endproc
+.LFE6:
+        .size   main, .-main
+        .ident  "GCC: (GNU) 9.2.0"
+        .section        .note.GNU-stack,"",@progbits
+