Few more fixes

slides/slides.tex

@@ -226,9 +226,39 @@ $1 = 84
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Compiling DWARF}
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\subsection{Example}
+
+\begin{frame}{Compilation example: original C, DWARF}
+    \lstinputlisting[language=C]{src/fib7/fib7.cfde}
+\end{frame}
+
+\begin{frame}[shrink]{Compilation example: generated C}
+    \lstinputlisting[language=C]{src/fib7/fib7.eh_elf_basic.c}
+\end{frame}
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \subsection{Compilation Strategy}
 
+\begin{frame}{Interface: libunwind}
+    \begin{itemize}
+        \item \alert{libunwind}: \textit{de facto} standard library for
+            unwinding
+        \item Uses DWARF in background
+
+        \item \texttt{libunwind-eh\_elf}: alternative implementation using
+            \ehelfs{}
+
+        \item{} Result: \alert{alternative implementation} of libunwind, nearly
+            plug-and-play for existing projects!
+            \begin{itemize}
+                \item[$\leadsto$] It is \alert{easy} to use \ehelfs{}: just
+                    link against the right library!
+            \end{itemize}
+    \end{itemize}
+\end{frame}
+
 \begin{frame}{Compilation overview}
     \begin{itemize}
         \item Compiled to \alert{C code}
@@ -301,6 +331,10 @@ $1 = 84
     \end{center}
 \end{frame}
 
+\begin{frame}{Example with outlining}
+    \lstinputlisting[language=C]{src/fib7/fib7.eh_elf_outline.c}
+\end{frame}
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Benchmarking}
 
@@ -364,21 +398,6 @@ $1 = 84
     \end{itemize}
 \end{frame}
 
-\subsection{Libunwind}
-\begin{frame}{libunwind implementation}
-    \begin{itemize}
-        \item \alert{libunwind}: \textit{de facto} standard library for
-            unwinding
-        \item Uses DWARF in background
-        \item \alert{Used by perf} as a backend for unwinding
-
-        \pause{}\vspace{1em} \item{} Easiest way to use \ehelfs{} in perf:
-            \alert{implement an alternative libunwind}
-        \item{} Result: \alert{alternative implementation} of libunwind, nearly
-            plug-and-play!
-    \end{itemize}
-\end{frame}
-
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Results}
 
@@ -474,6 +493,7 @@ $1 = 84
         \end{column}
     \end{columns}
 
+    \vspace{1.5em}
     \begin{center}
         \Huge\bfseries
         Thank you!

slides/src/fib7/fib7.c

@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+void fib7() {
+    int fibo[8];
+    fibo[0] = 1;
+    fibo[1] = 1;
+    for(int pos = 2; pos < 8; ++pos)
+        fibo[pos] =
+            fibo[pos - 1]
+            + fibo[pos - 2];
+    printf("%d\n", fibo[7]);
+}
+
+int main(void) {
+    fib7();
+    return 0;
+}

slides/src/fib7/fib7.cfde

@@ -0,0 +1,13 @@
+#include <stdio.h>                      DWARF
+                                        CFA     ra
+void fib7() {                           rsp+8   c-8
+    int fibo[8];                        rsp+48  c-8
+    fibo[0] = 1;
+    fibo[1] = 1;
+    for(int pos = 2; pos < 8; ++pos)
+        fibo[pos] =
+            fibo[pos - 1]
+            + fibo[pos - 2];
+    printf("%d\n", fibo[7]);
+                                        rsp+8   c-8
+}

slides/src/fib7/fib7.eh_elf_basic.c

@@ -0,0 +1,18 @@
+unwind_context_t _eh_elf(
+        unwind_context_t ctx, uintptr_t pc)
+{
+	unwind_context_t out_ctx;
+	switch(pc) {
+        // [...] Previous FDEs redacted
+		case 0x615 ... 0x618:
+			out_ctx.rsp = ctx.rsp + (8);
+			out_ctx.rip =
+                *((uintptr_t*)(out_ctx.rsp + (-8)));
+			out_ctx.flags = 3u;
+			return out_ctx;
+        // [...] Further lines and FDEs redacted
+		default:
+			out_ctx.flags = 128u;
+			return out_ctx;
+		}
+}

slides/src/fib7/fib7.eh_elf_outline.c

@@ -0,0 +1,16 @@
+unwind_context_t _eh_elf(
+        unwind_context_t ctx, uintptr_t pc)
+{
+	unwind_context_t out_ctx;
+    if(pc < 0x619) { /* [...] */ } else {
+        if(pc < 0x659) { // IP=0x619 ... 0x658
+            goto _factor_4;
+        } // [...]
+    }
+
+	_factor_4:
+	out_ctx.rsp = ctx.rsp + (48);
+	out_ctx.rip = *((uintptr_t*)(out_ctx.rsp + (-8)));
+	out_ctx.flags = 3u;
+	return out_ctx;
+}

slides/src/fib7/fib7.fde

@@ -0,0 +1,5 @@
+[...] FDE [...]  pc=615..65a
+   LOC           CFA      ra
+0000000000000615 rsp+8    c-8
+0000000000000619 rsp+48   c-8
+0000000000000659 rsp+8    c-8

slides/src/fib7/fib7.raw_fde

@@ -0,0 +1,7 @@
+[...] FDE [...] pc=615..65a
+  DW_CFA_def_cfa: r7 (rsp) ofs 8
+  DW_CFA_offset: r16 (rip) at cfa-8
+  DW_CFA_advance_loc: 4 to 0619
+  DW_CFA_def_cfa_offset: 48
+  DW_CFA_advance_loc1: 64 to 0659
+  DW_CFA_def_cfa_offset: 8

slides/src/fib7/fib7.s

@@ -0,0 +1,18 @@
+0000000000000615 <fib7>:
+ 615:	sub    $0x28,%rsp ; Alloc stack
+ 619:	movl   $0x1,(%rsp) ; fibo[0]
+ 620:	movl   $0x1,0x4(%rsp) ; fibo[1]
+ 628:	mov    %rsp,%rax ;     BEGIN FOR
+ 62b:	lea    0x18(%rax),%rcx
+ 62f:	mov    (%rax),%edx
+ 631:	add    0x4(%rax),%edx
+ 634:	mov    %edx,0x8(%rax)
+ 637:	add    $0x4,%rax
+ 63b:	cmp    %rcx,%rax
+ 63e:	jne    62f <fib7+0x1a> ; END FOR
+ 640:	mov    0x1c(%rsp),%esi
+ 644:	lea    0xb9(%rip),%rdi
+ 64b:	mov    $0x0,%eax
+ 650:	callq  520 <printf@plt>
+ 655:	add    $0x28,%rsp ; Restore rsp
+ 659:	retq