16 files changed, 955 insertions(+), 0 deletions(-)

A examples/corefile/1.c
A examples/points/Makefile
A examples/points/breakwatch.c
A examples/points/catch.c
A examples/points/hello.c
A examples/python/pretty-print/1.cpp
A examples/python/pretty-print/str.py
A examples/reverse/1.c
A examples/reverse/1.h
A examples/reverse/2.c
A examples/reverse/2.h
A examples/stap-probe/1.c
A examples/stap-probe/README
A examples/stap-probe/baz.c
A gdb-intro-kwlug.org
A gdb-intro-kwlug.tex

@@ 1,28 @@
+static void foo_segv (void);
+
+static void
+bar (void)
+{
+  foo_segv ();
+}
+
+static void
+foo_segv (void)
+{
+  int *x = 0;
+
+  *x = 5;
+}
+
+static void
+baz (void)
+{
+  bar ();
+}
+
+int
+main (int argc, char *argv[])
+{
+  baz ();
+  return 0;
+}

@@ 1,10 @@
+CC = gcc
+CFLAGS = -g3 -O0
+
+all: breakwatch catch hello
+
+%.o: %.c
+	$(CC) -o $@ -c $< $(CFLAGS)
+
+clean:
+	rm -f breakwatch catch hello

@@ 1,40 @@
+/* points.c -- Break and watch examples.  */
+
+#include <stdio.h>
+
+struct sttest
+{
+  int index;
+  char name[15];
+  int value;
+};
+
+int
+test_func (int n)
+{
+  int r;
+
+  r = n + 10;
+  r += 20;
+
+  return r;
+}
+
+int
+main (int argc, char **argv)
+{
+  int a, b, i;
+  struct sttest example_struct[10];
+
+  a = 5;
+  b = test_func (a) / 10;
+
+  for (i = 0; i < 10; i++)
+    {
+      example_struct[i].index = i;
+      sprintf (example_struct[i].name, "element %d", i);
+      example_struct[i].value = test_func (i);
+    }
+
+  return 0;
+}

@@ 1,31 @@
+/* catch.c -- Example for 'catch fork' and 'catch syscall'.  */
+
+#include <stdio.h>
+#include <unistd.h>
+
+void
+test (void)
+{
+  if (fork () == 0)
+    printf ("Child\n");
+
+  fork ();
+}
+
+void
+another_test (const char *p)
+{
+  chdir (p);
+}
+
+int
+main (int argc, char **argv)
+{
+  int a;
+
+  test ();
+
+  another_test (".");
+
+  return 0;
+}

@@ 1,28 @@
+/* hello.c -- Segfault example.  */
+
+#include <stdio.h>
+#include <string.h>
+
+int
+print (char *msg)
+{
+  printf ("%s\n", msg);
+  return 0;
+}
+
+int
+hello (char *param)
+{
+  strcpy (param, "Hello World!");
+  print (param);
+}
+
+int
+main (int argc, char **argv)
+{
+  char *str = "Hi!";
+
+  hello (str);
+
+  return 0;
+}

@@ 1,9 @@
+#include <string>
+
+int
+main ()
+{
+	std::string x = "Hello Upstream";
+
+	return 0;
+}

@@ 1,29 @@
+import gdb.printing
+import re
+
+class StdStringPrinter:
+
+	def __init__ (self, val):
+		self.val = val
+
+	def to_string (self):
+		return self.val['_M_dataplus']['_M_p']
+
+	def display_hint (self):
+		return 'string'
+
+def str_lookup_function(val):
+	bbb = {}
+	try:
+		bbb = val.type.fields ()
+	except:
+		pass
+	found = 0
+	for x in bbb:
+		if x.name == '_M_dataplus':
+			found = 1
+	if found == 1:
+		return StdStringPrinter(val)
+	return None
+
+gdb.printing.register_pretty_printer (gdb, str_lookup_function)

@@ 1,23 @@
+#include "2.h"
+
+void
+foo (int v)
+{
+  int a = 0;
+
+  a = 10 + 20;
+  a += v;
+
+  bar (&a);
+  bar (0);
+
+  a = 0;
+}
+
+int
+main (int argc, char *argv[])
+{
+  initialize ();
+
+  return 0;
+}

@@ 1,1 @@
+void foo (int v);

@@ 1,17 @@
+#include "1.h"
+
+void
+initialize (void)
+{
+  int n = 0;
+
+  n = 12314314 % 453;
+  foo (n);
+}
+
+void
+bar (int *v)
+{
+  if (v != 0)
+    *v += 12314314 % 453;
+}

@@ 1,3 @@
+void initialize (void);
+
+void bar (int *v);

@@ 1,41 @@
+#include <sys/sdt.h>
+
+struct baz
+  {
+    int a;
+    char b;
+    union
+      {
+	int c;
+	char d;
+      } u;
+  };
+
+static void
+foo (int a, const char *b)
+{
+  STAP_PROBE2 (test, probefoo, a, b);
+}
+
+static void
+bar (const struct baz *a)
+{
+  STAP_PROBE1 (test, probebar, a);
+}
+
+int
+main (int argc, char *argv[])
+{
+  int i1 = 1;
+  const char *s = "String test";
+  struct baz b;
+
+  b.a = 49;
+  b.b = 'y';
+  b.u.d = 'a';
+
+  foo (i1, s);
+  bar (&b);
+
+  return 0;
+}

@@ 1,2 @@
+Compiling with -Ox (x > 0) changes the layout of the symbols in the memory.
+If you want to access a structure field, refer to it explicitly in the probe argument.

@@ 1,12 @@
+struct baz
+  {
+    int a;
+    char b;
+    union
+      {
+	int c;
+	char d;
+      } u;
+  };
+
+struct baz blabla;

@@ 1,270 @@
+#+OPTIONS: toc:nil date:nil
+#+SELECT_TAGS: export
+#+EXCLUDE_TAGS: noexport
+#+CREATOR: Emacs 26.1 (Org mode 9.1.9)
+#+TITLE: GDB Intro
+#+AUTHOR: Sergio Durigan Junior @@latex:\\@@ sergiodj@{sergiodj.net,redhat.com,debian.org}
+#+LANGUAGE: en
+#+LATEX_HEADER: \usepackage{listings}
+#+LATEX_HEADER: \lstdefinestyle{customc}{belowcaptionskip=1\baselineskip,breaklines=true,frame=L,xleftmargin=\parindent,language=C,showstringspaces=false,basicstyle=\footnotesize\ttfamily,keywordstyle=\bfseries\color{green!40!black},commentstyle=\itshape\color{purple!40!black},identifierstyle=\color{blue},stringstyle=\color{orange},}
+
+* License
+
+- License: *Creative Commons Attribution 4.0 International License (CC-BY-4.0)*
+
+- https://creativecommons.org/licenses/by/4.0/
+
+* Agenda
+
+- Blabla
+
+* Introduction
+
+- =GDB=: =GNU= project's Debugger @@latex:\pause@@ (it is *not* a
+  /database/...).  Supports several programming languages.
+
+- Started around 1986 by Richard Stallman (after *GNU Emacs*, but
+  likely before *GCC*).
+
+* Compiling your program for GDB
+
+- Your program needs to contain *debug information* (also called
+  =DWARF=) for GDB to consume.
+
+#+BEAMER: \pause
+
+- The GCC flag to include debug information is =-g=.  We also use
+  =-g3=, which includes information about macros (=#define=).
+
+#+BEAMER: \pause
+
+- It's common to *disable optimizations* when building the binary, by
+  using the flag =-O0= (it's /dash-oh-zero/).
+
+  #+BEAMER: \pause
+
+  - =# gcc -O0 -g program.c -o program=, /or/
+
+  - ~# CFLAGS='-O0 -g' ./configure && make~
+
+* Running your program using GDB
+
+- In GDB's parlance, the program being debugged is called the
+  *inferior*.
+
+#+BEAMER: \pause
+
+- Some ways to start the debugger:
+
+  #+BEAMER: \pause
+
+  - =# gdb ./program=
+
+  #+BEAMER: \pause
+
+  - =# gdb --args ./program arg1 arg2=
+
+  #+BEAMER: \pause
+
+  - =# gdb= @@latex: \\@@
+    =(gdb) file ./program= @@latex: \\@@
+    =(gdb) run arg1 arg2=
+
+* {Break,Catch,Watch}points
+
+- A *breakpoint* is related to /source code/ (location, function).  A
+  *watchpoint* is related to /data/ (read/write of a variable).  A
+  *catchpoint* is related to an /event/ (enter/exit a syscall, fork,
+  receive a signal).
+
+#+BEAMER: \pause
+
+- Breakpoints (/code/)
+
+  - =break=
+
+  - =tbreak= (temporary)
+
+#+BEAMER: \pause
+
+- Watchpoints (/data/)
+
+  - =watch= (write), =rwatch= (read), =awatch= (access)
+
+  - Conditional watchpoints are supported.
+
+#+BEAMER: \pause
+
+- Catchpoints (/events/)
+
+  - =catch fork=
+
+  - =catch syscall=
+
+* Resuming the execution
+
+- After GDB has stopped the inferior (because a =*point= has been hit,
+  for example), you will probably want to resume its execution.
+
+#+BEAMER: \pause
+
+- You may just want to continue the program:
+
+  - =continue=
+
+#+BEAMER: \pause
+
+- Or maybe go to the next statement/instruction:
+
+  - =next= (/statement/), or =nexti= (/instruction/)
+
+#+BEAMER: \pause
+
+- Or step into a function:
+
+  - =step= (/statement/), or =stepi= (/instruction/)
+
+#+BEAMER: \pause
+
+- Or finish executing the current function, but stop at the end:
+
+  - =finish=
+
+
+
+* Examining data
+
+- The inferior has stopped...  Now what?
+
+#+BEAMER: \pause
+
+- You may want to print the value of some variable:
+
+  - =print VAR=
+
+#+BEAMER: \pause
+
+- Or examine a memory location:
+
+  - =x ADDRESS=
+
+#+BEAMER: \pause
+
+- The type of a variable?  Easy:
+
+  - =whatis VARIABLE=
+
+#+BEAMER: \pause
+
+- Hint: you may want to enable pretty-printing:
+
+  - =set print pretty on=
+
+* Examining the code
+
+- Yes, we have =ncurses=!  The @@latex:\textbf{T}@@ext
+  @@latex:\textbf{U}@@user @@latex:\textbf{I}@@nterface!
+
+  - =C-x a= (that's =CTRL x a=).
+
+#+BEAMER: \pause
+
+- If you want to list the current region, or if you don't want/can't
+  to use TUI:
+
+  - =list=
+
+#+BEAMER: \pause
+
+- You can also disassemble code:
+
+  - =disassemble=
+
+#+BEAMER: \pause
+
+- If GDB can't find the source code, you can specify its location
+  using the =dir= command.
+
+* Examining the call stack
+
+- If you want to see the call stack (A.K.A. stack trace) that lead to
+  the current function:
+
+  - =bt=
+
+#+BEAMER: \pause
+
+- And you can move through it:
+
+  - =up= and =down=
+
+  - You can also go to a specific frame: =frame NUMBER=
+
+* Corefiles
+
+- *Corefiles* are frozen images of the inferior.  You can inspect
+  everything that was happening when the process was running (but you
+  can't resurrect it).
+
+#+BEAMER: \pause
+
+- You can generate them /outside/ GDB, when a program crashes.  Make
+  sure you:
+
+  - =ulimit -c unlimited=
+
+  - Check if =systemd= is handling them
+    (=/proc/sys/kernel/core_pattern=).
+
+#+BEAMER: \pause
+
+- You can also generate them /inside/ GDB, at any moment:
+
+  - =generate-core-file=
+
+#+BEAMER: \pause
+
+- You can open a corefile using GDB:
+
+  - =# gdb program -c corefile.PID=
+
+* Other interesting information
+
+- =info breakpoints=
+
+- =info locals=
+
+- =info registers=
+
+- Many others!
+
+* Who you gonna call?
+
+- Our online documentation (=info=) is very good!
+
+- Every command has a =help=.
+
+- You can also use =apropos= when searching for a term.
+
+- =TAB=-completion is also useful.
+
+* Other advanced features
+
+- Python support.
+
+- Reverse debugging.
+
+- Support for /SystemTap SDT probes/.
+
+* End
+
+
+#+ATTR_LATEX: :options style=customc
+#+begin_src c -n
+int main ()
+{
+  const char *c = NULL;
+
+  return 0;
+}
+#+end_src

@@ 1,411 @@
+% Created 2019-06-02 Sun 21:20
+% Intended LaTeX compiler: pdflatex
+\documentclass[presentation]{beamer}
+\usepackage[utf8]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage{graphicx}
+\usepackage{grffile}
+\usepackage{longtable}
+\usepackage{wrapfig}
+\usepackage{rotating}
+\usepackage[normalem]{ulem}
+\usepackage{amsmath}
+\usepackage{textcomp}
+\usepackage{amssymb}
+\usepackage{capt-of}
+\usepackage{hyperref}
+\usepackage{color}
+\usepackage{listings}
+\usepackage{listings}
+\lstdefinestyle{customc}{belowcaptionskip=1\baselineskip,breaklines=true,frame=L,xleftmargin=\parindent,language=C,showstringspaces=false,basicstyle=\footnotesize\ttfamily,keywordstyle=\bfseries\color{green!40!black},commentstyle=\itshape\color{purple!40!black},identifierstyle=\color{blue},stringstyle=\color{orange},}
+\usetheme{default}
+\author{Sergio Durigan Junior \\ sergiodj@\{sergiodj.net,redhat.com,debian.org\}}
+\date{}
+\title{GDB Intro}
+\hypersetup{
+ pdfauthor={Sergio Durigan Junior \\ sergiodj@\{sergiodj.net,redhat.com,debian.org\}},
+ pdftitle={GDB Intro},
+ pdfkeywords={},
+ pdfsubject={},
+ pdfcreator={Emacs 26.1 (Org mode 9.1.9)}, 
+ pdflang={English}}
+\begin{document}
+
+\maketitle
+
+\begin{frame}[label={sec:orga1f4768}]{License}
+\begin{itemize}
+\item License: \alert{Creative Commons Attribution 4.0 International License (CC-BY-4.0)}
+
+\item \url{https://creativecommons.org/licenses/by/4.0/}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[label={sec:org13db7cc}]{Agenda}
+\begin{itemize}
+\item Blabla
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:orgcb90a6c}]{Introduction}
+ \begin{itemize}
+\item \texttt{GDB}: \texttt{GNU} project's Debugger \pause (it is \alert{not} a
+\emph{database}\ldots{}).  Supports several programming languages.
+
+\item Started around 1986 by Richard Stallman (after \alert{GNU Emacs}, but
+likely before \alert{GCC}).
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:orgb03390f}]{Compiling your program for GDB}
+ \begin{itemize}
+\item Your program needs to contain \alert{debug information} (also called
+\texttt{DWARF}) for GDB to consume.
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item The GCC flag to include debug information is \texttt{-g}.  We also use
+\texttt{-g3}, which includes information about macros (\texttt{\#define}).
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item It's common to \alert{disable optimizations} when building the binary, by
+using the flag \texttt{-O0} (it's \emph{dash-oh-zero}).
+
+\pause
+
+\begin{itemize}
+\item \texttt{\# gcc -O0 -g program.c -o program}, \emph{or}
+
+\item \texttt{\# CFLAGS='-O0 -g' ./configure \&\& make}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org71ced54}]{Running your program using GDB}
+ \begin{itemize}
+\item In GDB's parlance, the program being debugged is called the
+\alert{inferior}.
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Some ways to start the debugger:
+
+\pause
+
+\begin{itemize}
+\item \texttt{\# gdb ./program}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item \texttt{\# gdb -{}-args ./program arg1 arg2}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item \texttt{\# gdb}  \\
+\texttt{(gdb) file ./program}  \\
+\texttt{(gdb) run arg1 arg2}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org361654c}]{\{Break,Catch,Watch\}points}
+ \begin{itemize}
+\item A \alert{breakpoint} is related to \emph{source code} (location, function).  A
+\alert{watchpoint} is related to \emph{data} (read/write of a variable).  A
+\alert{catchpoint} is related to an \emph{event} (enter/exit a syscall, fork,
+receive a signal).
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Breakpoints (\emph{code})
+
+\begin{itemize}
+\item \texttt{break}
+
+\item \texttt{tbreak} (temporary)
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Watchpoints (\emph{data})
+
+\begin{itemize}
+\item \texttt{watch} (write), \texttt{rwatch} (read), \texttt{awatch} (access)
+
+\item Conditional watchpoints are supported.
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Catchpoints (\emph{events})
+
+\begin{itemize}
+\item \texttt{catch fork}
+
+\item \texttt{catch syscall}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org62a7e28}]{Resuming the execution}
+ \begin{itemize}
+\item After GDB has stopped the inferior (because a \texttt{*point} has been hit,
+for example), you will probably want to resume its execution.
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item You may just want to continue the program:
+
+\begin{itemize}
+\item \texttt{continue}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Or maybe go to the next statement/instruction:
+
+\begin{itemize}
+\item \texttt{next} (\emph{statement}), or \texttt{nexti} (\emph{instruction})
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Or step into a function:
+
+\begin{itemize}
+\item \texttt{step} (\emph{statement}), or \texttt{stepi} (\emph{instruction})
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Or finish executing the current function, but stop at the end:
+
+\begin{itemize}
+\item \texttt{finish}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+
+
+\begin{frame}[fragile,label={sec:org717537c}]{Examining data}
+ \begin{itemize}
+\item The inferior has stopped\ldots{}  Now what?
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item You may want to print the value of some variable:
+
+\begin{itemize}
+\item \texttt{print VAR}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Or examine a memory location:
+
+\begin{itemize}
+\item \texttt{x ADDRESS}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item The type of a variable?  Easy:
+
+\begin{itemize}
+\item \texttt{whatis VARIABLE}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item Hint: you may want to enable pretty-printing:
+
+\begin{itemize}
+\item \texttt{set print pretty on}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org71b8f2a}]{Examining the code}
+ \begin{itemize}
+\item Yes, we have \texttt{ncurses}!  The \textbf{T}ext
+\textbf{U}user \textbf{I}nterface!
+
+\begin{itemize}
+\item \texttt{C-x a} (that's \texttt{CTRL x a}).
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item If you want to list the current region, or if you don't want/can't
+to use TUI:
+
+\begin{itemize}
+\item \texttt{list}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item You can also disassemble code:
+
+\begin{itemize}
+\item \texttt{disassemble}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item If GDB can't find the source code, you can specify its location
+using the \texttt{dir} command.
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org1b45b5a}]{Examining the call stack}
+ \begin{itemize}
+\item If you want to see the call stack (A.K.A. stack trace) that lead to
+the current function:
+
+\begin{itemize}
+\item \texttt{bt}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item And you can move through it:
+
+\begin{itemize}
+\item \texttt{up} and \texttt{down}
+
+\item You can also go to a specific frame: \texttt{frame NUMBER}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org22c386a}]{Corefiles}
+ \begin{itemize}
+\item \alert{Corefiles} are frozen images of the inferior.  You can inspect
+everything that was happening when the process was running (but you
+can't resurrect it).
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item You can generate them \emph{outside} GDB, when a program crashes.  Make
+sure you:
+
+\begin{itemize}
+\item \texttt{ulimit -c unlimited}
+
+\item Check if \texttt{systemd} is handling them
+(\texttt{/proc/sys/kernel/core\_pattern}).
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item You can also generate them \emph{inside} GDB, at any moment:
+
+\begin{itemize}
+\item \texttt{generate-core-file}
+\end{itemize}
+\end{itemize}
+
+\pause
+
+\begin{itemize}
+\item You can open a corefile using GDB:
+
+\begin{itemize}
+\item \texttt{\# gdb program -c corefile.PID}
+\end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org7b2681d}]{Other interesting information}
+ \begin{itemize}
+\item \texttt{info breakpoints}
+
+\item \texttt{info locals}
+
+\item \texttt{info registers}
+
+\item Many others!
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org73ead26}]{Who you gonna call?}
+ \begin{itemize}
+\item Our online documentation (\texttt{info}) is very good!
+
+\item Every command has a \texttt{help}.
+
+\item You can also use \texttt{apropos} when searching for a term.
+
+\item \texttt{TAB}-completion is also useful.
+\end{itemize}
+\end{frame}
+
+\begin{frame}[label={sec:orgf6ce0ab}]{Other advanced features}
+\begin{itemize}
+\item Python support.
+
+\item Reverse debugging.
+
+\item Support for \emph{SystemTap SDT probes}.
+\end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label={sec:org0d39b0e}]{End}
+ \lstset{language=C,label= ,caption= ,captionpos=b,firstnumber=1,numbers=left,style=customc}
+\begin{lstlisting}
+int main ()
+{
+  const char *c = NULL;
+
+  return 0;
+}
+\end{lstlisting}
+\end{frame}
+\end{document}