[bootlin/training-materials updates] master: slides: debugging: add ratelimited variants and kptr_restrict explanations (38ee6911)

[Clément Léger]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/38ee691184e32de30b6b3137785ab129dabc34b4

>---------------------------------------------------------------

commit 38ee691184e32de30b6b3137785ab129dabc34b4
Author: Clément Léger <clement.leger at bootlin.com>
Date:   Fri Feb 3 10:26:34 2023 +0100

    slides: debugging: add ratelimited variants and kptr_restrict explanations
    
    Signed-off-by: Clément Léger <clement.leger at bootlin.com>


>---------------------------------------------------------------

38ee691184e32de30b6b3137785ab129dabc34b4
 common/printk.tex | 51 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/common/printk.tex b/common/printk.tex
index 24263ff1..4259cf75 100644
--- a/common/printk.tex
+++ b/common/printk.tex
@@ -29,29 +29,6 @@ pr_info("Booting CPU %d\n", cpu);
 \begin{frame}[fragile]
   \frametitle{Debugging using messages (2/3)}
   \begin{itemize}
-  \item The kernel defines much more format specifiers than the standard
-    \code{printf()} existing ones.
-  \begin{itemize}
-    % \path of package url directly supports percent characters, unless it is
-    % used inside arguments of other macros which is the case of the \code macro
-    \item {\codecolor \path{%p}}: Display the hashed value of pointer by default.
-    \item {\codecolor \path{%px}}: Always display the address of a pointer (use
-      carefully on non-sensitive addresses).
-    \item {\codecolor \path{%pK}}: Display hashed pointer value, zeros or the
-      pointer address depending on \code{kptr_restrict} sysctl value.
-    \item {\codecolor \path{%pOF}}: Device-tree node format specifier.
-    \item {\codecolor \path{%pr}}: Resource structure format specifier.
-    \item {\codecolor \path{%pa}}: Physical address display (work on all architectures 32/64
-      bits)
-  \end{itemize}
-  \item See \kdochtml{core-api/printk-formats} for an exhaustive list of supported format
-    specifiers
-  \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
-  \frametitle{Debugging using messages (3/3)}
-  \begin{itemize}
   \item The \code{dev_*()} family of functions: \kfunc{dev_emerg},
     \kfunc{dev_alert}, \kfunc{dev_crit}, \kfunc{dev_err},
     \kfunc{dev_warn}, \kfunc{dev_notice}, \kfunc{dev_info} \\
@@ -72,6 +49,34 @@ dev_info(&pdev->dev, "in probe\n");
 [   25.884873] serial 481a8000.serial: in probe
       \end{verbatim}
     \end{itemize}
+  \item \code{*_ratelimited()} version exists which limits the amount of print
+    if called too much based on \code{/proc/sys/kernel/printk_ratelimit{_burst}}
+    values
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Debugging using messages (3/3)}
+  \begin{itemize}
+  \item The kernel defines much more format specifiers than the standard
+    \code{printf()} existing ones.
+  \begin{itemize}
+    % \path of package url directly supports percent characters, unless it is
+    % used inside arguments of other macros which is the case of the \code macro
+    \item {\codecolor \path{%p}}: Display the hashed value of pointer by default.
+    \item {\codecolor \path{%px}}: Always display the address of a pointer (use
+      carefully on non-sensitive addresses).
+    \item {\codecolor \path{%pK}}: Display hashed pointer value, zeros or the
+      pointer address depending on \code{kptr_restrict} sysctl value.
+    \item {\codecolor \path{%pOF}}: Device-tree node format specifier.
+    \item {\codecolor \path{%pr}}: Resource structure format specifier.
+    \item {\codecolor \path{%pa}}: Physical address display (work on all architectures 32/64
+      bits)
+  \end{itemize}
+  \item \code{/proc/sys/kernel/kptr_restrict} should be set to \code{1} in order
+    to display pointers which uses {\codecolor \path{%pK}}
+  \item See \kdochtml{core-api/printk-formats} for an exhaustive list of supported format
+    specifiers
   \end{itemize}
 \end{frame}