[bootlin/training-materials updates] master: debugging: labs: remind about setting kgdboc before the sysrq trigger (82e9ce5f)

[Luca Ceresoli]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/82e9ce5fb737d705786e002e679ab7a327c9de90

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

commit 82e9ce5fb737d705786e002e679ab7a327c9de90
Author: Luca Ceresoli <luca.ceresoli at bootlin.com>
Date:   Fri Mar 24 19:28:27 2023 +0100

    debugging: labs: remind about setting kgdboc before the sysrq trigger
    
    Signed-off-by: Luca Ceresoli <luca.ceresoli at bootlin.com>


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82e9ce5fb737d705786e002e679ab7a327c9de90
 labs/debugging-kernel-debugging/debugging-kernel-debugging.tex | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/labs/debugging-kernel-debugging/debugging-kernel-debugging.tex b/labs/debugging-kernel-debugging/debugging-kernel-debugging.tex
index 90ea71e8..26686eb8 100644
--- a/labs/debugging-kernel-debugging/debugging-kernel-debugging.tex
+++ b/labs/debugging-kernel-debugging/debugging-kernel-debugging.tex
@@ -273,11 +273,13 @@ Then on the target, insert the module using insmod:
 # insmod kgdb_test.ko
 \end{bashinput}
 
-We can now enter KGDB mode and attach the external gdb to it. We will do that
-using using the magic SySrq 'g' key:
+We can now enter KGDB mode and attach the external gdb to it. We will do
+that using using the magic SySrq 'g' key. Before that, ensure the tty
+device for gdb already set, or set it now:
 
 \begin{bashinput}
-# echo g > /proc/sysrq_trigger
+# echo ttySTM0 > /sys/module/kgdboc/parameters/kgdboc
+# echo g > /proc/sysrq-trigger
 \end{bashinput}
 
 The kernel will then enter KGDB mode and will wait for a gdb connection. On the