From 710e42e80fe80a9af197bd2fe0e7029dec00d960 Mon Sep 17 00:00:00 2001
From: Ciro Santilli <ciro.santilli@gmail.com>
Date: Sun, 21 May 2017 09:26:47 +0100
Subject: [PATCH] qemu on background for debug

---
 README.md | 36 ++++++++++++++++++++++++------------
 rungdb    |  2 +-
 runqemu   | 20 ++++++++++++++++++--
 3 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/README.md b/README.md
index 30c5103..5cba3e4 100644
--- a/README.md
+++ b/README.md
@@ -44,13 +44,31 @@ We use `printk` a lot, and it shows on the QEMU terminal by default. If that ann
 
 See also: <https://superuser.com/questions/351387/how-to-stop-kernel-messages-from-flooding-my-console>
 
+## Text mode
+
+Show serial output of QEMU directly on the current terminal, without opening a QEMU window:
+
+    ./run -n
+
+To exit, just do a regular:
+
+    poweroff
+
+This is particularly useful to get full panic traces when you start making the kernel crashing :-)
+
+In case of a panic, you want your terminal back with `Ctrl + C, A` and type `quit`. See also: <http://stackoverflow.com/questions/14165158/how-to-switch-to-qemu-monitor-console-when-running-with-curses>
+
+See also: <https://unix.stackexchange.com/questions/208260/how-to-scroll-up-after-a-kernel-panic>
+
 ## Debugging
 
 To GDB the Linux kernel, first run:
 
     ./runqemu -d
 
-If you want to break immediately at a symbol, e.g. `start_kernel` of the boot sequence, open another terminal and run:
+This starts QEMU on the background of the shell, to prepare for running GDB.
+
+If you want to break immediately at a symbol, e.g. `start_kernel` of the boot sequence, run:
 
     ./rungdb start_kernel
 
@@ -83,21 +101,15 @@ And now you can control the counting from GDB:
 
 See also: <http://stackoverflow.com/questions/11408041/how-to-debug-the-linux-kernel-with-gdb-and-qemu>
 
-## Text mode
+If you are using text mode:
 
-Show serial output of QEMU directly on the current terminal, without opening a QEMU window:
+    ./runqemu -d -n
 
-    ./run -n
+QEMU cannot be put on the background of the current shell, so you will need to open a separate terminal and run:
 
-To exit, just do a regular:
+    ./rungdb
 
-    poweroff
-
-This is particularly useful to get full panic traces when you start making the kernel crashing :-)
-
-In case of a panic, you want your terminal back with `Ctrl + C, A` and type `quit`. See also: <http://stackoverflow.com/questions/14165158/how-to-switch-to-qemu-monitor-console-when-running-with-curses>
-
-See also: <https://unix.stackexchange.com/questions/208260/how-to-scroll-up-after-a-kernel-panic>
+manually.
 
 ## Table of contents
 
diff --git a/rungdb b/rungdb
index 5f159b5..763e4e6 100755
--- a/rungdb
+++ b/rungdb
@@ -6,6 +6,7 @@ else
 fi
 cd buildroot/output/build/linux-*.*.*/
 cmd="gdb \
+  -q \
   -ex 'add-auto-load-safe-path $(pwd)' \
   -ex 'file vmlinux' \
   -ex 'set arch i386:x86-64:intel' \
@@ -16,5 +17,4 @@ cmd="gdb \
   -ex 'set arch i386:x86-64' \
   -ex 'target remote localhost:1234'
 "
-echo "$cmd"
 eval "$cmd"
diff --git a/runqemu b/runqemu
index 0cbb7d0..9afdd44 100755
--- a/runqemu
+++ b/runqemu
@@ -3,23 +3,27 @@
 set -e
 
 # CLI handling.
+debug=false
+nographic=false
 extra_append=''
 extra_flags=''
 while getopts dn OPT; do
   case "$OPT" in
     d)
+      debug=true
       extra_flags="$extra_flags -S -s"
       ;;
     n)
       extra_append="$extra_append console=ttyS0"
       extra_flags="$extra_flags -nographic"
+      nographic=true
       ;;
   esac
 done
 
-qemu-system-x86_64 \
+cmd="qemu-system-x86_64 \
   -M pc \
-  -append "root=/dev/vda $extra_append" \
+  -append 'root=/dev/vda $extra_append' \
   -drive file=buildroot/output/images/rootfs.ext2,if=virtio,format=raw \
   -kernel buildroot/output/images/bzImage \
   -m 128M \
@@ -28,3 +32,15 @@ qemu-system-x86_64 \
   -smp 1 \
   $extra_flags \
 ;
+"
+
+if $debug && ! $nographic; then
+  eval nohup "$cmd" &>/dev/null &
+  # TODO: Ctrl +C gets sent to QEMU? Why? Does not happen if I run
+  # ./rungdb manually from outside this script!!! But why?!?!
+  # eval has nothing to do with it, minimized example with explicit
+  # commands also fails in the same way...
+  #./rungdb
+else
+  eval "$cmd"
+fi