kernel-dbg: fix ramfs vs ramdisk and use devtmpfs and update

busybox/kernel version

5 files changed, 22 insertions, 15 deletions

diff --git a/content/2019-10-27-kernel-debugging-qemu/Dockerfile b/content/2019-10-27-kernel-debugging-qemu/Dockerfile
index 9da22f3..a2fe4c8 100644
--- a/content/2019-10-27-kernel-debugging-qemu/Dockerfile
+++ b/content/2019-10-27-kernel-debugging-qemu/Dockerfile
@@ -22,6 +22,7 @@ RUN apt update                     \
       # Run & debug.
       qemu-system-x86              \
       gdb                          \
+      cgdb                         \
       telnet                       \
       # Convenience.
       ripgrep                      \
diff --git a/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh b/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh
index fd82990..f5bece4 100755
--- a/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh
+++ b/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh
@@ -6,7 +6,7 @@ fi
 
 set -e
 
-BUSYBOX=busybox-1.33.1
+BUSYBOX=busybox-1.36.1
 INITRD=$PWD/initramfs.cpio.gz
 
 ## Build busybox
@@ -20,7 +20,7 @@ echo "[+] configure & build $BUSYBOX ..."
 cd $BUSYBOX
 make defconfig
 sed -i 's/# CONFIG_STATIC .*/CONFIG_STATIC=y/' .config
-make -j4 busybox
+make -j$(nproc --ignore=2) busybox
 make install
 
 ## Create initrd
@@ -38,17 +38,13 @@ cat <<EOF > init
 
 mount -t proc none /proc
 mount -t sysfs none /sys
+mount -t devtmpfs none /dev
 
 exec setsid cttyhack sh
 EOF
 chmod +x init
 
-# 3. create device nodes
-$SUDO mknod dev/tty c 5 0
-$SUDO mknod dev/tty0 c 4 0
-$SUDO mknod dev/ttyS0 c 4 64
-
-# 4. created compressed initrd
+# 3. created compressed initrd
 find . -print0                      \
     | cpio --null -ov --format=newc \
     | gzip -9 > $INITRD
diff --git a/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh b/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh
index 7ae3014..2789a0e 100755
--- a/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh
+++ b/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh
@@ -2,8 +2,8 @@
 
 set -e
 
-LINUX=linux-5.13.2
-wget https://cdn.kernel.org/pub/linux/kernel/v5.x/$LINUX.tar.xz
+LINUX=linux-6.6.2
+wget https://cdn.kernel.org/pub/linux/kernel/v6.x/$LINUX.tar.xz
 unxz $LINUX.tar.xz && tar xf $LINUX.tar
 
 cd $LINUX
@@ -28,11 +28,15 @@ CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_PROC_FS=y
 CONFIG_SYSFS=y
 # debugging
+CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_INFO=y
+## tinyconfig sets DEBUG_INFO_NONE, overwrite with toolchain default else
+## DEBUG_INFO will not be enabled.
+CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
 CONFIG_PRINTK=y
 CONFIG_EARLY_PRINTK=y
 EOF
 
 make tinyconfig
 ./scripts/kconfig/merge_config.sh -n ./kernel_fragment.config
-make -j4
+make -j$(nproc --ignore=2)
diff --git a/content/2019-10-27-kernel-debugging-qemu/index.md b/content/2019-10-27-kernel-debugging-qemu/index.md
index 518b3d5..bda445b 100644
--- a/content/2019-10-27-kernel-debugging-qemu/index.md
+++ b/content/2019-10-27-kernel-debugging-qemu/index.md
@@ -8,6 +8,8 @@ tags = ["linux", "qemu"]
 **EDIT**:
 - 2021-07-15: Added `Appendix: Dockerfile for Kernel development` and updated
   busybox + Kernel versions.
+- 2023-11-23: Fix ramdisk vs ramfs ([ref][ramfs-vs-ramdisk]), and use
+  `devtmpfs` and updated busybox + Kernel versions.
 
 The other evening while starring at some Linux kernel code I thought, let me
 setup a minimal environment so I can easily step through the code and examine
@@ -15,7 +17,7 @@ the state.
 
 I ended up creating:
 - a [Linux kernel][linux-kernel] with minimal configuration
-- a minimal [ramdisk][initrd] to boot into which is based on [busybox][busybox]
+- a minimal [initramfs][initramfs] to boot into which is based on [busybox][busybox]
 
 In the remaing part of this article we will go through each step by first
 building the kernel, then building the initrd and then running the kernel using
@@ -31,7 +33,7 @@ This allows us to merge a fragment file into the current configuration by
 running the `scripts/kconfig/merge_config.sh` script.
 
 Let's quickly go over some customizations we do.
-The following two lines enable support for gzipped initramdisks:
+The following two lines enable support for gzipped initramfs:
 ```config
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_RD_GZIP=y
@@ -78,6 +80,7 @@ cat <<EOF > init
 
 mount -t proc none /proc
 mount -t sysfs none /sys
+mount -t devtmpfs none /dev
 
 exec setsid cttyhack sh
 EOF
@@ -217,6 +220,8 @@ docker run -it kernel-dev
 
 [linux-kernel]: https://www.kernel.org
 [initrd]: https://www.kernel.org/doc/html/latest/admin-guide/initrd.html
+[ramfs]: https://www.kernel.org/doc/html/latest/filesystems/ramfs-rootfs-initramfs.html
+[ramfs-vs-ramdisk]: https://www.kernel.org/doc/html/latest/filesystems/ramfs-rootfs-initramfs.html#ramfs-and-ramdisk
 [busybox]: https://busybox.net
 [qemu]: https://www.qemu.org
 [gdb]: https://www.gnu.org/software/gdb
diff --git a/content/2019-10-27-kernel-debugging-qemu/run.sh b/content/2019-10-27-kernel-debugging-qemu/run.sh
index b0a84ae..b9548ad 100755
--- a/content/2019-10-27-kernel-debugging-qemu/run.sh
+++ b/content/2019-10-27-kernel-debugging-qemu/run.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-VER=5.13.2
+VER=6.6.2
 
 # Launch the emulator with our kernel.
 qemu-system-x86_64                                                   \
@@ -21,4 +21,5 @@ trap "kill $QEMU_PID" EXIT
 sleep 0.5
 
 # Attach debugger to qemu and load the kernel symbols.
-gdb -ex 'target remote :1234' ./linux-$VER/vmlinux
+which cgdb >& /dev/null && GDB=cgdb || GDB=gdb
+$GDB -ex 'target remote :1234' -ex 'set style enabled off' ./linux-$VER/vmlinux