added dockerfile for kernel dev

6 files changed, 107 insertions, 5 deletions

diff --git a/content/20191027-kernel-debugging-qemu.md b/content/20191027-kernel-debugging-qemu.md
index 5189f86..7a97fbc 100644
--- a/content/20191027-kernel-debugging-qemu.md
+++ b/content/20191027-kernel-debugging-qemu.md
@@ -6,6 +6,10 @@ date = 2019-10-27
 tags = ["linux", "qemu"]
 +++
 
+**EDIT**:
+- 2021-07-15: Added `Appendix: Dockerfile for Kernel development` 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
 the state.
@@ -186,6 +190,32 @@ type = struct filename {
 }
 ```
 
+## Appendix: `Dockerfile` for Kernel development
+
+The following `Dockerfile` provides a development environment with all the
+required tools and dependencies, to re-produce all the steps of building and
+debugging the Linux kernel.
+```dockerfile
+{{ include(path="content/20191027-kernel-debugging-qemu/Dockerfile") }}
+```
+
+Save the listing above in a file called `Dockerfile` and build the docker image
+as follows.
+```sh
+docker build -t kernel-dev
+```
+> Optionally set `DOCKER_BUILDKIT=1` to use the newer image builder.
+
+Once the image has been built, an interactive container can be launched as
+follows.
+```sh
+# Some options for conveniene:
+#   -v <HOST>:<GUEST>     Mount host path to guest path.
+#   --rm                  Remove the container after exiting.
+
+docker run -it kernel-dev
+```
+
 [linux-kernel]: https://www.kernel.org
 [initrd]: https://www.kernel.org/doc/html/latest/admin-guide/initrd.html
 [busybox]: https://busybox.net
diff --git a/content/20191027-kernel-debugging-qemu/Dockerfile b/content/20191027-kernel-debugging-qemu/Dockerfile
new file mode 100644
index 0000000..42e1f05
--- /dev/null
+++ b/content/20191027-kernel-debugging-qemu/Dockerfile
@@ -0,0 +1,32 @@
+FROM ubuntu:20.04
+MAINTAINER Johannes Stoelp <johannes.stoelp@gmail.edu>
+
+RUN apt update                     \
+ && DEBIAN_FRONTEND=noninteractive \
+    apt install                    \
+      --yes                        \
+      --no-install-recommends      \
+      # Download & unpack.
+      wget                         \
+      ca-certificates              \
+      xz-utils                     \
+      # Build tools & deps (kernel).
+      make                         \
+      bc                           \
+      gcc g++                      \
+      flex bison                   \
+      libelf-dev                   \
+      # Build tools & deps (initrd).
+      cpio                         \
+      # Run & debug.
+      qemu-system-x86              \
+      gdb                          \
+      telnet                       \
+      # Convenience.
+      ripgrep                      \
+      fd-find                      \
+      neovim                       \
+ && rm -rf /var/lib/apt/lists/*    \
+ && apt-get clean
+
+WORKDIR /develop
diff --git a/content/20191027-kernel-debugging-qemu/Makefile b/content/20191027-kernel-debugging-qemu/Makefile
new file mode 100644
index 0000000..11e7c7b
--- /dev/null
+++ b/content/20191027-kernel-debugging-qemu/Makefile
@@ -0,0 +1,12 @@
+build:
+	scripts/build_kernel.sh
+	scripts/build_initrd.sh
+
+clean:
+	$(RM) -r linux-*
+	$(RM) -r busybox-*
+	$(RM) initramfs.cpio.gz
+
+docker:
+	DOCKER_BUILDKIT=1 docker build -t kernel-dev .
+	docker run -it --rm -v $(PWD):/develop/scripts -v $(PWD)/Makefile:/develop/Makefile kernel-dev
diff --git a/content/20191027-kernel-debugging-qemu/build_initrd.sh b/content/20191027-kernel-debugging-qemu/build_initrd.sh
index 74f9896..fd82990 100644..100755
--- a/content/20191027-kernel-debugging-qemu/build_initrd.sh
+++ b/content/20191027-kernel-debugging-qemu/build_initrd.sh
@@ -1,8 +1,12 @@
 #!/bin/bash
 
+if test $(id -u) -ne 0; then
+    SUDO=sudo
+fi
+
 set -e
 
-BUSYBOX=busybox-1.31.0
+BUSYBOX=busybox-1.33.1
 INITRD=$PWD/initramfs.cpio.gz
 
 ## Build busybox
@@ -40,9 +44,9 @@ 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
+$SUDO mknod dev/tty c 5 0
+$SUDO mknod dev/tty0 c 4 0
+$SUDO mknod dev/ttyS0 c 4 64
 
 # 4. created compressed initrd
 find . -print0                      \
diff --git a/content/20191027-kernel-debugging-qemu/build_kernel.sh b/content/20191027-kernel-debugging-qemu/build_kernel.sh
index f1e15bb..7ae3014 100644..100755
--- a/content/20191027-kernel-debugging-qemu/build_kernel.sh
+++ b/content/20191027-kernel-debugging-qemu/build_kernel.sh
@@ -2,7 +2,7 @@
 
 set -e
 
-LINUX=linux-5.3.7
+LINUX=linux-5.13.2
 wget https://cdn.kernel.org/pub/linux/kernel/v5.x/$LINUX.tar.xz
 unxz $LINUX.tar.xz && tar xf $LINUX.tar
 
diff --git a/content/20191027-kernel-debugging-qemu/run.sh b/content/20191027-kernel-debugging-qemu/run.sh
new file mode 100755
index 0000000..b0a84ae
--- /dev/null
+++ b/content/20191027-kernel-debugging-qemu/run.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+
+VER=5.13.2
+
+# Launch the emulator with our kernel.
+qemu-system-x86_64                                                   \
+  -kernel ./linux-$VER/arch/x86/boot/bzImage                         \
+  -nographic                                                         \
+  -append "earlyprintk=ttyS0 console=ttyS0 nokaslr init=/init debug" \
+  -initrd ./initramfs.cpio.gz                                        \
+  -serial telnet:localhost:12345,server,nowait                       \
+  -monitor none                                                      \
+  -gdb tcp::1234                                                     \
+  -S &
+
+# Kill qemu when we exit.
+QEMU_PID=$!
+trap "kill $QEMU_PID" EXIT
+
+# Give qemu some time to come up.
+sleep 0.5
+
+# Attach debugger to qemu and load the kernel symbols.
+gdb -ex 'target remote :1234' ./linux-$VER/vmlinux