diff options
Diffstat (limited to 'content')
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 |