[PATCH 1/2] host/rootfs: use initramfs in "make run"

Alyssa Ross
2022-09-01T10:47:08Z

This will allow us to stop compiling e.g. the virtio-blk module into
the kernel, because it will be loaded by the initramfs.

This introduces some duplication between the rootfs and initramfs's
Makefiles. I don't think it's worth the effort at the moment to try
to reduce that, because it would come at the expense of additional
complexity in the Makefiles. We can revisit this later if we want to.

Signed-off-by: Alyssa Ross <hi@alyssa.is>
---
host/rootfs/Makefile | 32 ++++++++++++++++++++++++++++----
host/rootfs/shell.nix | 10 ++++++++--
2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/host/rootfs/Makefile b/host/rootfs/Makefile
index 41cf87c..31f76d2 100644
--- a/host/rootfs/Makefile
+++ b/host/rootfs/Makefile
@@ -6,6 +6,9 @@
# QEMU_KVM = qemu-system-x86_64 -enable-kvm.
QEMU_KVM = qemu-kvm

+SCRIPTS = ../../scripts
+VERITYSETUP = veritysetup
+
# tar2ext4 will leave half a filesystem behind if it's interrupted
# half way through.
build/rootfs.ext4: build/rootfs.tar
@@ -116,16 +119,37 @@ clean:
rm -rf build
.PHONY: clean

-run: build/rootfs.ext4 $(EXT_FS)
+# veritysetup format produces two files, but Make only (portably)
+# supports one output per rule, so we combine the two outputs then
+# define two more rules to separate them again.
+build/rootfs.verity: build/rootfs.ext4
+ $(VERITYSETUP) format build/rootfs.ext4 build/rootfs.verity.superblock.tmp \
+ | awk -F ':[[:blank:]]*' '$$1 == "Root hash" {print $$2; exit}' \
+ > build/rootfs.verity.roothash.tmp
+ cat build/rootfs.verity.roothash.tmp build/rootfs.verity.superblock.tmp \
+ > $@
+ rm build/rootfs.verity.roothash.tmp build/rootfs.verity.superblock.tmp
+build/rootfs.verity.roothash: build/rootfs.verity
+ head -n 1 build/rootfs.verity > $@
+build/rootfs.verity.superblock: build/rootfs.verity
+ tail -n +2 build/rootfs.verity > $@
+
+build/live.img: $(SCRIPTS)/format-uuid.sh $(SCRIPTS)/make-gpt.sh build/rootfs.verity.superblock build/rootfs.verity.roothash build/rootfs.ext4
+ $(SCRIPTS)/make-gpt.sh $@.tmp \
+ build/rootfs.verity.superblock:2c7357ed-ebd2-46d9-aec1-23d437ec2bf5:$$($(SCRIPTS)/format-uuid.sh "$$(dd if=build/rootfs.verity.roothash bs=32 skip=1 count=1 status=none)") \
+ build/rootfs.ext4:4f68bce3-e8cd-4db1-96e7-fbcaf984b709:$$($(SCRIPTS)/format-uuid.sh "$$(head -c 32 build/rootfs.verity.roothash)")
+ mv $@.tmp $@
+
+run: build/live.img $(EXT_FS) build/rootfs.verity.roothash
$(QEMU_KVM) -cpu host -m 2G \
- -machine q35,kernel=$(KERNEL),kernel-irqchip=split \
+ -machine q35,kernel=$(KERNEL),kernel-irqchip=split,initrd=$(INITRAMFS) \
-display gtk,gl=on \
-qmp unix:vmm.sock,server,nowait \
-monitor vc \
-parallel none \
- -drive file=build/rootfs.ext4,if=virtio,format=raw,readonly=on \
+ -drive file=build/live.img,if=virtio,format=raw,readonly=on \
-drive file=$(EXT_FS),if=virtio,format=raw,readonly=on \
- -append "console=ttyS0 root=/dev/vda ext=/dev/vdb intel_iommu=on" \
+ -append "console=ttyS0 roothash=$$(< build/rootfs.verity.roothash) ext=/dev/vdb intel_iommu=on" \
-device intel-iommu,intremap=on \
-device virtio-vga-gl \
-device vhost-vsock-pci,guest-cid=3
diff --git a/host/rootfs/shell.nix b/host/rootfs/shell.nix
index 3b2310f..fe9df1b 100644
--- a/host/rootfs/shell.nix
+++ b/host/rootfs/shell.nix
@@ -1,18 +1,24 @@
# SPDX-License-Identifier: MIT
# SPDX-FileCopyrightText: 2021 Alyssa Ross <hi@alyssa.is>
+# SPDX-FileCopyrightText: 2022 Unikie

{ pkgs ? import <nixpkgs> {} }:

+let
+ rootfs = import ./. { inherit pkgs; };
+in
+
with pkgs;

-(import ./. { inherit pkgs; }).overrideAttrs (
+rootfs.overrideAttrs (
{ passthru ? {}, nativeBuildInputs ? [], ... }:

{
nativeBuildInputs = nativeBuildInputs ++ [
- jq netcat qemu_kvm reuse util-linux
+ cryptsetup jq netcat qemu_kvm reuse util-linux
];

EXT_FS = pkgsStatic.callPackage ../initramfs/extfs.nix { inherit pkgs; };
+ INITRAMFS = import ../initramfs { inherit pkgs rootfs; };
KERNEL = "${passthru.kernel}/${stdenv.hostPlatform.linux-kernel.target}";
})
--
2.37.1