docs/linux: describe how to setup s390x test environment

Signed-off-by: Alexander Egorenkov <Alexander.Egorenkov@ibm.com>

2 files changed, 175 insertions, 0 deletions

diff --git a/docs/linux/setup.md b/docs/linux/setup.md
index 924a1c071..a4a0a5297 100644
--- a/docs/linux/setup.md
+++ b/docs/linux/setup.md
@@ -8,6 +8,7 @@ Instructions for a particular VM type or kernel architecture can be found on the
 - [Setup: Linux host, QEMU vm, arm64 kernel](setup_linux-host_qemu-vm_arm64-kernel.md)
 - [Setup: Linux host, QEMU vm, arm kernel](setup_linux-host_qemu-vm_arm-kernel.md)
 - [Setup: Linux host, QEMU vm, riscv64 kernel](setup_linux-host_qemu-vm_riscv64-kernel.md)
+- [Setup: Linux host, QEMU vm, s390x kernel](setup_linux-host_qemu-vm_s390x-kernel.md)
 - [Setup: Linux host, Android device, arm32/64 kernel](setup_linux-host_android-device_arm-kernel.md)
 - [Setup: Linux isolated host](setup_linux-host_isolated.md)
 - [Setup: Ubuntu host, Odroid C2 board, arm64 kernel](setup_ubuntu-host_odroid-c2-board_arm64-kernel.md) [outdated]
diff --git a/docs/linux/setup_linux-host_qemu-vm_s390x-kernel.md b/docs/linux/setup_linux-host_qemu-vm_s390x-kernel.md
new file mode 100644
index 000000000..162016c62
--- /dev/null
+++ b/docs/linux/setup_linux-host_qemu-vm_s390x-kernel.md
@@ -0,0 +1,174 @@
+# Setup: Debian/Ubuntu/Fedora host, QEMU vm, s390x kernel
+
+## GCC
+
+Obtain `s390x-linux-gnu-gcc` at least GCC version 9. The latest Debian/Ubuntu/Fedora distributions
+should provide a recent enough version of a cross-compiler in the `gcc-s390x-linux-gnu` package.
+
+## Kernel
+
+Checkout Linux kernel source:
+
+``` bash
+git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git $KERNEL
+```
+
+Generate default configs:
+
+``` bash
+cd $KERNEL
+make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- defconfig
+make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- kvm_guest.config
+```
+
+Enable kernel config options required for syzkaller as described [here](kernel_configs.md).
+
+```
+./scripts/config --file .config \
+                 -d MODULES \
+                 -e KCOV \
+                 -e KCOV_INSTRUMENT_ALL \
+                 -e KCOV_ENABLE_COMPARISONS \
+                 -e KASAN \
+                 -e KASAN_INLINE \
+                 -e CONFIGFS_FS \
+                 -e SECURITYFS \
+                 -e DEBUG_INFO \
+                 -e GDB_SCRIPTS \
+                 -e PRINTK \
+                 -e EARLY_PRINTK \
+                 -e DEVTMPFS \
+                 -e TUN \
+                 -e VIRTIO_PCI \
+                 -e VIRTIO_NET \
+                 -e NET_9P_VIRTIO \
+                 -e NET_9P \
+                 -e 9P_FS \
+                 -e BINFMT_MISC \
+                 -e FAULT_INJECTION \
+                 -e FAILSLAB \
+                 -e FAIL_PAGE_ALLOC \
+                 -e FAIL_MAKE_REQUEST \
+                 -e FAIL_IO_TIMEOUT \
+                 -e FAIL_FUTEX \
+                 -e FAULT_INJECTION_DEBUG_FS \
+                 -e FAULT_INJECTION_STACKTRACE_FILTER \
+                 -e DEBUG_KMEMLEAK
+```
+
+Edit `.config` file manually and enable them (or do that through `make menuconfig` if you prefer).
+
+Since enabling these options results in more sub options being available, we need to regenerate config:
+
+``` bash
+make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- olddefconfig
+```
+
+Build the kernel:
+
+```
+make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- -j$(nproc)
+```
+
+Now you should have `vmlinux` (kernel binary) and `bzImage` (packed kernel image):
+
+``` bash
+$ ls $KERNEL/vmlinux
+$KERNEL/vmlinux
+$ ls $KERNEL/arch/s390/boot/bzImage 
+$KERNEL/arch/s390/boot/bzImage
+```
+
+## Image
+
+### Debian
+
+To create a Debian Buster Linux image with the minimal set of required packages do:
+
+```
+cd $IMAGE/
+wget https://raw.githubusercontent.com/google/syzkaller/master/tools/create-image.sh -O create-image.sh
+chmod +x create-image.sh
+./create-image.sh -a s390x -d buster
+```
+
+The result should be `$IMAGE/buster.img` disk image.
+
+For additional options of `create-image.sh`, please refer to `./create-image.sh -h`
+
+## QEMU
+
+### Debian
+
+Run:
+
+```shell
+qemu-system-s390x \
+	-M s390-ccw-virtio -cpu max,zpci=on -m 4G -smp 2 \
+	-kernel $KERNEL/arch/s390/boot/bzImage \
+	-drive file=$IMAGE/buster.img,if=virtio,format=raw \
+	-append "rootwait root=/dev/vda net.ifnames=0 biosdevname=0" \
+	-net nic,model=virtio -net user,host=10.0.2.10,hostfwd=tcp:127.0.0.1:10021-:22 \
+	-display none -serial mon:stdio \
+	-pidfile vm.pid 2>&1 | tee vm.log
+```
+
+After that you should be able to ssh to QEMU instance in another terminal:
+
+``` bash
+ssh -i $IMAGE/buster.id_rsa -p 10021 -o "StrictHostKeyChecking no" root@localhost
+```
+
+If this fails with "too many tries", ssh may be passing default keys before
+the one explicitly passed with `-i`. Append option `-o "IdentitiesOnly yes"`.
+
+To kill the running QEMU instance press `Ctrl+A` and then `X` or run:
+
+``` bash
+kill $(cat vm.pid)
+```
+
+If QEMU works, the kernel boots and ssh succeeds, you can shutdown QEMU and try to run syzkaller.
+
+## syzkaller
+
+Build syzkaller as described [here](/docs/linux/setup.md#go-and-syzkaller), with `s390x` target:
+
+```
+make TARGETOS=linux TARGETARCH=s390x
+```
+
+Then create a manager config like the following, replacing the environment
+variables `$GOPATH`, `$KERNEL` and `$IMAGE` with their actual values.
+
+```
+{
+	"target": "linux/s390x",
+	"http": "127.0.0.1:56741",
+	"workdir": "$GOPATH/src/github.com/google/syzkaller/workdir",
+	"kernel_obj": "$KERNEL",
+	"image": "$IMAGE/buster.img",
+	"sshkey": "$IMAGE/buster.id_rsa",
+	"syzkaller": "$GOPATH/src/github.com/google/syzkaller",
+	"procs": 8,
+	"type": "qemu",
+	"vm": {
+		"count": 4,
+		"kernel": "$KERNEL/arch/s390/boot/bzImage",
+		"cpu": 2,
+		"mem": 2048
+	}
+}
+```
+
+Run syzkaller manager:
+
+``` bash
+mkdir workdir
+./bin/syz-manager -config=my.cfg
+```
+
+Now syzkaller should be running, you can check manager status with your web browser at `127.0.0.1:56741`.
+
+If you get issues after `syz-manager` starts, consider running it with the `-debug` flag.
+Also see [this page](/docs/troubleshooting.md) for troubleshooting tips.