# Fuchsia support

For information about checking out and building Fuchsia see
[Getting Started](https://fuchsia.googlesource.com/fuchsia/+/master/docs/getting_started.md)
and [Source Code](https://fuchsia.googlesource.com/fuchsia/+/master/docs/development/source_code/README.md).

## Prerequisites

To run syzkaller with a fuchsia target, you will need:

* A fuchsia checkout.
* The [fuchsia
  sdk](https://chrome-infra-packages.appspot.com/p/fuchsia/sdk/core/linux-amd64/+/).
* [clang with fuchsia
  support](https://chrome-infra-packages.appspot.com/p/fuchsia/clang/linux-amd64/+/).

The rest of the document will use the following environment variables:

* `SOURCEDIR` path of your fuchsia checkout.
* `FX_SDK_PATH` path where you extracted the fuchsia sdk.
* `CLANG_PATH` path where you extracted clang.

### Build Go toolchain for fuchsia

Syzkaller needs to cross-compile it's Go binaries to run in fuchsia, so first
you need to compile a Go toolchain that can compile binaries for fuchsia.

Once you downloaded and extracted the fuchsia sdk and clang, run:

```
$ make TARGETOS=fuchsia TARGETARCH=amd64 \
    SOURCEDIR=path/to/fuchsia/checkout \
    FX_SDK_PATH=path/to/fuchsia/sdk \
    CLANG_PATH=path/to/clang \
    fuchsia_go
```

## Building binaries for fuchsia

To build all the binaries required for running syzkaller in fuchsia, run:

```
$ make TARGETOS=fuchsia TARGETARCH=amd64 \
    SOURCEDIR=path/to/fuchsia/checkout \
    FX_SDK_PATH=path/to/fuchsia/sdk \
    CLANG_PATH=path/to/clang
```

## Running syz-manager

Running syz-manager requires you to have built fuchsia previously, and added the ssh keys to the fuchsia.zbi image:

```
$ ${SOURCEDIR}/out/x64.zircon/tools/zbi -o ${SOURCEDIR}/out/x64/fuchsia-ssh.zbi ${SOURCEDIR}/out/x64/fuchsia.zbi --entry "data/ssh/authorized_keys=${SOURCEDIR}/.ssh/authorized_keys"
```

Run `syz-manager` with a config along the lines of:
```
{
        "name": "fuchsia",
        "target": "fuchsia/amd64",
        "http": ":12345",
        "workdir": "/workdir.fuchsia",
        "kernel_obj": "/fuchsia/out/x64.zircon/kernel-x64-gcc",
        "syzkaller": "/syzkaller",
        "image": "/fuchsia/out/x64/obj/build/images/fvm.blk",
        "sshkey": "/fuchsia/.ssh/pkey",
        "reproduce": false,
        "cover": false,
        "procs": 8,
        "type": "qemu",
        "vm": {
                "count": 10,
                "cpu": 4,
                "mem": 2048,
                "kernel": "/fuchsia/out/x64.zircon/multiboot.bin",
                "initrd": "/fuchsia/out/x64/fuchsia-ssh.zbi"
        }
}
```

## Update syscall and fidl definitions

Syscall descriptions live in the `sys/fuchsia` folder. To update a syscall, you need to modify the `.txt` file that contains it, make sure your new definition matches the one in zircon's [syscalls.abigen](https://fuchsia.googlesource.com/fuchsia/+/master/zircon/system/public/zircon/syscalls.abigen) file. **If the syscall was used in `executor/common_fuchsia.h`, you need to update the usages there as well**. FIDL definitions do not need manual updating because they are extracted automatically when you run make extract, but they require a fuchsia built for each architecture.

To build fuchsia run:
```shell
$ fx --dir "out/x64" set core.x64 --with-base "//bundles:tools"
$ fx clean-build
```

And

```shell
$ fx --dir "out/arm64" set core.arm64 --with-base "//bundles:tools"
$ fx clean-build
```

Once you updated the syscalls definitions, everything can be regenerated by running:

```
make extract TARGETOS=fuchsia SOURCEDIR=/path/to/fuchsia/checkout
make generate
```

## How to generate syscall description for FIDL

Syscall descriptions for FIDL are automatically generated as part of `make extract` as described above.

However, if you wish to manually generate syscall descriptions for a given `.fidl` file, do the following.

FIDL files should first be compiled into FIDL intermediate representation (JSON) files using `fidlc`:

```bash
/fuchsia/out/x64/host_x64/fidlc --json /tmp/io.json --files /fuchsia/zircon/system/fidl/fuchsia-io/io.fidl
```

Then run FIDL compiler backend `fidlgen` with syzkaller generator, which compiles a FIDL IR file into a syscall description file:

```bash
/fuchsia/out/x64/host_x64/fidlgen -generators syzkaller -json /tmp/io.json -output-base fidl_io -include-base fidl_io
```
## Running syz-ci locally

To run `syz-ci` locally for Fuchsia, you need:

- Go 1.12 toolchain (in `/go1.12` dir in the example below)
- bootstrapped Fuchsia checkout (in `/bootstrap/fuchsia` dir in the example below)
- bootstrap `syz-ci` binary (in the current dir, build with `make ci`)
- `syz-ci` config similar to the one below (in `ci.cfg` file in the current dir)

```
{
	"name": "testci",
	"http": ":50000",
	"manager_port_start": 50001,
	"goroot": "/go1.12",
	"syzkaller_repo": "https://github.com/google/syzkaller.git",
	"managers": [
		{
			"name": "fuchsia",
			"repo": "https://fuchsia.googlesource.com",
			"manager_config": {
				"target": "fuchsia/amd64",
				"type": "qemu",
				"cover": false,
				"procs": 8,
				"vm": {
					"count": 4,
					"cpu": 4,
					"mem": 1024
				}
			}
		}
	]
}
```

Run `syz-ci` as:
```
SOURCEDIR=/bootstrap/fuchsia ./syz-ci -config ci.cfg
```

## Troubleshooting

While running the `make extract` step, it's possible that the fidl definitions
are not up to date. It could happen that they have been removed or renamed.

If this is the case, you would see an error mentioning that the fidl.json file
could not be found:

```
go generate ./sys/fuchsia
cannot find /path-to-fuchsia/out/x64/fidling/gen/zircon/public/fidl/zircon-ethernet/zircon-ethernet.fidl.json
exit status 1
```

You can search for the string in the fuchsia repos or in the code-review tool to
see what happened to it. If the fidl interface was renamed or removed, you
should update `sys/fuchsia/fidlgen/main.go` to reflect this change, and remove the
stale autogenerated files.