pkg/mgrconfig: add a sample syzkaller config

Add a sample syzkaller config with comments so that we could refer to it
in the tutorials.

Author: a-nogikh

docs/configuration.md

@@ -2,5 +2,5 @@
 
 The operation of the syzkaller `syz-manager` process is governed by a
 configuration file, passed at invocation time with the `-config` option.
-This configuration can be based on the [example](/pkg/mgrconfig/testdata/qemu.cfg);
+This configuration can be based on the [example](/pkg/mgrconfig/testdata/qemu-example.cfg);
 the file is in JSON format and contains the the [following parameters](/pkg/mgrconfig/config.go).

docs/reproducing_crashes.md

@@ -241,7 +241,7 @@ https://groups.google.com/d/msg/syzkaller/fHZ42YrQM-Y/Z4Xf-BbUDgAJ.
 
 This process is automated to some degree in the `syz-repro` utility. You need to
 give it your manager config and a crash report file. And you can refer to the
-[example config file](/pkg/mgrconfig/testdata/qemu.cfg).
+[example config file](/pkg/mgrconfig/testdata/qemu-example.cfg).
 ```
 ./syz-repro -config my.cfg crash-qemu-1-1455745459265726910
 ```

pkg/mgrconfig/testdata/qemu-example.cfg

@@ -0,0 +1,27 @@
+{
+        "target": "linux/amd64",
+        "http": "0.0.0.0:56741",
+        # !! Replace /syzkaller with the path to the syzkaller checkout.
+        # Workdir can be in whatever folder, keeping it in the checkout is just most convenient.
+        "workdir": "./testdata/syzkaller/workdir",
+        # !! Replace /linux with the path to the kernel checkout.
+        # !! The kernel must be already built.
+        # Here are the kernel config options that facilitate fuzzing: https://github.com/google/syzkaller/blob/master/docs/linux/kernel_configs.md
+        "kernel_obj": "/linux",
+        # !! Replace with the path to the disk image file.
+        # The Buildroot image used by syzbot can be downloaded here: https://storage.googleapis.com/syzkaller/images/buildroot_amd64_2024.09.gz
+        # (Don't forget to uncompress it!).
+        "image": "./testdata/wheezy.img",
+	# !! Replace with the path to the syzkaller checkout.
+        "syzkaller": "./testdata/syzkaller",
+        "procs": 4,
+        "type": "qemu",
+        "vm": {
+                "count": 4,
+                # !! Adjust this path accordingly.
+                "kernel": "/linux/arch/x86/boot/bzImage",
+                # Note that syzkaller will use `count` * `cpu` CPUs and `count` * `mem` RAM.
+                "cpu": 2,
+                "mem": 2048
+        }
+}