Using SimicsFS

7.3 Using SimicsFS

SimicsFS gives you access to the file system of your real computer inside the simulated machine. This greatly simplifies the process of importing files into the simulated machine.

SimicsFS is supported for targets running Solaris 7, 8, 9 and 10, and Linux kernel versions 2.0 to 2.6.

SimicsFS is installed on disk dumps distributed by Virtutech. For users booting from other disks, there are a number of steps needed to configure the target system. This process is target OS specific, and is described in the following sections.

SimicsFS is not fully functional on all simulated operating systems. The following limitations apply:

Simulated OS	Limitations
Linux	Access is read-only. (Write support experimental.)
Solaris	Truncating files does not work.
Other	SimicsFS is not currently available.

7.3.1 Installing SimicsFS on a Simulated Linux System

For Linux kernel versions prior to 2.4, the SimicsFS kernel module is called hostfs rather than simicsfs, so for those kernels just replace the simicsfs part in file names with hostfs in the following description. When the instructions ask you to copy files into the simulated machine, one of the methods described elsewhere must be used (e.g., network, loopback disk access, or CD-ROM).

Since there are lots of different Linux kernels, and a module has to match the kernel version, Simics does not provide any pre-compiled simicsfs modules. To build your own simicsfs module, download the SimicsFS source code from https://www.simics.net/pub/simicsfs.tar.gz. The README_2.4 and README_2.6 files in the archive will explain how to add the SimicsFS sources to the Linux kernel tree and compile it with the kernel you want to use.

Create a new directory /lib/modules/version/kernel/fs/simicsfs/ on the simulated machine, where version is the simulated machine's kernel version.

Copy the newly compiled SimicsFS module file to the directory /lib/modules/version/kernel/fs/simicsfs/ on the simulated machine, and make sure it is called simicsfs.o for Linux 2.4 (and older), and simicsfs.ko for Linux 2.6.

Create the mount point on the simulated machine with mkdir /host.

Add the following line in the simulated machine's /etc/fstab (replace /host with your mount point):
```
special      /host      simicsfs     noauto,ro      0 0
```

Note:

ro

rw

Mount SimicsFS with the command mount /host on the simulated machine.

SimicsFS should now be working, and by issuing ls /host on the simulated machine, you should get a listing of the host machine's files.

7.3.2 Installing SimicsFS on a Simulated Solaris System

These are the steps needed to install SimicsFS on a simulated Solaris, version 7, 8, 9 and 10. When the instructions ask you to copy files into the simulated machine, one of the methods described above must be used (network, loopback disk access, CD-ROM...). Note that the driver included with earlier Simics distributions was called hostfs and not simicsfs.

Create a new directory /usr/lib/fs/simicsfs/ on the simulated machine.

Copy the file [simics]/import/sun4u/mount_simicsfs to /usr/lib/fs/simicsfs/ on the simulated disk, and rename it to mount.

Copy the file [simics]/import/sun4u/simicsfs-solversion (where version matches the version of Solaris running on your simulated machine) to /usr/kernel/fs/sparcv9/ on the simulated machine, and rename it to simicsfs.

Add the following line to /etc/vfstab on the simulated disk:
```
simicsfs  -       /host   simicsfs  -       no      -
```

Create the mount point on the simulated machine with mkdir /host.

When the simulated system is running, issue the command:
```
mount /host
```

You should now be able to do ls /host on the simulated system to get a list of the files on the host.

7.3.3 Using SimicsFS

By default, the simulated machine can access the entire file tree of the host computer from the mount point (typically /host).

This can sometimes be inconvenient (or dangerous, if the simulator runs untrusted or unreliable code), so it is recommended to set the directory that is visible to the simulated machine using the <hostfs>.root command, e.g.:

simics> hfs0.root /home/alice/sandbox

The command will take effect next time SimicsFS is mounted.

Because of implementation limitations, it is recommended that SimicsFS be chiefly used to copy files into and out from the target machine. In particular, executing binaries residing on the host machine may be unreliable.

Note: When saving a checkpoint while a SimicsFS is mounted, take care that the host files that were used at that time are kept unchanged when the checkpoint is loaded.

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