Re: [PATCH 02/23] TPM: Provide a facility for a userspace TPM emulator

Jarkko Sakkinen
2018-08-24T10:02:29Z

On Tue, Aug 21, 2018 at 12:31:40PM -0600, Jason Gunthorpe wrote:
> On Tue, Aug 21, 2018 at 04:57:03PM +0100, David Howells wrote:
> > Provide a misc device file (/dev/tpm_emul) by which a userspace TPM emulator
> > can set up a virtual TPM device under the control of the TPM frontend. The
> > way this works is:
> >
> > (1) The emulator opens /dev/tpm_emul which is provided by the tpm_user
> > driver.
> >
> > (2) tpm_user registers a TPM device and the tpm driver creates a /dev/tpmN
> > misc device for the trousers package and suchlike to access.
> >
> > (3) The emulator sits in read() on the emulator device waiting for a command
> > to come through.
> >
> > (4) tpm_user passes requests from /dev/tpmN to the emulator's read() call.
> >
> > (5) The emulator processes the request.
> >
> > (6) The emulator either write()'s the reply or calls ioctl(fd,0,0) to cancel
> > the command.
> >
> > (7) The emulator goes back to read() to wait for the next command.
> >
> > (8) tpm_user passes the reply back to the tpm driver which passes it back to
> > /dev/tpmN.
> >
> > When the emulator closes /dev/tpm_emul, the TPM driver is unregistered and the
> > /dev/tpmN misc device is then removed. Any outstanding requests are aborted
> > and -EIO will be returned from then on. Multiple TPMs can be registered.
> >
> > Signed-off-by: David Howells <dhowells@redhat.com>
> > ---
> >
> > drivers/char/tpm/Kconfig | 13 +
> > drivers/char/tpm/Makefile | 1
> > drivers/char/tpm/tpm_user_emul.c | 672 ++++++++++++++++++++++++++++++++++++++
> > include/linux/wait.h | 11 +
> > 4 files changed, 697 insertions(+)
> > create mode 100644 drivers/char/tpm/tpm_user_emul.c
>
> This looks to duplicate the vtpm stuff...

Yeah, this is a duplicate to tpm_vtpm_proxy.

>
> Jason

/Jarkko