This change introduces a new TPM backend driver that can communicate with
swtpm(software TPM emulator) using unix domain socket interface.
Swtpm uses two unix sockets, one for plain TPM commands and responses, and one
for out-of-band control messages.
The swtpm and associated tools can be found here:
https://github.com/stefanberger/swtpm
The swtpm's control channel protocol specification can be found here:
https://github.com/stefanberger/swtpm/wiki/Control-Channel-Specification
Usage:
# setup TPM state directory
mkdir /tmp/mytpm
chown -R tss:root /tmp/mytpm
/usr/bin/swtpm_setup --tpm-state /tmp/mytpm --createek
# Ask qemu to use TPM emulator with given tpm state directory
qemu-system-x86_64 \
[...] \
-tpmdev emulator,id=tpm0,tpmstatedir=/tmp/mytpm,logfile=/tmp/swtpm.log
\
-device tpm-tis,tpmdev=tpm0 \
[...]