On Fri, 27 Jul 2018 at 18:19, Mark Rutland <mark.rutl...@arm.com> wrote: > > On Thu, Jul 26, 2018 at 02:12:04PM +0530, Sumit Garg wrote: > > On Thu, 26 Jul 2018 at 13:20, Daniel Thompson <daniel.thomp...@linaro.org> > > wrote: > > > I guess it could implement a secure monitor call to provide it. In > > > fact I find it a rather pleasing approach. However I think it still loops > > > us round to pretty much the same question as before. Does TF-A "protec > > > " a normal world that makes an SMC to an OP-TEE that isn't there by > > > failing the call in a nice way? > > > > TF-A returns SMC call for OP-TEE as unknown (error code: -1 in "x0" > > register) if OP-TEE is not present. > > Be careful here; you can't use an arbitrary SMC since that could be > implemented by another trusted OS (with a completely different meaning). > > Assuming you know the system provides SMCCC, you can use the "Call UID > Query" in the trusted OS range, and check that returned value matches > OP-TEE's UID. > > i.e > > uid = smccc_uid_query(OPTEE_RANGE); > if (uid == OPTEEE_SMCCC_UID) { > [ OP-TEE present ] > } else { > [ unknown/no trusted OS present ] > } >
Thanks Mark for this useful suggestion. Will try to use it. -Sumit > Thanks, > Mark. _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel