On 3/25/20 4:29 PM, Matthew Garrett wrote: > On Wed, Mar 25, 2020 at 12:43 PM Ross Philipson > <ross.philipson@xxxxxxxxxx> wrote: >> To enable the kernel to be launched by GETSEC or SKINIT, a stub must be >> built into the setup section of the compressed kernel to handle the >> specific state that the late launch process leaves the BSP. This is a >> lot like the EFI stub that is found in the same area. Also this stub >> must measure everything that is going to be used as early as possible. >> This stub code and subsequent code must also deal with the specific >> state that the late launch leaves the APs in. > > How does this integrate with the EFI entry point? That's the expected > entry point on most modern x86. What's calling ExitBootServices() in > this flow, and does the secure launch have to occur after it? It'd be > a lot easier if you could still use the firmware's TPM code rather > than carrying yet another copy. It is not part of the EFI entry point as we are not entering the kernel from EFI but I will address that further in my response to Andy. The expectation is that if you are on an UEFI platform then EBS should have already been called. With respect to using the firmware's TPM code, one of the purposes of a TCG Dynamic Launch is to remove the firmware from the code being trusted in making the integrity measurement of the kernel. I trust the firmware to initialize the hardware because I have to and it does give a trust chain, aka the SRTM, that can attest to what was used during that process. When the OS kernel is being started that trust chain has become weak (or even broken). I want a new trust chain that can provide better footing for asserting the integrity of the kernel and this is what Dynamic Launch gives us. I would like to think I did a fair job explaining this at LSS last fall[1][2] and would recommend those that are curious to review the slides/watch the presentation. V/r, Daniel P. Smith [1] https://lssna19.sched.com/event/RHb0/trenchboot-how-to-nicely-boot-system-with-intel-txt-and-amd-svm-daniel-kiper-oracle-daniel-smith-apertus-solutions [2] https://youtu.be/DbpCU9iSi4g
