On Sun, Jan 17, 2021 at 02:21:27PM +0000, Wei Liu wrote: > On Sun, Jan 17, 2021 at 09:29:42AM +0100, Greg Kroah-Hartman wrote: > > On Sat, Jan 16, 2021 at 12:11:09PM +0000, Wei Liu wrote: > > > On Sat, Jan 16, 2021 at 11:55:29AM +0000, Wei Liu wrote: > > > > On Fri, Jan 15, 2021 at 04:49:57PM -0800, Randy Dunlap wrote: > > > > > Hi, > > > > > > > > > > On 1/15/21 4:12 PM, Wei Liu wrote: > > > > > > For built-in drivers, the order of initialization function > > > > > > invocation is > > > > > > determined by their link order. > > > > > > > > > > > > The original code linked TPM drivers before TEE driver when they > > > > > > were > > > > > > both built in. That caused fTPM's initialization to be deferred to a > > > > > > worker thread instead of running on PID 1. > > > > > > > > > > > > That is problematic because IMA's initialization routine, which > > > > > > runs on > > > > > > PID 1 as a late initcall, needs to have access to the default TPM > > > > > > instance. If fTPM's initialization is deferred, IMA will not be > > > > > > able to > > > > > > get hold of a TPM instance in time. > > > > > > > > > > > > Fix this by modifying Makefile to make sure TEE is initialized > > > > > > before > > > > > > fTPM when they are both built in. > > > > > > > > > > > > Signed-off-by: Wei Liu <wei....@kernel.org> > > > > > > --- > > > > > > drivers/Makefile | 5 +++++ > > > > > > 1 file changed, 5 insertions(+) > > > > > > > > > > > > diff --git a/drivers/Makefile b/drivers/Makefile > > > > > > index fd11b9ac4cc3..45ea5ec9d0fd 100644 > > > > > > --- a/drivers/Makefile > > > > > > +++ b/drivers/Makefile > > > > > > @@ -180,6 +180,11 @@ obj-$(CONFIG_NVMEM) += nvmem/ > > > > > > obj-$(CONFIG_FPGA) += fpga/ > > > > > > obj-$(CONFIG_FSI) += fsi/ > > > > > > obj-$(CONFIG_TEE) += tee/ > > > > > > + > > > > > > +# TPM drivers must come after TEE, otherwise fTPM initialization > > > > > > will be > > > > > > +# deferred, which causes IMA to not get a TPM device in time > > > > > > +obj-$(CONFIG_TCG_TPM) += char/tpm/ > > > > > > + > > > > > > obj-$(CONFIG_MULTIPLEXER) += mux/ > > > > > > obj-$(CONFIG_UNISYS_VISORBUS) += visorbus/ > > > > > > obj-$(CONFIG_SIOX) += siox/ > > > > > > > > > > > > > > > > As I suspected and then tested, since you did not remove the other > > > > > build > > > > > of char/tpm/, this ends up with multiple definition linker errors > > > > > (below). > > > > > > > > Oops, I didn't commit the hunk that removed the line in char/Makefile. > > > > > > > > But I will hold off sending out v2 until the following discussion is > > > > settled. > > > > > > > > > > > > > > I would think that instead of depending on Makefile order you should > > > > > use different > > > > > initcall levels as needed. Depending on Makefile order is what we did > > > > > 15 years ago. > > > > > > > > > > > > > No, not really. The same trick was used in 2014 (1bacc894c227). > > > > > > > > Both TEE and TPM are just drivers. I think they belong to the same level > > > > (at the moment device_initcall). Looking at the list of levels, I'm not > > > > sure how I can move TEE to a different level. > > > > > > > > Out of the seven levels, which one would you suggest I use for which > > > > driver? > > > > > > A bit more random thought. > > > > > > Moving one driver to a different level is not the solution either. What > > > if there is a dependency chain in the future in which more than 2 > > > drivers are involved? Do we invent more levels or abuse levels that > > > aren't supposed to be used by device drivers? > > > > > > The proper solution to me is to somehow sort the initcalls with their > > > dependencies in mind. The requires quite a bit of engineering > > > (integrating depmod into kernel build?). Given that there are only a few > > > cases, I don't think effort would be worth it. > > > > Make it an explicit dependancy in the driver, and then things will be > > loaded properly. > > I take it you mean using MODULE_SOFTDEP to do that?
That's one way, or just explicitly depend on a symbol in the other module. > > You can always defer your probe if you do not have all > > of the proper resources, which is how these types of things are handled, > > instead of worrying about creating new init levels. > > > fTPM's probe is already deferred in current Linux without this patch. What patch? > It > will eventually show up in Linux but at that point it is too late for > Linux's Integrity Measurement Architecture to use it. How can it be "too late"? > The probe getting deferred is exactly what I tried to avoid here. :-) Then don't start up IMA without it? I really don't know, but this feels like something is broken in your module... thanks, greg k-h
