Re: [PATCH edk2-platforms 6/7] Platform/DeveloperBox: add .DSC/.FDF description of MM components

[Leif Lindholm <leif.lindholm@linaro.org>]

On Mon, Jan 21, 2019 at 05:57:20PM +0100, Ard Biesheuvel wrote:
> On Thu, 17 Jan 2019 at 13:18, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> >
> > On Thu, 17 Jan 2019 at 13:08, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > >
> > > On Thu, Jan 17, 2019 at 12:10:01PM +0100, Ard Biesheuvel wrote:
> > > > > >  ################################################################################
> > > > > >  #
> > > > > > @@ -294,8 +295,10 @@ [PcdsFixedAtBuild.common]
> > > > > >  !endif
> > > > > >    gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareRevision|$(BUILD_NUMBER)
> > > > > >
> > > > > > -  gArmTokenSpaceGuid.PcdMmBufferBase|0xFFC00000
> > > > > > -  gArmTokenSpaceGuid.PcdMmBufferSize|0x00200000
> > > > > > +  gEfiSecurityPkgTokenSpaceGuid.PcdUserPhysicalPresence|TRUE
> > > > >
> > > > > So, I can see why you add this hard-wired for the purpose of testing.
> > > > > But please, add a *very* conspicuous, and strongly worded, comment
> > > > > statement preceding it.
> > > >
> > > > Well, I was talking to Peter about this the other day: according to
> > > > the spec, this setting should only matter before exit boot services,
> > > > and since this platform only supports serial and GOP consoles, one
> > > > could argue that only a physically present user could interact with it
> > > > before that time.
> > >
> > > But that also makes the Pcd pointless.
> > >
> > > > The obvious way of implementing this non-trivially on this platform is
> > > > to use a DIP switch, but that requires you to open the case to
> > > > enroll/delete the platform key. Perhaps that does not matter, and it
> > > > would in fact produce a less dangerous reference implementation.
> > >
> > > I would be totally OK with that.
> > > I would also be totally OK with a DynamicPcd settable through the UI
> > > (which is what most machines I come across have).
> > >
> >
> > That won't work for this implementation: the state of dynamic PCDs
> > does not propagate into the MM world (nor should it), and so no MM
> > driver implementing the dynamic PCD protocol exists.
> >
> > > But I would also be cool with a sufficiently evil "here be dragons"
> > > statement, pointing out that we don't care that much
> > > *on*this*specific*system* because the NOR isn't actually hw protected
> > > anyway, and this implementation is all about exercising the software
> > > stack..
> > >
> >
> > I'll go with that for the time being.
> 
> I'll add the following:
> 
> diff --git a/Platform/Socionext/DeveloperBox/DeveloperBox.dsc.inc
> b/Platform/Socionext/DeveloperBox/DeveloperBox.dsc.inc
> index f191edcb78dd..1ac8c8f95722 100644
> --- a/Platform/Socionext/DeveloperBox/DeveloperBox.dsc.inc
> +++ b/Platform/Socionext/DeveloperBox/DeveloperBox.dsc.inc
> @@ -301,6 +301,13 @@
>  !endif
>    gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareRevision|$(BUILD_NUMBER)
> 
> +  #
> +  # NOTE: this platform is not fully secure (the NOR flash is mapped
> non-secure)
> +  # and so the MM based secure boot implementation it provides should
> be treated
> +  # as a reference only. For this reason, it does not make a lot of sense to
> +  # implement an elaborate PlatformSecureLib implementation that can assert
> +  # physical presence, and instead, we'll stick with the default PCD based one.
> +  #
>    gEfiSecurityPkgTokenSpaceGuid.PcdUserPhysicalPresence|TRUE
> 
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000

Totally happy with that.
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>