linux-kernel - Re: [PATCH 3/6] libstub,tpm: provide indication of failure when getting event log

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Message-ID: <ZuQ2xmXo0FPZpJa-@PC2K9PVX.TheFacebook.com>
Date: Fri, 13 Sep 2024 08:57:42 -0400
From: Gregory Price <gourry@...rry.net>
To: Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	ardb@...nel.org, leitao@...ian.org, usamaarif642@...il.com,
	sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH 3/6] libstub,tpm: provide indication of failure when
 getting event log

On Fri, Sep 13, 2024 at 09:59:03AM +0300, Ilias Apalodimas wrote:
> Hi Gregory,
> 
> On Fri, 6 Sept 2024 at 23:28, Gregory Price <gourry@...rry.net> wrote:
> >
> > If get_event_log fails, at least provide an indicator of this failure
> > to assist debugging later failures that attempt to interact with it.
> >
> > Signed-off-by: Gregory Price <gourry@...rry.net>
> > ---
> >  drivers/firmware/efi/libstub/tpm.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
> > index df3182f2e63a..192914e04e0f 100644
> > --- a/drivers/firmware/efi/libstub/tpm.c
> > +++ b/drivers/firmware/efi/libstub/tpm.c
> > @@ -185,8 +185,10 @@ void efi_retrieve_eventlog(void)
> >                         get_efi_config_table(EFI_CC_FINAL_EVENTS_TABLE_GUID);
> >         }
> >
> > -       if (status != EFI_SUCCESS || !log_location)
> > +       if (status != EFI_SUCCESS || !log_location) {
> > +               efi_err("TPM unable to provide Event Log\n");
> 
> s/provide/retrieve/ and yes the print is going to be useful.  Do you
> know if the EventLog is mandatory. Reading at the spec GetEventlog
> only has 2 return values, which implies you can't return "Not
> supported", but it's not explicitly stated anywhere
> 

I believe it is mandatory from my reading of the spec - but the
"Final Event Log" was only added in 2.0.  We report an error when
2.0 is reported but the final event log is not supported, so i figure
we should probably report when the event log fails as well.

> Thanks
> /Ilias
> >                 return;
> > +       }
> >
> >         efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry,
> >                                    truncated, final_events_table);
> > --
> > 2.43.0
> >