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Re: [RFC 1/3] efi: add configuration table search function


From: Leif Lindholm
Subject: Re: [RFC 1/3] efi: add configuration table search function
Date: Tue, 1 Mar 2016 20:28:38 +0000
User-agent: Mutt/1.5.23 (2014-03-12)

On Tue, Mar 01, 2016 at 08:13:50PM +0000, Vladimir 'phcoder' Serbinenko wrote:
> Le mar. 1 mars 2016 21:09, Andrei Borzenkov <address@hidden> a écrit :
> 
> > 01.03.2016 20:41, Leif Lindholm пишет:
> > > Several places in the code iterates through the configuration tables
> > > presented by the system table.
> > > Add new function grub_efi_find_config_table to use for this instead.
> > > ---
> > >  grub-core/kern/efi/efi.c | 18 ++++++++++++++++++
> > >  include/grub/efi/efi.h   |  3 +++
> > >  2 files changed, 21 insertions(+)
> > >
> > > diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
> > > index caf9bcc..41686ee 100644
> > > --- a/grub-core/kern/efi/efi.c
> > > +++ b/grub-core/kern/efi/efi.c
> > > @@ -911,3 +911,21 @@ grub_efi_compare_device_paths (const
> > grub_efi_device_path_t *dp1,
> > >
> > >    return 0;
> > >  }
> > > +
> > > +/* Return pointer to vendor table identified by guid. */
> > > +void *
> > > +grub_efi_find_config_table (const grub_efi_guid_t *guid)
> > > +{
> > > +  grub_efi_uintn_t i;
> > > +
> > > +  for (i = 0; i < grub_efi_system_table->num_table_entries; i++)
> > > +    {
> > > +      grub_efi_configuration_table_t *table =
> > > +     &grub_efi_system_table->configuration_table[i];
> > > +
> > > +      if (! grub_memcmp (&table->vendor_guid, guid,
> > > +                      sizeof (grub_efi_packed_guid_t)))
> >
> > Either both types are exactly the same and one should be dropped or this
> > cannot be right. In view of recent discussion about structure member
> > alignments I am not sure why grub_efi_packed_guid_t is needed and the
> > code already was inconsistent in usage.
> >
> Types differ only in alignment, not in internal structure. We can guarantee
> alignment of structure that we allocated but not of some EFI pointer

Of course you can.
The UEFI specification explicitly states
"Unless otherwise specified, aligned on a 64-bit boundary."
which is double the natural alignment of the largest member
defined in this struct.

/
    Leif



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