On Mon, Oct 13, 2025 at 01:39:37PM +0200, Daniel Kiper wrote:
> On Thu, Oct 09, 2025 at 03:18:37PM +0800, Michael Chang via Grub-devel wrote:
> > This patch prepares for using an environment block stored in a reserved
> > area of the filesystem. It uses constant GRUB_ENV_BTRFS_OFFSET at 256
> > KiB in the Btrfs header. It also introduces the fs_envblk_spec and
> > fs_envblk structures together with the probe_fs_envblk function to
> > identify the root filesystem and to avoid configurations that involve
> > diskfilter or cryptodisk.
> >
> > The probe is only invoked when grub-editenv is working on the default
> > environment file path. This restriction ensures that probing and
> > possible raw device access are not triggered for arbitrary user supplied
> > paths, but only for the standard grubenv file. In that case the code
> > checks if the filename equals DEFAULT_ENVBLK_PATH and then calls
> > probe_fs_envblk with fs_envblk_spec. The result is stored in the global
> > fs_envblk handle. At this stage the external environment block is only
> > detected and recorded, and the behavior of grub-editenv is unchanged.
> >
> > Signed-off-by: Michael Chang <[email protected]>
> > Reviewed-by: Neal Gompa <[email protected]>
> > Reviewed-by: Avnish Chouhan <[email protected]>
> > ---
> >  util/grub-editenv.c | 164 +++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 163 insertions(+), 1 deletion(-)
> >
> > diff --git a/util/grub-editenv.c b/util/grub-editenv.c
> > index db6f187cc..e650cbcd0 100644
> > --- a/util/grub-editenv.c
> > +++ b/util/grub-editenv.c
> > @@ -23,8 +23,11 @@
> >  #include <grub/util/misc.h>
> >  #include <grub/lib/envblk.h>
> >  #include <grub/i18n.h>
> > -#include <grub/emu/hostfile.h>
> > +#include <grub/emu/hostdisk.h>
> >  #include <grub/util/install.h>
> > +#include <grub/emu/getroot.h>
> > +#include <grub/fs.h>
> > +#include <grub/crypto.h>
> >
> >  #include <stdio.h>
> >  #include <unistd.h>
> > @@ -120,6 +123,36 @@ block, use `rm %s'."),
> >    NULL, help_filter, NULL
> >  };
> >
> > +struct fs_envblk_spec {
> > +  const char *fs_name;
> > +  off_t offset;
> > +  size_t size;
> > +};
> > +typedef struct fs_envblk_spec fs_envblk_spec_t;
> > +
> > +struct fs_envblk {
> > +  fs_envblk_spec_t *spec;
> > +  const char *dev;
> > +};
> > +typedef struct fs_envblk *fs_envblk_t;
> > +
> > +/*
> > + * fs_envblk_spec describes the file-system specific layout of reserved raw
> > + * blocks used as environment blocks. At present only Btrfs is supported. 
> > Other
> > + * file-systems may be added if they provide a similar facility and avoid 
> > the
> > + * limitation of writing to COW.
> > + *
> > + * Note: If this table is modified, also update
> > + * grub-core/fs/btrfs.c::btrfs_head, which defines the layout in the Btrfs
> > + * header and exports GRUB_ENV_BTRFS_OFFSET, so that both stay consistent.
> > + */
> > +static fs_envblk_spec_t fs_envblk_spec[] = {
> > +  { "btrfs", GRUB_ENV_BTRFS_OFFSET, GRUB_DISK_SECTOR_SIZE },
> 
> Again, this change does not belong to this patch. It should be merged
> with patch #3. Then then patch #3 should be moved behind patch #9.

OK. I will merge the structs here into patch #3, which defines the
environment block in the Btrfs reserved area, and move the remaining
changes to patch #9.

> 
> Otherwise patch LGTM...

Thanks a lot for the review.

Michael

> 
> Daniel

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