Re: [PATCH v1 2/2] Fix prefix and root on ppc64le CDs

[Vladimir 'phcoder' Serbinenko]

The ,0 suffix sounds like a bug in a detection

As for the prefix, can‘t we solve it by setting prefix properly.

If there is really no better solution (doubtful) then it needs to be restricted to chrp platforms and even there, probably only a subset

On Fri, 13 Jan 2023 at 23:27, Robbie Harwood <rharwood@redhat.com> wrote:

CHRP requires grub at /boot/grub.  On CDs, this means any other prefix
will be invalid.  In particular, a distro grub might prefer /grub2 - but
prefix is hardcoded into the signed core.elf, and will always be wrong
here.

Also work around a conflict between OF naming and that used by
part_msdos: on CDs, we always want the raw device.  This fixes an issue
where grub would successfully load the menu from an image, but then
produce the error:

    error: ../../grub-core/net/net.c:1552:disk `ieee1275/cdrom,0' not found.

and fail to boot further.

Signed-off-by: Robbie Harwood <rharwood@redhat.com>
---
 grub-core/kern/main.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/grub-core/kern/main.c b/grub-core/kern/main.c
index 731c07c290..0a24fe38e4 100644
--- a/grub-core/kern/main.c
+++ b/grub-core/kern/main.c
@@ -216,6 +216,23 @@ grub_set_prefix_and_root (void)
          grub_free (prefix_set);
        }
       grub_env_set ("root", device);
+
+#ifdef __powerpc__
+      /* When booting from a CD, if part_msdos is enabled, grub will detect
+         and create access points starting at (ieee1275/cdrom,msdos1).
+         However, the device detection and OF name transformation will produce
+         a device named (ieee1275/cdrom,0) - i.e., missing the msdos and also
+         differently indexed.  Furthermore, CHRP mandates boot/grub as prefix,
+         but our signed images are built with /grub2 to reflect installed
+         systems.  Just ignore both messes.
+       */
+      if (!grub_strncmp (device[0] == '(' ? device + 1 : device,
+                         "ieee1275/cdrom", grub_strlen ("ieee1275/cdrom")))
+        {
+          grub_env_set ("prefix", "/boot/grub");
+          grub_env_set ("root", "ieee1275/cdrom");
+        }
+#endif
     }

   grub_free (device);
--
2.39.0


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--

Regards
Vladimir 'phcoder' Serbinenko