From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Daniel Axtens <dja@axtens.net>

Date: Mon, 19 Jul 2021 14:35:55 +1000

Subject: [PATCH] powerpc: adjust setting of prefix for signed binary case

On RHEL-signed powerpc grub, we sign a grub with -p /grub2 and expect

that there's a boot partition.

Unfortunately grub_set_prefix_and_root tries to convert this to

($fwdevice)/grub2. This ends up being (ieee1275/disk)/grub2 and that

falls apart pretty quickly - there's no file-system on ieee1275/disk,

and it makes the search routine try things like

(ieee1275/disk,msdos2)(ieee1275/disk)/grub2 which also doesn't work.

Detect if we would be about to create (ieee1275/disk)/path and don't:

preserve a prefix of /path instead and hope the search later finds us.

Related: rhbz#1899864

Signed-off-by: Daniel Axtens <dja@axtens.net>

---

 grub-core/kern/main.c | 38 +++++++++++++++++++++++++++++++++-----

 1 file changed, 33 insertions(+), 5 deletions(-)

diff --git a/grub-core/kern/main.c b/grub-core/kern/main.c

index 9bf6a8b231a..25dbcfef1f6 100644

--- a/grub-core/kern/main.c

+++ b/grub-core/kern/main.c

@@ -215,13 +215,41 @@ grub_set_prefix_and_root (void)

   if (device)

     {

       char *prefix_set;

-    

-      prefix_set = grub_xasprintf ("(%s)%s", device, path ? : "");

-      if (prefix_set)

+

+#ifdef __powerpc__

+      /* We have to be careful here on powerpc-ieee1275 + signed grub. We

+	 will have signed something with a prefix that doesn't have a device

+	 because we cannot know in advance what partition we're on.

+

+	 We will have had !device earlier, so we will have set device=fwdevice

+	 However, we want to make sure we do not end up setting prefix to be

+	 ($fwdevice)/path, because we will then end up trying to boot or search

+	 based on a prefix of (ieee1275/disk)/path, which will not work because

+	 it's missing a partition.

+

+	 Also:

+	  - You can end up with a device with an FS directly on it, without

+	    a partition, e.g. ieee1275/cdrom.

+

+	  - powerpc-ieee1275 + grub-install sets e.g. prefix=(,gpt2)/path,

+	    which will have now been extended to device=$fwdisk,partition

+	    and path=/path

+

+	 So we only need to act if device = ieee1275/disk exactly.

+       */

+      if (grub_strncmp (device, "ieee1275/disk", 14) == 0)

+        grub_env_set ("prefix", path);

+      else

+#endif

 	{

-	  grub_env_set ("prefix", prefix_set);

-	  grub_free (prefix_set);

+	  prefix_set = grub_xasprintf ("(%s)%s", device, path ? : "");

+	  if (prefix_set)

+	  {

+	    grub_env_set ("prefix", prefix_set);

+	    grub_free (prefix_set);

+	  }

 	}

+

       grub_env_set ("root", device);

     }