From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Daniel Axtens <dja@axtens.net>

Date: Thu, 24 Mar 2022 14:34:32 +1100

Subject: [PATCH] powerpc: prefix detection: support device names with commas

Frustratingly, the device name itself can contain an embedded comma:

e.g /pci@800000020000015/pci1014,034A@0/sas/disk@5000c50098a0ee8b

So my previous approach was wrong: we cannot rely upon the presence

of a comma to say that a partition has been specified!

It turns out for prefixes like (,gpt2)/grub2 we really want to make

up a full (device,partition)/patch prefix, because root discovery code

in 10_linux will reset the root variable and use search to fill it again.

If you have run grub-install, you probably don't have search built in,

and if you don't have prefix containing (device,partition), grub will

construct ($root)$prefix/powerpc-ieee1275/search.mod - but because $root

has just been changed, this will no longer work, and the boot will fail!

Retain the gist of the logic, but instead of looking for a comma, look for

a leading '('. This matches the earlier code better anyway.

There's certainly a better fix to be had. But any time you chose to build

with a bare prefix like '/grub2', you're almost certainly going to build in

search anyway, so this will do.

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

---

 grub-core/kern/main.c | 27 +++++++++++++++++++++------

 1 file changed, 21 insertions(+), 6 deletions(-)

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

index 993b8a8598..e94a2f78fb 100644

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

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

@@ -242,14 +242,29 @@ grub_set_prefix_and_root (void)

 	    what sorts of paths represent disks with partition tables and those

 	    without partition tables.

-	 So we act unless there is a comma in the device, which would indicate

-	 a partition has already been specified.

+          - Frustratingly, the device name itself can contain an embedded comma:

+            /pci@800000020000015/pci1014,034A@0/sas/disk@5000c50098a0ee8b

+            So we cannot even rely upon the presence of a comma to say that a

+            partition has been specified!

-	 (If we only have a path, the code in normal to discover config files

-	 will try both without partitions and then with any partitions so we

-	 will cover both CDs and HDs.)

+         If we only have a path in $prefix, the code in normal to discover

+	 config files will try all disks, both without partitions and then with

+	 any partitions so we will cover both CDs and HDs.

+

+         However, it doesn't then set the prefix to be something like

+         (discovered partition)/path, and so it is fragile against runtime

+         changes to $root. For example some of the stuff done in 10_linux to

+         reload $root sets root differently and then uses search to find it

+         again. If the search module is not built in, when we change root, grub

+         will look in (new root)/path/powerpc-ieee1275, that won't work, and we

+         will not be able to load the search module and the boot will fail.

+

+         This is particularly likely to hit us in the grub-install

+         (,msdos2)/grub2 case, so we act unless the supplied prefix starts with

+         '(', which would likely indicate a partition has already been

+         specified.

        */

-      if (grub_strchr (device, ',') == NULL)

+      if (prefix && prefix[0] != '(')

         grub_env_set ("prefix", path);

       else

 #endif