[PATCH SLOF 4/5] disk-label: add support for booting from GPT FAT partition

[Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>]

For a GPT+LVM combination disk, older bootloader that does not support
LVM, cannot load kernel from LVM.

The patch add support to read from BASIC_DATA UUID
partition. Installer has installed CHRP-BOOT config on a FAT file
system.

Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
---
 slof/fs/packages/disk-label.fs | 54 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/slof/fs/packages/disk-label.fs b/slof/fs/packages/disk-label.fs
index e317e93..821e959 100644
--- a/slof/fs/packages/disk-label.fs
+++ b/slof/fs/packages/disk-label.fs
@@ -266,7 +266,10 @@ CONSTANT /gpt-part-entry
 
 : try-dos-partition ( -- okay? )
    \ Read partition table and check magic.
-   no-mbr? IF cr ." No DOS disk-label found." cr false EXIT THEN
+   no-mbr? IF
+       debug-disk-label? IF cr ." No DOS disk-label found." cr THEN
+       false EXIT
+   THEN
 
    count-dos-logical-partitions TO dos-logical-partitions
 
@@ -381,18 +384,38 @@ AA268B49521E5A8B    CONSTANT GPT-PREP-PARTITION-4
    TRUE
 ;
 
-: load-from-gpt-prep-partition ( addr -- size )
+\ Check for GPT MSFT BASIC DATA GUID - fat based
+EBD0A0A2            CONSTANT GPT-BASIC-DATA-PARTITION-1
+B9E5                CONSTANT GPT-BASIC-DATA-PARTITION-2
+4433                CONSTANT GPT-BASIC-DATA-PARTITION-3
+87C068B6B72699C7    CONSTANT GPT-BASIC-DATA-PARTITION-4
+
+: gpt-basic-data-partition? ( -- true|false )
+   block gpt-part-entry>part-type-guid
+   dup l@-le     GPT-BASIC-DATA-PARTITION-1 <> IF DROP FALSE EXIT THEN
+   dup 4 + w@-le GPT-BASIC-DATA-PARTITION-2 <> IF DROP FALSE EXIT THEN
+   dup 6 + w@-le GPT-BASIC-DATA-PARTITION-3 <> IF DROP FALSE EXIT THEN
+       8 + x@    GPT-BASIC-DATA-PARTITION-4 <> IF FALSE EXIT THEN
+   TRUE
+;
+
+\ Can be called from two path
+\ 1) load-from-boot-partition for GPT PReP partition
+\ 2) try-partitions for gpt basic data partition having fat chrp-boot
+\
+: load-from-gpt-partition ( [ addr ] -- size | TRUE )
    no-gpt? IF drop FALSE EXIT THEN
    debug-disk-label? IF
       cr ." GPT partition found " cr
    THEN
-   1 read-sector block gpt>part-entry-lba l@-le
+   1 read-sector block gpt>part-entry-lba x@-le
    block-size * to seek-pos
    block gpt>part-entry-size l@-le to gpt-part-size
    block gpt>num-part-entry l@-le dup 0= IF FALSE EXIT THEN
    1+ 1 ?DO
       seek-pos 0 seek drop
-      block gpt-part-size read drop gpt-prep-partition? IF
+       block gpt-part-size read drop
+       gpt-prep-partition? IF
          debug-disk-label? IF
             ." GPT PReP partition found " cr
          THEN
@@ -404,6 +427,24 @@ AA268B49521E5A8B    CONSTANT GPT-PREP-PARTITION-4
          0 0 seek drop             ( addr len )
          block-size * read         ( size )
          UNLOOP EXIT
+     THEN
+     gpt-basic-data-partition? IF
+         debug-disk-label? IF
+            ." GPT LINUX DATA partition found " cr
+         THEN
+         block gpt-part-entry>first-lba x@ xbflip
+         dup to part-start
+         block gpt-part-entry>last-lba x@ xbflip
+         over - 1+                 ( addr offset len )
+         dup block-size * to part-size
+         swap                      ( addr len offset )
+         block-size * to part-offset
+         0 0 seek
+         block block-size read
+         3drop
+         block has-fat-filesystem 0= IF false UNLOOP EXIT THEN
+         TRUE
+         UNLOOP EXIT
       THEN
       seek-pos gpt-part-size i * + to seek-pos
    LOOP
@@ -495,11 +536,11 @@ AA268B49521E5A8B    CONSTANT GPT-PREP-PARTITION-4
 
    debug-disk-label? IF ." Trying CHRP boot " .s cr THEN
    1 disk-chrp-boot !
-   dup load-chrp-boot-file ?dup 0 <> IF .s cr nip EXIT THEN
+   dup load-chrp-boot-file ?dup 0 <> IF nip EXIT THEN
    0 disk-chrp-boot !
 
    debug-disk-label? IF ." Trying GPT boot " .s cr THEN
-   load-from-gpt-prep-partition
+   load-from-gpt-partition
    \ More boot partition formats ...
 ;
 
@@ -594,6 +635,7 @@ AA268B49521E5A8B    CONSTANT GPT-PREP-PARTITION-4
 
 : try-partitions ( -- found? )
    try-dos-partition IF try-files EXIT THEN
+   load-from-gpt-partition IF try-files EXIT THEN
    \ try-iso9660-partition IF try-files EXIT THEN
    \ ... more partition types here...
    false
-- 
1.8.3.1