Kernel fail to find rootfs with 2.02-rc[12]

[DUPONCHEEL Sébastien]

Hi,

It look like there is a grub regression when using grub2-2.02-rc[12] with a 
bios in MBR mode and GPT partitioning:

Grub does not give the boot parameters to the kernel that did not find the root 
partition although that the partition with the good PARTUUID is listed before 
the panic
 and that everything works when the bios is switched to the EFI mode (i haven't 
this issue with the 2.02-beta2 version).

You can get more details here: https://github.com/lede-project/source/pull/1026

Tests where made using LEDE and Virtualbox.

Partitioning :

sda1: ext4 (4 MB)

- /boot/vmlinuz
- /boot/grub/50092577.cfg
- /boot/grub/grub.cfg

serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1 --rtscts=off
terminal_input console serial; terminal_output console serial

set default="0"
set timeout="5"

search --file /boot/grub/50092577.cfg --set=root

menuentry "LEDE" {
    linux /boot/vmlinuz root=PARTUUID=09BBA8CF-313E-420B-B5A8-E6B13DE60002 
rootfstype=squashfs rootwait console=tty0 console=ttyS0,115200n8 noinitrd
}

menuentry "LEDE (failsafe)" {
    linux /boot/vmlinuz failsafe=true 
root=PARTUUID=09BBA8CF-313E-420B-B5A8-E6B13DE60002 rootfstype=squashfs rootwait 
console=tty0 console=ttyS0,115200n8 noinitrd
}

sda2: EF00 vfat (1 MB)

- /efi/boot/bootx64.efi (grub)
- /efi/boot/grub.cfg

search --file /boot/grub/50092577.cfg --set=root
configfile /boot/grub/grub.cfg

sda3: EF02 raw (1MB)

- grub modules 

sda4: ext4/squashfs 

- the rootfs with the GPT PARTUUID : 09BBA8CF-313E-420B-B5A8-E6B13DE60002

Best regards,
DUPONCHEEL Sebastien