[PATCH v2 2/2] efi_loader: identify EFI system partition

[AKASHI Takahiro]

On Mon, Apr 06, 2020 at 07:12:56AM +0200, Heinrich Schuchardt wrote:
> On 4/6/20 6:21 AM, AKASHI Takahiro wrote:
> > Heinrich,
> >
> > On Sun, Apr 05, 2020 at 11:28:18AM +0200, Heinrich Schuchardt wrote:
> >> For capsule updates we need to identify the EFI system partition.
> >
> > Right, but
> >
> >> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> >> ---
> >> v2:
> >> 	no change
> >> ---
> >>  include/efi_loader.h      |  7 +++++++
> >>  lib/efi_loader/efi_disk.c | 20 ++++++++++++++++++++
> >>  2 files changed, 27 insertions(+)
> >>
> >> diff --git a/include/efi_loader.h b/include/efi_loader.h
> >> index 3f2792892f..4a45033476 100644
> >> --- a/include/efi_loader.h
> >> +++ b/include/efi_loader.h
> >> @@ -45,6 +45,13 @@ static inline void *guidcpy(void *dst, const void *src)
> >>  /* Root node */
> >>  extern efi_handle_t efi_root;
> >>
> >> +/* EFI system partition */
> >> +extern struct efi_system_partition {
> >> +	enum if_type if_type;
> >> +	int devnum;
> >> +	u8 part;
> >> +} efi_system_partition;
> >> +
> >>  int __efi_entry_check(void);
> >>  int __efi_exit_check(void);
> >>  const char *__efi_nesting(void);
> >> diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> >> index fc0682bc48..2f752a5e99 100644
> >> --- a/lib/efi_loader/efi_disk.c
> >> +++ b/lib/efi_loader/efi_disk.c
> >> @@ -13,6 +13,8 @@
> >>  #include <part.h>
> >>  #include <malloc.h>
> >>
> >> +struct efi_system_partition efi_system_partition;
> >> +
> >>  const efi_guid_t efi_block_io_guid = EFI_BLOCK_IO_PROTOCOL_GUID;
> >>
> >>  /**
> >> @@ -372,6 +374,24 @@ static efi_status_t efi_disk_add_dev(
> >>  	diskobj->ops.media = &diskobj->media;
> >>  	if (disk)
> >>  		*disk = diskobj;
> >> +
> >> +	/* Store first EFI system partition */
> >
> > I don't think that the policy, first comes first serves as system
> > partition, is a right decision as
> > - the order of device probe on U-Boot is indeterministic, and
> 
> Indeterministic would mean that on two runs with the same media provided
> you will get different results. I cannot see any source for such
> randomness in the U-Boot code. In dm_init_and_scan() the device tree is
> scanned and drivers and bound in the sequence of occurrence in the
> device tree.
> 
> > - there can be several partitions that hold a system partition bit.
> >   You may have OS installed on eMMC, but also may have bootable DVD
> >   on the system.
> 
> This is a similar logic like finding the relevant boot.scr script to run.
> 
> What would be the alternative?

I think that most UEFI systems have ability for user to specify
"boot order."

-Takahiro Akashi
> 
> Definition via Kconfig would mean that a Linux distribution like Debian
> would have to provide a separate U-Boot build for each boot medium that
> a user might possibly use (eMMC, SD-card, USB, NVME, SCSI).
> 
> Best regards
> 
> Heinrich
> 
> >
> > -Takahiro Akashi
> >
> >> +	if (part && !efi_system_partition.if_type) {
> >> +		int r;
> >> +		disk_partition_t info;
> >> +
> >> +		r = part_get_info(desc, part, &info);
> >> +		if (r)
> >> +			return EFI_DEVICE_ERROR;
> >> +		if (info.bootable & PART_EFI_SYSTEM_PARTITION) {
> >> +			efi_system_partition.if_type = desc->if_type;
> >> +			efi_system_partition.devnum = desc->devnum;
> >> +			efi_system_partition.part = part;
> >> +			EFI_PRINT("EFI system partition: %s %d:%d\n",
> >> +				  blk_get_if_type_name(desc->if_type),
> >> +				  desc->devnum, part);
> >> +		}
> >> +	}
> >>  	return EFI_SUCCESS;
> >>  }
> >>
> >> --
> >> 2.25.1
> >>
>