[PATCH] lds: align u-boot-nodtb with 8 bytes boundary

[Eugen.Hristev at microchip.com]

On 12/15/22 16:24, Simon Glass wrote:
> Hi Eugen,
> 
> On Thu, 15 Dec 2022 at 03:58, Eugen Hristev <eugen.hristev at microchip.com> wrote:
>>
>> Newer DTC require that the DTB start address is aligned at 8 bytes.
>> In the u-boot.bin case, the u-boot-nodtb.bin is concatenated with the
>> DTB, but there is no alignment/padding to the next 8byte aligned address.
>> This causes the board to fail booting, because the FDT will claim
>> that the DTB inside u-boot.bin is not a valid DTB, it will fail with
>> -FDT_ERR_ALIGNMENT.
>> To solve this, have the u-boot binary `_end` aligned with 8 bytes.
>> The objcopy in the Makefile will create the u-boot-nodtb.bin and it has to
>> be truncated to 8 bytes to correspond to the u-boot.map file which will
>> have the `_end` aligned to 8 bytes.
>> The lds files which use devicetrees have been changed to align the `_end`
>> tag with 8 bytes.
>>
>> This patch is also a prerequisite to have the possibility to update the
>> dtc inside u-boot to newer versions (1.6.1+)
>>
>> Signed-off-by: Eugen Hristev <eugen.hristev at microchip.com>
>> ---
>> Hi,
>>
>> I could not test all affected boards, it's an impossible task.
>> I tried this on at91 boards which I have, and ran the CI on denx.
>> I cannot guarantee that no other boards are affected, so this patch is a bit
>> of an RFC.
>> If the u-boot-nodtb.bin does not have the size equal with the corresponding
>> one in u-boot.map, the binary_size_check will fail at build time with
>> something like this:
>>
>> u-boot.map shows a binary size of 502684
>> but u-boot-nodtb.bin shows 502688
>>
>> Thanks,
>> Eugen
>>
>>   Makefile                                    | 2 ++
>>   arch/arm/cpu/armv8/u-boot.lds               | 4 ++--
>>   arch/arm/cpu/u-boot-spl.lds                 | 1 +
>>   arch/arm/cpu/u-boot.lds                     | 1 +
>>   arch/arm/lib/elf_arm_efi.lds                | 5 +++++
>>   arch/arm/mach-at91/arm926ejs/u-boot-spl.lds | 2 +-
>>   arch/arm/mach-at91/armv7/u-boot-spl.lds     | 2 +-
>>   arch/arm/mach-zynq/u-boot-spl.lds           | 2 +-
>>   arch/mips/cpu/u-boot.lds                    | 2 +-
>>   arch/sandbox/cpu/u-boot.lds                 | 6 ++++++
>>   arch/sh/cpu/u-boot.lds                      | 2 ++
>>   board/ti/am335x/u-boot.lds                  | 1 +
>>   tools/binman/test/u_boot_binman_embed.lds   | 2 +-
>>   13 files changed, 25 insertions(+), 7 deletions(-)
>>
>> diff --git a/Makefile b/Makefile
>> index 9d84f96481..b4d387bcce 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -1317,6 +1317,8 @@ endif
>>
>>   u-boot-nodtb.bin: u-boot FORCE
>>          $(call if_changed,objcopy_uboot)
>> +# Make sure the size is 8 byte-aligned.
>> +       @truncate -s %8 $@
>>          $(BOARD_SIZE_CHECK)
> 
> I agree this line is needed, since otherwise we will only get 4-byte
> alignment. But it would be better if we could have the linker scripts
> fill bytes out to the required alignment. Is that possible?
> 
> Reviewed-by: Simon Glass <sjg at chromium.org>
> 
> Regards,
> Simon


Hi Simon,

I tried to check the objcopy option --pad-to , to use it at the time of 
objcopy, but this requires a real number to be passed to it.
And this number could only be found by inspecting the u-boot.map file, 
since u-boot-nodtb.bin still does not exist.
And if we pad to the size specified in u-boot.map, then 
binary_size_check does not make much sense anymore, as we will basically 
use the same information to fit the file, and it will always pass with a 
success. (even if we would pad many more bytes than 4 )
Hence it would lose it's purpose ( binary_size_check ), which I think 
was created to make sure no objects were lost when doing objcopy and 
creating the u-boot-nodtb.bin file.

On a side note, do you think I covered all the implied lds files ? I 
would hate to break someone's boards.

And also, P.S. : I would require to have the same change when building a 
FIT image with mkimage... all subimages inside a FIT must be aligned to 
8 bytes. However mkimage only aligns the start address and header of the 
FIT (-B option). Out of your knowledge, is this possible and where could 
I have a look to do this change ?

Thanks !
Eugen