[PATCH v2] drivers: crypto: mod_exp_sw: Re-add DM_FLAG_PRE_RELOC

Jan Kiszka jan.kiszka at siemens.com
Fri May 22 17:21:25 CEST 2020

On 22.05.20 16:55, Heinrich Schuchardt wrote:
> On 22.05.20 14:21, Jan Kiszka wrote:
>> On 22.05.20 13:38, Heinrich Schuchardt wrote:
>>> Am May 22, 2020 10:50:29 AM UTC schrieb Jan Kiszka <jan.kiszka at siemens.com>:
>>>> On 22.05.20 12:42, Heinrich Schuchardt wrote:
>>>>> On 5/20/20 2:22 PM, Tom Rini wrote:
>>>>>> On Thu, May 07, 2020 at 08:36:03PM +0200, Jan Kiszka wrote:
>>>>>>> From: Jan Kiszka <jan.kiszka at siemens.com>
>>>>>>> This driver is safe to use in SPL without relocation. Denying
>>>>>>> DM_FLAG_PRE_RELOC prevents its usability for verifying the main
>>>> U-Boot
>>>>>>> or other artifacts from the SPL unless needless enabling the full
>>>> driver
>>>>>>> set (SPL_OF_PLATDATA).
>>>>>>> Fixes: 17e117408571 ("drivers: crypto: rsa_mod_exp: avoid
>>>>>>> CC: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>>>>>> CC: Marek Vasut <marex at denx.de>
>>>>>>> Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
>>>>>> Applied to u-boot/master, thanks!
>>>>> With this patch applied pine64-lts_defconfig with CONFIG_RSA=y does
>>>> not
>>>>> boot anymore. See the output below. So something is wrong with this
>>>> driver.
>>>>> Do you have an idea how to analyze what is wrong? Unfortunately there
>>>> is
>>>>> no DEBUG_UART available on the Pine A64 LTS board.
>>>> I would start crippling it down until things start to boot again. Are
>>>> you using it (for image verification e.g.), or is this just the
>>>> registration that breaks already?
>>> RSA is needed in the UEFI subsystem for verifying variables and images. But there is no need in SPL for it at all.
>>> In my configuration RSA is not used at all. Something breaks before even the console becomes available.
>>> The pine64-lts_defconfig board boots via SPL->BL31->U-Boot
>> But then a workaround for you would be to turn this driver off in SPL.
>> UEFI is main U-Boot only, isn't it?
>> That said, understanding the reason for the breakage would still be nice
>> for the case someone needs to validate what SPL loads with the help of
>> RSA (which is the case for us on an AM65x board).
>> Jan
> As I described above I did *not* select RSA_SPL. The breakage is in main
> U-boot. SPL works fine loading TF-A BL31 which in turn loads U-Boot. But
> during driver initialization U-Boot does not even reach the point where
> we have a console due to something wrong with DM_FLAG_PRE_RELOC.

Sorry, missed that detail. But that is indeed weird because - to my
understanding - this driver should be totally passive until someone
calls rsa_mod_exp() (which should only happen late, when UEFI comes into

Can you validate that this function is not involved by emptying its body?

Also, until everything is understood, we could limit DM_FLAG_PRE_RELOC


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