Re: [PATCH] fastboot: inform user if barebox update falls back to raw copy

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Sascha,

On 09.06.22 09:19, Sascha Hauer wrote:
> On Tue, May 31, 2022 at 11:35:37AM +0200, Ahmad Fatoum wrote:
>> Fastboot code determines whether to go into barebox update handler by
>> checking whether filetype_is_barebox_image() returns true for the image.
>> This is different from the barebox_update command which leaves it to the
>> individual handlers to decide whether an image is suitable.
>>
>> Coupled with eMMC boot partitions, this could lead to
>> `barebox_update -t mmc` updating the boot partition, while a
>> `fastboot flash bbu-mmc` will write the image to the user area instead.
>>
>> It may be worth breaking backwards compatibility here and refuse update
>> in that case, but for now at least alert the user that a raw copy is
>> being attempted.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>> ---
>>  common/fastboot.c | 13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/common/fastboot.c b/common/fastboot.c
>> index f8ed40c86e00..50ea8421d92c 100644
>> --- a/common/fastboot.c
>> +++ b/common/fastboot.c
>> @@ -673,7 +673,7 @@ static void cb_flash(struct fastboot *fb, const char *cmd)
>>  		goto out;
>>  	}
>>  
>> -	if (IS_ENABLED(CONFIG_BAREBOX_UPDATE) && filetype_is_barebox_image(filetype)) {
>> +	if (IS_ENABLED(CONFIG_BAREBOX_UPDATE)) {
> 
> 
>>  		void *buf;
>>  		struct bbu_handler *handler;
>>  		struct bbu_data data = {
>> @@ -681,6 +681,17 @@ static void cb_flash(struct fastboot *fb, const char *cmd)
>>  			.flags = BBU_FLAG_YES,
>>  		};
>>  
>> +		if (!filetype_is_barebox_image(filetype)) {
>> +			if (strstarts(fentry->name, "bbu-")) {
>> +				fastboot_tx_print(fb, FASTBOOT_MSG_INFO,
>> +						  "This is _not_ a barebox image...");
>> +				fastboot_tx_print(fb, FASTBOOT_MSG_INFO,
>> +						  "Falling back to raw copy to %s", filename);
>> +			}
>> +
>> +			goto copy;
>> +		}
> 
> The handlers starting with "bbu-" are registered from the barebox update
> code, so falling back to copy is clearly wrong.
> 
> The logic to enter this barebox_update path should be:
> 
> 	if (IS_ENABLED(CONFIG_BAREBOX_UPDATE) &&
> 	    (filetype_is_barebox_image(filetype) || strstarts(fentry->name, "bbu-")))
> 
> That way we are sure that barebox_update is called when we need it. Also
> behaviour is consistent to what barebox_update does on the command line.

This is not consistent with barebox_update behavior. Calling it from command line
will leave it to update handlers to determine whether an image is a barebox
image. filetype_is_barebox_image() is exclusively used for fastboot.

I don't like the current behavior either, but I am wary of breaking existing
users, so I figured an info message would be a stop-gap solution for now.

You can add a

  pr_warn("fastboot: deprecated raw copy fallback for barebox_update\n");

for now. What do you think?

Cheers,
Ahmad

> 
> Sascha
> 


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