[PATCH 10/25] binman: Move section-building code into a function

[Alper Nebi Yasak]

On 26/10/2020 22:22, Simon Glass wrote:
> On Mon, 19 Oct 2020 at 15:29, Alper Nebi Yasak <alpernebiyasak at gmail.com> wrote:
>> On 19/10/2020 05:41, Simon Glass wrote:
>>>          for entry in self._entries.values():
>>>              data = entry.GetData()
>>> -            base = self.pad_before + (entry.offset or 0) - self._skip_at_start
>>> -            pad = base - len(section_data) + (entry.pad_before or 0)
>>> +            # Handle empty space before the entry
>>> +            pad = (entry.offset or 0) - self._skip_at_start - len(section_data)
>>>              if pad > 0:
>>>                  section_data += tools.GetBytes(self._pad_byte, pad)
>>> +
>>> +            # Handle padding before the entry
>>> +            if entry.pad_before:
>>> +                section_data += tools.GetBytes(self._pad_byte, entry.pad_before)
>>
>> Consider this fragment:
>>
>>     section {
>>         skip-at-start = <16>;
>>
>>         blob {
>>             pad-before = <16>;
>>             filename = "foo";
>>         }
>>     }
>>
>> Is this invalid as 'blob' isn't offset > skip-at-start? This wouldn't
>> be padded in the earlier code, but would be padded after this (assuming
>> it doesn't error out) -- was that a bug or undefined behaviour or
>> something?
> 
> You have very sharp eyes.

Thanks! I had actually tried to copy this to the fit etype before making
it use the section etype directly, so I did read and think about this
part (and Pack()) a lot to better understand how things were supposed to
work.

> The case you list seems to produce the same result before and after
> this patch. But if I put the padding at the top level it does strange
> things, so perhaps that's what you mean?

I was trying to write a case where a pad = (-16) + (16) = 0 gets split
into two (pad = -16, then entry.pad_before = 16) after that change,
causing a change in padding. Still looks correct to me, but I didn't
actually run anything so I'm probably getting something wrong.

> I've added a few test cases along these lines in v2, and one of them
> certainly different behaviour. This is good actually since it shows a
> simple case of what these padding changes are intended to fix.