Re: [PATCH v1 0/7 SECTOR: Support aligning to flash sector boundary

[Ulf Samuelsson <binutils@emagii.com>]

Since the proposal defines the begin, end and size of a sector as symbols,
you can do already today.
. = ALIGN(”bank00#04#size”).
Right now, the symbols are defined late, but that is easily changed.

Best Regards
Ulf Samuelsson

> 10 mars 2023 kl. 18:31 skrev Michael Matz <matz@suse.de>:
> 
> Hello.
> 
> On Fri, 10 Mar 2023, Ulf Samuelsson wrote:
> 
>>>    . = ALIGN(TOSECTOR)
>> 
>> I considered it, but came to the conclusion that it opens a bag of worms.
>> 
>> To fit this into the grammar, TOSECTOR (or maybe just SECTOR)
>> needs to be a valid expression, returning the size of the flash sector
>> where the location counter is.
>> 
>> Since expressions are available everywhere, you run into situations
>> where it really does not make sense for "SECTOR" to have a value.
> 
> So, make SECTOR an expression taking an address as well.  Call it 
> SECTORSIZE and make it return the sector size for the given argument (an 
> address, so that 'dot' can be given in output sections), or 1 if no sector 
> is associated with the argument.  Then your alignment expression will 
> become
> 
>  . = ALIGN(SECTORSIZE(.))
> 
> and SECTORSIZE now _can_ make sense in other than output sections (when 
> you for instance give it, say, a symbolname defined elsewhere in an 
> utput section).
> 
>> To create an function which collapses 100+ statements into a single 
>> expression may stress the expression evaluator in unpredictable ways.
>> 
>> Have the linker been tested with 100-200 lines+ expressions?
> 
> Yes.  Such thoughts shouldn't prevent an orthogonal implementation of 
> features anyway.  You can also open-code the implementation of SECTORSIZE 
> with a helper routine, not resorting to linkerscript expressions at all, 
> if you worry about performance of that.
> 
>> The alternative that I could consider is to add it in the Output Section 
>> Description There you can specify ALIGN_WITH_INPUT which has a similar 
>> syntax as ALIGN_SECTOR so alignment is specified either using an 
>> expression or a special keyword already today.
> 
> I think having it available as expression to be used in ALIGN (or other) 
> expressions is the better choice.
> 
> 
> Ciao,
> Michael.