RFC ARM: Add a generic macro for declaring proc_info structs

Quoted 12 lines · Russell King - ARM Linux

Quoted 10 lines · Dave Martin

Quoted 3 lines · Russell King - ARM Linux

It does look very much like a sledge hammer to me. All we're really after is whether the size of the region is what we expect it to be - which will tell us whether there's a T2 instruction in there.

True, although the intent was no to solve just that one problem, but to show how to avoid a whole variety of trivial mistakes. Since proc_info structs don't tend to get changed much after they're initially written, I guess that such mistakes don't actually occur very often, though.

Quoted 8 lines

We have several other structures encoded in assembly - and to do this for every one would be excessive. The amount of churn produced too would be large.

Historically we've had little problem with these structs being wrong - about once or twice pre-Thumb for a decade IIRC (where at least one was down to "using an old patch but didn't update it properly for the new proc-*.S files".)

What may be worth doing is something like this, where all entries follow a well defined naming scheme:

.macro processor_functions, name, dabort, pabort, suspend, nommu
.type \name\()_processor_functions, #object
ENTRY(\name\()_processor_functions)

	.word	\dabort\()_abort
	.word	\pabort\()_pabort
	.word	cpu_\name\()_proc_init
	.word	cpu_\name\()_proc_fin
	.word	cpu_\name\()_reset
	.word	cpu_\name\()_do_idle
	.word	cpu_\name\()_dcache_clean_area
	.word	cpu_\name\()_switch_mm
	.ifne \nommu
	.word	0
	.else
	.word	cpu_\name\()_set_pte_ext
	.endif
	.ifne \suspend
	.word	cpu_\name\()_suspend_size
	.word	cpu_\name\()_do_suspend
	.word	cpu_\name\()_do_resume
	.else
	.word	0
	.word	0
	.word	0
	.endif
	.size	\name\()_processor_functions, . - \name\()_processor_functions
	.endm

and this has great value to ensuring that the structure in assembly matches what is in the headers as it means that instead of having N places to update these structures, we're down to its header and one macro - and also ensures that proc files which miss out on the update won't link to an apparantly working kernel.

The cache and tlb structures follow a very similar naming scheme to the above.

The proc_info structures are much harder to deal with because they don't contain such commonality, but I'm sure it may be possible to come up with something along these lines.