Re: RFC: Sentosa boot fix

["Franck Bui-Huu" <vagabon.xyz@gmail.com>]

Maciej W. Rozycki wrote:
> On Thu, 1 Feb 2007, Franck Bui-Huu wrote:
>
>>> Checking for code correctness and validation of the toolchain (Linux is
>>> one of the few non-PIC users of (n)64) without having to chase hardware
>>> that would support running from XPHYS without serious pain (the firmware
>>> being the usual offender).
>> This use case was unknown by the time we introduced __pa_page_offset().
>
>  Well, I am afraid it was known well before.  I introduced it first to 2.4

sorry I meant it wasn't for _me_.

>
>  It hurts performance a little bit, so if you can assure the macro shall

Well __pa() is only used in a few places. Futhermore it's used
only during boot mem init so it really shouldn't hurt.

>
>> BTW, maybe we can simply remove BUILD_ELF64 at all, since it's only
>> used to add '-msym32' switch in the makefile. This switch could be
>> automatically be added by the makefile instead thanks the following
>> condition:
>>
>> if CONFIG_64BITS and ${load-y} in CKSEG0
>>    cflags-y += -msym32
>> endif
>>
>> what do you think ?
>
>  I do not see enough of justification for -msym32 to be forced.
>

It gives good default behaviours without both user's intervention or
configuration:

	if CONFIG_64BITS
		ifndef sym32
			if load-y in XKPHYS
				sym32 = ''		[1]
			elif load-y in CKSEG0
				sym32 = '-msym32'	[2]
		else
			if sym32 eq 'yes'
				sym32 = '-msym32'	[3]
		endef
	fi
	cflags-y += $(sym32)

[1] since there is no reason to add '-msym32' and it would generate
    wrong code anyways.
[2] since it's used by all platforms to generate smaller code.
    Warn if this option is not supported by the tool chains.
[3] if you really want to generate code loaded in CKSEG0 without
    -msym32 switch you could always do:

		$ make sym32=no

    IMHO, for normal users, this case is probably a configuration
    bug and that's the reason we should request for a user to ask for
    it explicitly.

-- 
               Franck