Messages in this thread | | | Date | Mon, 27 Apr 2009 05:47:21 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 14/15] x86: convert to use __HEAD and HEAD_TEXT macros. |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Sun, 26 Apr 2009, Sam Ravnborg wrote: > > > On Sun, Apr 26, 2009 at 10:12:47AM -0700, Linus Torvalds wrote: > > > > > > > > > On Sun, 26 Apr 2009, Linus Torvalds wrote: > > > > > > > > Btw, this one really needs to unify the two lds files first. Look at > > > > > > > > diff -u arch/x86/boot/compressed/vmlinux_*.lds > > > > > > > > output and realize that they're basially exctly the same except for > > > > trivial naming differences, and the fact that the64-bit version hs a > > > > "pgtable" thing. > > > > > > > > So this really needs to be done by first unifying the thing so that there > > > > is _one_ arch/x86/boot/compressed/vmlinux.lds.S file with a preprocessor > > > > that takes care of the trivial differences [..] > > > > > > Something like this? > > > > Looks good/correct. > > Acked-by: Sam Ravnborg <sam@ravnborg.org> > > > > You should add your s-o-b if you expect Ingo to pick it up. > > Sure. I don't tend to add SOB lines for stuff that I'd not be > ready to commit, but with some testing and other people looking at > it, I think it's good to go. > > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Thanks, applied to tip:x86/kbuild. I'll do some more testing of it before pushing it out.
> As mentioned, though, the much more interesting case would be the > _real_ kernel vmlinux.lds.S file, which is a lot more complex and > where the differences between 32-bit and 64-bit cases aren't > totally trivial. > > Looking at > > diff -u arch/x86/kernel/vmlinux_*.lds.S | less -S > > output, many of them are just whitespace, and others are trivial > and meaningless (comments in one, not the other, placement of > alignment etc, different ordering of sections like > "parainstructions"). Yet others seem to be things that we _could_ > do in general, but that don't matter on one architecture or other > (x86-64 has ".eh_frame" in the DISCARD section, i386 apparently > doesn't ever generate them, we could just use the x86-64 version).
We generally do these by separating the unification into at least 2-3 distinct steps - a mechanic, low-risk cleanup first, preparatory changes to bring the two files in sync second, and mechanic unification as the third and final step.
That way any bugs are easily bisectable to a reasonably sized (and reasonably risky) sub-patch. Review also gets much easier.
I've yet to see a non-trivial Makefile unification in arch/x86 that does not regress :-) They concentrate a lot of quirks and implicit dependencies and small but significant tricks. [usually we catch the bugs early on though - but even at an early stage it's good to have a reasonable splitup.]
Ingo
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