linux-kernel - Re: [GIT PULL] x86 trampoline rework for 3.5

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Date:	Tue, 29 May 2012 19:37:15 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
	"H.J. Lu" <hjl.tools@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Ingo Molnar <mingo@...nel.org>,
	Jarkko Sakkinen <jarkko.sakkinen@...el.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Len Brown <len.brown@...el.com>, Len Brown <lenb@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg@...hat.com>,
	Michal Marek <mmarek@...e.cz>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Sam Ravnborg <sam@...nborg.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [GIT PULL] x86 trampoline rework for 3.5

On Tue, May 29, 2012 at 4:25 PM, H. Peter Anvin <hpa@...ux.intel.com> wrote:
>
> The rework of relocs.c is already in upstream.  I know you don't like
> lambda merges, but I did one for this branch, because I found that
> without it git will silently mismerge relocs.c between your tree and
> this branch; with the lambda merge in place it merges correctly.

So as far as I can tell, the merge does nothing useful. I merged both
with and without your merge, and either way the result is dubious.

The reason I call it dubious is that when I do the merge by hand, it's
ambigiuous what the resolution should be (but I have an opinion on
what the correct thing likely is), and if I take yours that "resolves"
the ambiguous case, but not in the way you then claim in this email.

> If you prefer to do this manually, you can instead pull
> 61f5446169046c217a5479517edac3a890c3bee7; however, make sure that
> arch/x86/tools/relocs.c ends up being the one from your current
> upstream tree.

Both your merge, *and* mine end up having a simple issue: your
original import of that file happened separately two different times,
and they don't agree.

In particular, the two branches disagree about what the
sym_regex_realmode[S_NSYMTYPES] array should look like. In my previous
head (and the one you claim is the right one), it has just two
patterns:

 /*
  * These are 16-bit segment symbols when compiling 16-bit code.
  */
        [S_SEG] =
        "^real_mode_seg$",

 /*
  * These are offsets belonging to segments, as opposed to linear addresses,
  * when compiling 16-bit code.
  */
        [S_LIN] =
        "^pa_",

but in your branch that "^pa_" pattern is duplicated for S_REL:

 /*
  * These symbols are known to be relative, even if the linker marks them
  * as absolute (typically defined outside any section in the linker script.)
  */
        [S_REL] =
        "^pa_",

 /*
  * These are 16-bit segment symbols when compiling 16-bit code.
  */
        [S_SEG] =
        "^real_mode_seg$",

 /*
  * These are offsets belonging to segments, as opposed to linear addresses,
  * when compiling 16-bit code.
  */
        [S_LIN] =
        "^pa_",

which looks odd.

But that case with three patterns is the one you selected in your
merge - *not* the current state of relocs.c that you claim should be
selected.

So I'm not pulling or merging anything until I understand what's going
on. Should I take the two-pattern one (which is what I have now, and
that seems sensible), or should that "^pa_" pattern really be merged
for two different cases (doesn't that just mean that the last one will
effectively override the first one)?

Also, your branch adds an "x86-relocs" thing to the scripts/.gitignore
file that you seem to have removed in the merge. What was going on
there?

                          Linus
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