From: Ingo Molnar <mingo@elte.hu>
To: Alan Modra <amodra@gmail.com>
Cc: Jan Beulich <JBeulich@novell.com>,
"H.J. Lu" <hjl.tools@gmail.com>,
binutils@sourceware.org, linux-kernel@vger.kernel.org,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: PATCH: Add --size-check=[error|warning]
Date: Mon, 14 Mar 2011 12:26:00 -0000 [thread overview]
Message-ID: <20110314122539.GA27205@elte.hu> (raw)
In-Reply-To: <20110314122342.GA26825@elte.hu>
(resend, fixed the To line)
* Alan Modra <amodra@gmail.com> wrote:
> On Mon, Mar 14, 2011 at 10:55:34AM +0100, Ingo Molnar wrote:
> > The thing is, it is absolutely, breath-takingy incompetent for
>
> kernel developers to write such poor asm! And not notice the error
> for 4 years! [...]
It is not 'poor asm'.
The 'bug' is just a slight assymetry in ENTRY()/END() debug-symbols sequences, with
lots of assembly code between the ENTRY() and the END(). Here's an example:
ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs)
...
END(do_hypervisor_callback)
Human reviewers almost never catch such small mismatches, and binutils never even
warned about it either - for over a decade.
Now kernel bisections are insta-broken on latest binutils, and there's nothing to do
about it on the kernel side as during bisection all later fixes are unfolded. The
fix itself i already applied - but my argument was not about that:
> [...] Oh, and the binutils developers to write such a poor assembler in the first
> place. ;-)
>
> Seriously, you are complaining because something is fixed??
No, i reported this bug because the kernel build gets broken going back 130,000
commits, breaking bisection and causing other damage - while issuing a warning
message would achieve the same effect of warning the developer about the mismatch.
> > The correct solution is to turn it into a warning as me and others have suggested.
>
> I disagree. The whole world is not the linux kernel. I think HJ is
> bending over backwards to even offer a switch that turns the error
> into a warning.
It's not about a switch at all - it's to not break builds by default. I.e. the
default behavior should be to issue a warning and ignore the directive.
This is a very simple concept of compatibility: the build environment should always
be very permissive - stuff that build fine before should be allowed to build.
Also, i hope you are not suggesting to break projects just because they are not
important to you personally? The fix is exceedingly simple to do for the binutils
project - and impossible to do for the kernel project (because during bisection -
which is a very powerful debugging tool - older versions of the source get checked
out).
Thanks,
Ingo
next prev parent reply other threads:[~2011-03-14 12:26 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-11 16:58 H.J. Lu
2011-03-11 17:04 ` Jan Beulich
2011-03-11 17:20 ` H.J. Lu
2011-03-14 8:44 ` Jan Beulich
2011-03-14 9:55 ` Ingo Molnar
2011-03-14 10:41 ` Alan Modra
2011-03-14 10:50 ` Pekka Enberg
2011-03-14 18:04 ` Alan Cox
2011-03-14 10:52 ` Jan Beulich
[not found] ` <AANLkTi=3AiLaw5Gnis8Ha4eRXirk0s-Cnk2zzN12YDpH__45869.1711457961$1300099861$gmane$org@mail.gmail.com>
2011-03-14 11:03 ` Andreas Schwab
2011-03-14 11:12 ` Pekka Enberg
2011-03-14 12:02 ` Andreas Schwab
2011-03-14 12:13 ` Ingo Molnar
2011-03-14 12:55 ` Andreas Schwab
2011-03-14 13:17 ` Ingo Molnar
2011-03-14 14:11 ` Andreas Schwab
2011-03-14 12:11 ` Ingo Molnar
2011-03-14 12:23 ` Ingo Molnar
2011-03-14 12:26 ` Ingo Molnar [this message]
2011-03-14 13:16 ` git bisect plus fixes (was: PATCH: Add --size-check=[error|warning]) Ralf Wildenhues
2011-03-14 13:55 ` PATCH: Add --size-check=[error|warning] H.J. Lu
2011-03-16 23:56 ` Alan Modra
2011-03-18 11:20 ` Alan Modra
2011-03-18 11:59 ` Alan Modra
2011-03-14 11:02 Sedat Dilek
2011-03-14 11:25 ` Jan Beulich
2011-03-14 11:35 ` Ingo Molnar
2011-03-14 11:39 ` Sedat Dilek
2011-03-14 11:53 ` Sedat Dilek
2011-03-14 12:22 ` Jan Beulich
2011-03-14 12:38 ` Sedat Dilek
2011-03-14 15:56 ` Ian Lance Taylor
2011-03-14 18:02 ` H. Peter Anvin
2011-03-14 16:33 ` H. Peter Anvin
2011-03-14 19:24 ` Steven Rostedt
2011-03-14 20:06 ` Linus Torvalds
2011-03-14 12:57 ` Ingo Molnar
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