From: Michael Ellerman <mpe@ellerman.id.au>
To: Gabriel Paubert <paubert@iram.es>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>,
linuxppc-dev <linuxppc-dev@ozlabs.org>,
Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>,
Michael Neuling <mikey@neuling.org>,
Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH v3] ppc64/book3s: fix branching to out of line handlers in relocation kernel
Date: Fri, 01 Apr 2016 21:40:17 +1100 [thread overview]
Message-ID: <1459507217.10340.5.camel@ellerman.id.au> (raw)
In-Reply-To: <20160401063743.GA24955@visitor2.iram.es>
On Fri, 2016-04-01 at 08:37 +0200, Gabriel Paubert wrote:
> On Fri, Apr 01, 2016 at 05:14:35PM +1100, Michael Ellerman wrote:
> > If you build an allmodconfig, and turn on CONFIG_RELOCATABLE, and then look at
> > the disassembly, you see this:
> >
> > c000000000006ffc: 48 00 29 04 b c000000000009900 <.ret_from_except>
> >
> > c000000000007000 <__end_handlers>:
> >
> > At 0x7000 we have the FWNMI area, which is fixed and can't move. As you see
> > above we end up with only 4 bytes of space between the end of the handlers and
> > the FWNMI area.
>
> Nitpicking a bit, if I correctly read the above disassembly and there is an instuction
> at 0x6ffc, the free space is exactly 0!
Well spotted! It was of course an April fools .. joke ? :)
> > None of that's your fault, it's just the nature of the code in there, it's very
> > space constrained.
>
> Calling it space very constrained makes you win the understatement of the month
> award, on April fool's day :-)
Well there are some holes here and there, so we could write two instructions,
then branch to the next hole, five more instructions, branch to the next hole
etc. But that makes for hard to read code :)
cheers
next prev parent reply other threads:[~2016-04-01 10:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-30 18:19 [PATCH v3] ppc64/book3s: fix branching to out of line handlers in relocation kernel Hari Bathini
2016-04-01 6:14 ` Michael Ellerman
2016-04-01 6:37 ` Gabriel Paubert
2016-04-01 10:40 ` Michael Ellerman [this message]
2016-04-01 6:53 ` Hari Bathini
2016-04-01 10:37 ` Michael Ellerman
2016-04-01 19:41 ` Hari Bathini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1459507217.10340.5.camel@ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=hbathini@linux.vnet.ibm.com \
--cc=linuxppc-dev@ozlabs.org \
--cc=mahesh@linux.vnet.ibm.com \
--cc=mikey@neuling.org \
--cc=paubert@iram.es \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.