linux-kernel - Re: [RFC v2 0/7] linux: add linker tables

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Message-ID: <20160219211948.GW25240@wotan.suse.de>
Date:	Fri, 19 Feb 2016 22:19:48 +0100
From:	"Luis R. Rodriguez" <mcgrof@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...nel.org>, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, x86@...nel.org,
	linux-kernel@...r.kernel.org, luto@...capital.net,
	boris.ostrovsky@...cle.com, rusty@...tcorp.com.au,
	david.vrabel@...rix.com, konrad.wilk@...cle.com, mcb30@...e.org,
	jgross@...e.com, ming.lei@...onical.com,
	gregkh@...uxfoundation.org, arnd@...db.de,
	linux-arch@...r.kernel.org, linux@....linux.org.uk,
	benh@...nel.crashing.org, jbaron@...mai.com, ananth@...ibm.com,
	anil.s.keshavamurthy@...el.com, davem@...emloft.net,
	masami.hiramatsu.pt@...achi.com, andriy.shevchenko@...ux.intel.com,
	dwmw2@...radead.org, xen-devel@...ts.xensource.com
Subject: Re: [RFC v2 0/7] linux: add linker tables

On Fri, Feb 19, 2016 at 12:16:29PM -0800, H. Peter Anvin wrote:
> On 02/19/2016 05:45 AM, Luis R. Rodriguez wrote:
> > This is my v2 of the original linker table work [0], now with
> > six proof of concepts ports of existing code using custom section
> > with custom linker script modifications:
> > 
> >   * DEFINE_LINKTABLE_TEXT(char, kprobes);
> >   * DEFINE_LINKTABLE_DATA(struct jump_entry, __jump_table);
> >   * DEFINE_LINKTABLE_DATA(struct _ddebug, __verbose);
> >   * DEFINE_LINKTABLE_RO(struct builtin_fw, builtin_fw);
> >   * DEFINE_LINKTABLE_INIT(struct x86_init_fn, x86_init_fns);
> >   * DEFINE_LINKTABLE_INIT_DATA(unsigned long, _kprobe_blacklist);
> > 
> > I've tested all except jump tables, I'd appreaciate some help with that.
> > 
> 
> We should add support for read-mostly, probably. 

Sure, any candidate in mind? I actually don't see any hacks built
on top of READ_MOSTLY_DATA include/asm-generic/vmlinux.lds.h so
pointers appreciated for a case I could try.

> In fact, some of these probably *are* read-mostly.

To avoid regressions I made sure to use the same exact section that
these original solutions came from, do we want to move some? If so
I think perhaps that's best done as a separate atomic patch and
it may be easier to read and review once ported on linker tables?

 Luis