linux-kernel - Re: [Patch 4/4] module: trim exception table in module

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Message-Id: <200905281625.24974.rusty@rustcorp.com.au>
Date:	Thu, 28 May 2009 16:25:23 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, jdike@...toit.com, mingo@...e.hu,
	sparclinux@...r.kernel.org, linux-ia64@...r.kernel.org
Subject: Re: [Patch 4/4] module: trim exception table in module_free()

On Wed, 27 May 2009 05:16:11 pm Amerigo Wang wrote:
> Rusty Russell wrote:
> > __ex_table ends up with two entries:
> >
> > Contents of section __ex_table:
> >  0000 0c000000 00000000 0e000000 00000000  ................
> >  0010 10000000 0a000000 12000000 0a000000  ................
> >
> > The first is for the __put_user in .text (extable_not_init()) and the
> > second is for the one in .init.text (init()).
> >
> > Depending on how the module gets allocated, the one referring to
> > .init.text may be first or last.
>
> Hmm, how about the following? :-)
>
> struct exception_table_entry *p = mod->extable;
>
> for (;p <= mod->extable+mod->num_exentries; p++ )
>          if (with_in_module_init(p->insn, mod))
>                    trim_it(p);

More like this:

void trim_init_extable(struct module *m)
{
	/* Since entries are sorted, init entries are at the start... */
	while (m->num_exentries && within_module_init(m->extable[0].insn)) {
		m->extable++;
		m->num_exentries--;
	}

	/* ... or the end. */
	while (m->num_exentries && within_module_init(m->extable[m->num_exentries-1].insn))
		m->num_exentries--;
}

Cheers,
Rusty.
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