linux-kernel - Re: [PATCH v8 13/16] ARM: LPAE: Add identity mapping support for the 3-level page table format

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 11 Nov 2011 11:58:02 +0000
From:	Will Deacon <will.deacon@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 13/16] ARM: LPAE: Add identity mapping support for the
 3-level page table format

On Fri, Nov 11, 2011 at 11:36:01AM +0000, Catalin Marinas wrote:
> On Thu, Nov 10, 2011 at 10:55:17PM +0000, Russell King - ARM Linux wrote:
> > On Mon, Nov 07, 2011 at 04:16:55PM +0000, Catalin Marinas wrote:
> > > +		pmd += pmd_index(addr);
> > > +	} else
> > > +		pmd = pmd_offset(pud, addr);
> > > +
> > > +	do {
> > > +		next = pmd_addr_end(addr, end);
> > > +		*pmd = __pmd((addr & PMD_MASK) | prot);
> > > +		flush_pmd_entry(pmd);
> > > +	} while (pmd++, addr = next, addr != end);
> > > +}
> > > +#else	/* !CONFIG_ARM_LPAE */
> > 
> > I'm not convinced about the wiseness of this.  One of the places where
> > this code is called is from the reboot paths, which can happen in atomic
> > context.  Trying to allocate memory in such a context is going to lead
> > to problems, especially if support for panic'ing on OOM, and rebooting
> > on panic'ing are both enabled.
> 
> A solution would be to have pre-set page table for identity mappings
> (which may even come in handy for power management) and avoid the
> allocation in idmap.c.

Yup, that's what I do in my latest kexec series (v5) so this problem goes
away then.

> > Therefore, I think this patch depends on the work Will has been doing to
> > re-structure the kexec and restart support.
> 
> I think Will can rebase his patches on top of mine (I touched this file
> first :)).

Haha, but my code doesn't depend on yours in order to work correctly!

Will
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/