linux-kernel - Re: IRQF_SAMPLE

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Message-Id: <1239220294.31467.55.camel@calx>
Date:	Wed, 08 Apr 2009 12:51:34 -0700
From:	Matt Mackall <mpm@...enic.com>
To:	Robin Getz <rgetz@...ckfin.uclinux.org>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Chris Peterson <cpeterso@...terso.com>
Subject: Re: IRQF_SAMPLE_RANDOM question...

On Tue, 2009-04-07 at 17:44 -0400, Robin Getz wrote:
> On Tue 7 Apr 2009 10:57, Matt Mackall pondered:
> > On Tue, 2009-04-07 at 07:16 -0400, Robin Getz wrote:
> > > On Mon 6 Apr 2009 15:01, Matt Mackall pondered:
> > > > On Mon, 2009-04-06 at 14:30 -0400, Robin Getz wrote:
> > > > > We have lots of embedded headless systems (no keyboard/mouse, no
> > > > > soundcard, no video) systems with *no* sources of entropy - and
> > > > > people using SSL. 
> > > > 
> > > > I'd rather add a random_sample_network call somewhere reasonably
> > > > central in the network stack. Then we can use the knowledge that the
> > > > sample is network-connected in the random core to decide how to 
> > > > measure its entropy. The trouble with IRQF_SAMPLE_RANDOM is that 
> > > > many of its users are technically bogus as entropy sources in the
> > > > current model. 
> > > 
> > > OK - that makes more sense.
> > > 
> > > Does that mean we also shouldn't be using IRQF_SAMPLE_RANDOM on
> > > interrupt sources in subsystems which already have add_xxx_randomness()
> > > in them? (block devices, and input devices?)
> > > 
> > > block/blk-core.c -> blk_end_io() -> add_disk_randomness()
> > > drivers/input/input.c -> input_event() -> add_input_randomness()
> > > 
> > >  drivers/block/xen-blkfront.c, line 639
> > > 
> > >  drivers/input/touchscreen/wm97xx-core.c, line 374
> > >  drivers/input/keyboard/gpio_keys.c, line 145
> > >  drivers/input/keyboard/bf54x-keys.c, line 255
> > >  drivers/input/serio/hp_sdc.c, line 881
> >
> > Yes. The flag needs to be taken out and shot. 
> 
> In general or just for input and block devices?
> 
> There are still some in others:
> 
> arch/arm/mach-omap1/board-palmz71.c
> arch/arm/mach-pxa/lubbock.c
> arch/arm/mach-pxa/magician.c
> arch/arm/mach-pxa/palmtx.c
> arch/arm/mach-pxa/palmz72.c
> arch/arm/mach-pxa/trizeps4.c
> arch/sparc/kernel/ldc.c
> arch/um/drivers/line.c
> arch/um/drivers/mconsole_kern.c
> arch/um/drivers/port_kern.c
> arch/um/drivers/xterm_kern.c
> arch/um/kernel/sigio.c
> arch/x86/kernel/amd_iommu_init.c
> drivers/i2c/busses/i2c-pmcmsp.c
> drivers/mfd/tps65010.c
> drivers/power/pda_power.c
> drivers/serial/bfin_sport_uart.c
> drivers/serial/mpc52xx_uart.c
> drivers/serial/uartlite.c
> drivers/staging/comedi/interrupt.h
> drivers/usb/gadget/goku_udc.c
> drivers/usb/gadget/omap_udc.c
> drivers/usb/gadget/pxa25x_udc.c
> drivers/usb/otg/gpio_vbus.c
> drivers/usb/otg/isp1301_omap.c
> 
> > Everything going into the 
> > RNG should be made to go through an add_*_randomness interface only.
> > Preferably not at a per-driver level.
> 
> Is that "Everything in general, with a few exceptions", or "__Everything__"?
> 
> If it is the latter I'll remove the ones that I'm responsible for, and send 
> Sam something for checkpatch.pl to warn if this is used in the future.

Everything. We want every input point to better document the type of
entropy source.

-- 
http://selenic.com : development and support for Mercurial and Linux


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