Re: runtime check for omap-aes bus access permission (was: Re: 3.13-rc3 (commit 7ce93f3) breaks Nokia N900 DT boot)

["Pali Rohár" <pali.rohar@gmail.com>]

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On Wednesday 26 November 2014 18:54:12 Tony Lindgren wrote:
> * Pali Rohár <pali.rohar@gmail.com> [141125 13:33]:
> > On Tuesday 25 November 2014 22:08:17 Pali Rohár wrote:
> > > On Sunday 08 December 2013 00:22:06 Tony Lindgren wrote:
> > > > * Sebastian Reichel <sre@ring0.de> [131207 15:04]:
> > > > > On Sat, Dec 07, 2013 at 01:11:37PM -0800, Tony
> > > > > Lindgren
> > > 
> > > wrote:
> > > > > > > I asked Pali to send me his copy of the updated
> > > > > > > NOLO bootloader, so that I can test this. I just
> > > > > > > checked the omap documentation (I only have
> > > > > > > access to the public one) and crypto related
> > > > > > > stuff is not documented for the
> > > > > > > L3_PM_READ_PERMISSION register. There are a
> > > > > > > couple of reserved bits, which may be used for
> > > > > > > this, though.
> > > > > > > 
> > > > > > > I also CC'd Joel Fernandes, since he worked on the
> > > > > > > driver before and may have access to the
> > > > > > > documentation.
> > > > > > 
> > > > > > Looks like at least the 36xx public version
> > > > > > referenced here has them:
> > > > > > 
> > > > > > http://www.spinics.net/lists/linux-omap/msg21857.htm
> > > > > > l
> > > > > > 
> > > > > > I'd assume the registers are the same for 34xx since
> > > > > > we don't have them defined separately in the
> > > > > > kernel.
> > > > > 
> > > > > I can't find it in the omap36xx documentation either.
> > > > > Maybe I search at the wrong position. I tried to find
> > > > > something crypto related in
> > > > > 
> > > > > Table 9-89. L3_PM_READ_PERMISSION_i
> > > > 
> > > > Hmm maybe it's done based on the address in
> > > > L3_PM_ADDR_MATCH_k?
> > > > 
> > > > I guess the thing to do would be to compare the register
> > > > output between the two different firmware versions.
> > > > 
> > > > Regards,
> > > > 
> > > > Tony
> > > 
> > > Tony, if you can tell me how to read those registers I can
> > > provide output from both bootloaders (one that enable aes
> > > support in L3 firewall and one which not).
> > > 
> > > Also I can test other patches or provide other logs if you
> > > need something more...
> > 
> > CCing Nishanth Menon
> 
> Maybe just try dumping out the L3_PM_ADDR_MATCH_* registers
> during the boot?
> 
> > Problem is that when L3 firewall is not configured by signed
> > bootloader then loading omap aes driver cause kernel crash.
> > We need some code which can check if omap aes is enabled or
> > not at runtime in kernel...
> > 
> > More details with full email tread conversation is there:
> > http://thread.gmane.org/gmane.linux.ports.arm.omap/108397/
> 
> AFAIK we can't change the configuration, but it should be
> readable somewhere. Sorry don't know which registers would
> show the configuration other than the L3_PM_ADDR_MATCH_*
> registers.
> 
> Regards,
> 
> Tony

Hello, after playing with aes and non-aes version of bootloaders 
I found out that code which configure L3 firewall must be in 
signed X-Loader part. So probably we cannot change configuration 
at runtime...

Tony,
any idea how to dump L3_PM_ADDR_MATCH_* registers from userspace 
or from kernel? Now I have configured one N900 with original 
Nokia X-Loader (where loading omap aes driver cause kernel crash) 
and one N900 with aes X-Loader (where loading omap aes driver is 
working).

-- 
Pali Rohár
pali.rohar@gmail.com

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