Date: Thu, 07 Dec 2017 09:41:58 +0530 From: kaiwan.billimoria@...il.com To: "Tobin C. Harding" <me@...in.cc> Cc: Alexander Kapshuk <alexander.kapshuk@...il.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v3] scripts: leaking_addresses: add support for 32-bit kernel addresses On Thu, 2017-12-07 at 10:01 +1100, Tobin C. Harding wrote: > On Wed, Dec 06, 2017 at 05:21:30PM +0530, kaiwan.billimoria@...il.com wrote: > > On Wed, 2017-12-06 at 15:04 +1100, Tobin C. Harding wrote: > > > > > Sure, lets try for a generic ver! > > Cool. > > > Thanks for your help on this.. > > No problem. > > > As your experience woth the R Pi shows, we may have to just resort to building a > > generic framework of sorts, letting folks "plugin" appropriate "truth values" > > for their particular platform; this way, we support as much as we can for now > > and, going forward, it's generic. > > As of right now though, am unsure what this "generic framework" is.. > > ATM the best I can come up with is having two flags > > --page-offset-32bit=0xc0000000 (exactly as we have now) > --32-bit > > Now for the klunky bit, I can only see two options > > 1. Default to 64 bit, for 32 bit scan require one of the above options > to be set. Yes, agreed.. > > 2. Parse config file for all architectures, if CONFIG_PAGE_OFFSET is set > us it. > > I particularly don't like option 2. If we can find a reliable way to get > the architecture the we have a better option. At the moment the method > we use relies on the architecture of the machine that the Perl binary > was built on (AFAICT). > > (/usr/bin/arch does not work on RPi either) Right, reg arch: nor on some of the Yocto platforms I tested. > > I'm happy with option 1 unless there is a better proposal. > thanks, > Tobin. Okay, I can start working on the approach above. So, that implies that the is_supported_architecture sub (and it's descendants) are now redundant, correct? Also, I think we can perhaps still make use of the 'uname -m' to advantage: 1. A scenario: the user runs the script with no options; we default to 64-bit. But, the platform is actually 32-bit. So, we run a sanity check regardless - if we find that the platform is indeed 32-bit but the user has not run with the --32-bit (or --page-offset-32bit) option switch(es), we could: - (a) emit a noisy Warning message to stderr and continue, ("batch mode"), OR - (b) fail, with the error message and a failure code. Of course if we go with (a), the results will be meaningless; so, just failing might be better. Again, I realize that all this will only work if detection of 32-bit actually works! I'll take a stab at this.. 2. Modify the show_detected_architecture sub to use it (for 'debug' case). What do you think? Thanks, Kaiwan.
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