Date: Thu, 7 Dec 2017 16:24:06 +1100 From: "Tobin C. Harding" <me@...in.cc> To: kaiwan.billimoria@...il.com 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, Dec 07, 2017 at 09:41:58AM +0530, kaiwan.billimoria@...il.com wrote: > 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? We still need it for differentiating between 64 bit architectures. So far it appears to work (x86_64 and ppc64). > 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 Yeah, I see no problem with this. > - (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). Yep, I say keep it for debugging. thanks, Tobin.
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