Messages in this thread | | | Date | Thu, 7 Jun 2018 09:30:21 +1000 | From | "Tobin C. Harding" <> | Subject | Re: [PATCH v6 0/4] enable early printing of hashed pointers |
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On Wed, Jun 06, 2018 at 03:02:20PM +0200, Thomas Gleixner wrote: > On Mon, 28 May 2018, Tobin C. Harding wrote: > > > Currently printing pointers early in the boot sequence can result in a > > dummy string '(____ptrval____)' being printed. While resolving this > > issue it was noticed that we can use the hw RNG if available for hashing > > pointers. > > > > Patch one and two do the ground work to be able to use hw RNG removing > > from get_random_bytes_arch() the call to get_random_bytes() and > > returning the number of bytes of random material successfully returned. > > > > Patch three uses the hw RNG to get keying material if it is available. > > > > Patch four further assists debugging early in the boot sequence for > > machines that do not have a hw RNG by adding a command line option > > 'debug_boot_weak_hash'. If enabled, non-cryptographically secure hashing > > is used instead of siphash so we can hash at any time. > > > > During the versions of this set I have been totally confused about which > > patches go through which tree. This version again puts all 4 patches > > together in the hope they will go through Andrew's tree. > > > > > > Steve, > > > > Could you please take a quick squiz at the final 2 patches if you get a > > chance. I assumed we are in preemptible context during early_init based > > on your code (and code comment) and called static_branch_disable() > > directly if hw RNG returned keying material. It's a pretty simple > > change but I'd love to get someone else to check I've not noob'ed it. > > early_initcalls() are not that early :) They run in thread context fully > preemtible so calling static_branch_disable() is perfectly fine.
Thanks for the explanation.
Tobin.
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