On 06/20/2018 03:30 PM, Tobin C. Harding wrote: > On Wed, Jun 20, 2018 at 09:09:49AM -0700, Randy Dunlap wrote: >> On 06/19/2018 09:20 PM, Tobin C. Harding wrote: >>> Currently printing [hashed] pointers requires enough entropy to be >>> available. Early in the boot sequence this may not be the case >>> resulting in a dummy string '(____ptrval____)' being printed. This >>> makes debugging the early boot sequence difficult. We can relax the >>> requirement to use cryptographically secure hashing during debugging. >>> This enables debugging while keeping development/production kernel >>> behaviour the same. >>> >>> If new command line option debug_boot_weak_hash is enabled use >>> cryptographically insecure hashing and hash pointer value immediately. >>> >>> Signed-off-by: Tobin C. Harding <m...@tobin.cc> >>> Reviewed-by: Steven Rostedt (VMware) <rost...@goodmis.org> >>> --- >>> Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ >>> lib/vsprintf.c | 17 +++++++++++++++++ >>> 2 files changed, 26 insertions(+) >>> >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt >>> b/Documentation/admin-guide/kernel-parameters.txt >>> index 638342d0a095..a116fc0366b0 100644 >>> --- a/Documentation/admin-guide/kernel-parameters.txt >>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>> @@ -748,6 +748,15 @@ >>> >>> debug [KNL] Enable kernel debugging (events log level). >>> >>> + debug_boot_weak_hash >>> + [KNL] Enable printing pointers early in the boot >>> + sequence. If enabled, we use a weak hash instead of >>> + siphash to hash pointers. Use this option if you need >>> + to see pointer values during early boot (i.e you are >> >> maybe: >> to see hashed pointer values >> i.e., not raw pointers. > > You cannot see 'raw pointers' anyways?
only if using %px ? Maybe it's just terminology. I don't consider a hashed value as a pointer value. It's just a key or handle or some other number, but it's not a pointer. >> >>> + seeing instances of '(___ptrval___)'). >>> + Cryptographically insecure, please do not use on >>> + production kernels. > > thanks for the review, I don't quiet see how to use your suggestion to > make the text clearer. If you still feel this change is needed perhaps > you could write so I understand i.e 'Use this option if ...' OK, if you are good with it, I am too. :) thanks, -- ~Randy
