Messages in this thread | | | From | "Tobin C. Harding" <> | Subject | [PATCH v3 0/4] enable early printing of hashed pointers | Date | Fri, 4 May 2018 09:07:37 +1000 |
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Currently if an attempt is made to print a pointer before there is enough entropy then '(____ptrval____)' is printed. This makes debugging stack traces during early boot difficult.
It was observed that we can relax the requirement for cryptographically secure hashing when debugging while still maintaining pointer hashing behaviour. This allows kernels to be debugged without developers relying on different pointer printing behavior.
Using the hw RNG if available solves this problem for those machines that have a hardware RNG, we would like to solve it for _all_ machines.
Patch 1 - Whitespace fixes. Patch 2 - Fix get_random_bytes_arch() Patch 3 - Use hw RNG for pointer hashing if available (by default). Patch 4 - Use insecure hashing with command line option 'debug_early_boot'.
thanks, Tobin.
v2 -> v3 - Add __ro_after_init (suggested by Kees).
v1 -> v2 - Use min_t() instead of min() (thanks checkpatch). - Add __must_check to function declaration (thanks Steve). - Use hw RNG by default if available (as originally suggested by Kees). - Add command line option to use cryptographically insecure hashing. If debug_early_boot is enabled use hash_long() instead of siphash (as requested by Steve, and solves original problem for Anna-Maria).
Tobin C. Harding (4): random: Fix whitespace pre random-bytes work random: Return nbytes filled from hw RNG vsprintf: Use hw RNG for ptr_key vsprintf: Add command line option debug_early_boot
Documentation/admin-guide/kernel-parameters.txt | 8 ++++++ drivers/char/random.c | 19 +++++++------ include/linux/random.h | 2 +- lib/vsprintf.c | 37 +++++++++++++++++++++++-- 4 files changed, 53 insertions(+), 13 deletions(-)
-- 2.7.4
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