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| author |   Jason A. Donenfeld <Jason@zx2c4.com> | 2022-07-05 20:48:41 +0200 |
|---|---|---|
| committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-07-18 15:03:37 +0200 |
| commit | 9592eef7c16ec5fb9f36c4d9abe8eeffc2e1d2f3 (patch) | |
| tree | c6342d647f5b03d9c2d5b4eca67e56e4af31aef4 /arch/s390/Kconfig | |
| parent | random: cap jitter samples per bit to factor of HZ (diff) | |
| download | linux-dev-9592eef7c16ec5fb9f36c4d9abe8eeffc2e1d2f3.tar.xz linux-dev-9592eef7c16ec5fb9f36c4d9abe8eeffc2e1d2f3.zip | |
random: remove CONFIG_ARCH_RANDOM
When RDRAND was introduced, there was much discussion on whether it
should be trusted and how the kernel should handle that. Initially, two
mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and
"nordrand", a boot-time switch.
Later the thinking evolved. With a properly designed RNG, using RDRAND
values alone won't harm anything, even if the outputs are malicious.
Rather, the issue is whether those values are being *trusted* to be good
or not. And so a new set of options were introduced as the real
ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu".
With these options, RDRAND is used, but it's not always credited. So in
the worst case, it does nothing, and in the best case, maybe it helps.
Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the
center and became something certain platforms force-select.
The old options don't really help with much, and it's a bit odd to have
special handling for these instructions when the kernel can deal fine
with the existence or untrusted existence or broken existence or
non-existence of that CPU capability.
Simplify the situation by removing CONFIG_ARCH_RANDOM and using the
ordinary asm-generic fallback pattern instead, keeping the two options
that are actually used. For now it leaves "nordrand" for now, as the
removal of that will take a different route.
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'arch/s390/Kconfig')
| -rw-r--r-- | arch/s390/Kconfig | 15 |
1 files changed, 0 insertions, 15 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 8cd9e56c629b..9b6e4e7cb17b 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -507,21 +507,6 @@ config KEXEC_SIG verification for the corresponding kernel image type being loaded in order for this to work. -config ARCH_RANDOM - def_bool y - prompt "s390 architectural random number generation API" - help - Enable the s390 architectural random number generation API - to provide random data for all consumers within the Linux - kernel. - - When enabled the arch_random_* functions declared in linux/random.h - are implemented. The implementation is based on the s390 CPACF - instruction subfunction TRNG which provides a real true random - number generator. - - If unsure, say Y. - config KERNEL_NOBP def_bool n prompt "Enable modified branch prediction for the kernel by default" |