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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/powerpc/platforms | |
| 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/powerpc/platforms')
| -rw-r--r-- | arch/powerpc/platforms/microwatt/Kconfig | 1 | ||||
| -rw-r--r-- | arch/powerpc/platforms/powernv/Kconfig | 1 | ||||
| -rw-r--r-- | arch/powerpc/platforms/pseries/Kconfig | 1 |
3 files changed, 0 insertions, 3 deletions
diff --git a/arch/powerpc/platforms/microwatt/Kconfig b/arch/powerpc/platforms/microwatt/Kconfig index 5e320f49583a..6af443a1db99 100644 --- a/arch/powerpc/platforms/microwatt/Kconfig +++ b/arch/powerpc/platforms/microwatt/Kconfig @@ -6,7 +6,6 @@ config PPC_MICROWATT select PPC_ICS_NATIVE select PPC_ICP_NATIVE select PPC_UDBG_16550 - select ARCH_RANDOM help This option enables support for FPGA-based Microwatt implementations. diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig index 161dfe024085..e1a05c5a9004 100644 --- a/arch/powerpc/platforms/powernv/Kconfig +++ b/arch/powerpc/platforms/powernv/Kconfig @@ -12,7 +12,6 @@ config PPC_POWERNV select EPAPR_BOOT select PPC_INDIRECT_PIO select PPC_UDBG_16550 - select ARCH_RANDOM select CPU_FREQ select PPC_DOORBELL select MMU_NOTIFIER diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig index f7fd91d153a4..f4a647c1f0b2 100644 --- a/arch/powerpc/platforms/pseries/Kconfig +++ b/arch/powerpc/platforms/pseries/Kconfig @@ -19,7 +19,6 @@ config PPC_PSERIES select PPC_UDBG_16550 select PPC_DOORBELL select HOTPLUG_CPU - select ARCH_RANDOM select FORCE_SMP select SWIOTLB default y |