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random: remove early archrandom abstraction

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The arch_get_random*_early() abstraction is not completely useful and
adds complexity, because it's not a given that there will be no calls to
arch_get_random*() between random_init_early(), which uses
arch_get_random*_early(), and init_cpu_features(). During that gap,
crng_reseed() might be called, which uses arch_get_random*(), since it's
mostly not init code.

Instead we can test whether we're in the early phase in
arch_get_random*() itself, and in doing so avoid all ambiguity about
where we are. Fortunately, the only architecture that currently
implements arch_get_random*_early() also has an alternatives-based cpu
feature system, one flag of which determines whether the other flags
have been initialized. This makes it possible to do the early check with
zero cost once the system is initialized.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2022-10-29 01:18:04 +02:00
parent b9b01a5625
commit 2c03e16f44
3 changed files with 12 additions and 60 deletions
Download patch file Download diff file Expand all files Collapse all files

20
include/linux/random.h
View file

@ -154,26 +154,6 @@ declare_get_random_var_wait(long, unsigned long)
#include <asm/archrandom.h>
/*
* Called from the boot CPU during startup; not valid to call once
* secondary CPUs are up and preemption is possible.
*/
#ifndef arch_get_random_seed_longs_early
static inline size_t __init arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
{
WARN_ON(system_state != SYSTEM_BOOTING);
return arch_get_random_seed_longs(v, max_longs);
}
#endif
#ifndef arch_get_random_longs_early
static inline bool __init arch_get_random_longs_early(unsigned long *v, size_t max_longs)
{
WARN_ON(system_state != SYSTEM_BOOTING);
return arch_get_random_longs(v, max_longs);
}
#endif
#ifdef CONFIG_SMP
int random_prepare_cpu(unsigned int cpu);
int random_online_cpu(unsigned int cpu);