arm64: Use v8.5-RNG entropy for KASLR seed (2e8e1ea8) · Commits · 戴 / test

When seeding KALSR on a system where we have architecture level random number generation make use of that entropy, mixing it in with the seed passed by the bootloader. Since this is run very early in init before feature detection is complete we open code rather than use archrandom.h. Signed-off-by:

Mark Brown <broonie@kernel.org> Reviewed-by:

Mark Rutland <mark.rutland@arm.com> Reviewed-by:

Ard Biesheuvel <ardb@kernel.org> Signed-off-by:

Will Deacon <will@kernel.org>

arch/arm64/include/asm/archrandom.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -59,9 +59,17 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
		return ok;
		}

		static inline bool __init __early_cpu_has_rndr(void)
		{
		/* Open code as we run prior to the first call to cpufeature. */
		unsigned long ftr = read_sysreg_s(SYS_ID_AA64ISAR0_EL1);
		return (ftr >> ID_AA64ISAR0_RNDR_SHIFT) & 0xf;
		}

		#else

		static inline bool __arm64_rndr(unsigned long *v) { return false; }
		static inline bool __init __early_cpu_has_rndr(void) { return false; }

		#endif /* CONFIG_ARCH_RANDOM */
		#endif /* _ASM_ARCHRANDOM_H */

arch/arm64/kernel/kaslr.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -120,6 +120,17 @@ u64 __init kaslr_early_init(u64 dt_phys)
		return 0;
		}

		/*
		* Mix in any entropy obtainable architecturally, open coded
		* since this runs extremely early.
		*/
		if (__early_cpu_has_rndr()) {
		unsigned long raw;

		if (__arm64_rndr(&raw))
		seed ^= raw;
		}

		if (!seed) {
		kaslr_status = KASLR_DISABLED_NO_SEED;
		return 0;

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