From: Mark Brown broonie@kernel.org
mainline inclusion from mainline-v5.5-rc3 commit 2e8e1ea88cbcb19a77b7acb67f6ffe39cc15740c category:feature bugzilla:NA CVE:NA
-------------------
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 Signed-off-by: Chen Jun chenjun102@huawei.com Reviewed-by: Xie XiuQi xiexiuqi@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/arm64/include/asm/archrandom.h | 8 ++++++++ arch/arm64/kernel/kaslr.c | 11 +++++++++++ 2 files changed, 19 insertions(+)
diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h index 5ea5a1ce5a5f..3fe02da70004 100644 --- a/arch/arm64/include/asm/archrandom.h +++ b/arch/arm64/include/asm/archrandom.h @@ -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 */ diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index 415ae2e512aa..49146e5ccffe 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -126,6 +126,17 @@ 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;