From: Peter Collingbourne <pcc@google.com> To: Catalin Marinas <catalin.marinas@arm.com>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com> Cc: Peter Collingbourne <pcc@google.com>, Evgenii Stepanov <eugenis@google.com>, Andrey Konovalov <andreyknvl@gmail.com>, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org Subject: [PATCH v2] arm64: mte: initialize RGSR_EL1.SEED in __cpu_setup Date: Fri, 7 May 2021 11:59:05 -0700 [thread overview] Message-ID: <20210507185905.1745402-1-pcc@google.com> (raw) A valid implementation choice for the ChooseRandomNonExcludedTag() pseudocode function used by IRG is to behave in the same way as with GCR_EL1.RRND=0. This would mean that RGSR_EL1.SEED is used as an LFSR which must have a non-zero value in order for IRG to properly produce pseudorandom numbers. However, RGSR_EL1 is reset to an UNKNOWN value on soft reset and thus may reset to 0. Therefore we must initialize RGSR_EL1.SEED to a non-zero value in order to ensure that IRG behaves as expected. Signed-off-by: Peter Collingbourne <pcc@google.com> Fixes: 3b714d24ef17 ("arm64: mte: CPU feature detection and initial sysreg configuration") Cc: <stable@vger.kernel.org> # 5.10 Link: https://linux-review.googlesource.com/id/I2b089b6c7d6f17ee37e2f0db7df5ad5bcc04526c --- arch/arm64/mm/proc.S | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 0a48191534ff..97d7bcd8d4f2 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -447,6 +447,18 @@ SYM_FUNC_START(__cpu_setup) mov x10, #(SYS_GCR_EL1_RRND | SYS_GCR_EL1_EXCL_MASK) msr_s SYS_GCR_EL1, x10 + /* + * If GCR_EL1.RRND=1 is implemented the same way as RRND=0, then + * RGSR_EL1.SEED must be non-zero for IRG to produce + * pseudorandom numbers. As RGSR_EL1 is UNKNOWN out of reset, we + * must initialize it. + */ + mrs x10, CNTVCT_EL0 + ands x10, x10, #SYS_RGSR_EL1_SEED_MASK + csinc x10, x10, xzr, ne + lsl x10, x10, #SYS_RGSR_EL1_SEED_SHIFT + msr_s SYS_RGSR_EL1, x10 + /* clear any pending tag check faults in TFSR*_EL1 */ msr_s SYS_TFSR_EL1, xzr msr_s SYS_TFSRE0_EL1, xzr -- 2.31.1.607.g51e8a6a459-goog
WARNING: multiple messages have this Message-ID (diff)
From: Peter Collingbourne <pcc@google.com> To: Catalin Marinas <catalin.marinas@arm.com>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com> Cc: Peter Collingbourne <pcc@google.com>, Evgenii Stepanov <eugenis@google.com>, Andrey Konovalov <andreyknvl@gmail.com>, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org Subject: [PATCH v2] arm64: mte: initialize RGSR_EL1.SEED in __cpu_setup Date: Fri, 7 May 2021 11:59:05 -0700 [thread overview] Message-ID: <20210507185905.1745402-1-pcc@google.com> (raw) A valid implementation choice for the ChooseRandomNonExcludedTag() pseudocode function used by IRG is to behave in the same way as with GCR_EL1.RRND=0. This would mean that RGSR_EL1.SEED is used as an LFSR which must have a non-zero value in order for IRG to properly produce pseudorandom numbers. However, RGSR_EL1 is reset to an UNKNOWN value on soft reset and thus may reset to 0. Therefore we must initialize RGSR_EL1.SEED to a non-zero value in order to ensure that IRG behaves as expected. Signed-off-by: Peter Collingbourne <pcc@google.com> Fixes: 3b714d24ef17 ("arm64: mte: CPU feature detection and initial sysreg configuration") Cc: <stable@vger.kernel.org> # 5.10 Link: https://linux-review.googlesource.com/id/I2b089b6c7d6f17ee37e2f0db7df5ad5bcc04526c --- arch/arm64/mm/proc.S | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 0a48191534ff..97d7bcd8d4f2 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -447,6 +447,18 @@ SYM_FUNC_START(__cpu_setup) mov x10, #(SYS_GCR_EL1_RRND | SYS_GCR_EL1_EXCL_MASK) msr_s SYS_GCR_EL1, x10 + /* + * If GCR_EL1.RRND=1 is implemented the same way as RRND=0, then + * RGSR_EL1.SEED must be non-zero for IRG to produce + * pseudorandom numbers. As RGSR_EL1 is UNKNOWN out of reset, we + * must initialize it. + */ + mrs x10, CNTVCT_EL0 + ands x10, x10, #SYS_RGSR_EL1_SEED_MASK + csinc x10, x10, xzr, ne + lsl x10, x10, #SYS_RGSR_EL1_SEED_SHIFT + msr_s SYS_RGSR_EL1, x10 + /* clear any pending tag check faults in TFSR*_EL1 */ msr_s SYS_TFSR_EL1, xzr msr_s SYS_TFSRE0_EL1, xzr -- 2.31.1.607.g51e8a6a459-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2021-05-07 18:59 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-07 18:59 Peter Collingbourne [this message] 2021-05-07 18:59 ` [PATCH v2] arm64: mte: initialize RGSR_EL1.SEED in __cpu_setup Peter Collingbourne 2021-05-10 15:31 ` Mark Rutland 2021-05-10 15:31 ` Mark Rutland 2021-05-10 18:00 ` Catalin Marinas 2021-05-10 18:00 ` Catalin Marinas
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