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authorPeter Collingbourne <pcc@google.com>2021-05-07 11:59:05 -0700
committerCatalin Marinas <catalin.marinas@arm.com>2021-05-10 18:56:25 +0100
commit37a8024d265564eba680575df6421f19db21dfce (patch)
treedd261c684b25c33c1ee9c748ed16c0d83367c8ea /arch/arm64
parenta1bed090fc56e6e24517d96bc076595544fb5317 (diff)
arm64: mte: initialize RGSR_EL1.SEED in __cpu_setup
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 Acked-by: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20210507185905.1745402-1-pcc@google.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/mm/proc.S12
1 files changed, 12 insertions, 0 deletions
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