From 47fe91694258cf5e2eb195795793b7774a135c9f Mon Sep 17 00:00:00 2001
From: Roland Shoemaker <roland@golang.org>
Date: Wed, 10 Jul 2024 17:53:02 -0500
Subject: [PATCH] cpu: add support for DIT detection

Change-Id: I9f0991da9684ebd297e40a754e34130c418c34d0
Reviewed-on: https://go-review.googlesource.com/c/sys/+/597377
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 cpu/cpu.go       | 1 +
 cpu/cpu_arm64.go | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/cpu/cpu.go b/cpu/cpu.go
index 8fa707aa..11a0abc1 100644
--- a/cpu/cpu.go
+++ b/cpu/cpu.go
@@ -105,6 +105,7 @@ var ARM64 struct {
 	HasSVE      bool // Scalable Vector Extensions
 	HasSVE2     bool // Scalable Vector Extensions 2
 	HasASIMDFHM bool // Advanced SIMD multiplication FP16 to FP32
+	HasDIT      bool // Data Independent Timing support
 	_           CacheLinePad
 }
 
diff --git a/cpu/cpu_arm64.go b/cpu/cpu_arm64.go
index 0e27a21e..98956a5b 100644
--- a/cpu/cpu_arm64.go
+++ b/cpu/cpu_arm64.go
@@ -168,6 +168,11 @@ func parseARM64SystemRegisters(isar0, isar1, pfr0 uint64) {
 
 		parseARM64SVERegister(getzfr0())
 	}
+
+	switch extractBits(pfr0, 48, 51) {
+	case 1:
+		ARM64.HasDIT = true
+	}
 }
 
 func parseARM64SVERegister(zfr0 uint64) {