From 0ecb11e11f01aec558a75bd6fa0ddb4f77836c1a Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Tue, 30 Jul 2024 09:07:00 +0000
Subject: [PATCH] On arm64, check whether the CPU has the BT feature to
 determine the expected outcome of the test.

---
 regress/sys/btcfi/foobar.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/regress/sys/btcfi/foobar.c b/regress/sys/btcfi/foobar.c
index 8ed60c1d876..5efbfec6f24 100644
--- a/regress/sys/btcfi/foobar.c
+++ b/regress/sys/btcfi/foobar.c
@@ -22,14 +22,43 @@ handler(int sig, siginfo_t *si, void *context)
 }
 
 #if defined(__amd64__)
+
 static int
-has_cet_ibt(void)
+has_btcfi(void)
 {
 	uint32_t d;
 
 	asm("cpuid" : "=d" (d) : "a" (7), "c" (0));
 	return (d & (1U << 20)) ? 1 : 0;
 }
+
+#elif defined(__aarch64__)
+
+#include <sys/types.h>
+#include <sys/sysctl.h>
+
+#include <machine/armreg.h>
+#include <machine/cpu.h>
+
+static int
+has_btcfi(void)
+{
+	int mib[] = { CTL_MACHDEP, CPU_ID_AA64PFR1 };
+	uint64_t id_aa64pfr1 = 0;
+	size_t size = sizeof(id_aa64pfr1);
+
+	sysctl(mib, 2, &id_aa64pfr1, &size, NULL, 0);
+	return ID_AA64PFR1_BT(id_aa64pfr1) >= ID_AA64PFR1_BT_IMPL;
+}
+
+#else
+
+static int
+has_btcfi(void)
+{
+	return 0;
+}
+
 #endif
 
 int
@@ -37,13 +66,11 @@ main(void)
 {
 	struct sigaction sa;
 
-#if defined(__amd64__)
-	if (!has_cet_ibt()) {
+	if (!has_btcfi()) {
 		printf("Unsupported CPU\n");
 		printf("SKIPPED\n");
 		exit(0);
 	}
-#endif
 
 	sa.sa_sigaction = handler;
 	sa.sa_mask = 0;
-- 
2.20.1