3 files changed, 25 insertions, 2 deletions
diff --git a/pkg/sentry/platform/kvm/testutil/testutil_arm64.s b/pkg/sentry/platform/kvm/testutil/testutil_arm64.s
index 2cd28b2d2..0bebee852 100644
--- a/pkg/sentry/platform/kvm/testutil/testutil_arm64.s
+++ b/pkg/sentry/platform/kvm/testutil/testutil_arm64.s
@@ -50,6 +50,21 @@ TEXT ·SpinLoop(SB),NOSPLIT,$0
 start:
 	B start
 
+TEXT ·FloatingPointWorks(SB),NOSPLIT,$0-8
+	NO_LOCAL_POINTERS
+	FMOVD $(9.9), F0
+	MOVD $SYS_GETPID, R8 // getpid
+	SVC
+	FMOVD $(9.9), F1
+	FCMPD F0, F1
+	BNE isNaN
+	MOVD $1, R0
+	MOVD R0, ret+0(FP)
+	RET
+isNaN:
+	MOVD $0, ret+0(FP)
+	RET
+
 // MVN: bitwise logical NOT
 // This case simulates an application that modified R0-R30.
 #define TWIDDLE_REGS() \
diff --git a/pkg/sentry/platform/ptrace/subprocess_amd64.go b/pkg/sentry/platform/ptrace/subprocess_amd64.go
index a55cff507..606dc2b1d 100644
--- a/pkg/sentry/platform/ptrace/subprocess_amd64.go
+++ b/pkg/sentry/platform/ptrace/subprocess_amd64.go
@@ -167,8 +167,14 @@ func patchSignalInfo(regs *syscall.PtraceRegs, signalInfo *arch.SignalInfo) {
 	}
 }
 
-// enableCpuidFault enable cpuid-faulting; this may fail on older kernels or hardware,
-// so we just disregard the result. Host CPUID will be enabled.
+// enableCpuidFault enables cpuid-faulting.
+//
+// This may fail on older kernels or hardware, so we just disregard the result.
+// Host CPUID will be enabled.
+//
+// This is safe to call in an afterFork context.
+//
+//go:nosplit
 func enableCpuidFault() {
 	syscall.RawSyscall6(syscall.SYS_ARCH_PRCTL, linux.ARCH_SET_CPUID, 0, 0, 0, 0, 0)
 }
diff --git a/pkg/sentry/platform/ptrace/subprocess_arm64.go b/pkg/sentry/platform/ptrace/subprocess_arm64.go
index aed34e7ee..62a686ee7 100644
--- a/pkg/sentry/platform/ptrace/subprocess_arm64.go
+++ b/pkg/sentry/platform/ptrace/subprocess_arm64.go
@@ -151,6 +151,8 @@ func patchSignalInfo(regs *syscall.PtraceRegs, signalInfo *arch.SignalInfo) {
 }
 
 // Noop on arm64.
+//
+//go:nosplit
 func enableCpuidFault() {
 }