misc/spectre: add spectre index test

Test for CL 222660.

Change-Id: I1dae41a9746dfc4144a0d29c02201de8ecd216fd
Reviewed-on: https://go-review.googlesource.com/c/go/+/222978
Reviewed-by: Keith Randall <[email protected]>

misc/spectre/asm_amd64.s

@@ -0,0 +1,51 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+TEXT ·clflush(SB),NOSPLIT,$0-8
+	MOVQ arg+0(FP), AX
+	CLFLUSH 0(AX)
+	RET
+
+TEXT ·rdtscp(SB),NOSPLIT,$0-8
+	RDTSCP
+	SHLQ $32, DX
+	ORQ DX, AX
+	MOVQ AX, ret+0(FP)
+	RET
+
+TEXT ·nop(SB),NOSPLIT,$0-0
+	RET
+
+TEXT ·cpuid(SB),NOSPLIT,$0-0
+	CPUID
+	RET
+
+TEXT ·features(SB),NOSPLIT,$0-2
+	MOVL $0, AX
+	MOVL $0, CX
+	CPUID
+	CMPL AX, $1
+	JLT none
+
+	MOVL $1, AX
+	MOVL $0, CX
+	CPUID
+	SHRL $19, DX
+	ANDL $1, DX
+	MOVB DX, hasCLFLUSH+0(FP)
+
+	MOVL $0x80000001, AX
+	MOVL $0, CX
+	CPUID
+	SHRL $27, DX
+	ANDL $1, DX
+	MOVB DX, hasRDTSCP+0(FP)
+	RET
+
+none:
+	MOVB $0, hasCLFLUSH+0(FP)
+	MOVB $0, hasRDTSCP+1(FP)
+	RET

misc/spectre/doc.go

@@ -0,0 +1,7 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package spectre contains a Spectre test.
+// It only runs on certain architectures.
+package spectre

misc/spectre/index_test.go

@@ -0,0 +1,59 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package spectre
+
+import "testing"
+
+func shouldPanic(f func()) {
+	defer func() {
+		if recover() == nil {
+			panic("index did not panic")
+		}
+	}()
+	f()
+}
+
+var (
+	Zero  = 0
+	One   = 1
+	Two   = 2
+	Three = 3
+	Four  = 4
+	Five  = 5
+)
+
+func TestIndex(t *testing.T) {
+	xs := "hello"
+	xi := []int{10, 20, 30, 40, 50}
+	xf := []float64{10, 20, 30, 40, 50}
+
+	xs = xs[Zero:Five]
+	xi = xi[Zero:Five]
+	xf = xf[Zero:Five]
+
+	if xs[Four] != 'o' {
+		t.Errorf("xs[4] = %q, want %q", xs[Four], 'o')
+	}
+	if xi[Four] != 50 {
+		t.Errorf("xi[4] = %d, want 50", xi[Four])
+	}
+	if xf[Four] != 50 {
+		t.Errorf("xf[4] = %v, want 50", xf[Four])
+	}
+
+	xs1 := xs[One:]
+	xi1 := xi[One:]
+	xf1 := xf[One:]
+
+	if xs1[Three] != 'o' {
+		t.Errorf("xs1[3] = %q, want %q", xs1[Three], 'o')
+	}
+	if xi1[Three] != 50 {
+		t.Errorf("xi1[3] = %d, want 50", xi1[Three])
+	}
+	if xf1[Three] != 50 {
+		t.Errorf("xf1[3] = %v, want 50", xf1[Three])
+	}
+}