Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

4 files changed, 163 insertions, 0 deletions

diff --git a/pkg/sentry/hostcpu/BUILD b/pkg/sentry/hostcpu/BUILD
new file mode 100644
index 000000000..9457618d8
--- /dev/null
+++ b/pkg/sentry/hostcpu/BUILD
@@ -0,0 +1,20 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "hostcpu",
+    srcs = [
+        "getcpu_amd64.s",
+        "hostcpu.go",
+    ],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/hostcpu",
+    visibility = ["//:sandbox"],
+)
+
+go_test(
+    name = "hostcpu_test",
+    size = "small",
+    srcs = ["hostcpu_test.go"],
+    embed = [":hostcpu"],
+)
diff --git a/pkg/sentry/hostcpu/getcpu_amd64.s b/pkg/sentry/hostcpu/getcpu_amd64.s
new file mode 100644
index 000000000..7f6247d81
--- /dev/null
+++ b/pkg/sentry/hostcpu/getcpu_amd64.s
@@ -0,0 +1,24 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "textflag.h"
+
+// func GetCPU() (cpu uint32)
+TEXT ·GetCPU(SB), NOSPLIT, $0-4
+	BYTE $0x0f; BYTE $0x01; BYTE $0xf9; // RDTSCP
+	// On Linux, the bottom 12 bits of IA32_TSC_AUX are CPU and the upper 20
+	// are node. See arch/x86/entry/vdso/vma.c:vgetcpu_cpu_init().
+	ANDL	$0xfff, CX
+	MOVL	CX, cpu+0(FP)
+	RET
diff --git a/pkg/sentry/hostcpu/hostcpu.go b/pkg/sentry/hostcpu/hostcpu.go
new file mode 100644
index 000000000..fa46499ad
--- /dev/null
+++ b/pkg/sentry/hostcpu/hostcpu.go
@@ -0,0 +1,67 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package hostcpu provides utilities for working with CPU information provided
+// by a host Linux kernel.
+package hostcpu
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+	"unicode"
+)
+
+// GetCPU returns the caller's current CPU number, without using the Linux VDSO
+// (which is not available to the sentry) or the getcpu(2) system call (which
+// is relatively slow).
+func GetCPU() uint32
+
+// MaxPossibleCPU returns the highest possible CPU number, which is guaranteed
+// not to change for the lifetime of the host kernel.
+func MaxPossibleCPU() (uint32, error) {
+	const path = "/sys/devices/system/cpu/possible"
+	data, err := ioutil.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	str := string(data)
+	// Linux: drivers/base/cpu.c:show_cpus_attr() =>
+	// include/linux/cpumask.h:cpumask_print_to_pagebuf() =>
+	// lib/bitmap.c:bitmap_print_to_pagebuf()
+	i, err := maxValueInLinuxBitmap(str)
+	if err != nil {
+		return 0, fmt.Errorf("invalid %s (%q): %v", path, str, err)
+	}
+	return uint32(i), nil
+}
+
+// maxValueInLinuxBitmap returns the maximum value specified in str, which is a
+// string emitted by Linux's lib/bitmap.c:bitmap_print_to_pagebuf(list=true).
+func maxValueInLinuxBitmap(str string) (uint64, error) {
+	str = strings.TrimSpace(str)
+	// Find the last decimal number in str.
+	idx := strings.LastIndexFunc(str, func(c rune) bool {
+		return !unicode.IsDigit(c)
+	})
+	if idx != -1 {
+		str = str[idx+1:]
+	}
+	i, err := strconv.ParseUint(str, 10, 64)
+	if err != nil {
+		return 0, err
+	}
+	return i, nil
+}
diff --git a/pkg/sentry/hostcpu/hostcpu_test.go b/pkg/sentry/hostcpu/hostcpu_test.go
new file mode 100644
index 000000000..a82e1a271
--- /dev/null
+++ b/pkg/sentry/hostcpu/hostcpu_test.go
@@ -0,0 +1,52 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hostcpu
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestMaxValueInLinuxBitmap(t *testing.T) {
+	for _, test := range []struct {
+		str string
+		max uint64
+	}{
+		{"0", 0},
+		{"0\n", 0},
+		{"0,2", 2},
+		{"0-63", 63},
+		{"0-3,8-11", 11},
+	} {
+		t.Run(fmt.Sprintf("%q", test.str), func(t *testing.T) {
+			max, err := maxValueInLinuxBitmap(test.str)
+			if err != nil || max != test.max {
+				t.Errorf("maxValueInLinuxBitmap: got (%d, %v), wanted (%d, nil)", max, err, test.max)
+			}
+		})
+	}
+}
+
+func TestMaxValueInLinuxBitmapErrors(t *testing.T) {
+	for _, str := range []string{"", "\n"} {
+		t.Run(fmt.Sprintf("%q", str), func(t *testing.T) {
+			max, err := maxValueInLinuxBitmap(str)
+			if err == nil {
+				t.Errorf("maxValueInLinuxBitmap: got (%d, nil), wanted (_, error)", max)
+			}
+			t.Log(err)
+		})
+	}
+}