Use uname machine field to get CPU variant if fails at /proc/cpuinfo

When images/containers in ARM arch were built/executed on x86 host,
getCPUVariant will fail as it tries to look for /proc/cpuinfo, whose
content is from the host. Adding a new method as fallback to check uname
machine when it happens.

Signed-off-by: Tony Fang <nenghui.fang@gmail.com>

platforms/cpuinfo.go

@@ -17,14 +17,9 @@
 package platforms
 
 import (
-	"bufio"
-	"fmt"
-	"os"
 	"runtime"
-	"strings"
 	"sync"
 
-	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
 )
 
@@ -37,108 +32,12 @@ var cpuVariantOnce sync.Once
 func cpuVariant() string {
 	cpuVariantOnce.Do(func() {
 		if isArmArch(runtime.GOARCH) {
-			cpuVariantValue = getCPUVariant()
+			var err error
+			cpuVariantValue, err = getCPUVariant()
+			if err != nil {
+				log.L.Errorf("Error getCPUVariant for OS %s : %v", runtime.GOOS, err)
+			}
 		}
 	})
 	return cpuVariantValue
 }
-
-// For Linux, the kernel has already detected the ABI, ISA and Features.
-// So we don't need to access the ARM registers to detect platform information
-// by ourselves. We can just parse these information from /proc/cpuinfo
-func getCPUInfo(pattern string) (info string, err error) {
-	if !isLinuxOS(runtime.GOOS) {
-		return "", fmt.Errorf("getCPUInfo for OS %s: %w", runtime.GOOS, errdefs.ErrNotImplemented)
-	}
-
-	cpuinfo, err := os.Open("/proc/cpuinfo")
-	if err != nil {
-		return "", err
-	}
-	defer cpuinfo.Close()
-
-	// Start to Parse the Cpuinfo line by line. For SMP SoC, we parse
-	// the first core is enough.
-	scanner := bufio.NewScanner(cpuinfo)
-	for scanner.Scan() {
-		newline := scanner.Text()
-		list := strings.Split(newline, ":")
-
-		if len(list) > 1 && strings.EqualFold(strings.TrimSpace(list[0]), pattern) {
-			return strings.TrimSpace(list[1]), nil
-		}
-	}
-
-	// Check whether the scanner encountered errors
-	err = scanner.Err()
-	if err != nil {
-		return "", err
-	}
-
-	return "", fmt.Errorf("getCPUInfo for pattern: %s: %w", pattern, errdefs.ErrNotFound)
-}
-
-func getCPUVariant() string {
-	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
-		// Windows/Darwin only supports v7 for ARM32 and v8 for ARM64 and so we can use
-		// runtime.GOARCH to determine the variants
-		var variant string
-		switch runtime.GOARCH {
-		case "arm64":
-			variant = "v8"
-		case "arm":
-			variant = "v7"
-		default:
-			variant = "unknown"
-		}
-
-		return variant
-	}
-	if runtime.GOOS == "freebsd" {
-		// FreeBSD supports ARMv6 and ARMv7 as well as ARMv4 and ARMv5 (though deprecated)
-		// detecting those variants is currently unimplemented
-		var variant string
-		switch runtime.GOARCH {
-		case "arm64":
-			variant = "v8"
-		default:
-			variant = "unknown"
-		}
-
-		return variant
-	}
-
-	variant, err := getCPUInfo("Cpu architecture")
-	if err != nil {
-		log.L.WithError(err).Error("failure getting variant")
-		return ""
-	}
-
-	// handle edge case for Raspberry Pi ARMv6 devices (which due to a kernel quirk, report "CPU architecture: 7")
-	// https://www.raspberrypi.org/forums/viewtopic.php?t=12614
-	if runtime.GOARCH == "arm" && variant == "7" {
-		model, err := getCPUInfo("model name")
-		if err == nil && strings.HasPrefix(strings.ToLower(model), "armv6-compatible") {
-			variant = "6"
-		}
-	}
-
-	switch strings.ToLower(variant) {
-	case "8", "aarch64":
-		variant = "v8"
-	case "7", "7m", "?(12)", "?(13)", "?(14)", "?(15)", "?(16)", "?(17)":
-		variant = "v7"
-	case "6", "6tej":
-		variant = "v6"
-	case "5", "5t", "5te", "5tej":
-		variant = "v5"
-	case "4", "4t":
-		variant = "v4"
-	case "3":
-		variant = "v3"
-	default:
-		variant = "unknown"
-	}
-
-	return variant
-}

platforms/cpuinfo_linux.go

@@ -0,0 +1,161 @@
+/*
+   Copyright The containerd Authors.
+
+   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 platforms
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+
+	"github.com/containerd/containerd/errdefs"
+	"golang.org/x/sys/unix"
+)
+
+// getMachineArch retrieves the machine architecture through system call
+func getMachineArch() (string, error) {
+	var uname unix.Utsname
+	err := unix.Uname(&uname)
+	if err != nil {
+		return "", err
+	}
+
+	arch := string(uname.Machine[:bytes.IndexByte(uname.Machine[:], 0)])
+
+	return arch, nil
+}
+
+// For Linux, the kernel has already detected the ABI, ISA and Features.
+// So we don't need to access the ARM registers to detect platform information
+// by ourselves. We can just parse these information from /proc/cpuinfo
+func getCPUInfo(pattern string) (info string, err error) {
+
+	cpuinfo, err := os.Open("/proc/cpuinfo")
+	if err != nil {
+		return "", err
+	}
+	defer cpuinfo.Close()
+
+	// Start to Parse the Cpuinfo line by line. For SMP SoC, we parse
+	// the first core is enough.
+	scanner := bufio.NewScanner(cpuinfo)
+	for scanner.Scan() {
+		newline := scanner.Text()
+		list := strings.Split(newline, ":")
+
+		if len(list) > 1 && strings.EqualFold(strings.TrimSpace(list[0]), pattern) {
+			return strings.TrimSpace(list[1]), nil
+		}
+	}
+
+	// Check whether the scanner encountered errors
+	err = scanner.Err()
+	if err != nil {
+		return "", err
+	}
+
+	return "", fmt.Errorf("getCPUInfo for pattern: %s: %w", pattern, errdefs.ErrNotFound)
+}
+
+// getCPUVariantFromArch get CPU variant from arch through a system call
+func getCPUVariantFromArch(arch string) (string, error) {
+
+	var variant string
+
+	arch = strings.ToLower(arch)
+
+	if arch == "aarch64" {
+		variant = "8"
+	} else if len(arch) >= 5 {
+		//Valid arch format is in form of armvXx
+		switch arch[3:5] {
+		case "v8":
+			variant = "8"
+		case "v7":
+			variant = "7"
+		case "v6":
+			variant = "6"
+		case "v5":
+			variant = "5"
+		case "v4":
+			variant = "4"
+		case "v3":
+			variant = "3"
+		default:
+			variant = "unknown"
+		}
+	} else {
+		return "", fmt.Errorf("getCPUVariantFromArch invalid arch : %s, %v", arch, errdefs.ErrInvalidArgument)
+	}
+	return variant, nil
+}
+
+// getCPUVariant returns cpu variant for ARM
+// We first try reading "Cpu architecture" field from /proc/cpuinfo
+// If we can't find it, then fall back using a system call
+// This is to cover running ARM in emulated environment on x86 host as this field in /proc/cpuinfo
+// was not present.
+func getCPUVariant() (string, error) {
+
+	variant, err := getCPUInfo("Cpu architecture")
+	if err != nil {
+		if errdefs.IsNotFound(err) {
+			//Let's try getting CPU variant from machine architecture
+			arch, err := getMachineArch()
+			if err != nil {
+				return "", fmt.Errorf("failure getting machine architecture : %v", err)
+			}
+
+			variant, err = getCPUVariantFromArch(arch)
+			if err != nil {
+				return "", fmt.Errorf("failure getting CPU variant from machine architecture : %v", err)
+			}
+		} else {
+			return "", fmt.Errorf("failure getting CPU variant : %v", err)
+		}
+	}
+
+	// handle edge case for Raspberry Pi ARMv6 devices (which due to a kernel quirk, report "CPU architecture: 7")
+	// https://www.raspberrypi.org/forums/viewtopic.php?t=12614
+	if runtime.GOARCH == "arm" && variant == "7" {
+		model, err := getCPUInfo("model name")
+		if err == nil && strings.HasPrefix(strings.ToLower(model), "armv6-compatible") {
+			variant = "6"
+		}
+	}
+
+	switch strings.ToLower(variant) {
+	case "8", "aarch64":
+		variant = "v8"
+	case "7", "7m", "?(12)", "?(13)", "?(14)", "?(15)", "?(16)", "?(17)":
+		variant = "v7"
+	case "6", "6tej":
+		variant = "v6"
+	case "5", "5t", "5te", "5tej":
+		variant = "v5"
+	case "4", "4t":
+		variant = "v4"
+	case "3":
+		variant = "v3"
+	default:
+		variant = "unknown"
+	}
+
+	return variant, nil
+}

platforms/cpuinfo_linux_test.go

@@ -22,13 +22,18 @@ import (
 )
 
 func TestCPUVariant(t *testing.T) {
-	if !isArmArch(runtime.GOARCH) || !isLinuxOS(runtime.GOOS) {
+	if !isArmArch(runtime.GOARCH) {
 		t.Skip("only relevant on linux/arm")
 	}
 
 	variants := []string{"v8", "v7", "v6", "v5", "v4", "v3"}
 
-	p := getCPUVariant()
+	p, err := getCPUVariant()
+	if err != nil {
+		t.Fatalf("Error getting CPU variant: %v\n", err)
+		return
+	}
+
 	for _, variant := range variants {
 		if p == variant {
 			t.Logf("got valid variant as expected: %#v = %#v\n", p, variant)
@@ -38,3 +43,11 @@ func TestCPUVariant(t *testing.T) {
 
 	t.Fatalf("could not get valid variant as expected: %v\n", variants)
 }
+
+func TestGetCPUVariantFromArch(t *testing.T) {
+
+	if !isArmArch(runtime.GOARCH) {
+		t.Skip("only relevant on linux/arm")
+	}
+
+}

platforms/cpuinfo_other.go

@@ -0,0 +1,57 @@
+//go:build !linux
+// +build !linux
+
+/*
+   Copyright The containerd Authors.
+
+   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 platforms
+
+import (
+	"runtime"
+)
+
+func getCPUVariant() (string, error) {
+
+	var variant string
+
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
+		// Windows/Darwin only supports v7 for ARM32 and v8 for ARM64 and so we can use
+		// runtime.GOARCH to determine the variants
+		switch runtime.GOARCH {
+		case "arm64":
+			variant = "v8"
+		case "arm":
+			variant = "v7"
+		default:
+			variant = "unknown"
+		}
+	} else if runtime.GOOS == "freebsd" {
+		// FreeBSD supports ARMv6 and ARMv7 as well as ARMv4 and ARMv5 (though deprecated)
+		// detecting those variants is currently unimplemented
+		switch runtime.GOARCH {
+		case "arm64":
+			variant = "v8"
+		default:
+			variant = "unknown"
+		}
+
+	} else {
+		return "", fmt.Errorf("getCPUVariant for OS %s: %v", runtime.GOOS, errdefs.ErrNotImplemented)
+
+	}
+
+	return variant, nil
+}

platforms/database.go

@@ -21,13 +21,6 @@ import (
 	"strings"
 )
 
-// isLinuxOS returns true if the operating system is Linux.
-//
-// The OS value should be normalized before calling this function.
-func isLinuxOS(os string) bool {
-	return os == "linux"
-}
-
 // These function are generated from https://golang.org/src/go/build/syslist.go.
 //
 // We use switch statements because they are slightly faster than map lookups