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
-}