did something

vendor/periph.io/x/host/v3/pmem/pagemap.go

@@ -0,0 +1,65 @@
+// Copyright 2016 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package pmem
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+)
+
+// ReadPageMap reads a physical address mapping for a virtual page address from
+// /proc/self/pagemap.
+//
+// It returns the physical address that corresponds to the start of the virtual
+// page within which the virtual address virtAddr is located.
+//
+// The meaning of the return value is documented at
+// https://www.kernel.org/doc/Documentation/vm/pagemap.txt
+func ReadPageMap(virtAddr uintptr) (uint64, error) {
+	if !isLinux || isWSL() {
+		return 0, errors.New("pmem: pagemap is not supported on this platform")
+	}
+	return readPageMapLinux(virtAddr)
+}
+
+//
+
+var (
+	pageMap    fileIO
+	pageMapErr error
+)
+
+func readPageMapLinux(virtAddr uintptr) (uint64, error) {
+	var b [8]byte
+	mu.Lock()
+	defer mu.Unlock()
+	if pageMap == nil && pageMapErr == nil {
+		// Open /proc/self/pagemap.
+		//
+		// It is a uint64 array where the index represents the virtual 4Kb page
+		// number and the value represents the physical page properties backing
+		// this virtual page.
+		pageMap, pageMapErr = openFile("/proc/self/pagemap", os.O_RDONLY|os.O_SYNC)
+	}
+	if pageMapErr != nil {
+		return 0, pageMapErr
+	}
+	// Convert address to page number, then index in uint64 array.
+	offset := int64(virtAddr / pageSize * 8)
+	if _, err := pageMap.Seek(offset, io.SeekStart); err != nil {
+		return 0, fmt.Errorf("pmem: failed to seek at 0x%x for 0x%x: %v", offset, virtAddr, err)
+	}
+	n, err := pageMap.Read(b[:])
+	if err != nil {
+		return 0, fmt.Errorf("pmem: failed to read at 0x%x for 0x%x: %v", offset, virtAddr, err)
+	}
+	if n != len(b) {
+		return 0, fmt.Errorf("pmem: failed to read the amount of data %d", len(b))
+	}
+	return binary.LittleEndian.Uint64(b[:]), nil
+}