feat: display content of process memory pages

This commit extends `memparse` sub-command with the ability to display
the content of process memory pages content in a hexdump-like format when
the `--pid` flag is provided. Additionally, the output can be written to a
file using the `--output` flag.

Signed-off-by: Kouame Behouba Manasse <[email protected]>

Author: behouba

checkpointctl.go

@@ -12,17 +12,18 @@ import (
 )
 
 var (
-	name      string
-	version   string
-	format    string
-	stats     bool
-	mounts    bool
-	pID       uint32
-	psTree    bool
-	psTreeCmd bool
-	psTreeEnv bool
-	files     bool
-	showAll   bool
+	name           string
+	version        string
+	format         string
+	stats          bool
+	mounts         bool
+	outputFilePath string
+	pID            uint32
+	psTree         bool
+	psTreeCmd      bool
+	psTreeEnv      bool
+	files          bool
+	showAll        bool
 )
 
 func main() {
@@ -274,6 +275,23 @@ func setupMemParse() *cobra.Command {
 		Args:  cobra.MinimumNArgs(1),
 	}
 
+	flags := cmd.Flags()
+
+	flags.Uint32VarP(
+		&pID,
+		"pid",
+		"p",
+		0,
+		"Specify the pid of a process to analyze",
+	)
+	flags.StringVarP(
+		&outputFilePath,
+		"output",
+		"o",
+		"",
+		"Specify a file where the ouput should be written",
+	)
+
 	return cmd
 }
 
@@ -293,5 +311,9 @@ func memparse(cmd *cobra.Command, args []string) error {
 	}
 	defer cleanupTasks(tasks)
 
+	if pID != 0 {
+		return printProcessMemoryPages(tasks[0])
+	}
+
 	return showProcessMemorySizeTables(tasks)
 }

memparse.go

@@ -5,7 +5,9 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 
@@ -14,6 +16,12 @@ import (
 	"github.com/olekukonko/tablewriter"
 )
 
+const (
+	// chunkSize represents the default size of memory chunk (in bytes)
+	// to read for each output line when printing memory pages content in hexdump-like format.
+	chunkSize = 16
+)
+
 // Display processes memory sizes within the given container checkpoints.
 func showProcessMemorySizeTables(tasks []task) error {
 	// Initialize the table
@@ -81,3 +89,93 @@ func showProcessMemorySizeTables(tasks []task) error {
 
 	return nil
 }
+
+func printProcessMemoryPages(task task) error {
+	memReader, err := crit.NewMemoryReader(
+		filepath.Join(task.outputDir, metadata.CheckpointDirectory),
+		pID, pageSize,
+	)
+	if err != nil {
+		return err
+	}
+
+	// Write the output to stdout by default
+	var output io.Writer = os.Stdout
+	var compact bool
+
+	if outputFilePath != "" {
+		// Write to ouput to file if --output is provided
+		output, err = os.Create(outputFilePath)
+		if err != nil {
+			return err
+		}
+	} else {
+		compact = true // Use a compact format when writing the output to stdout
+		fmt.Printf("\nDisplaying memory pages content for Process ID: %d from checkpoint: %s\n\n", pID, task.checkpointFilePath)
+	}
+
+	fmt.Fprintf(output, "Address           Hexadecimal                                       ASCII            \n")
+	fmt.Fprintf(output, "-------------------------------------------------------------------------------------\n")
+
+	pagemapEntries := memReader.GetPagemapEntries()
+	for _, entry := range pagemapEntries {
+		start := entry.GetVaddr()
+		end := start + (uint64(pageSize) * uint64(entry.GetNrPages()))
+		buf, err := memReader.GetMemPages(start, end)
+		if err != nil {
+			return err
+		}
+
+		hexdump(output, buf, start, compact)
+	}
+	return nil
+}
+
+// hexdump generates a hexdump of the buffer 'buf' starting at the virtual address 'start'
+// and writes the output to 'out'. If compact is true, consecutive duplicate rows will be represented
+// with an asterisk (*).
+func hexdump(out io.Writer, buf *bytes.Buffer, vaddr uint64, compact bool) {
+	prevAscii := ""
+	duplicate := 0
+	for buf.Len() > 0 {
+		row := buf.Next(chunkSize)
+		hex, ascii := generateHexAndAscii(row)
+
+		if compact {
+			if prevAscii == ascii {
+				if duplicate == 1 {
+					fmt.Fprint(out, "*\n")
+				}
+				duplicate++
+			} else {
+				printHexdumpRow(out, vaddr, hex, ascii)
+				duplicate = 0
+			}
+		} else {
+			printHexdumpRow(out, vaddr, hex, ascii)
+		}
+
+		vaddr += chunkSize
+		prevAscii = ascii
+	}
+}
+
+func printHexdumpRow(out io.Writer, vaddr uint64, hex string, ascii string) {
+	fmt.Fprintf(out, "%016x  %s |%s|\n", vaddr, hex, ascii)
+}
+
+// generateHexAndAscii takes a byte slice and generates its hexadecimal and ASCII representations.
+func generateHexAndAscii(data []byte) (hex, ascii string) {
+	s := string(data)
+	for i := 0; i < len(s); i++ {
+		if s[i] < 32 || s[i] >= 127 {
+			ascii += "."
+			hex += fmt.Sprintf("%02x ", s[i])
+		} else {
+			ascii += string(s[i])
+			hex += fmt.Sprintf("%02x ", s[i])
+		}
+	}
+
+	return hex, ascii
+}