feat(crit): add SearchPattern method on MemoryReader

crit/mempages.go

@@ -4,8 +4,10 @@
 	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
+	"regexp"
 
 	"github.com/checkpoint-restore/go-criu/v7/crit/images/mm"
 	"github.com/checkpoint-restore/go-criu/v7/crit/images/pagemap"
@@ -193,3 +195,100 @@
 
 	return size, nil
 }
+
+// PatternMatch represents a match when searching for a pattern in memory.
+type PatternMatch struct {
+	Vaddr   uint64
+	Length  int
+	Context int
+	Match   string
+}
+
+// SearchPattern searches for a pattern in the process memory pages.
+func (mr *MemoryReader) SearchPattern(pattern string, escapeRegExpCharacters bool, context, chunkSize int) ([]PatternMatch, error) {
+	if context < 0 {
+		return nil, errors.New("context size cannot be negative")
+	}
+
+	// Set a default chunk size of 10MB to be read at a time
+	if chunkSize <= 0 {
+		chunkSize = 10 * 1024 * 1024
+	}
+
+	// Escape regular expression characters in the pattern
+	if escapeRegExpCharacters {
+		pattern = regexp.QuoteMeta(pattern)
+	}
+
+	regexPattern, err := regexp.Compile(pattern)
+	if err != nil {
+		return nil, err
+	}
+
+	var results []PatternMatch
+
+	f, err := os.Open(filepath.Join(mr.checkpointDir, fmt.Sprintf("pages-%d.img", mr.pagesID)))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	for _, entry := range mr.pagemapEntries {
+		startAddr := entry.GetVaddr()
+		endAddr := startAddr + uint64(entry.GetNrPages())*uint64(mr.pageSize)
+
+		initialOffset := uint64(0)
+		for _, e := range mr.pagemapEntries {
+			if e == entry {
+				break
+			}
+			initialOffset += uint64(e.GetNrPages()) * uint64(mr.pageSize)
+		}
+
+		for offset := uint64(0); offset < endAddr-startAddr; offset += uint64(chunkSize) {
+			readSize := chunkSize
+			if endAddr-startAddr-offset < uint64(chunkSize) {
+				readSize = int(endAddr - startAddr - offset)
+			}
+
+			buff := make([]byte, readSize)
+			if _, err := f.ReadAt(buff, int64(initialOffset+offset)); err != nil {
+				if err == io.EOF {
+					break
+				}
+				return nil, err
+			}
+
+			// Replace non-printable ASCII characters in the buffer with a question mark (0x3f) to prevent unexpected behavior
+			// during regex matching. Non-printable characters might cause incorrect interpretation or premature
+			// termination of strings, leading to inaccuracies in pattern matching.
+			for i := range buff {
+				if buff[i] < 32 || buff[i] >= 127 {
+					buff[i] = 0x3F
+				}
+			}
+
+			indexes := regexPattern.FindAllIndex(buff, -1)
+			for _, index := range indexes {
+				startContext := index[0] - context
+				if startContext < 0 {
+					startContext = 0
+				}
+
+				endContext := index[1] + context
+				if endContext > len(buff) {
+					endContext = len(buff)
+				}
+
+				results = append(results, PatternMatch{
+					Vaddr:   startAddr + offset + uint64(index[0]),
+					Length:  index[1] - index[0],
+					Context: context,
+					Match:   string(buff[startContext:endContext]),
+				})
+			}
+		}
+	}
+
+	return results, nil
+}

crit/mempages_test.go

@@ -248,7 +248,7 @@ func TestGetPsArgsAndEnvVars(t *testing.T) {
 	}
 }
 
-func TestGetShmemSize(t *testing.T) {
+func TestSearchPattern(t *testing.T) {
 	pid, err := getTestImgPID()
 	if err != nil {
 		t.Fatal(err)
@@ -259,15 +259,92 @@ func TestGetShmemSize(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	size, err := mr.GetShmemSize()
-	if err != nil {
-		t.Fatal(err)
+	testCases := []struct {
+		name                   string
+		pattern                string
+		context                int
+		escapeRegExpCharacters bool
+		shouldMatch            bool
+		expectedError          error
+	}{
+		{
+			name:        "PATH environment variable",
+			pattern:     "PATH=",
+			shouldMatch: true,
+		},
+		{
+			name:        "PATH environment variable regex",
+			pattern:     `\bPATH=([^\s]+)\b`,
+			shouldMatch: true,
+		},
+		{
+			name:        "PATH environment variable regex with 10 bytes context",
+			pattern:     `\bPATH=([^\s]+)\b`,
+			context:     10,
+			shouldMatch: true,
+		},
+		{
+			name:          "PATH environment variable regex with a negative context",
+			pattern:       `\bPATH=([^\s]+)\b`,
+			context:       -1,
+			expectedError: errors.New("context size cannot be negative"),
+		},
+		{
+			name:        "PATH environment variable regex with a large context",
+			pattern:     `\bPATH=([^\s]+)\b`,
+			context:     100000,
+			shouldMatch: true,
+		},
+		{
+			name:    "Non-existent pattern",
+			pattern: "NON_EXISTENT_PATTERN",
+		},
+		{
+			name:        "PASSWORD environment variable value as regex",
+			pattern:     "123 Hello.*?",
+			shouldMatch: true,
+		},
+		{
+			name:                   "PASSWORD environment variable value with regex metacharacters to escape",
+			pattern:                `123 Hello.*?[^]@WORLD(|x)`,
+			escapeRegExpCharacters: true,
+			shouldMatch:            true,
+		},
 	}
 
-	// Verify that the shared memory size is as expected (0)
-	expectedSize := int64(0)
-	if size != expectedSize {
-		t.Fatalf("Expected shared memory size: %d, but got: %d", expectedSize, size)
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			matches, err := mr.SearchPattern(tc.pattern, tc.escapeRegExpCharacters, tc.context, 0)
+			if err != nil && tc.expectedError == nil {
+				t.Errorf("Unexpected error for pattern %s: %v", tc.pattern, err)
+			} else if err == nil && tc.expectedError != nil {
+				t.Errorf("Expected error for pattern %s: %v", tc.pattern, tc.expectedError)
+			}
+
+			if tc.shouldMatch && len(matches) == 0 {
+				t.Errorf("Expected to find a match for pattern \"%s\"", tc.pattern)
+			} else if !tc.shouldMatch && len(matches) > 0 {
+				t.Errorf("Expected not to find any match for pattern \"%s\"", tc.pattern)
+			}
+
+			for _, match := range matches {
+				content, err := mr.GetMemPages(match.Vaddr, match.Vaddr+uint64(match.Length))
+				if err != nil {
+					t.Fatalf("Failed to get memory pages: %v", err)
+				}
+
+				buff := content.Bytes()
+				for i := range buff {
+					if buff[i] < 32 || buff[i] >= 127 {
+						buff[i] = 0x3F
+					}
+				}
+
+				if !strings.Contains(match.Match, content.String()) {
+					t.Errorf("Expected to find %s in matched pattern %s", content.String(), match.Match)
+				}
+			}
+		})
 	}
 }
 

test/loop/loop.c

@@ -12,6 +12,13 @@ int main(void)
 	int res = EXIT_FAILURE;
 	int start_pipe[2];
 
+	// Set a PASSWORD environment variable to test the search pattern
+	// within process memory pages using regex metacharacters.
+	if (setenv("PASSWORD", "123 Hello.*?[^]@WORLD(|x)", 1) != 0) {
+		perror("setenv");
+		return 1;
+	}
+
 	if (pipe(start_pipe)) {
 		perror("pipe failed!");
 		goto out;