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Merge pull request #133 from behouba/read-memory-pages
crit: add features to retrieve memory pages
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Original file line number | Diff line number | Diff line change |
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package crit | ||
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import ( | ||
"bytes" | ||
"errors" | ||
"fmt" | ||
"os" | ||
"path/filepath" | ||
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"github.com/checkpoint-restore/go-criu/v6/crit/images/mm" | ||
"github.com/checkpoint-restore/go-criu/v6/crit/images/pagemap" | ||
) | ||
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var sysPageSize = os.Getpagesize() | ||
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// MemoryReader is a struct used to retrieve | ||
// the content of memory associated with a specific process ID (pid). | ||
// New instances should be created with NewMemoryReader() | ||
type MemoryReader struct { | ||
checkpointDir string | ||
pid uint32 | ||
pagesID uint32 | ||
pageSize int | ||
pagemapEntries []*pagemap.PagemapEntry | ||
} | ||
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// NewMemoryReader creates a new instance of MemoryReader with all the fields populated | ||
func NewMemoryReader(checkpointDir string, pid uint32, pageSize int) (*MemoryReader, error) { | ||
if pageSize == 0 { | ||
pageSize = sysPageSize | ||
} | ||
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// Check if the given page size is a positive power of 2, otherwise return an error | ||
if (pageSize & (pageSize - 1)) != 0 { | ||
return nil, errors.New("page size should be a positive power of 2") | ||
} | ||
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pagemapImg, err := getImg(filepath.Join(checkpointDir, fmt.Sprintf("pagemap-%d.img", pid)), &pagemap.PagemapHead{}) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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pagesID := pagemapImg.Entries[0].Message.(*pagemap.PagemapHead).GetPagesId() | ||
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pagemapEntries := make([]*pagemap.PagemapEntry, 0) | ||
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for _, entry := range pagemapImg.Entries[1:] { | ||
pagemapEntries = append(pagemapEntries, entry.Message.(*pagemap.PagemapEntry)) | ||
} | ||
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return &MemoryReader{ | ||
checkpointDir: checkpointDir, | ||
pid: pid, | ||
pageSize: pageSize, | ||
pagesID: pagesID, | ||
pagemapEntries: pagemapEntries, | ||
}, nil | ||
} | ||
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// GetMemPages retrieves the content of memory pages | ||
// associated with a given process ID (pid). | ||
// It retrieves the memory content within the | ||
// specified range defined by the start and end addresses. | ||
func (mr *MemoryReader) GetMemPages(start, end uint64) (*bytes.Buffer, error) { | ||
size := end - start | ||
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startPage := start / uint64(mr.pageSize) | ||
endPage := end / uint64(mr.pageSize) | ||
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var buffer bytes.Buffer | ||
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for pageNumber := startPage; pageNumber <= endPage; pageNumber++ { | ||
var page []byte = nil | ||
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pageMem, err := mr.getPage(pageNumber) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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if pageMem != nil { | ||
page = pageMem | ||
} else { | ||
page = bytes.Repeat([]byte("\x00"), mr.pageSize) | ||
} | ||
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var nSkip, nRead uint64 | ||
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if pageNumber == startPage { | ||
nSkip = start - pageNumber*uint64(mr.pageSize) | ||
if startPage == endPage { | ||
nRead = size | ||
} else { | ||
nRead = uint64(mr.pageSize) - nSkip | ||
} | ||
} else if pageNumber == endPage { | ||
nSkip = 0 | ||
nRead = end - pageNumber*uint64(mr.pageSize) | ||
} else { | ||
nSkip = 0 | ||
nRead = uint64(mr.pageSize) | ||
} | ||
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if _, err := buffer.Write(page[nSkip : nSkip+nRead]); err != nil { | ||
return nil, err | ||
} | ||
} | ||
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return &buffer, nil | ||
} | ||
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// getPage retrieves a memory page from the pages.img file. | ||
func (mr *MemoryReader) getPage(pageNo uint64) ([]byte, error) { | ||
var offset uint64 = 0 | ||
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// Iterate over pagemap entries to find the corresponding page | ||
for _, m := range mr.pagemapEntries { | ||
found := false | ||
for i := 0; i < int(*m.NrPages); i++ { | ||
if m.GetVaddr()+uint64(i)*uint64(mr.pageSize) == pageNo*uint64(mr.pageSize) { | ||
found = true | ||
break | ||
} | ||
offset += uint64(mr.pageSize) | ||
} | ||
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if !found { | ||
continue | ||
} | ||
f, err := os.Open(filepath.Join(mr.checkpointDir, fmt.Sprintf("pages-%d.img", mr.pagesID))) | ||
if err != nil { | ||
return nil, err | ||
} | ||
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defer f.Close() | ||
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buff := make([]byte, mr.pageSize) | ||
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if _, err := f.ReadAt(buff, int64(offset)); err != nil { | ||
return nil, err | ||
} | ||
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return buff, nil | ||
} | ||
return nil, nil | ||
} | ||
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// GetPsArgs retrieves process arguments from memory pages | ||
func (mr *MemoryReader) GetPsArgs() (*bytes.Buffer, error) { | ||
mmImg, err := getImg(filepath.Join(mr.checkpointDir, fmt.Sprintf("mm-%d.img", mr.pid)), &mm.MmEntry{}) | ||
if err != nil { | ||
return nil, err | ||
} | ||
mm := mmImg.Entries[0].Message.(*mm.MmEntry) | ||
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return mr.GetMemPages(*mm.MmArgStart, *mm.MmArgEnd) | ||
} | ||
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// GetPsArgs retrieves process environment variables from memory pages. | ||
func (mr *MemoryReader) GetPsEnvVars() (*bytes.Buffer, error) { | ||
mmImg, err := getImg(filepath.Join(mr.checkpointDir, fmt.Sprintf("mm-%d.img", mr.pid)), &mm.MmEntry{}) | ||
if err != nil { | ||
return nil, err | ||
} | ||
mm := mmImg.Entries[0].Message.(*mm.MmEntry) | ||
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return mr.GetMemPages(*mm.MmEnvStart, *mm.MmEnvEnd) | ||
} | ||
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func (mr *MemoryReader) GetPagemapEntries() []*pagemap.PagemapEntry { | ||
return mr.pagemapEntries | ||
} |
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