- undoable: added support for checking the modification time of the base disk

- store r/o disk timestamp in FAT format in reserved field of redolog header
  - use the VVFAT function fat_datetime() to convert the mtime value
  - update redolog header if timestamp is undefined (first usage)
  - Bochs now panics if the r/o disk has been modified after the first usage with
    the undoable disk image mode to avoid journal file corruption.
- undoable: fixed r/o disk size check

bochs/iodev/hdimage.cc

@@ -159,6 +159,7 @@ int default_image_t::open(const char* pathname, int flags)
   if (hFile != INVALID_HANDLE_VALUE) {
     ULARGE_INTEGER FileSize;
     FileSize.LowPart = GetFileSize(hFile, &FileSize.HighPart);
+    GetFileTime(hFile, NULL, NULL, &mtime);
     CloseHandle(hFile);
     if ((FileSize.LowPart != INVALID_FILE_SIZE) || (GetLastError() == NO_ERROR)) {
       hd_size = FileSize.QuadPart;
@@ -195,6 +196,7 @@ int default_image_t::open(const char* pathname, int flags)
   {
     hd_size = (Bit64u)stat_buf.st_size; // standard unix procedure to get size of regular files
   }
+  mtime = stat_buf.st_mtime;
 #endif
   BX_INFO(("hd_size: "FMT_LL"u", hd_size));
   if (hd_size <= 0) BX_PANIC(("size of disk image not detected / invalid"));
@@ -224,6 +226,11 @@ ssize_t default_image_t::write(const void* buf, size_t count)
   return ::write(fd, (char*) buf, count);
 }
 
+Bit32u default_image_t::get_timestamp()
+{
+  return (fat_datetime(mtime, 1) | (fat_datetime(mtime, 0) << 16));
+}
+
 char increment_string(char *str, int diff)
 {
   // find the last character of the string, and increment it.
@@ -1032,6 +1039,7 @@ int redolog_t::make_header(const char* type, Bit64u size)
     else entries *= 2;
   } while (maxsize < size);
 
+  header.specific.timestamp = 0;
   header.specific.disk = htod64(size);
 
   print_header();
@@ -1201,6 +1209,20 @@ Bit64u redolog_t::get_size()
   return dtoh64(header.specific.disk);
 }
 
+Bit32u redolog_t::get_timestamp()
+{
+  return dtoh32(header.specific.timestamp);
+}
+
+bx_bool redolog_t::set_timestamp(Bit32u timestamp)
+{
+  header.specific.timestamp = htod32(timestamp);
+  // Update header
+  ::lseek(fd, 0, SEEK_SET);
+  ::write(fd, &header, dtoh32(header.standard.header));
+  return 1;
+}
+
 Bit64s redolog_t::lseek(Bit64s offset, int whence)
 {
   if ((offset % 512) != 0) {
@@ -1444,6 +1466,7 @@ undoable_image_t::~undoable_image_t()
 int undoable_image_t::open(const char* pathname)
 {
   char *logname=NULL;
+  Bit32u timestamp1, timestamp2;
 
   if (ro_disk->open(pathname, O_RDONLY)<0)
     return -1;
@@ -1463,19 +1486,27 @@ int undoable_image_t::open(const char* pathname)
     sprintf(logname, "%s%s", pathname, UNDOABLE_REDOLOG_EXTENSION);
   }
 
-  if (redolog->open(logname,REDOLOG_SUBTYPE_UNDOABLE) < 0)
-  {
-    if (redolog->create(logname, REDOLOG_SUBTYPE_UNDOABLE, hd_size) < 0)
-    {
+  if (redolog->open(logname,REDOLOG_SUBTYPE_UNDOABLE) < 0) {
+    if (redolog->create(logname, REDOLOG_SUBTYPE_UNDOABLE, hd_size) < 0) {
       BX_PANIC(("Can't open or create redolog '%s'",logname));
       return -1;
     }
-    if (hd_size != redolog->get_size())
-    {
+  }
+  if (hd_size != redolog->get_size()) {
     BX_PANIC(("size reported by redolog doesn't match r/o disk size"));
     free(logname);
     return -1;
   }
+  timestamp1 = ro_disk->get_timestamp();
+  timestamp2 = redolog->get_timestamp();
+  if (timestamp2 != 0) {
+    if (timestamp1 != timestamp2) {
+      BX_PANIC(("unexpected modification time of the r/o disk"));
+      free(logname);
+      return -1;
+    }
+  } else if (timestamp1 != 0) {
+    redolog->set_timestamp(timestamp1);
   }
 
   BX_INFO(("'undoable' disk opened: ro-file is '%s', redolog is '%s'", pathname, logname));
@@ -1484,7 +1515,7 @@ int undoable_image_t::open(const char* pathname)
   return 0;
 }
 
-void undoable_image_t::close ()
+void undoable_image_t::close()
 {
   redolog->close();
   ro_disk->close();

bochs/iodev/hdimage.h

@@ -78,7 +78,7 @@
    Bit32u  catalog;    // #entries in the catalog
    Bit32u  bitmap;     // bitmap size in bytes
    Bit32u  extent;     // extent size in bytes
-   Bit32u  reserved;   // for data alignment
+   Bit32u  timestamp;  // modification time in FAT format (subtype 'undoable' only)
    Bit64u  disk;       // disk size in bytes
  } redolog_specific_header_t;
 
@@ -182,8 +182,16 @@ class default_image_t : public device_image_t
       // written (count).
       ssize_t write(const void* buf, size_t count);
 
+      // Get modification time in FAT format
+      Bit32u get_timestamp();
+
   private:
       int fd;
+#ifndef WIN32
+      time_t mtime;
+#else
+      FILETIME mtime;
+#endif
 };
 
 // CONCAT MODE
@@ -349,6 +357,8 @@ class redolog_t
       int open(const char* filename, const char* type);
       void close();
       Bit64u get_size();
+      Bit32u get_timestamp();
+      bx_bool set_timestamp(Bit32u timestamp);
 
       Bit64s lseek(Bit64s offset, int whence);
       ssize_t read(void* buf, size_t count);

bochs/iodev/vvfat.cc

@@ -487,7 +487,7 @@ static inline Bit8u fat_chksum(const direntry_t* entry)
 
 // if return_time==0, this returns the fat_date, else the fat_time
 #ifndef WIN32
-static Bit16u fat_datetime(time_t time, int return_time)
+Bit16u fat_datetime(time_t time, int return_time)
 {
   struct tm* t;
   struct tm t1;
@@ -499,7 +499,7 @@ static Bit16u fat_datetime(time_t time, int return_time)
   return htod16((t->tm_mday) | ((t->tm_mon+1)<<5) | ((t->tm_year-80)<<9));
 }
 #else
-static Bit16u fat_datetime(FILETIME time, int return_time)
+Bit16u fat_datetime(FILETIME time, int return_time)
 {
   FILETIME localtime;
   SYSTEMTIME systime;

bochs/iodev/vvfat.h

@@ -106,6 +106,12 @@ typedef struct mapping_t {
   int read_only;
 } mapping_t;
 
+#ifndef WIN32
+Bit16u fat_datetime(time_t time, int return_time);
+#else
+Bit16u fat_datetime(FILETIME time, int return_time);
+#endif
+
 class vvfat_image_t : public device_image_t
 {
   public: