Re: [PATCH] biosdisk, getroot for Cygwin

[Christian Franke]

Robert Millan wrote:
> On Fri, May 09, 2008 at 07:32:42PM +0200, Christian Franke wrote:
>   
> > > > +  char devpath[sizeof ("/dev/sda15") + 13];
> > > >    
> > > >         
> > > Where does this 13 come from?  Would be nice to make it explicit (e.g.
> > > sizeof(something) or so).
> > >       
> > 13 "paranoia" bytes added to the required size :-)
> >     
>
> A comment saying that would be nice.
>
>   

Done.


> On Sun, May 11, 2008 at 11:04:39PM +0200, Christian Franke wrote:
>   
> > Probably more readable and extensible - Use early returns:
> >     
>
> Yeah I like that better too.
>
>   
> > #ifndef __CYGWIN__
> >  /* This might be truly slow, but is there any better way?  */
> >  os_dev = find_root_device ("/dev", st.st_dev);
> >
> > #else /* __CYGWIN__ */
> >  /* Cygwin specific function.  */
> >  os_dev = find_cygwin_root_device (dir, st.st_dev);
> >
> > #endif /* __CYGWIN__ */
> >     
>
> I'd suggest removing the double-negation here;  it looks more readable
> with "#ifdef / #else" IMHO (and is easier to add more OS-specific checks
> like "#if defined(__CYGWIN__) / #elif defined(...) / #else".
>
>   

Done, new patch below. If there are no further comments, I will commit 
it in a few days.

Christian

2008-05-13  Christian Franke  <address@hidden>

        * util/biosdisk.c: [__CYGWIN__] Add includes.
        (grub_util_biosdisk_open): Use Linux code also for Cygwin.
        (get_os_disk): Move variable declarations to OS specific
        parts to avoid warning.
        [__GNU__] (get_os_disk): Fix /dev/sdXsN case.
        [__CYGWIN__] (get_os_disk): Add Cygwin /dev/sdXN device names.
        (grub_util_biosdisk_get_grub_dev): Use Linux code also for
        Cygwin.

        * util/getroot.c: [__CYGWIN__] Add includes.
        (strip_extra_slashes): Fix "/" case.
        [__CYGWIN__] (get_win32_path): New function.
        [__CYGWIN__] (grub_get_prefix): Add conversion to win32 path.
        [__CYGWIN__] (find_root_device): Disable.
        [__CYGWIN__] (get_bootsec_serial): New function.
        [__CYGWIN__] (find_cygwin_root_device): Likewise.
        [__linux__] (grub_guess_root_device): Add early returns to simplify
        structure.
        [__CYGWIN__] (grub_guess_root_device): Call find_cygwin_root_device.
        [__linux__] (grub_util_get_dev_abstraction): Enable LVM and RAID
        check for Linux only.



diff --git a/util/biosdisk.c b/util/biosdisk.c
index fcf01a4..ddb3718 100644
--- a/util/biosdisk.c
+++ b/util/biosdisk.c
@@ -77,6 +77,14 @@ struct hd_geometry
 # endif /* ! LOOP_MAJOR */
 #endif /* __linux__ */
 
+#ifdef __CYGWIN__
+# include <sys/ioctl.h>
+# include <cygwin/fs.h> /* BLKGETSIZE64 */
+# include <cygwin/hdreg.h> /* HDIO_GETGEO */
+# define MAJOR(dev)    ((unsigned) ((dev) >> 16))
+# define FLOPPY_MAJOR  2
+#endif
+
 static char *map[256];
 
 #ifdef __linux__
@@ -162,7 +170,7 @@ grub_util_biosdisk_open (const char *name, grub_disk_t disk)
   disk->id = drive;
 
   /* Get the size.  */
-#ifdef __linux__
+#if defined(__linux__) || defined(__CYGWIN__)
   {
     unsigned long long nr;
     int fd;
@@ -616,16 +624,14 @@ make_device_name (int drive, int dos_part, int bsd_part)
 static char *
 get_os_disk (const char *os_dev)
 {
-  char *path, *p;
-  
 #if defined(__linux__)
-  path = xmalloc (PATH_MAX);
+  char *path = xmalloc (PATH_MAX);
   if (! realpath (os_dev, path))
     return 0;
   
   if (strncmp ("/dev/", path, 5) == 0)
     {
-      p = path + 5;
+      char *p = path + 5;
 
       /* If this is an IDE disk.  */
       if (strncmp ("ide/", p, 4) == 0)
@@ -692,15 +698,21 @@ get_os_disk (const char *os_dev)
   return path;
   
 #elif defined(__GNU__)
-  path = xstrdup (os_dev);
+  char *path = xstrdup (os_dev);
   if (strncmp ("/dev/sd", path, 7) == 0 || strncmp ("/dev/hd", path, 7) == 0)
     {
-      p = strchr (path, 's');
+      char *p = strchr (path + 7, 's');
       if (p)
        *p = '\0';
     }
   return path;
 
+#elif defined(__CYGWIN__)
+  char *path = xstrdup (os_dev);
+  if (strncmp ("/dev/sd", path, 7) == 0 && 'a' <= path[7] && path[7] <= 'z')
+    path[8] = 0;
+  return path;
+
 #else
 # warning "The function `get_os_disk' might not work on your OS correctly."
   return xstrdup (os_dev);
@@ -751,11 +763,15 @@ grub_util_biosdisk_get_grub_dev (const char *os_dev)
   if (! S_ISBLK (st.st_mode))
     return make_device_name (drive, -1, -1);
   
-#if defined(__linux__)
+#if defined(__linux__) || defined(__CYGWIN__)
   /* Linux counts partitions uniformly, whether a BSD partition or a DOS
      partition, so mapping them to GRUB devices is not trivial.
      Here, get the start sector of a partition by HDIO_GETGEO, and
-     compare it with each partition GRUB recognizes.  */
+     compare it with each partition GRUB recognizes.
+
+     Cygwin /dev/sdXN emulation uses Windows partition mapping. It
+     does not count the extended partition and missing primary
+     partitions.  Use same method as on Linux here.  */
   {
     char *name;
     grub_disk_t disk;
diff --git a/util/getroot.c b/util/getroot.c
index 5a98218..1202a5c 100644
--- a/util/getroot.c
+++ b/util/getroot.c
@@ -22,6 +22,13 @@
 #include <string.h>
 #include <dirent.h>
 
+#ifdef __CYGWIN__
+# include <sys/fcntl.h>
+# include <sys/cygwin.h>
+# include <limits.h>
+# define DEV_CYGDRIVE_MAJOR 98
+#endif
+
 #include <grub/util/misc.h>
 #include <grub/util/biosdisk.h>
 #include <grub/util/getroot.h>
@@ -40,7 +47,8 @@ strip_extra_slashes (char *dir)
        }
       else if (p[1] == '\0')
        {
-         p[0] = '\0';
+         if (p > dir)
+           p[0] = '\0';
          break;
        }
       
@@ -64,6 +72,30 @@ xgetcwd (void)
   return path;
 }
 
+#ifdef __CYGWIN__
+/* Convert POSIX path to Win32 path,
+   remove drive letter, replace backslashes.  */
+static char *
+get_win32_path (const char *path)
+{
+  char winpath[PATH_MAX];
+  cygwin_conv_to_full_win32_path (path, winpath);
+
+  int len = strlen (winpath);
+  if (len > 2 && winpath[1] == ':')
+    {
+      len -= 2;
+      memmove (winpath, winpath + 2, len + 1);
+    }
+
+  int i;
+  for (i = 0; i < len; i++)
+    if (winpath[i] == '\\')
+      winpath[i] = '/';
+  return xstrdup (winpath);
+}
+#endif
+
 char *
 grub_get_prefix (const char *dir)
 {
@@ -116,6 +148,19 @@ grub_get_prefix (const char *dir)
   if (chdir (saved_cwd) < 0)
     grub_util_error ("Cannot change directory to `%s'", dir);
 
+#ifdef __CYGWIN__
+  if (st.st_dev != (DEV_CYGDRIVE_MAJOR << 16))
+    {
+      /* Reached some mount point not below /cygdrive.
+        GRUB does not know Cygwin's emulated mounts,
+        convert to Win32 path.  */
+      grub_util_info ("Cygwin prefix = %s", prefix);
+      char * wprefix = get_win32_path (prefix);
+      free (prefix);
+      prefix = wprefix;
+    }
+#endif
+
   free (saved_cwd);
   free (abs_dir);
   free (prev_dir);
@@ -124,6 +169,8 @@ grub_get_prefix (const char *dir)
   return prefix;
 }
 
+#ifndef __CYGWIN__
+
 static char *
 find_root_device (const char *dir, dev_t dev)
 {
@@ -216,6 +263,92 @@ find_root_device (const char *dir, dev_t dev)
   return 0;
 }
 
+#else /* __CYGWIN__ */
+
+/* Read drive/partition serial number from mbr/boot sector,
+   return 0 on read error, ~0 on unknown serial.  */
+static unsigned
+get_bootsec_serial (const char *os_dev, int mbr)
+{
+  /* Read boot sector.  */
+  int fd = open (os_dev, O_RDONLY);
+  if (fd < 0)
+    return 0;
+  unsigned char buf[0x200];
+  int n = read (fd, buf, sizeof (buf));
+  close (fd);
+  if (n != sizeof(buf))
+    return 0;
+
+  /* Check signature.  */
+  if (!(buf[0x1fe] == 0x55 && buf[0x1ff] == 0xaa))
+    return ~0;
+
+  /* Serial number offset depends on boot sector type.  */
+  if (mbr)
+    n = 0x1b8;
+  else if (memcmp (buf + 0x03, "NTFS", 4) == 0)
+    n = 0x048;
+  else if (memcmp (buf + 0x52, "FAT32", 5) == 0)
+    n = 0x043;
+  else if (memcmp (buf + 0x36, "FAT", 3) == 0)
+    n = 0x027;
+  else
+    return ~0;
+
+  unsigned serial = *(unsigned *)(buf + n);
+  if (serial == 0)
+    return ~0;
+  return serial;
+}
+
+static char *
+find_cygwin_root_device (const char *path, dev_t dev)
+{
+  /* No root device for /cygdrive.  */
+  if (dev == (DEV_CYGDRIVE_MAJOR << 16))
+    return 0;
+
+  /* Convert to full POSIX and Win32 path.  */
+  char fullpath[PATH_MAX], winpath[PATH_MAX];
+  cygwin_conv_to_full_posix_path (path, fullpath);
+  cygwin_conv_to_full_win32_path (fullpath, winpath);
+
+  /* If identical, this is no real filesystem path.  */
+  if (strcmp (fullpath, winpath) == 0)
+    return 0;
+
+  /* Check for floppy drive letter.  */
+  if (winpath[0] && winpath[1] == ':' && strchr ("AaBb", winpath[0]))
+    return xstrdup (strchr ("Aa", winpath[0]) ? "/dev/fd0" : "/dev/fd1");
+
+  /* Cygwin returns the partition serial number in stat.st_dev.
+     This is never identical to the device number of the emulated
+     /dev/sdXN device, so above find_root_device () does not work.
+     Search the partion with the same serial in boot sector instead.  */
+  char devpath[sizeof ("/dev/sda15") + 13]; /* Size + Paranoia.  */
+  int d;
+  for (d = 'a'; d <= 'z'; d++)
+    {
+      sprintf (devpath, "/dev/sd%c", d);
+      if (get_bootsec_serial (devpath, 1) == 0)
+       continue;
+      int p;
+      for (p = 1; p <= 15; p++)
+       {
+         sprintf (devpath, "/dev/sd%c%d", d, p);
+         unsigned ser = get_bootsec_serial (devpath, 0);
+         if (ser == 0)
+           break;
+         if (ser != (unsigned)~0 && dev == (dev_t)ser)
+           return xstrdup (devpath);
+       }
+    }
+  return 0;
+}
+
+#endif /* __CYGWIN__ */
+
 char *
 grub_guess_root_device (const char *dir)
 {
@@ -230,17 +363,24 @@ grub_guess_root_device (const char *dir)
      we don't do this, we get useless device names like /dev/dm-0 for
      LVM.  */
   os_dev = find_root_device ("/dev/mapper", st.st_dev);
+  if (os_dev)
+    return os_dev;
 
   /* The same applies to /dev/evms directory (for EVMS volumes).  */
-  if (! os_dev)
-    os_dev = find_root_device ("/dev/evms", st.st_dev);
+  os_dev = find_root_device ("/dev/evms", st.st_dev);
+  if (os_dev)
+    return os_dev;
+#endif
 
-  if (! os_dev)
+#ifdef __CYGWIN__
+  /* Cygwin specific function.  */
+  os_dev = find_cygwin_root_device (dir, st.st_dev);
+
+#else
+
+  /* This might be truly slow, but is there any better way?  */
+  os_dev = find_root_device ("/dev", st.st_dev);
 #endif
-    {
-      /* This might be truly slow, but is there any better way?  */
-      os_dev = find_root_device ("/dev", st.st_dev);
-    }
 
   return os_dev;
 }
@@ -248,6 +388,7 @@ grub_guess_root_device (const char *dir)
 int
 grub_util_get_dev_abstraction (const char *os_dev)
 {
+#ifdef __linux__
   /* Check for LVM.  */
   if (!strncmp (os_dev, "/dev/mapper/", 12))
     return GRUB_DEV_ABSTRACTION_LVM;
@@ -255,6 +396,7 @@ grub_util_get_dev_abstraction (const char *os_dev)
   /* Check for RAID.  */
   if (!strncmp (os_dev, "/dev/md", 7))
     return GRUB_DEV_ABSTRACTION_RAID;
+#endif
 
   /* No abstraction found.  */
   return GRUB_DEV_ABSTRACTION_NONE;