fat: handle .. pointing back to the root directory

.. pointing back to the root directory will have a cluster number of
0, even for FAT32 where there is an actual cluster number for the root
directory.  Handle this as a special case.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/core/fs/fat/fat.c b/core/fs/fat/fat.c
index 6850993..5902f48 100644 (file)
--- a/core/fs/fat/fat.c
+++ b/core/fs/fat/fat.c
@@ -276,26 +276,32 @@ static void mangle_dos_name(char *mangle_buf, const char *src)
     int i;
     unsigned char c;
 
-    i = 0;
-    while (i < 11) {
-       c = *src++;
-
+    if (src[0] == '.' && (!src[1] || (src[1] == '.' && !src[2]))) {
+       /* . and .. mangle to their respective zero-padded version */
+       i = stpcpy(mangle_buf, src) - mangle_buf;
+    } else {
+       i = 0;
+       while (i < 11) {
+           c = *src++;
+           
        if ((c <= ' ') || (c == '/'))
            break;
-
+       
        if (c == '.') {
            while (i < 8)
                mangle_buf[i++] = ' ';
            i = 8;
            continue;
        }
-
+       
        c = codepage.upper[c];
        if (i == 0 && c == 0xe5)
            c = 0x05;           /* Special hack for the first byte only! */
-
+       
        mangle_buf[i++] = c;
+       }
     }
+
     while (i < 11)
        mangle_buf[i++] = ' ';
 
@@ -408,7 +414,10 @@ static inline sector_t first_sector(struct fs_info *fs,
     sector_t sector;
 
     first_clust = (dir->first_cluster_high << 16) + dir->first_cluster_low;
-    sector = ((first_clust - 2) << sbi->clust_shift) + sbi->data;
+    if (first_clust == 0)
+       sector = sbi->root;     /* first_clust == 0 means root directory */
+    else
+       sector = ((first_clust - 2) << sbi->clust_shift) + sbi->data;
 
     return sector;
 }
@@ -533,7 +542,16 @@ found:
     inode->size = de->file_size;
     PVT(inode)->start_cluster = 
        (de->first_cluster_high << 16) + de->first_cluster_low;
-    PVT(inode)->start = PVT(inode)->here = first_sector(fs, de);
+    if (PVT(inode)->start_cluster == 0) {
+       /* Root directory */
+       int root_size = FAT_SB(fs)->root_size;
+
+       PVT(inode)->start_cluster = FAT_SB(fs)->root_cluster;
+       inode->size = root_size ? root_size << fs->sector_shift : ~0;
+       PVT(inode)->start = PVT(inode)->here = FAT_SB(fs)->root;
+    } else {
+       PVT(inode)->start = PVT(inode)->here = first_sector(fs, de);
+    }
     inode->mode = get_inode_mode(de->attr);
 
     return inode;