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Diffstat (limited to 'fs/fat/fat.c')
-rw-r--r--fs/fat/fat.c98
1 files changed, 79 insertions, 19 deletions
diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 19f6a8c0af6..41ae15eeb97 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -328,13 +328,16 @@ get_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer, unsigned long size)
}
/*
- * Read at most 'maxsize' bytes from the file associated with 'dentptr'
+ * Read at most 'maxsize' bytes from 'pos' in the file associated with 'dentptr'
* into 'buffer'.
* Return the number of bytes read or -1 on fatal errors.
*/
+__u8 get_contents_vfatname_block[MAX_CLUSTSIZE]
+ __aligned(ARCH_DMA_MINALIGN);
+
static long
-get_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
- unsigned long maxsize)
+get_contents(fsdata *mydata, dir_entry *dentptr, unsigned long pos,
+ __u8 *buffer, unsigned long maxsize)
{
unsigned long filesize = FAT2CPU32(dentptr->size), gotsize = 0;
unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
@@ -344,12 +347,59 @@ get_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
debug("Filesize: %ld bytes\n", filesize);
- if (maxsize > 0 && filesize > maxsize)
- filesize = maxsize;
+ if (pos >= filesize) {
+ debug("Read position past EOF: %lu\n", pos);
+ return gotsize;
+ }
+
+ if (maxsize > 0 && filesize > pos + maxsize)
+ filesize = pos + maxsize;
debug("%ld bytes\n", filesize);
actsize = bytesperclust;
+
+ /* go to cluster at pos */
+ while (actsize <= pos) {
+ curclust = get_fatent(mydata, curclust);
+ if (CHECK_CLUST(curclust, mydata->fatsize)) {
+ debug("curclust: 0x%x\n", curclust);
+ debug("Invalid FAT entry\n");
+ return gotsize;
+ }
+ actsize += bytesperclust;
+ }
+
+ /* actsize > pos */
+ actsize -= bytesperclust;
+ filesize -= actsize;
+ pos -= actsize;
+
+ /* align to beginning of next cluster if any */
+ if (pos) {
+ actsize = min(filesize, bytesperclust);
+ if (get_cluster(mydata, curclust, get_contents_vfatname_block,
+ (int)actsize) != 0) {
+ printf("Error reading cluster\n");
+ return -1;
+ }
+ filesize -= actsize;
+ actsize -= pos;
+ memcpy(buffer, get_contents_vfatname_block + pos, actsize);
+ gotsize += actsize;
+ if (!filesize)
+ return gotsize;
+ buffer += actsize;
+
+ curclust = get_fatent(mydata, curclust);
+ if (CHECK_CLUST(curclust, mydata->fatsize)) {
+ debug("curclust: 0x%x\n", curclust);
+ debug("Invalid FAT entry\n");
+ return gotsize;
+ }
+ }
+
+ actsize = bytesperclust;
endclust = curclust;
do {
@@ -433,9 +483,6 @@ static int slot2str(dir_slot *slotptr, char *l_name, int *idx)
* into 'retdent'
* Return 0 on success, -1 otherwise.
*/
-__u8 get_vfatname_block[MAX_CLUSTSIZE]
- __aligned(ARCH_DMA_MINALIGN);
-
static int
get_vfatname(fsdata *mydata, int curclust, __u8 *cluster,
dir_entry *retdent, char *l_name)
@@ -474,13 +521,13 @@ get_vfatname(fsdata *mydata, int curclust, __u8 *cluster,
return -1;
}
- if (get_cluster(mydata, curclust, get_vfatname_block,
+ if (get_cluster(mydata, curclust, get_contents_vfatname_block,
mydata->clust_size * mydata->sect_size) != 0) {
debug("Error: reading directory block\n");
return -1;
}
- slotptr2 = (dir_slot *)get_vfatname_block;
+ slotptr2 = (dir_slot *)get_contents_vfatname_block;
while (counter > 0) {
if (((slotptr2->id & ~LAST_LONG_ENTRY_MASK)
& 0xff) != counter)
@@ -491,7 +538,7 @@ get_vfatname(fsdata *mydata, int curclust, __u8 *cluster,
/* Save the real directory entry */
realdent = (dir_entry *)slotptr2;
- while ((__u8 *)slotptr2 > get_vfatname_block) {
+ while ((__u8 *)slotptr2 > get_contents_vfatname_block) {
slotptr2--;
slot2str(slotptr2, l_name, &idx);
}
@@ -770,11 +817,12 @@ exit:
return ret;
}
-__u8 do_fat_read_block[MAX_CLUSTSIZE]
+__u8 do_fat_read_at_block[MAX_CLUSTSIZE]
__aligned(ARCH_DMA_MINALIGN);
long
-do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols)
+do_fat_read_at(const char *filename, unsigned long pos, void *buffer,
+ unsigned long maxsize, int dols)
{
char fnamecopy[2048];
boot_sector bs;
@@ -888,12 +936,12 @@ do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols)
(mydata->fatsize == 32) ?
(mydata->clust_size) :
PREFETCH_BLOCKS,
- do_fat_read_block) < 0) {
+ do_fat_read_at_block) < 0) {
debug("Error: reading rootdir block\n");
goto exit;
}
- dentptr = (dir_entry *) do_fat_read_block;
+ dentptr = (dir_entry *) do_fat_read_at_block;
}
for (i = 0; i < DIRENTSPERBLOCK; i++) {
@@ -913,7 +961,7 @@ do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols)
get_vfatname(mydata,
root_cluster,
- do_fat_read_block,
+ do_fat_read_at_block,
dentptr, l_name);
if (dols == LS_ROOT) {
@@ -1116,7 +1164,7 @@ rootdir_done:
subname = nextname;
}
- ret = get_contents(mydata, dentptr, buffer, maxsize);
+ ret = get_contents(mydata, dentptr, pos, buffer, maxsize);
debug("Size: %d, got: %ld\n", FAT2CPU32(dentptr->size), ret);
exit:
@@ -1124,6 +1172,12 @@ exit:
return ret;
}
+long
+do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols)
+{
+ return do_fat_read_at(filename, 0, buffer, maxsize, dols);
+}
+
int file_fat_detectfs(void)
{
boot_sector bs;
@@ -1192,8 +1246,14 @@ int file_fat_ls(const char *dir)
return do_fat_read(dir, NULL, 0, LS_YES);
}
-long file_fat_read(const char *filename, void *buffer, unsigned long maxsize)
+long file_fat_read_at(const char *filename, unsigned long pos, void *buffer,
+ unsigned long maxsize)
{
printf("reading %s\n", filename);
- return do_fat_read(filename, buffer, maxsize, LS_NO);
+ return do_fat_read_at(filename, pos, buffer, maxsize, LS_NO);
+}
+
+long file_fat_read(const char *filename, void *buffer, unsigned long maxsize)
+{
+ return file_fat_read_at(filename, 0, buffer, maxsize);
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-10 17:16:02 +0000