[PATCH 06/18] fs: fat: create correct short names
Heinrich Schuchardt
xypron.glpk at gmx.de
Sun Nov 29 03:02:04 CET 2020
The current function set_name() used to create short names has the
following deficiencies resolved by this patch:
* Long names (e.g. FOO.TXT) are stored even if a short name is enough.
* Short names with spaces are created, e.g. "A ~1.TXT".
* Short names with illegal characters are created, e.g. "FOO++BAR".
* Debug output does not not consider that the short file name has no
concluding '\0'.
The solution for the following bug is split of into a separate patch:
* Short file names must be unique.
This patch only provides the loop over possible short file names.
Fixes: c30a15e590c ("FAT: Add FAT write feature")
Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
---
fs/fat/fat_write.c | 215 +++++++++++++++++++++++++++++----------------
lib/Kconfig | 2 +-
2 files changed, 140 insertions(+), 77 deletions(-)
diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
index 4da342f9c9..058b566629 100644
--- a/fs/fat/fat_write.c
+++ b/fs/fat/fat_write.c
@@ -8,25 +8,140 @@
#include <common.h>
#include <command.h>
#include <config.h>
+#include <div64.h>
#include <fat.h>
#include <log.h>
#include <malloc.h>
-#include <asm/byteorder.h>
#include <part.h>
+#include <rand.h>
+#include <asm/byteorder.h>
#include <asm/cache.h>
#include <linux/ctype.h>
-#include <div64.h>
#include <linux/math64.h>
#include "fat.c"
-static void uppercase(char *str, int len)
+/* Characters that may only be used in long file names */
+static const char LONG_ONLY_CHARS[] = "+,;=[]";
+
+/**
+ * str2fat() - convert string to valid FAT name characters
+ *
+ * Stop when reaching end of @src or a period.
+ * Ignore spaces.
+ * Replace characters that may only be used in long names by underscores.
+ * Convert lower case characters to upper case.
+ *
+ * To avoid assumptions about the code page we do not use characters
+ * above 0x7f for the short name.
+ *
+ * @dest: destination buffer
+ * @src: source buffer
+ * @length: size of destination buffer
+ * Return: number of bytes in destination buffer
+ */
+static int str2fat(char *dest, char *src, int length)
+{
+ int i;
+
+ for (i = 0; i < length; ++src) {
+ char c = *src;
+
+ if (!c || c == '.')
+ break;
+ if (c == ' ')
+ continue;
+ if (strchr(LONG_ONLY_CHARS, c) || c > 0x7f)
+ c = '_';
+ else if (c >= 'a' && c <= 'z')
+ c &= 0xdf;
+ dest[i] = c;
+ ++i;
+ }
+ return i;
+}
+
+/**
+ * set_name() - set short name in directory entry
+ *
+ * The function determines if the @filename is a valid short name.
+ * In this case no long name is needed.
+ *
+ * If a long name is needed, a short name is constructed.
+ *
+ * @dirent: directory entry
+ * @filename: long file name
+ * Return: number of directory entries needed, negative on error
+ */
+static int set_name(dir_entry *dirent, const char *filename)
{
+ char *period;
+ char *pos;
+ int period_location;
+ char buf[13];
int i;
- for (i = 0; i < len; i++) {
- *str = toupper(*str);
- str++;
+ if (!filename)
+ return -EIO;
+
+ /* Initialize buffers */
+ memset(dirent->name, ' ', sizeof(dirent->name));
+ memset(dirent->ext, ' ', sizeof(dirent->ext));
+
+ /* Convert filename to upper case short name */
+ period = strrchr(filename, '.');
+ pos = (char *)filename;
+ if (*pos == '.') {
+ pos = period + 1;
+ period = 0;
+ }
+ if (period)
+ str2fat(dirent->ext, period + 1, sizeof(dirent->ext));
+ period_location = str2fat(dirent->name, pos, sizeof(dirent->name));
+ if (period_location < 0)
+ return period_location;
+ if (*dirent->name == ' ')
+ *dirent->name = '_';
+ /* 0xe5 signals a deleted directory entry. Replace it by 0x05. */
+ if (*dirent->name == 0xe5)
+ *dirent->name = 0x05;
+
+ /* If filename and short name are the same, quit. */
+ sprintf(buf, "%.*s.%.3s", period_location, dirent->name, dirent->ext);
+ if (!strcmp(buf, filename))
+ return 1;
+
+ /* Construct an indexed short name */
+ for (i = 1; i < 0x200000; ++i) {
+ int suffix_len;
+ int suffix_start;
+ int j;
+
+ /* To speed up the search use random numbers */
+ if (i < 10) {
+ j = i;
+ } else {
+ j = 30 - fls(i);
+ j = 10 + (rand() >> j);
+ }
+ sprintf(buf, "~%d", j);
+ suffix_len = strlen(buf);
+ suffix_start = 8 - suffix_len;
+ if (suffix_start > period_location)
+ suffix_start = period_location;
+ memcpy(dirent->name + suffix_start, buf, suffix_len);
+ if (*dirent->ext != ' ')
+ sprintf(buf, "%.*s.%.3s", suffix_start + suffix_len,
+ dirent->name, dirent->ext);
+ else
+ sprintf(buf, "%.*s", suffix_start + suffix_len,
+ dirent->name);
+ debug("short name: %s\n", buf);
+ /* TODO: Check that the short name does not exist yet. */
+
+ /* Each long name directory entry takes 13 characters. */
+ return (strlen(filename) + 25) / 13;
}
+ return -EIO;
}
static int total_sector;
@@ -50,67 +165,6 @@ static int disk_write(__u32 block, __u32 nr_blocks, void *buf)
return ret;
}
-/**
- * set_name() - set short name in directory entry
- *
- * @dirent: directory entry
- * @filename: long file name
- */
-static void set_name(dir_entry *dirent, const char *filename)
-{
- char s_name[VFAT_MAXLEN_BYTES];
- char *period;
- int period_location, len, i, ext_num;
-
- if (filename == NULL)
- return;
-
- len = strlen(filename);
- if (len == 0)
- return;
-
- strncpy(s_name, filename, VFAT_MAXLEN_BYTES - 1);
- s_name[VFAT_MAXLEN_BYTES - 1] = '\0';
- uppercase(s_name, len);
-
- period = strchr(s_name, '.');
- if (period == NULL) {
- period_location = len;
- ext_num = 0;
- } else {
- period_location = period - s_name;
- ext_num = len - period_location - 1;
- }
-
- /* Pad spaces when the length of file name is shorter than eight */
- if (period_location < 8) {
- memcpy(dirent->name, s_name, period_location);
- for (i = period_location; i < 8; i++)
- dirent->name[i] = ' ';
- } else if (period_location == 8) {
- memcpy(dirent->name, s_name, period_location);
- } else {
- memcpy(dirent->name, s_name, 6);
- /*
- * TODO: Translating two long names with the same first six
- * characters to the same short name is utterly wrong.
- * Short names must be unique.
- */
- dirent->name[6] = '~';
- dirent->name[7] = '1';
- }
-
- if (ext_num < 3) {
- memcpy(dirent->ext, s_name + period_location + 1, ext_num);
- for (i = ext_num; i < 3; i++)
- dirent->ext[i] = ' ';
- } else
- memcpy(dirent->ext, s_name + period_location + 1, 3);
-
- debug("name : %s\n", dirent->name);
- debug("ext : %s\n", dirent->ext);
-}
-
/*
* Write fat buffer into block device
*/
@@ -1181,13 +1235,15 @@ int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
memset(itr->dent, 0, sizeof(*itr->dent));
- /* Calculate checksum for short name */
- set_name(itr->dent, filename);
-
- /* Set long name entries */
- if (fill_dir_slot(itr, filename)) {
- ret = -EIO;
+ /* Check if long name is needed */
+ ret = set_name(itr->dent, filename);
+ if (ret < 0)
goto exit;
+ if (ret > 1) {
+ /* Set long name entries */
+ ret = fill_dir_slot(itr, filename);
+ if (ret)
+ goto exit;
}
/* Set short name entry */
@@ -1441,9 +1497,16 @@ int fat_mkdir(const char *new_dirname)
memset(itr->dent, 0, sizeof(*itr->dent));
- /* Set short name to set alias checksum field in dir_slot */
- set_name(itr->dent, dirname);
- fill_dir_slot(itr, dirname);
+ /* Check if long name is needed */
+ ret = set_name(itr->dent, dirname);
+ if (ret < 0)
+ goto exit;
+ if (ret > 1) {
+ /* Set long name entries */
+ ret = fill_dir_slot(itr, dirname);
+ if (ret)
+ goto exit;
+ }
/* Set attribute as archive for regular file */
fill_dentry(itr->fsdata, itr->dent, dirname, 0, 0,
diff --git a/lib/Kconfig b/lib/Kconfig
index 7673d2e4e0..06eb8d07dc 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -168,7 +168,7 @@ config REGEX
choice
prompt "Pseudo-random library support type"
depends on NET_RANDOM_ETHADDR || RANDOM_UUID || CMD_UUID || \
- RNG_SANDBOX || UT_LIB && AES
+ RNG_SANDBOX || UT_LIB && AES || FAT_WRITE
default LIB_RAND
help
Select the library to provide pseudo-random number generator
--
2.29.2
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