From 5593ba9b9f5e81f77f80aa1a0bc989848e7cc194 Mon Sep 17 00:00:00 2001
From: Philipp Skadorov <philipp.skadorov@savoirfairelinux.com>
Date: Thu, 15 Dec 2016 15:52:53 -0500
Subject: [PATCH] fat: fatwrite: fix the command for FAT12

The u-boot command fatwrite empties FAT clusters from the beginning
till the end of the file.
Specifically for FAT12 it fails to detect the end of the file and goes
beyond the file bounds thus corrupting the file system.

Additionally, FAT entry chaining-up into a file is not implemented
for FAT12.

The users normally workaround this by re-formatting the partition as
FAT16/FAT32, like here:
https://github.com/FEDEVEL/openrex-uboot-v2015.10/issues/1

The patch fixes the bounds of a file and FAT12 entries chaining into
a file, including EOF markup.

Signed-off-by: Philipp Skadorov <philipp.skadorov@savoirfairelinux.com>
(cherry picked from commit 49abbd9cc309235895c9ff7ccb6ad75c40fca4a9)
Signed-off-by: Hariharan K <quic_harihk@quicinc.com>

Change-Id: Ib9c75d4553ea576cbc592f3291cfdebc45b8376b
---
 fs/fat/fat_write.c | 61 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
index 41759079db..d48d1ea42d 100644
--- a/fs/fat/fat_write.c
+++ b/fs/fat/fat_write.c
@@ -466,11 +466,12 @@ get_long_file_name(fsdata *mydata, int curclust, __u8 *cluster,
 }
 
 /*
- * Set the entry at index 'entry' in a FAT (16/32) table.
+ * Set the entry at index 'entry' in a FAT (12/16/32) table.
  */
 static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value)
 {
-	__u32 bufnum, offset;
+	__u32 bufnum, offset, off16;
+	__u16 val1, val2;
 
 	switch (mydata->fatsize) {
 	case 32:
@@ -481,6 +482,10 @@ static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value)
 		bufnum = entry / FAT16BUFSIZE;
 		offset = entry - bufnum * FAT16BUFSIZE;
 		break;
+	case 12:
+		bufnum = entry / FAT12BUFSIZE;
+		offset = entry - bufnum * FAT12BUFSIZE;
+		break;
 	default:
 		/* Unsupported FAT size */
 		return -1;
@@ -518,6 +523,45 @@ static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value)
 		break;
 	case 16:
 		((__u16 *) mydata->fatbuf)[offset] = cpu_to_le16(entry_value);
+		break;
+	case 12:
+		off16 = (offset * 3) / 4;
+
+		switch (offset & 0x3) {
+		case 0:
+			val1 = cpu_to_le16(entry_value) & 0xfff;
+			((__u16 *)mydata->fatbuf)[off16] &= ~0xfff;
+			((__u16 *)mydata->fatbuf)[off16] |= val1;
+			break;
+		case 1:
+			val1 = cpu_to_le16(entry_value) & 0xf;
+			val2 = (cpu_to_le16(entry_value) >> 4) & 0xff;
+
+			((__u16 *)mydata->fatbuf)[off16] &= ~0xf000;
+			((__u16 *)mydata->fatbuf)[off16] |= (val1 << 12);
+
+			((__u16 *)mydata->fatbuf)[off16 + 1] &= ~0xff;
+			((__u16 *)mydata->fatbuf)[off16 + 1] |= val2;
+			break;
+		case 2:
+			val1 = cpu_to_le16(entry_value) & 0xff;
+			val2 = (cpu_to_le16(entry_value) >> 8) & 0xf;
+
+			((__u16 *)mydata->fatbuf)[off16] &= ~0xff00;
+			((__u16 *)mydata->fatbuf)[off16] |= (val1 << 8);
+
+			((__u16 *)mydata->fatbuf)[off16 + 1] &= ~0xf;
+			((__u16 *)mydata->fatbuf)[off16 + 1] |= val2;
+			break;
+		case 3:
+			val1 = cpu_to_le16(entry_value) & 0xfff;
+			((__u16 *)mydata->fatbuf)[off16] &= ~0xfff0;
+			((__u16 *)mydata->fatbuf)[off16] |= (val1 << 4);
+			break;
+		default:
+			break;
+		}
+
 		break;
 	default:
 		return -1;
@@ -527,7 +571,7 @@ static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value)
 }
 
 /*
- * Determine the entry value at index 'entry' in a FAT (16/32) table
+ * Determine the next free cluster after 'entry' in a FAT (12/16/32) table
  */
 static __u32 determine_fatent(fsdata *mydata, __u32 entry)
 {
@@ -647,6 +691,8 @@ static void flush_dir_table(fsdata *mydata, dir_entry **dentptr)
 		set_fatent_value(mydata, dir_newclust, 0xffffff8);
 	else if (mydata->fatsize == 16)
 		set_fatent_value(mydata, dir_newclust, 0xfff8);
+	else if (mydata->fatsize == 12)
+		set_fatent_value(mydata, dir_newclust, 0xff8);
 
 	dir_curclust = dir_newclust;
 
@@ -666,16 +712,13 @@ static int clear_fatent(fsdata *mydata, __u32 entry)
 {
 	__u32 fat_val;
 
-	while (1) {
+	while (!CHECK_CLUST(entry, mydata->fatsize)) {
 		fat_val = get_fatent_value(mydata, entry);
 		if (fat_val != 0)
 			set_fatent_value(mydata, entry, 0);
 		else
 			break;
 
-		if (fat_val == 0xfffffff || fat_val == 0xffff)
-			break;
-
 		entry = fat_val;
 	}
 
@@ -746,7 +789,9 @@ set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
 		*gotsize += actsize;
 
 		/* Mark end of file in FAT */
-		if (mydata->fatsize == 16)
+		if (mydata->fatsize == 12)
+			newclust = 0xfff;
+		else if (mydata->fatsize == 16)
 			newclust = 0xffff;
 		else if (mydata->fatsize == 32)
 			newclust = 0xfffffff;