From 5875bf287d95314c58add01184f361cc5aa38429 Mon Sep 17 00:00:00 2001

From: Tetsuhiro Kohada <kohada.t2@gmail.com>

Date: Fri, 29 May 2020 19:14:59 +0900

Subject: [Backport 5875bf287d95] exfat: standardize checksum calculation

To clarify that it is a 16-bit checksum, the parts related to the 16-bit

checksum are renamed and change type to u16.

Furthermore, replace checksum calculation in exfat_load_upcase_table()

with exfat_calc_checksum32().

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>

Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

---

 src/dir.c      | 12 ++++++------

 src/exfat_fs.h |  5 ++---

 src/misc.c     | 10 ++++------

 src/nls.c      | 19 +++++++------------

 4 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/src/dir.c b/src/dir.c

index 2902d285bf20412af3a57b0e96a6768e49d6c5ac..de43534aa2997aa87994a9447f95578de9931258 100644

--- a/src/dir.c

+++ b/src/dir.c

@@ -491,7 +491,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,

 	int ret = 0;

 	int i, num_entries;

 	sector_t sector;

-	unsigned short chksum;

+	u16 chksum;

 	struct exfat_dentry *ep, *fep;

 	struct buffer_head *fbh, *bh;

@@ -500,7 +500,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,

 		return -EIO;

 	num_entries = fep->dentry.file.num_ext + 1;

-	chksum = exfat_calc_chksum_2byte(fep, DENTRY_SIZE, 0, CS_DIR_ENTRY);

+	chksum = exfat_calc_chksum16(fep, DENTRY_SIZE, 0, CS_DIR_ENTRY);

 	for (i = 1; i < num_entries; i++) {

 		ep = exfat_get_dentry(sb, p_dir, entry + i, &bh, NULL);

@@ -508,7 +508,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,

 			ret = -EIO;

 			goto release_fbh;

 		}

-		chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,

+		chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,

 				CS_DEFAULT);

 		brelse(bh);

 	}

@@ -593,8 +593,8 @@ void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es)

 	for (i = 0; i < es->num_entries; i++) {

 		ep = exfat_get_dentry_cached(es, i);

-		chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,

-						 chksum_type);

+		chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,

+					     chksum_type);

 		chksum_type = CS_DEFAULT;

 	}

 	ep = exfat_get_dentry_cached(es, 0);

@@ -1000,7 +1000,7 @@ int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,

 			}

 			if (entry_type == TYPE_STREAM) {

-				unsigned short name_hash;

+				u16 name_hash;

 				if (step != DIRENT_STEP_STRM) {

 					step = DIRENT_STEP_FILE;

diff --git a/src/exfat_fs.h b/src/exfat_fs.h

index 8c2a70bfaa10d4743c46aad74254e363d4079c74..595f3117f4924893a07eba48b55ef3d7d6edbee6 100644

--- a/src/exfat_fs.h

+++ b/src/exfat_fs.h

@@ -137,7 +137,7 @@ struct exfat_dentry_namebuf {

 struct exfat_uni_name {

 	/* +3 for null and for converting */

 	unsigned short name[MAX_NAME_LENGTH + 3];

-	unsigned short name_hash;

+	u16 name_hash;

 	unsigned char name_len;

 };

@@ -512,8 +512,7 @@ void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,

 void exfat_truncate_atime(struct timespec64 *ts);

 void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,

 		u8 *tz, __le16 *time, __le16 *date, u8 *time_cs);

-unsigned short exfat_calc_chksum_2byte(void *data, int len,

-		unsigned short chksum, int type);

+u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type);

 u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type);

 void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync);

 void exfat_chain_set(struct exfat_chain *ec, unsigned int dir,

diff --git a/src/misc.c b/src/misc.c

index b82d2dd5bd7cb291ffe5ed5091c9214593c32a69..17d41f3d3709287f6654dd52bd540e3f60fee285 100644

--- a/src/misc.c

+++ b/src/misc.c

@@ -136,17 +136,15 @@ void exfat_truncate_atime(struct timespec64 *ts)

 	ts->tv_nsec = 0;

 }

-unsigned short exfat_calc_chksum_2byte(void *data, int len,

-		unsigned short chksum, int type)

+u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type)

 {

 	int i;

-	unsigned char *c = (unsigned char *)data;

+	u8 *c = (u8 *)data;

 	for (i = 0; i < len; i++, c++) {

-		if (((i == 2) || (i == 3)) && (type == CS_DIR_ENTRY))

+		if (unlikely(type == CS_DIR_ENTRY && (i == 2 || i == 3)))

 			continue;

-		chksum = (((chksum & 1) << 15) | ((chksum & 0xFFFE) >> 1)) +

-			(unsigned short)*c;

+		chksum = ((chksum << 15) | (chksum >> 1)) + *c;

 	}

 	return chksum;

 }

diff --git a/src/nls.c b/src/nls.c

index 1ebda90cbdd7c81c507f662332a53eb52bf92606..19321773dd078a42f8c9659e15032502b33bddcd 100644

--- a/src/nls.c

+++ b/src/nls.c

@@ -527,7 +527,7 @@ static int exfat_utf8_to_utf16(struct super_block *sb,

 	*uniname = '\0';

 	p_uniname->name_len = unilen;

-	p_uniname->name_hash = exfat_calc_chksum_2byte(upname, unilen << 1, 0,

+	p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,

 			CS_DEFAULT);

 	if (p_lossy)

@@ -623,7 +623,7 @@ static int exfat_nls_to_ucs2(struct super_block *sb,

 	*uniname = '\0';

 	p_uniname->name_len = unilen;

-	p_uniname->name_hash = exfat_calc_chksum_2byte(upname, unilen << 1, 0,

+	p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,

 			CS_DEFAULT);

 	if (p_lossy)

@@ -655,7 +655,8 @@ static int exfat_load_upcase_table(struct super_block *sb,

 {

 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	unsigned int sect_size = sb->s_blocksize;

-	unsigned int i, index = 0, checksum = 0;

+	unsigned int i, index = 0;

+	u32 chksum = 0;

 	int ret;

 	unsigned char skip = false;

 	unsigned short *upcase_table;

@@ -681,13 +682,6 @@ static int exfat_load_upcase_table(struct super_block *sb,

 		for (i = 0; i < sect_size && index <= 0xFFFF; i += 2) {

 			unsigned short uni = get_unaligned_le16(bh->b_data + i);

-			checksum = ((checksum & 1) ? 0x80000000 : 0) +

-				(checksum >> 1) +

-				*(((unsigned char *)bh->b_data) + i);

-			checksum = ((checksum & 1) ? 0x80000000 : 0) +

-				(checksum >> 1) +

-				*(((unsigned char *)bh->b_data) + (i + 1));

-

 			if (skip) {

 				index += uni;

 				skip = false;

@@ -701,13 +695,14 @@ static int exfat_load_upcase_table(struct super_block *sb,

 			}

 		}

 		brelse(bh);

+		chksum = exfat_calc_chksum32(bh->b_data, i, chksum, CS_DEFAULT);

 	}

-	if (index >= 0xFFFF && utbl_checksum == checksum)

+	if (index >= 0xFFFF && utbl_checksum == chksum)

 		return 0;

 	exfat_err(sb, "failed to load upcase table (idx : 0x%08x, chksum : 0x%08x, utbl_chksum : 0x%08x)",

-		  index, checksum, utbl_checksum);

+		  index, chksum, utbl_checksum);

 	ret = -EINVAL;

 free_table:

 	exfat_free_upcase_table(sbi);

-- 

2.31.1