2021-04-07 21:06:30

by Shreeya Patel

[permalink] [raw]
Subject: [PATCH v7 0/4] Make UTF-8 encoding loadable

utf8data.h_shipped has a large database table which is an auto-generated
decodification trie for the unicode normalization functions and it is not
necessary to carry this large table in the kernel.
Goal is to make UTF-8 encoding loadable by converting it into a module
and adding a layer between the filesystems and the utf8 module which will
load the module whenever any filesystem that needs unicode is mounted.
Currently only UTF-8 encoding is supported but if any other encodings
are supported in future then the layer file would be responsible for
loading the desired encoding module.

1st patch in the series resolves the warning reported by kernel test
robot by using strscpy instead of strncpy.

Unicode is the subsystem and utf8 is a charachter encoding for the
subsystem, hence 2nd and 3rd patches in the series are renaming functions
and file name to unicode for better understanding the difference between
UTF-8 module and unicode layer.

Last patch in the series adds the layer and utf8 module and also uses
static calls which gives performance benefit when compared to indirect
calls using function pointers.

---
Changes in v7
- Update the help text in Kconfig
- Handle the unicode_load_static_call function failure by decrementing
the reference.
- Correct the code for handling built-in utf8 option as well.
- Correct the synchronization for accessing utf8mod.
- Make changes to unicode_unload() for handling the situation where
utf8mod != NULL and um == NULL.

Changes in v6
- Add spinlock to protect utf8mod and avoid NULL pointer
dereference.
- Change the static call function names for being consistent with
kernel coding style.
- Merge the unicode_load_module function with unicode_load as it is
not really needed to have a separate function.
- Use try_then_module_get instead of module_get to avoid loading the
module even when it is already loaded.
- Improve the commit message.

Changes in v5
- Remove patch which adds NULL check in ext4/super.c and f2fs/super.c
before calling unicode_unload().
- Rename global variables and default static call functions for better
understanding
- Make only config UNICODE_UTF8 visible and config UNICODE to be always
enabled provided UNICODE_UTF8 is enabled.
- Improve the documentation for Kconfig
- Improve the commit message.

Changes in v4
- Return error from the static calls instead of doing nothing and
succeeding even without loading the module.
- Remove the complete usage of utf8_ops and use static calls at all
places.
- Restore the static calls to default values when module is unloaded.
- Decrement the reference of module after calling the unload function.
- Remove spinlock as there will be no race conditions after removing
utf8_ops.

Changes in v3
- Add a patch which checks if utf8 is loaded before calling utf8_unload()
in ext4 and f2fs filesystems
- Return error if strscpy() returns value < 0
- Correct the conditions to prevent NULL pointer dereference while
accessing functions via utf8_ops variable.
- Add spinlock to avoid race conditions.
- Use static_call() for preventing speculative execution attacks.

Changes in v2
- Remove the duplicate file from the last patch.
- Make the wrapper functions inline.
- Remove msleep and use try_module_get() and module_put()
for ensuring that module is loaded correctly and also
doesn't get unloaded while in use.
- Resolve the warning reported by kernel test robot.
- Resolve all the checkpatch.pl warnings.

Shreeya Patel (4):
fs: unicode: Use strscpy() instead of strncpy()
fs: unicode: Rename function names from utf8 to unicode
fs: unicode: Rename utf8-core file to unicode-core
fs: unicode: Add utf8 module and a unicode layer

fs/ext4/hash.c | 2 +-
fs/ext4/namei.c | 12 +-
fs/ext4/super.c | 6 +-
fs/f2fs/dir.c | 12 +-
fs/f2fs/super.c | 6 +-
fs/libfs.c | 6 +-
fs/unicode/Kconfig | 26 +++-
fs/unicode/Makefile | 5 +-
fs/unicode/unicode-core.c | 162 +++++++++++++++++++++
fs/unicode/{utf8-core.c => unicode-utf8.c} | 98 ++++++++-----
fs/unicode/utf8-selftest.c | 8 +-
include/linux/unicode.h | 100 +++++++++++--
12 files changed, 361 insertions(+), 82 deletions(-)
create mode 100644 fs/unicode/unicode-core.c
rename fs/unicode/{utf8-core.c => unicode-utf8.c} (57%)

--
2.30.2


2021-04-07 21:06:34

by Shreeya Patel

[permalink] [raw]
Subject: [PATCH v7 1/4] fs: unicode: Use strscpy() instead of strncpy()

Following warning was reported by Kernel Test Robot.

In function 'utf8_parse_version',
inlined from 'utf8_load' at fs/unicode/utf8mod.c:195:7:
>> fs/unicode/utf8mod.c:175:2: warning: 'strncpy' specified bound 12 equals
destination size [-Wstringop-truncation]
175 | strncpy(version_string, version, sizeof(version_string));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The -Wstringop-truncation warning highlights the unintended
uses of the strncpy function that truncate the terminating NULL
character from the source string.
Unlike strncpy(), strscpy() always null-terminates the destination string,
hence use strscpy() instead of strncpy().

Fixes: 9d53690f0d4e5 (unicode: implement higher level API for string handling)
Acked-by: Gabriel Krisman Bertazi <[email protected]>
Signed-off-by: Shreeya Patel <[email protected]>
Reported-by: kernel test robot <[email protected]>
---
fs/unicode/utf8-core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
index dc25823bfed9..f9e6a2718aba 100644
--- a/fs/unicode/utf8-core.c
+++ b/fs/unicode/utf8-core.c
@@ -179,8 +179,10 @@ static int utf8_parse_version(const char *version, unsigned int *maj,
{1, "%d.%d.%d"},
{0, NULL}
};
+ int ret = strscpy(version_string, version, sizeof(version_string));

- strncpy(version_string, version, sizeof(version_string));
+ if (ret < 0)
+ return ret;

if (match_token(version_string, token, args) != 1)
return -EINVAL;
--
2.30.2

2021-04-07 21:06:35

by Shreeya Patel

[permalink] [raw]
Subject: [PATCH v7 2/4] fs: unicode: Rename function names from utf8 to unicode

utf8data.h_shipped has a large database table which is an auto-generated
decodification trie for the unicode normalization functions and it is not
necessary to carry this large table in the kernel.
Goal is to make UTF-8 encoding loadable by converting it into a module
and adding a unicode subsystem layer between the filesystems and the
utf8 module.

This layer will load the module whenever any filesystem that
needs unicode is mounted.
Currently, only UTF-8 encoding is supported but if any other encodings
are supported in future then the layer file would be responsible for
loading the desired encoding module.

utf8-core will be converted into this layer file in the future patches.
Rename the function names from utf8 to unicode which will denote the
functions as the unicode subsystem layer functions and this will also be
the first step towards the transformation of utf8-core file into the
unicode subsystem layer file.

Signed-off-by: Shreeya Patel <[email protected]>
---
fs/ext4/hash.c | 2 +-
fs/ext4/namei.c | 12 ++++----
fs/ext4/super.c | 6 ++--
fs/f2fs/dir.c | 12 ++++----
fs/f2fs/super.c | 6 ++--
fs/libfs.c | 6 ++--
fs/unicode/utf8-core.c | 57 +++++++++++++++++++-------------------
fs/unicode/utf8-selftest.c | 8 +++---
include/linux/unicode.h | 32 ++++++++++-----------
9 files changed, 70 insertions(+), 71 deletions(-)

diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index a92eb79de0cc..8890a76abe86 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -285,7 +285,7 @@ int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
if (!buff)
return -ENOMEM;

- dlen = utf8_casefold(um, &qstr, buff, PATH_MAX);
+ dlen = unicode_casefold(um, &qstr, buff, PATH_MAX);
if (dlen < 0) {
kfree(buff);
goto opaque_seq;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 686bf982c84e..dde5ce795416 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1290,9 +1290,9 @@ int ext4_ci_compare(const struct inode *parent, const struct qstr *name,
int ret;

if (quick)
- ret = utf8_strncasecmp_folded(um, name, entry);
+ ret = unicode_strncasecmp_folded(um, name, entry);
else
- ret = utf8_strncasecmp(um, name, entry);
+ ret = unicode_strncasecmp(um, name, entry);

if (ret < 0) {
/* Handle invalid character sequence as either an error
@@ -1324,9 +1324,9 @@ void ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
if (!cf_name->name)
return;

- len = utf8_casefold(dir->i_sb->s_encoding,
- iname, cf_name->name,
- EXT4_NAME_LEN);
+ len = unicode_casefold(dir->i_sb->s_encoding,
+ iname, cf_name->name,
+ EXT4_NAME_LEN);
if (len <= 0) {
kfree(cf_name->name);
cf_name->name = NULL;
@@ -2201,7 +2201,7 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,

#ifdef CONFIG_UNICODE
if (sb_has_strict_encoding(sb) && IS_CASEFOLDED(dir) &&
- sb->s_encoding && utf8_validate(sb->s_encoding, &dentry->d_name))
+ sb->s_encoding && unicode_validate(sb->s_encoding, &dentry->d_name))
return -EINVAL;
#endif

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ad34a37278cd..2fb845752c90 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1259,7 +1259,7 @@ static void ext4_put_super(struct super_block *sb)
fs_put_dax(sbi->s_daxdev);
fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy);
#ifdef CONFIG_UNICODE
- utf8_unload(sb->s_encoding);
+ unicode_unload(sb->s_encoding);
#endif
kfree(sbi);
}
@@ -4304,7 +4304,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
goto failed_mount;
}

- encoding = utf8_load(encoding_info->version);
+ encoding = unicode_load(encoding_info->version);
if (IS_ERR(encoding)) {
ext4_msg(sb, KERN_ERR,
"can't mount with superblock charset: %s-%s "
@@ -5165,7 +5165,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
crypto_free_shash(sbi->s_chksum_driver);

#ifdef CONFIG_UNICODE
- utf8_unload(sb->s_encoding);
+ unicode_unload(sb->s_encoding);
#endif

#ifdef CONFIG_QUOTA
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index e6270a867be1..f160f9dd667d 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -84,10 +84,10 @@ int f2fs_init_casefolded_name(const struct inode *dir,
GFP_NOFS);
if (!fname->cf_name.name)
return -ENOMEM;
- fname->cf_name.len = utf8_casefold(sb->s_encoding,
- fname->usr_fname,
- fname->cf_name.name,
- F2FS_NAME_LEN);
+ fname->cf_name.len = unicode_casefold(sb->s_encoding,
+ fname->usr_fname,
+ fname->cf_name.name,
+ F2FS_NAME_LEN);
if ((int)fname->cf_name.len <= 0) {
kfree(fname->cf_name.name);
fname->cf_name.name = NULL;
@@ -237,7 +237,7 @@ static int f2fs_match_ci_name(const struct inode *dir, const struct qstr *name,
entry.len = decrypted_name.len;
}

- res = utf8_strncasecmp_folded(um, name, &entry);
+ res = unicode_strncasecmp_folded(um, name, &entry);
/*
* In strict mode, ignore invalid names. In non-strict mode,
* fall back to treating them as opaque byte sequences.
@@ -246,7 +246,7 @@ static int f2fs_match_ci_name(const struct inode *dir, const struct qstr *name,
res = name->len == entry.len &&
memcmp(name->name, entry.name, name->len) == 0;
} else {
- /* utf8_strncasecmp_folded returns 0 on match */
+ /* unicode_strncasecmp_folded returns 0 on match */
res = (res == 0);
}
out:
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 7069793752f1..b4a92e763e27 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1430,7 +1430,7 @@ static void f2fs_put_super(struct super_block *sb)
for (i = 0; i < NR_PAGE_TYPE; i++)
kvfree(sbi->write_io[i]);
#ifdef CONFIG_UNICODE
- utf8_unload(sb->s_encoding);
+ unicode_unload(sb->s_encoding);
#endif
kfree(sbi);
}
@@ -3560,7 +3560,7 @@ static int f2fs_setup_casefold(struct f2fs_sb_info *sbi)
return -EINVAL;
}

- encoding = utf8_load(encoding_info->version);
+ encoding = unicode_load(encoding_info->version);
if (IS_ERR(encoding)) {
f2fs_err(sbi,
"can't mount with superblock charset: %s-%s "
@@ -4073,7 +4073,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
kvfree(sbi->write_io[i]);

#ifdef CONFIG_UNICODE
- utf8_unload(sb->s_encoding);
+ unicode_unload(sb->s_encoding);
sb->s_encoding = NULL;
#endif
free_options:
diff --git a/fs/libfs.c b/fs/libfs.c
index e2de5401abca..766556165bb5 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1404,7 +1404,7 @@ static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
* If the dentry name is stored in-line, then it may be concurrently
* modified by a rename. If this happens, the VFS will eventually retry
* the lookup, so it doesn't matter what ->d_compare() returns.
- * However, it's unsafe to call utf8_strncasecmp() with an unstable
+ * However, it's unsafe to call unicode_strncasecmp() with an unstable
* string. Therefore, we have to copy the name into a temporary buffer.
*/
if (len <= DNAME_INLINE_LEN - 1) {
@@ -1414,7 +1414,7 @@ static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
/* prevent compiler from optimizing out the temporary buffer */
barrier();
}
- ret = utf8_strncasecmp(um, name, &qstr);
+ ret = unicode_strncasecmp(um, name, &qstr);
if (ret >= 0)
return ret;

@@ -1443,7 +1443,7 @@ static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
if (!dir || !needs_casefold(dir))
return 0;

- ret = utf8_casefold_hash(um, dentry, str);
+ ret = unicode_casefold_hash(um, dentry, str);
if (ret < 0 && sb_has_strict_encoding(sb))
return -EINVAL;
return 0;
diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
index f9e6a2718aba..730dbaedf593 100644
--- a/fs/unicode/utf8-core.c
+++ b/fs/unicode/utf8-core.c
@@ -10,7 +10,7 @@

#include "utf8n.h"

-int utf8_validate(const struct unicode_map *um, const struct qstr *str)
+int unicode_validate(const struct unicode_map *um, const struct qstr *str)
{
const struct utf8data *data = utf8nfdi(um->version);

@@ -18,10 +18,10 @@ int utf8_validate(const struct unicode_map *um, const struct qstr *str)
return -1;
return 0;
}
-EXPORT_SYMBOL(utf8_validate);
+EXPORT_SYMBOL(unicode_validate);

-int utf8_strncmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2)
+int unicode_strncmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2)
{
const struct utf8data *data = utf8nfdi(um->version);
struct utf8cursor cur1, cur2;
@@ -45,10 +45,10 @@ int utf8_strncmp(const struct unicode_map *um,

return 0;
}
-EXPORT_SYMBOL(utf8_strncmp);
+EXPORT_SYMBOL(unicode_strncmp);

-int utf8_strncasecmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2)
+int unicode_strncasecmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2)
{
const struct utf8data *data = utf8nfdicf(um->version);
struct utf8cursor cur1, cur2;
@@ -72,14 +72,14 @@ int utf8_strncasecmp(const struct unicode_map *um,

return 0;
}
-EXPORT_SYMBOL(utf8_strncasecmp);
+EXPORT_SYMBOL(unicode_strncasecmp);

/* String cf is expected to be a valid UTF-8 casefolded
* string.
*/
-int utf8_strncasecmp_folded(const struct unicode_map *um,
- const struct qstr *cf,
- const struct qstr *s1)
+int unicode_strncasecmp_folded(const struct unicode_map *um,
+ const struct qstr *cf,
+ const struct qstr *s1)
{
const struct utf8data *data = utf8nfdicf(um->version);
struct utf8cursor cur1;
@@ -100,10 +100,10 @@ int utf8_strncasecmp_folded(const struct unicode_map *um,

return 0;
}
-EXPORT_SYMBOL(utf8_strncasecmp_folded);
+EXPORT_SYMBOL(unicode_strncasecmp_folded);

-int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen)
+int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen)
{
const struct utf8data *data = utf8nfdicf(um->version);
struct utf8cursor cur;
@@ -123,10 +123,10 @@ int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
}
return -EINVAL;
}
-EXPORT_SYMBOL(utf8_casefold);
+EXPORT_SYMBOL(unicode_casefold);

-int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
- struct qstr *str)
+int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
+ struct qstr *str)
{
const struct utf8data *data = utf8nfdicf(um->version);
struct utf8cursor cur;
@@ -144,10 +144,10 @@ int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
str->hash = end_name_hash(hash);
return 0;
}
-EXPORT_SYMBOL(utf8_casefold_hash);
+EXPORT_SYMBOL(unicode_casefold_hash);

-int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen)
+int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen)
{
const struct utf8data *data = utf8nfdi(um->version);
struct utf8cursor cur;
@@ -167,11 +167,10 @@ int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
}
return -EINVAL;
}
+EXPORT_SYMBOL(unicode_normalize);

-EXPORT_SYMBOL(utf8_normalize);
-
-static int utf8_parse_version(const char *version, unsigned int *maj,
- unsigned int *min, unsigned int *rev)
+static int unicode_parse_version(const char *version, unsigned int *maj,
+ unsigned int *min, unsigned int *rev)
{
substring_t args[3];
char version_string[12];
@@ -194,7 +193,7 @@ static int utf8_parse_version(const char *version, unsigned int *maj,
return 0;
}

-struct unicode_map *utf8_load(const char *version)
+struct unicode_map *unicode_load(const char *version)
{
struct unicode_map *um = NULL;
int unicode_version;
@@ -202,7 +201,7 @@ struct unicode_map *utf8_load(const char *version)
if (version) {
unsigned int maj, min, rev;

- if (utf8_parse_version(version, &maj, &min, &rev) < 0)
+ if (unicode_parse_version(version, &maj, &min, &rev) < 0)
return ERR_PTR(-EINVAL);

if (!utf8version_is_supported(maj, min, rev))
@@ -227,12 +226,12 @@ struct unicode_map *utf8_load(const char *version)

return um;
}
-EXPORT_SYMBOL(utf8_load);
+EXPORT_SYMBOL(unicode_load);

-void utf8_unload(struct unicode_map *um)
+void unicode_unload(struct unicode_map *um)
{
kfree(um);
}
-EXPORT_SYMBOL(utf8_unload);
+EXPORT_SYMBOL(unicode_unload);

MODULE_LICENSE("GPL v2");
diff --git a/fs/unicode/utf8-selftest.c b/fs/unicode/utf8-selftest.c
index 6fe8af7edccb..796c1ed922ea 100644
--- a/fs/unicode/utf8-selftest.c
+++ b/fs/unicode/utf8-selftest.c
@@ -235,7 +235,7 @@ static void check_utf8_nfdicf(void)
static void check_utf8_comparisons(void)
{
int i;
- struct unicode_map *table = utf8_load("12.1.0");
+ struct unicode_map *table = unicode_load("12.1.0");

if (IS_ERR(table)) {
pr_err("%s: Unable to load utf8 %d.%d.%d. Skipping.\n",
@@ -249,7 +249,7 @@ static void check_utf8_comparisons(void)
const struct qstr s2 = {.name = nfdi_test_data[i].dec,
.len = sizeof(nfdi_test_data[i].dec)};

- test_f(!utf8_strncmp(table, &s1, &s2),
+ test_f(!unicode_strncmp(table, &s1, &s2),
"%s %s comparison mismatch\n", s1.name, s2.name);
}

@@ -259,11 +259,11 @@ static void check_utf8_comparisons(void)
const struct qstr s2 = {.name = nfdicf_test_data[i].ncf,
.len = sizeof(nfdicf_test_data[i].ncf)};

- test_f(!utf8_strncasecmp(table, &s1, &s2),
+ test_f(!unicode_strncasecmp(table, &s1, &s2),
"%s %s comparison mismatch\n", s1.name, s2.name);
}

- utf8_unload(table);
+ unicode_unload(table);
}

static void check_supported_versions(void)
diff --git a/include/linux/unicode.h b/include/linux/unicode.h
index 74484d44c755..de23f9ee720b 100644
--- a/include/linux/unicode.h
+++ b/include/linux/unicode.h
@@ -10,27 +10,27 @@ struct unicode_map {
int version;
};

-int utf8_validate(const struct unicode_map *um, const struct qstr *str);
+int unicode_validate(const struct unicode_map *um, const struct qstr *str);

-int utf8_strncmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2);
+int unicode_strncmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2);

-int utf8_strncasecmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2);
-int utf8_strncasecmp_folded(const struct unicode_map *um,
- const struct qstr *cf,
- const struct qstr *s1);
+int unicode_strncasecmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2);
+int unicode_strncasecmp_folded(const struct unicode_map *um,
+ const struct qstr *cf,
+ const struct qstr *s1);

-int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen);
+int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen);

-int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen);
+int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen);

-int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
- struct qstr *str);
+int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
+ struct qstr *str);

-struct unicode_map *utf8_load(const char *version);
-void utf8_unload(struct unicode_map *um);
+struct unicode_map *unicode_load(const char *version);
+void unicode_unload(struct unicode_map *um);

#endif /* _LINUX_UNICODE_H */
--
2.30.2

2021-04-07 21:06:53

by Shreeya Patel

[permalink] [raw]
Subject: [PATCH v7 3/4] fs: unicode: Rename utf8-core file to unicode-core

utf8data.h_shipped has a large database table which is an auto-generated
decodification trie for the unicode normalization functions and it is not
necessary to carry this large table in the kernel.
Goal is to make UTF-8 encoding loadable by converting it into a module
and adding a unicode subsystem layer between the filesystems and the
utf8 module.

This layer will load the module whenever any filesystem that
needs unicode is mounted.
Currently, only UTF-8 encoding is supported but if any other encodings
are supported in future then the layer file would be responsible for
loading the desired encoding module.

Rename the file name from utf8-core to unicode-core for transformation of
utf8-core file into the unicode subsystem layer file and also for better
understanding.
Implementation for unicode-core file to act as layer will be added in the
future patches.

Signed-off-by: Shreeya Patel <[email protected]>
---
fs/unicode/Makefile | 2 +-
fs/unicode/{utf8-core.c => unicode-core.c} | 0
2 files changed, 1 insertion(+), 1 deletion(-)
rename fs/unicode/{utf8-core.c => unicode-core.c} (100%)

diff --git a/fs/unicode/Makefile b/fs/unicode/Makefile
index b88aecc86550..fbf9a629ed0d 100644
--- a/fs/unicode/Makefile
+++ b/fs/unicode/Makefile
@@ -3,7 +3,7 @@
obj-$(CONFIG_UNICODE) += unicode.o
obj-$(CONFIG_UNICODE_NORMALIZATION_SELFTEST) += utf8-selftest.o

-unicode-y := utf8-norm.o utf8-core.o
+unicode-y := utf8-norm.o unicode-core.o

$(obj)/utf8-norm.o: $(obj)/utf8data.h

diff --git a/fs/unicode/utf8-core.c b/fs/unicode/unicode-core.c
similarity index 100%
rename from fs/unicode/utf8-core.c
rename to fs/unicode/unicode-core.c
--
2.30.2

2021-04-07 21:07:07

by Shreeya Patel

[permalink] [raw]
Subject: [PATCH v7 4/4] fs: unicode: Add utf8 module and a unicode layer

utf8data.h_shipped has a large database table which is an auto-generated
decodification trie for the unicode normalization functions.
It is not necessary to load this large table in the kernel if no
filesystem is using it, hence make UTF-8 encoding loadable by converting
it into a module.

Modify the file called unicode-core which will act as a layer for
unicode subsystem. It will load the UTF-8 module and access it's functions
whenever any filesystem that needs unicode is mounted.
Currently, only UTF-8 encoding is supported but if any other encodings
are supported in future then the layer file would be responsible for
loading the desired encoding module.

Also, indirect calls using function pointers are slow, use static calls to
avoid overhead caused in case of repeated indirect calls. Static calls
improves the performance by directly calling the functions as opposed to
indirect calls.

Signed-off-by: Shreeya Patel <[email protected]>
---
Changes in v7
- Update the help text in Kconfig
- Handle the unicode_load_static_call function failure by decrementing
the reference.
- Correct the code for handling built-in utf8 option as well.
- Correct the synchronization for accessing utf8mod.
- Make changes to unicode_unload() for handling the situation where
utf8mod != NULL and um == NULL.

Changes in v6
- Add spinlock to protect utf8mod and avoid NULL pointer
dereference.
- Change the static call function names for being consistent with
kernel coding style.
- Merge the unicode_load_module function with unicode_load as it is
not really needed to have a separate function.
- Use try_then_module_get instead of module_get to avoid loading the
module even when it is already loaded.
- Improve the commit message.

Changes in v5
- Rename global variables and default static call functions for better
understanding
- Make only config UNICODE_UTF8 visible and config UNICODE to be always
enabled provided UNICODE_UTF8 is enabled.
- Improve the documentation for Kconfig
- Improve the commit message.

Changes in v4
- Return error from the static calls instead of doing nothing and
succeeding even without loading the module.
- Remove the complete usage of utf8_ops and use static calls at all
places.
- Restore the static calls to default values when module is unloaded.
- Decrement the reference of module after calling the unload function.
- Remove spinlock as there will be no race conditions after removing
utf8_ops.

Changes in v3
- Add a patch which checks if utf8 is loaded before calling utf8_unload()
in ext4 and f2fs filesystems
- Return error if strscpy() returns value < 0
- Correct the conditions to prevent NULL pointer dereference while
accessing functions via utf8_ops variable.
- Add spinlock to avoid race conditions.
- Use static_call() for preventing speculative execution attacks.

Changes in v2
- Remove the duplicate file from the last patch.
- Make the wrapper functions inline.
- Remove msleep and use try_module_get() and module_put()
for ensuring that module is loaded correctly and also
doesn't get unloaded while in use.
- Resolve the warning reported by kernel test robot.
- Resolve all the checkpatch.pl warnings.

fs/unicode/Kconfig | 26 +++-
fs/unicode/Makefile | 5 +-
fs/unicode/unicode-core.c | 297 ++++++++++++++------------------------
fs/unicode/unicode-utf8.c | 264 +++++++++++++++++++++++++++++++++
include/linux/unicode.h | 96 ++++++++++--
5 files changed, 483 insertions(+), 205 deletions(-)
create mode 100644 fs/unicode/unicode-utf8.c

diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
index 2c27b9a5cd6c..0c69800a2a37 100644
--- a/fs/unicode/Kconfig
+++ b/fs/unicode/Kconfig
@@ -2,13 +2,31 @@
#
# UTF-8 normalization
#
+# CONFIG_UNICODE will be automatically enabled if CONFIG_UNICODE_UTF8
+# is enabled. This config option adds the unicode subsystem layer which loads
+# the UTF-8 module whenever any filesystem needs it.
config UNICODE
- bool "UTF-8 normalization and casefolding support"
+ bool
+
+config UNICODE_UTF8
+ tristate "UTF-8 module"
+ select UNICODE
help
- Say Y here to enable UTF-8 NFD normalization and NFD+CF casefolding
- support.
+ Say M here to enable UTF-8 NFD normalization and NFD+CF casefolding
+ support as a loadable module or say Y for building it into the kernel.
+
+ utf8data.h_shipped has a large database table which is an
+ auto-generated decodification trie for the unicode normalization
+ functions and it is not necessary to carry this large table in the
+ kernel. Hence, enabling UNICODE_UTF8 as M will allow you to avoid
+ carrying this large table into the kernel and module will only be
+ loaded whenever required by any filesystem.
+ Please note, in this case utf8 module will only be available after
+ booting into the compiled kernel. If your filesystem requires it to
+ have utf8 during boot time then you should have it built into the
+ kernel by saying Y here to avoid boot failure.

config UNICODE_NORMALIZATION_SELFTEST
tristate "Test UTF-8 normalization support"
- depends on UNICODE
+ depends on UNICODE_UTF8
default n
diff --git a/fs/unicode/Makefile b/fs/unicode/Makefile
index fbf9a629ed0d..49d50083e6ee 100644
--- a/fs/unicode/Makefile
+++ b/fs/unicode/Makefile
@@ -1,11 +1,14 @@
# SPDX-License-Identifier: GPL-2.0

obj-$(CONFIG_UNICODE) += unicode.o
+obj-$(CONFIG_UNICODE_UTF8) += utf8.o
obj-$(CONFIG_UNICODE_NORMALIZATION_SELFTEST) += utf8-selftest.o

-unicode-y := utf8-norm.o unicode-core.o
+unicode-y := unicode-core.o
+utf8-y := unicode-utf8.o utf8-norm.o

$(obj)/utf8-norm.o: $(obj)/utf8data.h
+$(obj)/unicode-utf8.o: $(obj)/utf8-norm.o

# In the normal build, the checked-in utf8data.h is just shipped.
#
diff --git a/fs/unicode/unicode-core.c b/fs/unicode/unicode-core.c
index 730dbaedf593..d9e9e410893d 100644
--- a/fs/unicode/unicode-core.c
+++ b/fs/unicode/unicode-core.c
@@ -1,228 +1,132 @@
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/module.h>
#include <linux/kernel.h>
-#include <linux/string.h>
#include <linux/slab.h>
-#include <linux/parser.h>
#include <linux/errno.h>
#include <linux/unicode.h>
-#include <linux/stringhash.h>
+#include <linux/spinlock.h>

-#include "utf8n.h"
+DEFINE_SPINLOCK(utf8mod_lock);

-int unicode_validate(const struct unicode_map *um, const struct qstr *str)
-{
- const struct utf8data *data = utf8nfdi(um->version);
+static struct module *utf8mod;
+static bool utf8mod_loaded;

- if (utf8nlen(data, str->name, str->len) < 0)
- return -1;
- return 0;
+int unicode_validate_default(const struct unicode_map *um,
+ const struct qstr *str)
+{
+ WARN_ON(1);
+ return -EIO;
}
-EXPORT_SYMBOL(unicode_validate);
+EXPORT_SYMBOL(unicode_validate_default);

-int unicode_strncmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2)
+int unicode_strncmp_default(const struct unicode_map *um,
+ const struct qstr *s1,
+ const struct qstr *s2)
{
- const struct utf8data *data = utf8nfdi(um->version);
- struct utf8cursor cur1, cur2;
- int c1, c2;
-
- if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
- return -EINVAL;
-
- if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
- return -EINVAL;
-
- do {
- c1 = utf8byte(&cur1);
- c2 = utf8byte(&cur2);
-
- if (c1 < 0 || c2 < 0)
- return -EINVAL;
- if (c1 != c2)
- return 1;
- } while (c1);
-
- return 0;
+ WARN_ON(1);
+ return -EIO;
}
-EXPORT_SYMBOL(unicode_strncmp);
+EXPORT_SYMBOL(unicode_strncmp_default);

-int unicode_strncasecmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2)
+int unicode_strncasecmp_default(const struct unicode_map *um,
+ const struct qstr *s1,
+ const struct qstr *s2)
{
- const struct utf8data *data = utf8nfdicf(um->version);
- struct utf8cursor cur1, cur2;
- int c1, c2;
-
- if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
- return -EINVAL;
-
- if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
- return -EINVAL;
-
- do {
- c1 = utf8byte(&cur1);
- c2 = utf8byte(&cur2);
-
- if (c1 < 0 || c2 < 0)
- return -EINVAL;
- if (c1 != c2)
- return 1;
- } while (c1);
-
- return 0;
+ WARN_ON(1);
+ return -EIO;
}
-EXPORT_SYMBOL(unicode_strncasecmp);
-
-/* String cf is expected to be a valid UTF-8 casefolded
- * string.
- */
-int unicode_strncasecmp_folded(const struct unicode_map *um,
- const struct qstr *cf,
- const struct qstr *s1)
+EXPORT_SYMBOL(unicode_strncasecmp_default);
+
+int unicode_strncasecmp_folded_default(const struct unicode_map *um,
+ const struct qstr *cf,
+ const struct qstr *s1)
{
- const struct utf8data *data = utf8nfdicf(um->version);
- struct utf8cursor cur1;
- int c1, c2;
- int i = 0;
-
- if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
- return -EINVAL;
-
- do {
- c1 = utf8byte(&cur1);
- c2 = cf->name[i++];
- if (c1 < 0)
- return -EINVAL;
- if (c1 != c2)
- return 1;
- } while (c1);
-
- return 0;
+ WARN_ON(1);
+ return -EIO;
}
-EXPORT_SYMBOL(unicode_strncasecmp_folded);
+EXPORT_SYMBOL(unicode_strncasecmp_folded_default);

-int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen)
+int unicode_normalize_default(const struct unicode_map *um,
+ const struct qstr *str,
+ unsigned char *dest, size_t dlen)
{
- const struct utf8data *data = utf8nfdicf(um->version);
- struct utf8cursor cur;
- size_t nlen = 0;
-
- if (utf8ncursor(&cur, data, str->name, str->len) < 0)
- return -EINVAL;
-
- for (nlen = 0; nlen < dlen; nlen++) {
- int c = utf8byte(&cur);
+ WARN_ON(1);
+ return -EIO;
+}
+EXPORT_SYMBOL(unicode_normalize_default);

- dest[nlen] = c;
- if (!c)
- return nlen;
- if (c == -1)
- break;
- }
- return -EINVAL;
+int unicode_casefold_default(const struct unicode_map *um,
+ const struct qstr *str,
+ unsigned char *dest, size_t dlen)
+{
+ WARN_ON(1);
+ return -EIO;
}
-EXPORT_SYMBOL(unicode_casefold);
+EXPORT_SYMBOL(unicode_casefold_default);

-int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
- struct qstr *str)
+int unicode_casefold_hash_default(const struct unicode_map *um,
+ const void *salt, struct qstr *str)
{
- const struct utf8data *data = utf8nfdicf(um->version);
- struct utf8cursor cur;
- int c;
- unsigned long hash = init_name_hash(salt);
-
- if (utf8ncursor(&cur, data, str->name, str->len) < 0)
- return -EINVAL;
-
- while ((c = utf8byte(&cur))) {
- if (c < 0)
- return -EINVAL;
- hash = partial_name_hash((unsigned char)c, hash);
- }
- str->hash = end_name_hash(hash);
- return 0;
+ WARN_ON(1);
+ return -EIO;
}
-EXPORT_SYMBOL(unicode_casefold_hash);
+EXPORT_SYMBOL(unicode_casefold_hash_default);

-int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen)
+struct unicode_map *unicode_load_default(const char *version)
{
- const struct utf8data *data = utf8nfdi(um->version);
- struct utf8cursor cur;
- ssize_t nlen = 0;
+ WARN_ON(1);
+ return ERR_PTR(-EIO);
+}
+EXPORT_SYMBOL(unicode_load_default);

- if (utf8ncursor(&cur, data, str->name, str->len) < 0)
- return -EINVAL;
+DEFINE_STATIC_CALL(unicode_validate_static_call, unicode_validate_default);
+EXPORT_STATIC_CALL(unicode_validate_static_call);

- for (nlen = 0; nlen < dlen; nlen++) {
- int c = utf8byte(&cur);
+DEFINE_STATIC_CALL(unicode_strncmp_static_call, unicode_strncmp_default);
+EXPORT_STATIC_CALL(unicode_strncmp_static_call);

- dest[nlen] = c;
- if (!c)
- return nlen;
- if (c == -1)
- break;
- }
- return -EINVAL;
-}
-EXPORT_SYMBOL(unicode_normalize);
+DEFINE_STATIC_CALL(unicode_strncasecmp_static_call,
+ unicode_strncasecmp_default);
+EXPORT_STATIC_CALL(unicode_strncasecmp_static_call);

-static int unicode_parse_version(const char *version, unsigned int *maj,
- unsigned int *min, unsigned int *rev)
-{
- substring_t args[3];
- char version_string[12];
- static const struct match_token token[] = {
- {1, "%d.%d.%d"},
- {0, NULL}
- };
- int ret = strscpy(version_string, version, sizeof(version_string));
+DEFINE_STATIC_CALL(unicode_strncasecmp_folded_static_call,
+ unicode_strncasecmp_folded_default);
+EXPORT_STATIC_CALL(unicode_strncasecmp_folded_static_call);

- if (ret < 0)
- return ret;
+DEFINE_STATIC_CALL(unicode_normalize_static_call, unicode_normalize_default);
+EXPORT_STATIC_CALL(unicode_normalize_static_call);

- if (match_token(version_string, token, args) != 1)
- return -EINVAL;
+DEFINE_STATIC_CALL(unicode_casefold_static_call, unicode_casefold_default);
+EXPORT_STATIC_CALL(unicode_casefold_static_call);

- if (match_int(&args[0], maj) || match_int(&args[1], min) ||
- match_int(&args[2], rev))
- return -EINVAL;
+DEFINE_STATIC_CALL(unicode_casefold_hash_static_call,
+ unicode_casefold_hash_default);
+EXPORT_STATIC_CALL(unicode_casefold_hash_static_call);

- return 0;
+DEFINE_STATIC_CALL(unicode_load_static_call, unicode_load_default);
+EXPORT_STATIC_CALL(unicode_load_static_call);
+
+static bool utf8mod_get(void)
+{
+ bool ret;
+
+ spin_lock(&utf8mod_lock);
+ ret = utf8mod_loaded && try_module_get(utf8mod);
+ spin_unlock(&utf8mod_lock);
+ return ret;
}

struct unicode_map *unicode_load(const char *version)
{
- struct unicode_map *um = NULL;
- int unicode_version;
-
- if (version) {
- unsigned int maj, min, rev;
-
- if (unicode_parse_version(version, &maj, &min, &rev) < 0)
- return ERR_PTR(-EINVAL);
-
- if (!utf8version_is_supported(maj, min, rev))
- return ERR_PTR(-EINVAL);
-
- unicode_version = UNICODE_AGE(maj, min, rev);
- } else {
- unicode_version = utf8version_latest();
- printk(KERN_WARNING"UTF-8 version not specified. "
- "Assuming latest supported version (%d.%d.%d).",
- (unicode_version >> 16) & 0xff,
- (unicode_version >> 8) & 0xff,
- (unicode_version & 0xff));
- }
+ struct unicode_map *um;

- um = kzalloc(sizeof(struct unicode_map), GFP_KERNEL);
- if (!um)
- return ERR_PTR(-ENOMEM);
-
- um->charset = "UTF-8";
- um->version = unicode_version;
+ if (!try_then_request_module(utf8mod_get(), "utf8")) {
+ pr_err("Failed to load UTF-8 module\n");
+ return ERR_PTR(-ENODEV);
+ }
+ um = static_call(unicode_load_static_call)(version);
+ if (IS_ERR(um))
+ module_put(utf8mod);

return um;
}
@@ -230,8 +134,29 @@ EXPORT_SYMBOL(unicode_load);

void unicode_unload(struct unicode_map *um)
{
- kfree(um);
+ if (um) {
+ kfree(um);
+ module_put(utf8mod);
+ }
}
EXPORT_SYMBOL(unicode_unload);

+void unicode_register(struct module *owner)
+{
+ spin_lock(&utf8mod_lock);
+ utf8mod = owner;
+ utf8mod_loaded = true;
+ spin_unlock(&utf8mod_lock);
+}
+EXPORT_SYMBOL(unicode_register);
+
+void unicode_unregister(void)
+{
+ spin_lock(&utf8mod_lock);
+ utf8mod = NULL;
+ utf8mod_loaded = false;
+ spin_unlock(&utf8mod_lock);
+}
+EXPORT_SYMBOL(unicode_unregister);
+
MODULE_LICENSE("GPL v2");
diff --git a/fs/unicode/unicode-utf8.c b/fs/unicode/unicode-utf8.c
new file mode 100644
index 000000000000..e0180f1c5ea8
--- /dev/null
+++ b/fs/unicode/unicode-utf8.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/parser.h>
+#include <linux/errno.h>
+#include <linux/unicode.h>
+#include <linux/stringhash.h>
+#include <linux/static_call.h>
+
+#include "utf8n.h"
+
+static int utf8_validate(const struct unicode_map *um, const struct qstr *str)
+{
+ const struct utf8data *data = utf8nfdi(um->version);
+
+ if (utf8nlen(data, str->name, str->len) < 0)
+ return -1;
+ return 0;
+}
+
+static int utf8_strncmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2)
+{
+ const struct utf8data *data = utf8nfdi(um->version);
+ struct utf8cursor cur1, cur2;
+ int c1, c2;
+
+ if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
+ return -EINVAL;
+
+ if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
+ return -EINVAL;
+
+ do {
+ c1 = utf8byte(&cur1);
+ c2 = utf8byte(&cur2);
+
+ if (c1 < 0 || c2 < 0)
+ return -EINVAL;
+ if (c1 != c2)
+ return 1;
+ } while (c1);
+
+ return 0;
+}
+
+static int utf8_strncasecmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2)
+{
+ const struct utf8data *data = utf8nfdicf(um->version);
+ struct utf8cursor cur1, cur2;
+ int c1, c2;
+
+ if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
+ return -EINVAL;
+
+ if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
+ return -EINVAL;
+
+ do {
+ c1 = utf8byte(&cur1);
+ c2 = utf8byte(&cur2);
+
+ if (c1 < 0 || c2 < 0)
+ return -EINVAL;
+ if (c1 != c2)
+ return 1;
+ } while (c1);
+
+ return 0;
+}
+
+/* String cf is expected to be a valid UTF-8 casefolded
+ * string.
+ */
+static int utf8_strncasecmp_folded(const struct unicode_map *um,
+ const struct qstr *cf,
+ const struct qstr *s1)
+{
+ const struct utf8data *data = utf8nfdicf(um->version);
+ struct utf8cursor cur1;
+ int c1, c2;
+ int i = 0;
+
+ if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
+ return -EINVAL;
+
+ do {
+ c1 = utf8byte(&cur1);
+ c2 = cf->name[i++];
+ if (c1 < 0)
+ return -EINVAL;
+ if (c1 != c2)
+ return 1;
+ } while (c1);
+
+ return 0;
+}
+
+static int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen)
+{
+ const struct utf8data *data = utf8nfdicf(um->version);
+ struct utf8cursor cur;
+ size_t nlen = 0;
+
+ if (utf8ncursor(&cur, data, str->name, str->len) < 0)
+ return -EINVAL;
+
+ for (nlen = 0; nlen < dlen; nlen++) {
+ int c = utf8byte(&cur);
+
+ dest[nlen] = c;
+ if (!c)
+ return nlen;
+ if (c == -1)
+ break;
+ }
+ return -EINVAL;
+}
+
+static int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
+ struct qstr *str)
+{
+ const struct utf8data *data = utf8nfdicf(um->version);
+ struct utf8cursor cur;
+ int c;
+ unsigned long hash = init_name_hash(salt);
+
+ if (utf8ncursor(&cur, data, str->name, str->len) < 0)
+ return -EINVAL;
+
+ while ((c = utf8byte(&cur))) {
+ if (c < 0)
+ return -EINVAL;
+ hash = partial_name_hash((unsigned char)c, hash);
+ }
+ str->hash = end_name_hash(hash);
+ return 0;
+}
+
+static int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen)
+{
+ const struct utf8data *data = utf8nfdi(um->version);
+ struct utf8cursor cur;
+ ssize_t nlen = 0;
+
+ if (utf8ncursor(&cur, data, str->name, str->len) < 0)
+ return -EINVAL;
+
+ for (nlen = 0; nlen < dlen; nlen++) {
+ int c = utf8byte(&cur);
+
+ dest[nlen] = c;
+ if (!c)
+ return nlen;
+ if (c == -1)
+ break;
+ }
+ return -EINVAL;
+}
+
+static int utf8_parse_version(const char *version, unsigned int *maj,
+ unsigned int *min, unsigned int *rev)
+{
+ substring_t args[3];
+ char version_string[12];
+ static const struct match_token token[] = {
+ {1, "%d.%d.%d"},
+ {0, NULL}
+ };
+
+ int ret = strscpy(version_string, version, sizeof(version_string));
+
+ if (ret < 0)
+ return ret;
+
+ if (match_token(version_string, token, args) != 1)
+ return -EINVAL;
+
+ if (match_int(&args[0], maj) || match_int(&args[1], min) ||
+ match_int(&args[2], rev))
+ return -EINVAL;
+
+ return 0;
+}
+
+static struct unicode_map *utf8_load(const char *version)
+{
+ struct unicode_map *um = NULL;
+ int unicode_version;
+
+ if (version) {
+ unsigned int maj, min, rev;
+
+ if (utf8_parse_version(version, &maj, &min, &rev) < 0)
+ return ERR_PTR(-EINVAL);
+
+ if (!utf8version_is_supported(maj, min, rev))
+ return ERR_PTR(-EINVAL);
+
+ unicode_version = UNICODE_AGE(maj, min, rev);
+ } else {
+ unicode_version = utf8version_latest();
+ pr_warn("UTF-8 version not specified. Assuming latest supported version (%d.%d.%d).",
+ (unicode_version >> 16) & 0xff,
+ (unicode_version >> 8) & 0xff,
+ (unicode_version & 0xfe));
+ }
+
+ um = kzalloc(sizeof(*um), GFP_KERNEL);
+ if (!um)
+ return ERR_PTR(-ENOMEM);
+
+ um->charset = "UTF-8";
+ um->version = unicode_version;
+
+ return um;
+}
+
+static int __init utf8_init(void)
+{
+ static_call_update(unicode_validate_static_call, utf8_validate);
+ static_call_update(unicode_strncmp_static_call, utf8_strncmp);
+ static_call_update(unicode_strncasecmp_static_call, utf8_strncasecmp);
+ static_call_update(unicode_strncasecmp_folded_static_call,
+ utf8_strncasecmp_folded);
+ static_call_update(unicode_normalize_static_call, utf8_normalize);
+ static_call_update(unicode_casefold_static_call, utf8_casefold);
+ static_call_update(unicode_casefold_hash_static_call,
+ utf8_casefold_hash);
+ static_call_update(unicode_load_static_call, utf8_load);
+
+ unicode_register(THIS_MODULE);
+ return 0;
+}
+
+static void __exit utf8_exit(void)
+{
+ static_call_update(unicode_validate_static_call,
+ unicode_validate_default);
+ static_call_update(unicode_strncmp_static_call, unicode_strncmp_default);
+ static_call_update(unicode_strncasecmp_static_call,
+ unicode_strncasecmp_default);
+ static_call_update(unicode_strncasecmp_folded_static_call,
+ unicode_strncasecmp_folded_default);
+ static_call_update(unicode_normalize_static_call,
+ unicode_normalize_default);
+ static_call_update(unicode_casefold_static_call,
+ unicode_casefold_default);
+ static_call_update(unicode_casefold_hash_static_call,
+ unicode_casefold_hash_default);
+ static_call_update(unicode_load_static_call, unicode_load_default);
+
+ unicode_unregister();
+}
+
+module_init(utf8_init);
+module_exit(utf8_exit);
+
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/unicode.h b/include/linux/unicode.h
index de23f9ee720b..0b157c6830c6 100644
--- a/include/linux/unicode.h
+++ b/include/linux/unicode.h
@@ -4,33 +4,101 @@

#include <linux/init.h>
#include <linux/dcache.h>
+#include <linux/static_call.h>
+

struct unicode_map {
const char *charset;
int version;
};

-int unicode_validate(const struct unicode_map *um, const struct qstr *str);
+int unicode_validate_default(const struct unicode_map *um,
+ const struct qstr *str);
+
+int unicode_strncmp_default(const struct unicode_map *um,
+ const struct qstr *s1,
+ const struct qstr *s2);
+
+int unicode_strncasecmp_default(const struct unicode_map *um,
+ const struct qstr *s1,
+ const struct qstr *s2);
+
+int unicode_strncasecmp_folded_default(const struct unicode_map *um,
+ const struct qstr *cf,
+ const struct qstr *s1);
+
+int unicode_normalize_default(const struct unicode_map *um,
+ const struct qstr *str,
+ unsigned char *dest, size_t dlen);
+
+int unicode_casefold_default(const struct unicode_map *um,
+ const struct qstr *str,
+ unsigned char *dest, size_t dlen);
+
+int unicode_casefold_hash_default(const struct unicode_map *um,
+ const void *salt, struct qstr *str);

-int unicode_strncmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2);
+struct unicode_map *unicode_load_default(const char *version);

-int unicode_strncasecmp(const struct unicode_map *um,
- const struct qstr *s1, const struct qstr *s2);
-int unicode_strncasecmp_folded(const struct unicode_map *um,
- const struct qstr *cf,
- const struct qstr *s1);
+DECLARE_STATIC_CALL(unicode_validate_static_call, unicode_validate_default);
+DECLARE_STATIC_CALL(unicode_strncmp_static_call, unicode_strncmp_default);
+DECLARE_STATIC_CALL(unicode_strncasecmp_static_call,
+ unicode_strncasecmp_default);
+DECLARE_STATIC_CALL(unicode_strncasecmp_folded_static_call,
+ unicode_strncasecmp_folded_default);
+DECLARE_STATIC_CALL(unicode_normalize_static_call, unicode_normalize_default);
+DECLARE_STATIC_CALL(unicode_casefold_static_call, unicode_casefold_default);
+DECLARE_STATIC_CALL(unicode_casefold_hash_static_call,
+ unicode_casefold_hash_default);
+DECLARE_STATIC_CALL(unicode_load_static_call, unicode_load_default);

-int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen);

-int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
- unsigned char *dest, size_t dlen);
+static inline int unicode_validate(const struct unicode_map *um, const struct qstr *str)
+{
+ return static_call(unicode_validate_static_call)(um, str);
+}

-int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
- struct qstr *str);
+static inline int unicode_strncmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2)
+{
+ return static_call(unicode_strncmp_static_call)(um, s1, s2);
+}
+
+static inline int unicode_strncasecmp(const struct unicode_map *um,
+ const struct qstr *s1, const struct qstr *s2)
+{
+ return static_call(unicode_strncasecmp_static_call)(um, s1, s2);
+}
+
+static inline int unicode_strncasecmp_folded(const struct unicode_map *um,
+ const struct qstr *cf,
+ const struct qstr *s1)
+{
+ return static_call(unicode_strncasecmp_folded_static_call)(um, cf, s1);
+}
+
+static inline int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen)
+{
+ return static_call(unicode_normalize_static_call)(um, str, dest, dlen);
+}
+
+static inline int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
+ unsigned char *dest, size_t dlen)
+{
+ return static_call(unicode_casefold_static_call)(um, str, dest, dlen);
+}
+
+static inline int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
+ struct qstr *str)
+{
+ return static_call(unicode_casefold_hash_static_call)(um, salt, str);
+}

struct unicode_map *unicode_load(const char *version);
void unicode_unload(struct unicode_map *um);

+void unicode_register(struct module *owner);
+void unicode_unregister(void);
+
#endif /* _LINUX_UNICODE_H */
--
2.30.2

2021-04-08 00:53:00

by Eric Biggers

[permalink] [raw]
Subject: Re: [PATCH v7 1/4] fs: unicode: Use strscpy() instead of strncpy()

On Wed, Apr 07, 2021 at 08:18:42PM +0530, Shreeya Patel wrote:
> The -Wstringop-truncation warning highlights the unintended
> uses of the strncpy function that truncate the terminating NULL
> character from the source string.
> Unlike strncpy(), strscpy() always null-terminates the destination string,
> hence use strscpy() instead of strncpy().

This explanation is a bit misleading. It would be clearer to phrase this in
terms of fixing how overly-long strings are handled: start returning an error
instead of creating a non-null-terminated string.

>
> Fixes: 9d53690f0d4e5 (unicode: implement higher level API for string handling)

There should be quotes around the commit title here.

- Eric

2021-04-08 01:01:45

by Eric Biggers

[permalink] [raw]
Subject: Re: [PATCH v7 4/4] fs: unicode: Add utf8 module and a unicode layer

On Wed, Apr 07, 2021 at 08:18:45PM +0530, Shreeya Patel wrote:
> diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
> index 2c27b9a5cd6c..0c69800a2a37 100644
> --- a/fs/unicode/Kconfig
> +++ b/fs/unicode/Kconfig
> @@ -2,13 +2,31 @@
> #
> # UTF-8 normalization
> #
> +# CONFIG_UNICODE will be automatically enabled if CONFIG_UNICODE_UTF8
> +# is enabled. This config option adds the unicode subsystem layer which loads
> +# the UTF-8 module whenever any filesystem needs it.
> config UNICODE
> - bool "UTF-8 normalization and casefolding support"
> + bool
> +
> +config UNICODE_UTF8
> + tristate "UTF-8 module"
> + select UNICODE
> help
> - Say Y here to enable UTF-8 NFD normalization and NFD+CF casefolding
> - support.
> + Say M here to enable UTF-8 NFD normalization and NFD+CF casefolding
> + support as a loadable module or say Y for building it into the kernel.
> +
> + utf8data.h_shipped has a large database table which is an
> + auto-generated decodification trie for the unicode normalization
> + functions and it is not necessary to carry this large table in the
> + kernel. Hence, enabling UNICODE_UTF8 as M will allow you to avoid
> + carrying this large table into the kernel and module will only be
> + loaded whenever required by any filesystem.
> + Please note, in this case utf8 module will only be available after
> + booting into the compiled kernel. If your filesystem requires it to
> + have utf8 during boot time then you should have it built into the
> + kernel by saying Y here to avoid boot failure.

This help text seems to contradict itself; it says "it is not necessary to carry
this large table in the kernel", and then later it says that in some cases it is
in fact necessary.

It would also be helpful for the help text to mention which filesystems actually
support this feature.

> diff --git a/fs/unicode/unicode-core.c b/fs/unicode/unicode-core.c
> index 730dbaedf593..d9e9e410893d 100644
> --- a/fs/unicode/unicode-core.c
> +++ b/fs/unicode/unicode-core.c
> @@ -1,228 +1,132 @@
> /* SPDX-License-Identifier: GPL-2.0 */
> #include <linux/module.h>
> #include <linux/kernel.h>
> -#include <linux/string.h>
> #include <linux/slab.h>
> -#include <linux/parser.h>
> #include <linux/errno.h>
> #include <linux/unicode.h>
> -#include <linux/stringhash.h>
> +#include <linux/spinlock.h>
>
> -#include "utf8n.h"
> +DEFINE_SPINLOCK(utf8mod_lock);

This spinlock should be 'static'.

- Eric

2021-04-08 19:10:41

by Gabriel Krisman Bertazi

[permalink] [raw]
Subject: Re: [PATCH v7 4/4] fs: unicode: Add utf8 module and a unicode layer

Shreeya Patel <[email protected]> writes:

> utf8data.h_shipped has a large database table which is an auto-generated
> decodification trie for the unicode normalization functions.
> It is not necessary to load this large table in the kernel if no
> filesystem is using it, hence make UTF-8 encoding loadable by converting
> it into a module.
>
> Modify the file called unicode-core which will act as a layer for
> unicode subsystem. It will load the UTF-8 module and access it's functions
> whenever any filesystem that needs unicode is mounted.
> Currently, only UTF-8 encoding is supported but if any other encodings
> are supported in future then the layer file would be responsible for
> loading the desired encoding module.
>
> Also, indirect calls using function pointers are slow, use static calls to
> avoid overhead caused in case of repeated indirect calls. Static calls
> improves the performance by directly calling the functions as opposed to
> indirect calls.
>
> Signed-off-by: Shreeya Patel <[email protected]>
> ---
> Changes in v7
> - Update the help text in Kconfig
> - Handle the unicode_load_static_call function failure by decrementing
> the reference.
> - Correct the code for handling built-in utf8 option as well.
> - Correct the synchronization for accessing utf8mod.
> - Make changes to unicode_unload() for handling the situation where
> utf8mod != NULL and um == NULL.
>
> Changes in v6
> - Add spinlock to protect utf8mod and avoid NULL pointer
> dereference.
> - Change the static call function names for being consistent with
> kernel coding style.
> - Merge the unicode_load_module function with unicode_load as it is
> not really needed to have a separate function.
> - Use try_then_module_get instead of module_get to avoid loading the
> module even when it is already loaded.
> - Improve the commit message.
>
> Changes in v5
> - Rename global variables and default static call functions for better
> understanding
> - Make only config UNICODE_UTF8 visible and config UNICODE to be always
> enabled provided UNICODE_UTF8 is enabled.
> - Improve the documentation for Kconfig
> - Improve the commit message.
>
> Changes in v4
> - Return error from the static calls instead of doing nothing and
> succeeding even without loading the module.
> - Remove the complete usage of utf8_ops and use static calls at all
> places.
> - Restore the static calls to default values when module is unloaded.
> - Decrement the reference of module after calling the unload function.
> - Remove spinlock as there will be no race conditions after removing
> utf8_ops.
>
> Changes in v3
> - Add a patch which checks if utf8 is loaded before calling utf8_unload()
> in ext4 and f2fs filesystems
> - Return error if strscpy() returns value < 0
> - Correct the conditions to prevent NULL pointer dereference while
> accessing functions via utf8_ops variable.
> - Add spinlock to avoid race conditions.
> - Use static_call() for preventing speculative execution attacks.
>
> Changes in v2
> - Remove the duplicate file from the last patch.
> - Make the wrapper functions inline.
> - Remove msleep and use try_module_get() and module_put()
> for ensuring that module is loaded correctly and also
> doesn't get unloaded while in use.
> - Resolve the warning reported by kernel test robot.
> - Resolve all the checkpatch.pl warnings.
>
> fs/unicode/Kconfig | 26 +++-
> fs/unicode/Makefile | 5 +-
> fs/unicode/unicode-core.c | 297 ++++++++++++++------------------------
> fs/unicode/unicode-utf8.c | 264 +++++++++++++++++++++++++++++++++
> include/linux/unicode.h | 96 ++++++++++--
> 5 files changed, 483 insertions(+), 205 deletions(-)
> create mode 100644 fs/unicode/unicode-utf8.c
>
> diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
> index 2c27b9a5cd6c..0c69800a2a37 100644
> --- a/fs/unicode/Kconfig
> +++ b/fs/unicode/Kconfig
> @@ -2,13 +2,31 @@
> #
> # UTF-8 normalization
> #
> +# CONFIG_UNICODE will be automatically enabled if CONFIG_UNICODE_UTF8
> +# is enabled. This config option adds the unicode subsystem layer which loads
> +# the UTF-8 module whenever any filesystem needs it.
> config UNICODE
> - bool "UTF-8 normalization and casefolding support"
> + bool
> +
> +config UNICODE_UTF8
> + tristate "UTF-8 module"

"UTF-8 module" is the text that will appear in menuconfig and other
configuration utilities. This string not very helpful to describe what
this code is about or why it is different from NLS_utf8. People come to
this option looking for the case-insensitive feature in ext4, so I'd
prefer to keep the mention to 'casefolding'. or even improve the
original a bit to say:

tristate: "UTF-8 support for native Case-Insensitive filesystems"

Other than these and what Eric mentioned, the code looks good to me. I
gave this series a try and it seems to work fine.

It does raise a new warning, though

/home/krisman/src/linux/fs/unicode/unicode-core.c: In function ‘unicode_load’:
/home/krisman/src/linux/include/linux/kmod.h:28:8: warning: the omitted middle operand in ‘?:’ will always be ‘true’, suggest explicit middle operand [-Wparentheses]
28 | ((x) ?: (__request_module(true, mod), (x)))
| ^
/home/krisman/src/linux/fs/unicode/unicode-core.c:123:7: note: in expansion of macro ‘try_then_request_module’
123 | if (!try_then_request_module(utf8mod_get(), "utf8")) {

But in this specific case, i think gcc is just being silly. What would
be the right way to avoid it?

--
Gabriel Krisman Bertazi