Re: [resend][PATCH] fs: use kernel's hex_to_bin() method

Andrew Morton
2011-01-04T23:21:14Z

On Fri, 10 Dec 2010 12:55:05 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: linux-fsdevel@vger.kernel.org
> ---
> fs/binfmt_misc.c | 7 +++----
> 1 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
> index 1befe2e..a0fb271 100644
> --- a/fs/binfmt_misc.c
> +++ b/fs/binfmt_misc.c
> @@ -28,6 +28,7 @@
> #include <linux/mount.h>
> #include <linux/syscalls.h>
> #include <linux/fs.h>
> +#include <linux/kernel.h>
>
> #include <asm/uaccess.h>
>
> @@ -244,10 +245,8 @@ static int unquote(char *from)
> while ((c = *s++) != '\0') {
> if (c == '\\' && *s == 'x') {
> s++;
> - c = toupper(*s++);
> - *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
> - c = toupper(*s++);
> - *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
> + *p = hex_to_bin(*s++) << 4;
> + *p++ |= hex_to_bin(*s++);
> continue;
> }
> *p++ = c;

Calling hex_to_bin() twice is a bit sad - we need a library function
which does hex-to-bin on a digit string.

And lo, one just got added in linux-next. However it cruelly didn't
return anything useful, so...

From: Andrew Morton <akpm@linux-foundation.org>

As a convenience to callers.

Not a terribly convenient convenience, as most callers will need to cast
away the constness of the return value. Oh well, those callers should
have been using a `const char *' anyway.

Cc: Mimi Zohar <zohar@us.ibm.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/kernel.h | 2 +-
lib/hexdump.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

diff -puN lib/hexdump.c~lib-hexdumpc-make-hex2bin-return-the-updated-src-address lib/hexdump.c
--- a/lib/hexdump.c~lib-hexdumpc-make-hex2bin-return-the-updated-src-address
+++ a/lib/hexdump.c
@@ -39,13 +39,14 @@ EXPORT_SYMBOL(hex_to_bin);
* @src: ascii hexadecimal string
* @count: result length
*/
-void hex2bin(u8 *dst, const char *src, size_t count)
+const char *hex2bin(u8 *dst, const char *src, size_t count)
{
while (count--) {
*dst = hex_to_bin(*src++) << 4;
*dst += hex_to_bin(*src++);
dst++;
}
+ return src;
}
EXPORT_SYMBOL(hex2bin);

diff -puN include/linux/kernel.h~lib-hexdumpc-make-hex2bin-return-the-updated-src-address include/linux/kernel.h
--- a/include/linux/kernel.h~lib-hexdumpc-make-hex2bin-return-the-updated-src-address
+++ a/include/linux/kernel.h
@@ -278,7 +278,7 @@ static inline char *pack_hex_byte(char *
}

extern int hex_to_bin(char ch);
-extern void hex2bin(u8 *dst, const char *src, size_t count);
+extern const char *hex2bin(u8 *dst, const char *src, size_t count);

/*
* General tracing related utility functions - trace_printk(),
_

After which we can change your patch thusly:

--- a/fs/binfmt_misc.c~fs-binfmt_miscc-use-kernels-hex_to_bin-method-fix
+++ a/fs/binfmt_misc.c
@@ -244,9 +244,7 @@ static int unquote(char *from)

while ((c = *s++) != '\0') {
if (c == '\\' && *s == 'x') {
- s++;
- *p = hex_to_bin(*s++) << 4;
- *p++ |= hex_to_bin(*s++);
+ s = (char *)hex2bin(p, s + 1, 1);
continue;
}
*p++ = c;
_