diff mbox

[1/9] Provide a function to create a NUL-terminated string from unterminated data

Message ID 149382748241.30481.12971647975706869540.stgit@warthog.procyon.org.uk (mailing list archive)
State New, archived
Headers show

Commit Message

David Howells May 3, 2017, 4:04 p.m. UTC 
Provide a function, kstrcreate(), that will create a NUL-terminated string
from an unterminated character array where the length is known in advance.

This is better than kstrndup() in situations where we already know the
string length as the strnlen() in kstrndup() is superfluous.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/linux/string.h |    1 +
 mm/util.c              |   22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)


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Comments

Jeff Layton May 3, 2017, 4:55 p.m. UTC | #1 
On Wed, 2017-05-03 at 17:04 +0100, David Howells wrote:
> Provide a function, kstrcreate(), that will create a NUL-terminated string
> from an unterminated character array where the length is known in advance.
> 
> This is better than kstrndup() in situations where we already know the
> string length as the strnlen() in kstrndup() is superfluous.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> 
>  include/linux/string.h |    1 +
>  mm/util.c              |   22 ++++++++++++++++++++++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 26b6f6a66f83..5596ae56ce0a 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -122,6 +122,7 @@ extern void kfree_const(const void *x);
>  extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
>  extern const char *kstrdup_const(const char *s, gfp_t gfp);
>  extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
> +extern char *kstrcreate(const char *s, size_t len, gfp_t gfp);
>  extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
>  
>  extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
> diff --git a/mm/util.c b/mm/util.c
> index 656dc5e37a87..01887bbdb11e 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -103,6 +103,28 @@ char *kstrndup(const char *s, size_t max, gfp_t gfp)
>  EXPORT_SYMBOL(kstrndup);
>  
>  /**
> + * kstrcreate - Create a NUL-terminated string from unterminated data
> + * @s: The data to stringify
> + * @len: The size of the data
> + * @gfp: the GFP mask used in the kmalloc() call when allocating memory
> + */
> +char *kstrcreate(const char *s, size_t len, gfp_t gfp)
> +{
> +	char *buf;
> +
> +	if (!s)
> +		return NULL;
> +
> +	buf = kmalloc_track_caller(len + 1, gfp);
> +	if (buf) {
> +		memcpy(buf, s, len);
> +		buf[len] = '\0';
> +	}
> +	return buf;
> +}
> +EXPORT_SYMBOL(kstrcreate);
> +
> +/**
>   * kmemdup - duplicate region of memory
>   *
>   * @src: memory region to duplicate
> 
> 

I haven't gotten to the part where this gets used yet, but it looks like
a nice helper.

Reviewed-by: Jeff Layton <jlayton@poochiereds.net>
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Rasmus Villemoes May 3, 2017, 7:26 p.m. UTC | #2 
On Wed, May 03 2017, David Howells <dhowells@redhat.com> wrote:

> Provide a function, kstrcreate()

<bikeshed>why not kmemdup_nul, since it seems to be to kmemdup exactly as
memdup_user_nul is to memdup_user?</bikeshed> 

Rasmus
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David Howells May 3, 2017, 8:13 p.m. UTC | #3 
Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> > Provide a function, kstrcreate()
> 
> <bikeshed>why not kmemdup_nul, since it seems to be to kmemdup exactly as
> memdup_user_nul is to memdup_user?</bikeshed> 

Yeah, that would work too.  Or kmem2str().

David
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diff mbox

Patch

diff --git a/include/linux/string.h b/include/linux/string.h
index 26b6f6a66f83..5596ae56ce0a 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -122,6 +122,7 @@  extern void kfree_const(const void *x);
 extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
 extern const char *kstrdup_const(const char *s, gfp_t gfp);
 extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
+extern char *kstrcreate(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
 
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
diff --git a/mm/util.c b/mm/util.c
index 656dc5e37a87..01887bbdb11e 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -103,6 +103,28 @@  char *kstrndup(const char *s, size_t max, gfp_t gfp)
 EXPORT_SYMBOL(kstrndup);
 
 /**
+ * kstrcreate - Create a NUL-terminated string from unterminated data
+ * @s: The data to stringify
+ * @len: The size of the data
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ */
+char *kstrcreate(const char *s, size_t len, gfp_t gfp)
+{
+	char *buf;
+
+	if (!s)
+		return NULL;
+
+	buf = kmalloc_track_caller(len + 1, gfp);
+	if (buf) {
+		memcpy(buf, s, len);
+		buf[len] = '\0';
+	}
+	return buf;
+}
+EXPORT_SYMBOL(kstrcreate);
+
+/**
  * kmemdup - duplicate region of memory
  *
  * @src: memory region to duplicate