linux-kernel - Re: [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data

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Date:   Wed, 03 May 2017 12:55:56 -0400
From:   Jeff Layton <jlayton@...chiereds.net>
To:     David Howells <dhowells@...hat.com>, viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, mszeredi@...hat.com
Subject: Re: [PATCH 1/9] Provide a function to create a NUL-terminated
 string from unterminated data

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@...hat.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@...chiereds.net>