On Wed, Aug 28, 2024 at 11:03:19AM GMT, Yafang Shao wrote:
> These three functions follow the same pattern. To deduplicate the code,
> let's introduce a common helper __kmemdup_nul().
>
> Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> Cc: Simon Horman <horms@xxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Alejandro Colomar <alx@xxxxxxxxxx>
> ---
Reviewed-by: Alejandro Colomar <alx@xxxxxxxxxx>
Cheers,
Alex
> mm/util.c | 68 ++++++++++++++++++++++---------------------------------
> 1 file changed, 27 insertions(+), 41 deletions(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index 9a77a347c385..42714fe13e24 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -45,33 +45,41 @@ void kfree_const(const void *x)
> EXPORT_SYMBOL(kfree_const);
>
> /**
> - * kstrdup - allocate space for and copy an existing string
> - * @s: the string to duplicate
> + * __kmemdup_nul - Create a NUL-terminated string from @s, which might be unterminated.
> + * @s: The data to copy
> + * @len: The size of the data, not including the NUL terminator
> * @gfp: the GFP mask used in the kmalloc() call when allocating memory
> *
> - * Return: newly allocated copy of @s or %NULL in case of error
> + * Return: newly allocated copy of @s with NUL-termination or %NULL in
> + * case of error
> */
> -noinline
> -char *kstrdup(const char *s, gfp_t gfp)
> +static __always_inline char *__kmemdup_nul(const char *s, size_t len, gfp_t gfp)
> {
> - size_t len;
> char *buf;
>
> - if (!s)
> + /* '+1' for the NUL terminator */
> + buf = kmalloc_track_caller(len + 1, gfp);
> + if (!buf)
> return NULL;
>
> - len = strlen(s) + 1;
> - buf = kmalloc_track_caller(len, gfp);
> - if (buf) {
> - memcpy(buf, s, len);
> - /* During memcpy(), the string might be updated to a new value,
> - * which could be longer than the string when strlen() is
> - * called. Therefore, we need to add a NUL termimator.
> - */
> - buf[len - 1] = '\0';
> - }
> + memcpy(buf, s, len);
> + /* Ensure the buf is always NUL-terminated, regardless of @s. */
> + buf[len] = '\0';
> return buf;
> }
> +
> +/**
> + * kstrdup - allocate space for and copy an existing string
> + * @s: the string to duplicate
> + * @gfp: the GFP mask used in the kmalloc() call when allocating memory
> + *
> + * Return: newly allocated copy of @s or %NULL in case of error
> + */
> +noinline
> +char *kstrdup(const char *s, gfp_t gfp)
> +{
> + return s ? __kmemdup_nul(s, strlen(s), gfp) : NULL;
> +}
> EXPORT_SYMBOL(kstrdup);
>
> /**
> @@ -106,19 +114,7 @@ EXPORT_SYMBOL(kstrdup_const);
> */
> char *kstrndup(const char *s, size_t max, gfp_t gfp)
> {
> - size_t len;
> - char *buf;
> -
> - if (!s)
> - return NULL;
> -
> - len = strnlen(s, max);
> - buf = kmalloc_track_caller(len+1, gfp);
> - if (buf) {
> - memcpy(buf, s, len);
> - buf[len] = '\0';
> - }
> - return buf;
> + return s ? __kmemdup_nul(s, strnlen(s, max), gfp) : NULL;
> }
> EXPORT_SYMBOL(kstrndup);
>
> @@ -192,17 +188,7 @@ EXPORT_SYMBOL(kvmemdup);
> */
> char *kmemdup_nul(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;
> + return s ? __kmemdup_nul(s, len, gfp) : NULL;
> }
> EXPORT_SYMBOL(kmemdup_nul);
>
> --
> 2.43.5
>
--
<https://www.alejandro-colomar.es/>
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