Messages in this thread Patch in this message | | | From | Sergey Senozhatsky <> | Subject | [RFC][PATCH] lib/string: introduce sysfs_strncpy() and sysfs_strlcpy() | Date | Tue, 21 Aug 2018 15:24:59 +0900 |
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In sysfs ->store() callbacks we usually need to remember that a supplied sysfs input string might or might not contain whitespaces and a trailing new-line symbol, which we need to take care of. Examples: echo "newline" > /sys/.../attr echo -n "no_newine" > /sys/.../attr
That's why a typical sysfs ->store() should do something like below when it copies a string:
ssize_t FOO_store(struct device *dev, ....) { .... strlcpy(value, buf, MAX_SZ); sz = strlen(value); if (sz > 0 && value[sz - 1] == '\n') value[sz - 1] = 0x00; ... }
or use a sysfs-string friendly strcmp() function when comparing a given string to a pre-defined one:
ssize_t FOO_store(struct device *dev, ....) { ... if (sysfs_streq(buf, "normal")) mode = m_normal; ... }
Per Andrew Morton: : There's a LOT of code which does basically-the-same-thing with sysfs : input. And a lot of it misses things, such as leading whitespace. : Passing all this through helpers would provide consistency as well : as code-size reductions, improved reviewability, etc.
This patch introduces two such helpers - sysfs_strncpy() and sysfs_strlcpy(), which, basically, do what strncpy() and strlcpy() do, but additionally they remove leading and trailing white-spaces and tailing new-line symbols. So a FOO_store() example which was posted above may be rewritten to:
ssize_t FOO_store(struct device *dev, ....) { .... sysfs_strlcpy(value, buf, MAX_SZ); ... }
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Andrew Morton <akpm@linux-foundation.org> --- include/linux/string.h | 3 +++ lib/string.c | 51 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 54 insertions(+)
diff --git a/include/linux/string.h b/include/linux/string.h index 4a5a0eb7df51..62b08bbc3ada 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -175,6 +175,9 @@ extern char **argv_split(gfp_t gfp, const char *str, int *argcp); extern void argv_free(char **argv); extern bool sysfs_streq(const char *s1, const char *s2); +extern char *sysfs_strncpy(char *dest, const char *src, size_t count); +extern size_t sysfs_strlcpy(char *dest, const char *src, size_t size); + extern int kstrtobool(const char *s, bool *res); static inline int strtobool(const char *s, bool *res) { diff --git a/lib/string.c b/lib/string.c index 2c0900a5d51a..e81b1be00796 100644 --- a/lib/string.c +++ b/lib/string.c @@ -631,6 +631,57 @@ bool sysfs_streq(const char *s1, const char *s2) } EXPORT_SYMBOL(sysfs_streq); +/** + * sysfs_strncpy - Trim a length-limited C-string (wgutesoaces and a trailing + * newline symbol) and copy into a buffer + * @dest: Where to copy the string to + * @src: Where to copy the string from + * @count: The maximum number of bytes to copy + * + * A wrapper around strncpy(). + * + */ +char *sysfs_strncpy(char *dest, const char *src, size_t count) +{ + char *c; + + strncpy(dest, skip_spaces(src), count); + + c = dest + count - 1; + while (c >= dest && (isspace(*c) || *c == '\n' || *c == '\0')) { + *c = '\0'; + c--; + } + return dest; +} +EXPORT_SYMBOL(sysfs_strncpy); + +/** + * sysfs_strlcpy - Trim a C-string (whitespaces and a trailing newline symbol) + * and copy it into a sized buffer + * @dest: Where to copy the string to + * @src: Where to copy the string from + * @size: size of destination buffer + * + * A wrapper around strlcpy(). + * + */ +size_t sysfs_strlcpy(char *dest, const char *src, size_t size) +{ + size_t ret; + char *c; + + ret = strlcpy(dest, skip_spaces(src), size); + + size = strlen(dest); + c = dest + size - 1; + while (c >= dest && (isspace(*c) || *c == '\n')) + c--; + *(c + 1) = '\0'; + return ret; +} +EXPORT_SYMBOL(sysfs_strlcpy); + /** * match_string - matches given string in an array * @array: array of strings -- 2.18.0
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