From 3942bb49728ad9e1f94d953a88af169a8f5d8099 Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula@intel.com>
Date: Wed, 14 Aug 2024 13:00:34 +0300
Subject: [PATCH] string: add mem_is_zero() helper to check if memory area is
all zeros
Almost two thirds of the memchr_inv() usages check if the memory area is
all zeros, with no interest in where in the buffer the first non-zero
byte is located. Checking for !memchr_inv(s, 0, n) is also not very
intuitive or discoverable. Add an explicit mem_is_zero() helper for this
use case.
Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240814100035.3100852-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
include/linux/string.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/include/linux/string.h b/include/linux/string.h
index 9edace076ddbf..5855c5626b4b7 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -279,6 +279,18 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
void *memchr_inv(const void *s, int c, size_t n);
char *strreplace(char *str, char old, char new);
+/**
+ * mem_is_zero - Check if an area of memory is all 0's.
+ * @s: The memory area
+ * @n: The size of the area
+ *
+ * Return: True if the area of memory is all 0's.
+ */
+static inline bool mem_is_zero(const void *s, size_t n)
+{
+ return !memchr_inv(s, 0, n);
+}
+
extern void kfree_const(const void *x);
extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
--
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