[dpdk-dev v4 1/2] eal: Add mem equal and non-equal to prevent timing attacks memcmp.

[Kai Ji <kai.ji@intel.com>]

Bugzilla ID: 1773
Cc: stable@dpdk.org

[0] https://bugs.dpdk.org/show_bug.cgi?id=1773

Signed-off-by: Kai Ji <kai.ji@intel.com>
---
 lib/eal/include/rte_memory.h | 68 ++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/lib/eal/include/rte_memory.h b/lib/eal/include/rte_memory.h
index dcc0e69cfe..bbdef8e939 100644
--- a/lib/eal/include/rte_memory.h
+++ b/lib/eal/include/rte_memory.h
@@ -746,6 +746,74 @@ __rte_experimental
 void
 rte_memzero_explicit(void *dst, size_t sz);
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Constant-time memory inequality comparison.
+ *
+ * This function compares two memory regions in constant time, making it
+ * resistant to timing side-channel attacks. The execution time depends only
+ * on the length parameter, not on the actual data values being compared.
+ *
+ * This is particularly important for cryptographic operations where timing
+ * differences could leak information about secret keys, passwords, or other
+ * sensitive data.
+ *
+ * @param a
+ *   Pointer to the first memory region to compare
+ * @param b
+ *   Pointer to the second memory region to compare
+ * @param n
+ *   Number of bytes to compare
+ * @return
+ *   false if the memory regions are identical, true if they differ
+ */
+__rte_experimental
+static inline bool
+rte_memneq_consttime(const void *a, const void *b, size_t n)
+{
+	const volatile uint8_t *pa = (const volatile uint8_t *)a;
+	const volatile uint8_t *pb = (const volatile uint8_t *)b;
+	uint8_t result = 0;
+	size_t i;
+
+	for (i = 0; i < n; i++)
+		result |= pa[i] ^ pb[i];
+
+	return result != 0;
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Constant-time memory equality comparison.
+ *
+ * This function compares two memory regions in constant time, making it
+ * resistant to timing side-channel attacks. The execution time depends only
+ * on the length parameter, not on the actual data values being compared.
+ *
+ * This is particularly important for cryptographic operations where timing
+ * differences could leak information about secret keys, passwords, or other
+ * sensitive data.
+ *
+ * @param a
+ *   Pointer to the first memory region to compare
+ * @param b
+ *   Pointer to the second memory region to compare
+ * @param n
+ *   Number of bytes to compare
+ * @return
+ *   true if the memory regions are identical, false if they differ
+ */
+__rte_experimental
+static inline bool
+rte_memeq_consttime(const void *a, const void *b, size_t n)
+{
+	return !rte_memneq_consttime(a, b, n);
+}
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.34.1