[PATCH v12 2/3] eal: add workaround for UBSAN alignment false positive

scott.k.mitch1
2026-01-10T01:57:19Z

From: Scott <scott_mitchell@apple.com>

The optimized __rte_raw_cksum() uses unaligned_uint16_t pointer access
which triggers UBSAN alignment warnings even though the access is safe
due to the unaligned type definition.

Add __rte_no_ubsan_alignment attribute to suppress these false positive
warnings while preserving other UBSAN checks.

Signed-off-by: Scott Mitchell <scott.k.mitch1@gmail.com>
---
lib/eal/include/rte_common.h | 9 +++++++++
lib/net/rte_cksum.h | 1 +
2 files changed, 10 insertions(+)

diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h
index 9e7d84f929..00d428e295 100644
--- a/lib/eal/include/rte_common.h
+++ b/lib/eal/include/rte_common.h
@@ -546,6 +546,15 @@ static void __attribute__((destructor(RTE_PRIO(prio)), used)) func(void)
#define __rte_no_asan
#endif

+/**
+ * Disable UndefinedBehaviorSanitizer alignment check on some code
+ */
+#if defined(RTE_CC_CLANG) || defined(RTE_CC_GCC)
+#define __rte_no_ubsan_alignment __attribute__((no_sanitize("alignment")))
+#else
+#define __rte_no_ubsan_alignment
+#endif
+
/*********** Macros for pointer arithmetic ********/

/**
diff --git a/lib/net/rte_cksum.h b/lib/net/rte_cksum.h
index 8dbe1179e8..9a7fda563d 100644
--- a/lib/net/rte_cksum.h
+++ b/lib/net/rte_cksum.h
@@ -39,6 +39,7 @@ extern "C" {
* @return
* sum += Sum of all words in the buffer.
*/
+__rte_no_ubsan_alignment
static inline uint32_t
__rte_raw_cksum(const void *buf, size_t len, uint32_t sum)
{
--
2.39.5 (Apple Git-154)