From: Scott Mitchell <[email protected]> Add __rte_may_alias attribute to unaligned_uint{16,32,64}_t typedefs to prevent GCC strict-aliasing optimization bugs. GCC has a bug where it incorrectly elides struct initialization when strict aliasing is enabled, causing reads from uninitialized memory.
The __rte_may_alias attribute signals to the compiler that these types can alias other types, preventing the incorrect optimization. Signed-off-by: Scott Mitchell <[email protected]> --- lib/eal/include/rte_common.h | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h index 9e7d84f929..ac70270cfb 100644 --- a/lib/eal/include/rte_common.h +++ b/lib/eal/include/rte_common.h @@ -121,14 +121,27 @@ extern "C" { #define __rte_aligned(a) __attribute__((__aligned__(a))) #endif +/** + * Macro to mark a type that is not subject to type-based aliasing rules + */ +#ifdef RTE_TOOLCHAIN_MSVC +#define __rte_may_alias +#else +#define __rte_may_alias __attribute__((__may_alias__)) +#endif + +/** + * __rte_may_alias avoids compiler bugs (GCC) that elide initialization + * of memory when strict-aliasing is enabled. + */ #ifdef RTE_ARCH_STRICT_ALIGN -typedef uint64_t unaligned_uint64_t __rte_aligned(1); -typedef uint32_t unaligned_uint32_t __rte_aligned(1); -typedef uint16_t unaligned_uint16_t __rte_aligned(1); +typedef uint64_t unaligned_uint64_t __rte_may_alias __rte_aligned(1); +typedef uint32_t unaligned_uint32_t __rte_may_alias __rte_aligned(1); +typedef uint16_t unaligned_uint16_t __rte_may_alias __rte_aligned(1); #else -typedef uint64_t unaligned_uint64_t; -typedef uint32_t unaligned_uint32_t; -typedef uint16_t unaligned_uint16_t; +typedef uint64_t unaligned_uint64_t __rte_may_alias; +typedef uint32_t unaligned_uint32_t __rte_may_alias; +typedef uint16_t unaligned_uint16_t __rte_may_alias; #endif /** @@ -159,15 +172,6 @@ typedef uint16_t unaligned_uint16_t; #define __rte_packed_end __attribute__((__packed__)) #endif -/** - * Macro to mark a type that is not subject to type-based aliasing rules - */ -#ifdef RTE_TOOLCHAIN_MSVC -#define __rte_may_alias -#else -#define __rte_may_alias __attribute__((__may_alias__)) -#endif - /******* Macro to mark functions and fields scheduled for removal *****/ #ifdef RTE_TOOLCHAIN_MSVC #define __rte_deprecated -- 2.39.5 (Apple Git-154)
