From: Heiko Carstens <hca@xxxxxxxxxxxxx> commit fd7eea27a3aed79b63b1726c00bde0d50cf207e2 upstream. With INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO enabled the kernel will be compiled with -ftrivial-auto-var-init=<...> which causes initialization of stack variables at function entry time. In order to avoid the performance impact that comes with this users can use the "uninitialized" attribute to prevent such initialization. Therefore provide the __uninitialized macro which can be used for cases where INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO is enabled, but only selected variables should not be initialized. Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx> Link: https://lore.kernel.org/r/20240205154844.3757121-2-hca@xxxxxxxxxxxxx Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/compiler_attributes.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -265,6 +265,18 @@ #define __used __attribute__((__used__)) /* + * Optional: only supported since gcc >= 12 + * + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-uninitialized-variable-attribute + * clang: https://clang.llvm.org/docs/AttributeReference.html#uninitialized + */ +#if __has_attribute(__uninitialized__) +# define __uninitialized __attribute__((__uninitialized__)) +#else +# define __uninitialized +#endif + +/* * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute */ Patches currently in stable-queue which might be from hca@xxxxxxxxxxxxx are queue-5.4/s390-mark-psw-in-__load_psw_mask-as-__unitialized.patch queue-5.4/s390-pkey-wipe-sensitive-data-on-failure.patch queue-5.4/compiler-attributes-add-__uninitialized-macro.patch
