From 94ffdde326f507b1d71b42e0b6f92abeeefa8cd2 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 5 Feb 2024 16:48:43 +0100 Subject: [PATCH] Compiler Attributes: Add __uninitialized macro 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 Reviewed-by: Nathan Chancellor Link: https://lore.kernel.org/r/20240205154844.3757121-2-hca@linux.ibm.com Signed-off-by: Heiko Carstens Signed-off-by: Greg Kroah-Hartman --- include/linux/compiler_attributes.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 08eb06301791..3982c2dc541e 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -269,6 +269,18 @@ */ #define __section(section) __attribute__((__section__(section))) +/* + * 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-unused-function-attribute * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute