From f0202b8ca48cef152d4cdf775f39be6d3b372e1e Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 8 Feb 2022 14:53:44 -0800 Subject: [PATCH] Compiler Attributes: Add __pass_object_size for Clang In order to gain greater visibility to type information when using __builtin_object_size(), Clang has a function attribute "pass_object_size" that will make size information available for marked arguments in a function by way of implicit additional function arguments that are then wired up the __builtin_object_size(). This is needed to implement FORTIFY_SOURCE in Clang, as a workaround to Clang's __builtin_object_size() having limited visibility[1] into types across function calls (even inlines). This attribute has an additional benefit that it can be used even on non-inline functions to gain argument size information. [1] https://github.com/llvm/llvm-project/issues/53516 Cc: Nick Desaulniers Cc: Nathan Chancellor Cc: llvm@lists.linux.dev Reviewed-by: Miguel Ojeda Signed-off-by: Kees Cook Reviewed-by: Nick Desaulniers Link: https://lore.kernel.org/r/20220208225350.1331628-3-keescook@chromium.org --- include/linux/compiler_attributes.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 37e2600..d0c5037 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -264,6 +264,20 @@ #define __packed __attribute__((__packed__)) /* + * Note: the "type" argument should match any __builtin_object_size(p, type) usage. + * + * Optional: not supported by gcc. + * Optional: not supported by icc. + * + * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size + */ +#if __has_attribute(__pass_object_size__) +# define __pass_object_size(type) __attribute__((__pass_object_size__(type))) +#else +# define __pass_object_size(type) +#endif + +/* * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute */ #define __pure __attribute__((__pure__)) -- 2.7.4