Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH 1/4] Compiler Attributes: Add Clang's __pass_object_size | Date | Tue, 1 Feb 2022 16:30:30 -0800 |
| |
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 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: Miguel Ojeda <ojeda@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Nathan Chancellor <nathan@kernel.org> Cc: llvm@lists.linux.dev Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/compiler_attributes.h | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 37e260020221..cc751e0770f5 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -263,6 +263,17 @@ */ #define __packed __attribute__((__packed__)) +/* + * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size + * + * The "type" argument should match the __builtin_object_size(p, type) usage. + */ +#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 */ -- 2.30.2
| |