lkml.org 
[lkml]   [2022]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/4] Compiler Attributes: Add Clang's __pass_object_size
Date
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
\
 
 \ /
  Last update: 2022-02-02 01:31    [W:0.186 / U:1.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site