define __compiletime_object_size for include/linux/compiler-clang.h

[nickdesaulniers]

This is defined for GCC but not clang.

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h                                                                                                                                                               
index 04c0a5a717f7..4de31f83b7e7 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -10,6 +10,8 @@
  */
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 
+#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
+
 /* all clang versions usable with the kernel support KASAN ABI version 5 */
 #define KASAN_ABI_VERSION 5

[nickdesaulniers]

I though this might make a difference in stack usage for calls to check_copy_size, but it seems it did not.

[nickdesaulniers]

include/linux/fortify-string.h seems to be using __builtin_object_size open coded but probably should be using __compiletime_object_size I think when the second param is 0. Looks like all compilers support it: https://godbolt.org/z/PM7dKxshc. I think it would be better just to delete __compiletime_object_size seeing as it has only 1 caller:

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 48750243db4c..a5199db5708a 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -41,8 +41,6 @@
 
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 
-#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
-
 #define __compiletime_warning(message) __attribute__((__warning__(message)))
 #define __compiletime_error(message) __attribute__((__error__(message)))
 
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index e5dd5a4ae946..d300415f1f49 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -282,10 +282,6 @@ struct ftrace_likely_data {
        (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
         sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 
-/* Compile time object size, -1 for unknown */
-#ifndef __compiletime_object_size
-# define __compiletime_object_size(obj) -1
-#endif
 #ifndef __compiletime_warning
 # define __compiletime_warning(message)
 #endif
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 157762db9d4b..a8928ae1a65a 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -202,7 +202,7 @@ static inline void copy_overflow(int size, unsigned long count)
 static __always_inline __must_check bool
 check_copy_size(const void *addr, size_t bytes, bool is_source)
 {
-       int sz = __compiletime_object_size(addr);
+       int sz = __builtin_object_size(addr, 0);
        if (unlikely(sz >= 0 && sz < bytes)) {
                if (!__builtin_constant_p(bytes))
                        copy_overflow(sz, bytes);

[kees]

I have, uh, solved this, I guess? :)

[nickdesaulniers]

commit c80d92f ("compiler_types.h: Remove __compiletime_object_size()")

v5.16-rc1