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authorKees Cook <keescook@chromium.org>2022-02-10 03:40:41 +0300
committerKees Cook <keescook@chromium.org>2022-02-17 01:30:37 +0300
commit230f6fa2c1db6a3f3e668cfe95995ac8e6eee212 (patch)
tree0efbee5d1df73b95483adf495bb6e2232342fc7d /include/linux/overflow.h
parente1be43d9b5d0d1310dbd90185a8e5c7145dde40f (diff)
downloadlinux-230f6fa2c1db6a3f3e668cfe95995ac8e6eee212.tar.xz
overflow: Provide constant expression struct_size
There have been cases where struct_size() (or flex_array_size()) needs to be calculated for an initializer, which requires it be a constant expression. This is possible when the "count" argument is a constant expression, so provide this ability for the helpers. Cc: Gustavo A. R. Silva <gustavoars@kernel.org> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Tested-by: Gustavo A. R. Silva <gustavoars@kernel.org> Link: https://lore.kernel.org/lkml/20220210010407.GA701603@embeddedor
Diffstat (limited to 'include/linux/overflow.h')
-rw-r--r--include/linux/overflow.h10
1 files changed, 7 insertions, 3 deletions
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 59d7228104d0..f1221d11f8e5 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -4,6 +4,7 @@
#include <linux/compiler.h>
#include <linux/limits.h>
+#include <linux/const.h>
/*
* We need to compute the minimum and maximum values representable in a given
@@ -221,8 +222,9 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
* Return: number of bytes needed or SIZE_MAX on overflow.
*/
#define flex_array_size(p, member, count) \
- size_mul(count, \
- sizeof(*(p)->member) + __must_be_array((p)->member))
+ __builtin_choose_expr(__is_constexpr(count), \
+ (count) * sizeof(*(p)->member) + __must_be_array((p)->member), \
+ size_mul(count, sizeof(*(p)->member) + __must_be_array((p)->member)))
/**
* struct_size() - Calculate size of structure with trailing flexible array.
@@ -237,6 +239,8 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
* Return: number of bytes needed or SIZE_MAX on overflow.
*/
#define struct_size(p, member, count) \
- size_add(sizeof(*(p)), flex_array_size(p, member, count))
+ __builtin_choose_expr(__is_constexpr(count), \
+ sizeof(*(p)) + flex_array_size(p, member, count), \
+ size_add(sizeof(*(p)), flex_array_size(p, member, count)))
#endif /* __LINUX_OVERFLOW_H */