diff options
| author | Przemek Kitszel <przemyslaw.kitszel@intel.com> | 2023-09-12 07:59:31 -0400 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-10-03 12:17:10 -0700 |
| commit | 26dd68d293fd1c5ac966fb5dd5f6d89de322a541 (patch) | |
| tree | c38efdaa9ea3b814df341afd7d7ecdd92bb06036 /include/linux/overflow.h | |
| parent | e643597346c72ebb961ee79ebec34acc042e8ac2 (diff) | |
overflow: add DEFINE_FLEX() for on-stack allocs
Add DEFINE_FLEX() macro for on-stack allocations of structs with
flexible array member.
Expose __struct_size() macro outside of fortify-string.h, as it could be
used to read size of structs allocated by DEFINE_FLEX().
Move __member_size() alongside it.
-Kees
Using underlying array for on-stack storage lets us to declare
known-at-compile-time structures without kzalloc().
Actual usage for ice driver is in following patches of the series.
Missing __has_builtin() workaround is moved up to serve also assembly
compilation with m68k-linux-gcc, see [1].
Error was (note the .S file extension):
In file included from ../include/linux/linkage.h:5,
from ../arch/m68k/fpsp040/skeleton.S:40:
../include/linux/compiler_types.h:331:5: warning: "__has_builtin" is not defined, evaluates to 0 [-Wundef]
331 | #if __has_builtin(__builtin_dynamic_object_size)
| ^~~~~~~~~~~~~
../include/linux/compiler_types.h:331:18: error: missing binary operator before token "("
331 | #if __has_builtin(__builtin_dynamic_object_size)
| ^
[1] https://lore.kernel.org/netdev/202308112122.OuF0YZqL-lkp@intel.com/
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://lore.kernel.org/r/20230912115937.1645707-2-przemyslaw.kitszel@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/linux/overflow.h')
| -rw-r--r-- | include/linux/overflow.h | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/overflow.h b/include/linux/overflow.h index f9b60313eaea..7b5cf4a5cd19 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -309,4 +309,39 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) #define struct_size_t(type, member, count) \ struct_size((type *)NULL, member, count) +/** + * _DEFINE_FLEX() - helper macro for DEFINE_FLEX() family. + * Enables caller macro to pass (different) initializer. + * + * @type: structure type name, including "struct" keyword. + * @name: Name for a variable to define. + * @member: Name of the array member. + * @count: Number of elements in the array; must be compile-time const. + * @initializer: initializer expression (could be empty for no init). + */ +#define _DEFINE_FLEX(type, name, member, count, initializer) \ + _Static_assert(__builtin_constant_p(count), \ + "onstack flex array members require compile-time const count"); \ + union { \ + u8 bytes[struct_size_t(type, member, count)]; \ + type obj; \ + } name##_u initializer; \ + type *name = (type *)&name##_u + +/** + * DEFINE_FLEX() - Define an on-stack instance of structure with a trailing + * flexible array member. + * + * @type: structure type name, including "struct" keyword. + * @name: Name for a variable to define. + * @member: Name of the array member. + * @count: Number of elements in the array; must be compile-time const. + * + * Define a zeroed, on-stack, instance of @type structure with a trailing + * flexible array member. + * Use __struct_size(@name) to get compile-time size of it afterwards. + */ +#define DEFINE_FLEX(type, name, member, count) \ + _DEFINE_FLEX(type, name, member, count, = {}) + #endif /* __LINUX_OVERFLOW_H */ |