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Compiler Attributes: Add __uninitialized macro

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With INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO enabled the kernel will
be compiled with -ftrivial-auto-var-init=<...> which causes initialization
of stack variables at function entry time.

In order to avoid the performance impact that comes with this users can use
the "uninitialized" attribute to prevent such initialization.

Therefore provide the __uninitialized macro which can be used for cases
where INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO is enabled, but only
selected variables should not be initialized.

Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240205154844.3757121-2-hca@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2024-02-05 16:48:43 +01:00
parent 9e99049a80
commit fd7eea27a3
1 changed files with 12 additions and 0 deletions
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12
include/linux/compiler_attributes.h
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@ -333,6 +333,18 @@
*/
#define __section(section) __attribute__((__section__(section)))
/*
* Optional: only supported since gcc >= 12
*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-uninitialized-variable-attribute
* clang: https://clang.llvm.org/docs/AttributeReference.html#uninitialized
*/
#if __has_attribute(__uninitialized__)
# define __uninitialized __attribute__((__uninitialized__))
#else
# define __uninitialized
#endif
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute