diff options
Diffstat (limited to 'include/qemu/compiler.h')
| -rw-r--r-- | include/qemu/compiler.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h index 496dac5..65b8995 100644 --- a/include/qemu/compiler.h +++ b/include/qemu/compiler.h @@ -208,6 +208,26 @@ #endif /* + * Disable -ftrivial-auto-var-init on a local variable. + * + * Use this in cases where there a method in the device I/O path (or other + * important hot paths), that has large variables on the stack. A rule of + * thumb is that "large" means a method with 4kb data in the local stack + * frame. Any variables which are KB in size, should be annotated with this + * attribute, to pre-emptively eliminate any potential overhead from the + * compiler's implicit zero'ing of memory. + * + * Given that this turns off a security hardening feature, when using this + * to flag variables, it is important that the code is double-checked to + * ensure there is no possible use of uninitialized data in the method. + */ +#if __has_attribute(uninitialized) +# define QEMU_UNINITIALIZED __attribute__((uninitialized)) +#else +# define QEMU_UNINITIALIZED +#endif + +/* * http://clang.llvm.org/docs/ThreadSafetyAnalysis.html * * TSA is available since clang 3.6-ish. |