How does "latent_entropy" modify linux kernel functions? So in the linux kernel, we have the following function's method signature in /kernel/fork.c: static __latent_entropy struct task_struct *copy_process( struct pid *pid, int trace, int node, struct kernel_clone_args *args) What kind of C language feature is letting us use the __latent_entropy "attribute" (or what is it?) to modify this function? I'm not necessarily asking in particular what latent_entropy does, since I googled that, I'm more curious about C method signature syntax. I didn't realize you could add extra flags like latent_entropy to a method signature. What kind of language feature is this / what can I google for to understand this better? Thanks.

It’s a macro, which by default is replaced by nothing:


#ifndef __latent_entropy
# define __latent_entropy
#endif


With GCC, in some cases it becomes an attribute instead:


#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
#define __latent_entropy __attribute__((latent_entropy))
#endif


This is used by the GCC entropy plugin.