c - Does kallsyms have all the symbol of kernel functions?

Question

In the Linux kernel I want to probe the kernel function effective_prio(). It defined as static. When I go to search the symbol of it in the kallsyms I cannot find it. Does kallsyms have all the symbol of the kernel functions? If not, which symbols are not included?

Answer 1

There are two possibilities for a function not appearing in /proc/kallsyms:

1. If the function is marked as static, and the compiler decides to inline the function (with or without the inline keyword)

2. If a config option or another #define removes a function from being compiled, e.g.:

   #ifdef CONFIG_OPT
   void foo(void) {
   }
   #endif
   

As far as I know, if a function does not appear in /proc/kallsyms, it is not possible to call or probe it from a module. However, /proc/kallsyms contains all functions of the kernel, not just the ones exported via EXPORT_SYMBOL/EXPORT_SYMBOL_GPL.