Question

How to get function’s name from function’s pointer in C?

Edit: The real case is: I’m writing a linux kernel module and I’m calling kernel functions. Some of these functions are pointers and I want to inspect the code of that function in the kernel source. But I don’t know which function it is pointing to. I thought it could be done because, when the system fails (kernel panic) it prints out in the screen the current callstack with function’s names. But, I guess I was wrong… am I?

Answer 1

That’s not directly possible without additional assistance.

You could:

1. maintain a table in your program mapping function pointers to names

2. examine the executable’s symbol table, if it has one.

The latter, however, is hard, and is not portable. The method will depend on the operating system’s binary format (ELF, a.out, .exe, etc), and also on any relocation done by the linker.

EDIT: Since you’ve now explained what your real use case is, the answer is actually not that hard. The kernel symbol table is available in /proc/kallsyms, and there’s an API for accessing it:

#include <linux/kallsyms.h>  const char *kallsyms_lookup(unsigned long addr, unsigned long *symbolsize,                             unsigned long *ofset, char **modname, char *namebuf)  void print_symbol(const char *fmt, unsigned long addr) 

For simple debug purposes the latter will probably do exactly what you need – it takes the address, formats it, and sends it to printk, or you can use printk with the %pF format specifier.