How to include C backtrace in a kernel module code?

Question

So I am trying to find out what kernel processes are calling some functions in a block driver. I thought including backtrace() in the C library would make it easy. But I am havi

Answer 1

If you need to save the stack trace and process its elements somehow, save_stack_trace() or dump_trace() might be also an option. These functions are declared in and , respectively.

It is not as easy to use these as dump_stack() but if you need more flexibility, they may be helpful.

Here is how save_stack_trace() can be used (replace HOW_MANY_ENTRIES_TO_STORE with the value that suits your needs, 16-32 is usually more than enough):

unsigned long stack_entries[HOW_MANY_ENTRIES_TO_STORE];
struct stack_trace trace = {
    .nr_entries = 0,
    .entries = &stack_entries[0],

    .max_entries = HOW_MANY_ENTRIES_TO_STORE,

    /* How many "lower entries" to skip. */
    .skip = 0
}; 
save_stack_trace(&trace);

Now stack_entries array contains the appropriate call addresses. The number of elements filled is nr_entries.

One more thing to point out. If it is desirable not to output the stack entries that belong to the implementation of save_stack_trace(), dump_trace() or dump_stack() themselves (on different systems, the number of such entries may vary), the following trick can be applied if you use save_stack_trace(). You can use __builtin_return_address(0) as an "anchor" entry and process only the entries "not lower" than that.