(Linux Kernel) Adding new functions in available_filter_functions

Hardware - Raspberry pi 4 Model B 8GB OS - Raspberry pi OS Buster(10)(2020-05-27-raspios-buster-full-armhf.img)(linux kerenl 4.19.y)

I added rpi_get_interrupt_info() and modified show_interrupts() in proc.c

Full code for rpi_get_interrupt_info() and show_interrupts()

void rpi_get_interrupt_info(struct irqaction *action_p)
{
    unsigned int irq_num = action_p->irq;
    void *irq_handler = NULL;
    
    if (action_p->handler) {
        irq_handler = (void*)action_p->handler;
    }

    if (irq_handler) {
        trace_printk("[%s] %d: %s, irq_handler: %pS \n",
                        current->comm, irq_num, action_p->name, irq_handler);
    }
}
    
int show_interrupts(struct seq_file *p, void *v)
{
    static int prec;

    unsigned long flags, any_count = 0;
    int i = *(loff_t *) v, j;
    struct irqaction *action;
    struct irq_desc *desc;

    if (i > ACTUAL_NR_IRQS)
        return 0;

    if (i == ACTUAL_NR_IRQS)
        return arch_show_interrupts(p, prec);

    /* print header and calculate the width of the first column */
    if (i == 0) {
        for (prec = 3, j = 1000; prec < 10 && j <= nr_irqs; ++prec)
            j *= 10;

        seq_printf(p, "%*s", prec + 8, "");
        for_each_online_cpu(j)
            seq_printf(p, "CPU%-8d", j);
        seq_putc(p, '\n');
    }

    rcu_read_lock();
    desc = irq_to_desc(i);
    if (!desc)
        goto outsparse;

    if (desc->kstat_irqs)
        for_each_online_cpu(j)
            any_count |= *per_cpu_ptr(desc->kstat_irqs, j);

    if ((!desc->action || irq_desc_is_chained(desc)) && !any_count)
        goto outsparse;

    seq_printf(p, "%*d: ", prec, i);
    for_each_online_cpu(j)
        seq_printf(p, "%10u ", desc->kstat_irqs ?
                    *per_cpu_ptr(desc->kstat_irqs, j) : 0);

    raw_spin_lock_irqsave(&desc->lock, flags);
    if (desc->irq_data.chip) {
        if (desc->irq_data.chip->irq_print_chip)
            desc->irq_data.chip->irq_print_chip(&desc->irq_data, p);
        else if (desc->irq_data.chip->name)
            seq_printf(p, " %8s", desc->irq_data.chip->name);
        else
            seq_printf(p, " %8s", "-");
    } else {
        seq_printf(p, " %8s", "None");
    }
    if (desc->irq_data.domain)
        seq_printf(p, " %*d", prec, (int) desc->irq_data.hwirq);
    else
        seq_printf(p, " %*s", prec, "");
#ifdef CONFIG_GENERIC_IRQ_SHOW_LEVEL
    seq_printf(p, " %-8s", irqd_is_level_type(&desc->irq_data) ? "Level" : "Edge");
#endif
    if (desc->name)
        seq_printf(p, "-%-8s", desc->name);

    action = desc->action;

    if (action)
        rpi_get_interrupt_info(action);

    if (action) {
        seq_printf(p, "  %s", action->name);
        while ((action = action->next) != NULL)
            seq_printf(p, ", %s", action->name);
    }

    seq_putc(p, '\n');
    raw_spin_unlock_irqrestore(&desc->lock, flags);
outsparse:
    rcu_read_unlock();
    return 0;
}
#endif

Code that I changed

void rpi_get_interrupt_info(struct irqaction *action_p)
{
    unsigned int irq_num = action_p->irq;
    void *irq_handler = NULL;
    
    if (action_p->handler) {
        irq_handler = (void*)action_p->handler;
    }

    if (irq_handler) {
        trace_printk("[%s] %d: %s, irq_handler: %pS \n",
                        current->comm, irq_num, action_p->name, irq_handler);
    }
}

....

if (action)
        rpi_get_interrupt_info(action);

When I try echo rpi_get_interrupt_info > /sys/kernel/debug/tracing/set_ftrace_filter,

an error occurs: echo: write error: Invalid argument

So I looked /sys/kernel/debug/tracing/available_filter_functions, and there's no rpi_get_interrupt_info

I tried noinline void rpi_get_interrupt_info(struct irqaction *action_p), but it doesn't work.

Sorry, I was making some mistakes in configureing bcm2711_defconfig file. Thanks for everyone for trying to help me:)