For the following program:

    #include <linux/interrupt.h>

    // remember t(last-interrupt) on interface
    int kprobe__handle_irq_event_percpu(struct pt_regs *ctx, struct irq_desc *desc) {
        const char *irqname = desc->action->name;

        char c;

        bpf_probe_read(&c, 1, &irqname[0]);
        if (c != 'e') return 0;

        bpf_probe_read(&c, 1, &irqname[1]);
        if (c != 't') return 0;

        ...

LLVM gives warnings because irqaction->name is `const char *`:

    /virtual/main.c:10:27: warning: passing 'const char *' to parameter of type 'void *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
        bpf_probe_read(&c, 1, &irqname[0]);
                              ^~~~~~~~~~~
    /virtual/main.c:13:27: warning: passing 'const char *' to parameter of type 'void *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
        bpf_probe_read(&c, 1, &irqname[1]);
                              ^~~~~~~~~~~
    ...

Instead of adding casts in source everywhere fix bpf_probe_read* signature to
indicate the memory referenced by src won't be modified, as it should be.

P.S.

bpf_probe_read_str was in fact already marked so in several places in comments
but not in actual signature.