// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Facebook

#include <linux/ptrace.h>
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"

const struct {
        unsigned a[4];
        /*
         * if the struct's size is multiple of 16, compiler will put it into
         * .rodata.cst16 section, which is not recognized by libbpf; work
         * around this by ensuring we don't have 16-aligned struct
         */
        char _y;
} rdonly_values = { .a = {2, 3, 4, 5} };

struct {
        unsigned did_run;
        unsigned iters;
        unsigned sum;
} res = {};

SEC("raw_tracepoint/sys_enter:skip_loop")
int skip_loop(struct pt_regs *ctx)
{
        /* prevent compiler to optimize everything out */
        unsigned * volatile p = (void *)&rdonly_values.a;
        unsigned iters = 0, sum = 0;

        /* we should never enter this loop */
        while (*p & 1) {
                iters++;
                sum += *p;
                p++;
        }
        res.did_run = 1;
        res.iters = iters;
        res.sum = sum;
        return 0;
}

SEC("raw_tracepoint/sys_enter:part_loop")
int part_loop(struct pt_regs *ctx)
{
        /* prevent compiler to optimize everything out */
        unsigned * volatile p = (void *)&rdonly_values.a;
        unsigned iters = 0, sum = 0;

        /* validate verifier can derive loop termination */
        while (*p < 5) {
                iters++;
                sum += *p;
                p++;
        }
        res.did_run = 1;
        res.iters = iters;
        res.sum = sum;
        return 0;
}

SEC("raw_tracepoint/sys_enter:full_loop")
int full_loop(struct pt_regs *ctx)
{
        /* prevent compiler to optimize everything out */
        unsigned * volatile p = (void *)&rdonly_values.a;
        int i = ARRAY_SIZE(rdonly_values.a);
        unsigned iters = 0, sum = 0;

        /* validate verifier can allow full loop as well */
        while (i > 0 ) {
                iters++;
                sum += *p;
                p++;
                i--;
        }
        res.did_run = 1;
        res.iters = iters;
        res.sum = sum;
        return 0;
}

char _license[] SEC("license") = "GPL";