// SPDX-License-Identifier: GPL-2.0 // Copyright (c) 2019 Facebook #include <linux/ptrace.h> #include <linux/bpf.h> #include <bpf/bpf_helpers.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 = sizeof(rdonly_values.a) / sizeof(rdonly_values.a[0]); 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";