// SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2021 Google */ #include "vmlinux.h" #include <bpf/bpf_helpers.h> extern const int bpf_prog_active __ksym; /* int type global var. */ SEC("raw_tp/sys_enter") int handler1(const void *ctx) { int *active; __u32 cpu; cpu = bpf_get_smp_processor_id(); active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu); if (active) { /* Kernel memory obtained from bpf_{per,this}_cpu_ptr * is read-only, should _not_ pass verification. */ /* WRITE_ONCE */ *(volatile int *)active = -1; } return 0; } __noinline int write_active(int *p) { return p ? (*p = 42) : 0; } SEC("raw_tp/sys_enter") int handler2(const void *ctx) { int *active; __u32 cpu; active = bpf_this_cpu_ptr(&bpf_prog_active); write_active(active); return 0; } char _license[] SEC("license") = "GPL";