1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021, Oracle and/or its affiliates. */
6 #include <bpf/bpf_helpers.h>
7 #include <bpf/bpf_tracing.h>
8 #include <bpf/bpf_core_read.h>
10 char _license[] SEC("license") = "GPL";
12 unsigned int exception_triggered;
15 /* TRACE_EVENT(task_newtask,
16 * TP_PROTO(struct task_struct *p, u64 clone_flags)
18 SEC("tp_btf/task_newtask")
19 int BPF_PROG(trace_task_newtask, struct task_struct *task, u64 clone_flags)
21 int pid = bpf_get_current_pid_tgid() >> 32;
22 struct callback_head *work;
28 /* To verify we hit an exception we dereference task->task_works->func.
29 * If task work has been added,
30 * - task->task_works is non-NULL; and
31 * - task->task_works->func is non-NULL also (the callback function
32 * must be specified for the task work.
34 * However, for a newly-created task, task->task_works is NULLed,
35 * so we know the exception handler triggered if task_works is
36 * NULL and func is NULL.
38 work = task->task_works;
40 /* Currently verifier will fail for `btf_ptr |= btf_ptr` * instruction.
41 * To workaround the issue, use barrier_var() and rewrite as below to
42 * prevent compiler from generating verifier-unfriendly code.
50 exception_triggered++;