diff options
Diffstat (limited to 'tools/testing/selftests/bpf/progs/exhandler_kern.c')
-rw-r--r-- | tools/testing/selftests/bpf/progs/exhandler_kern.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/exhandler_kern.c b/tools/testing/selftests/bpf/progs/exhandler_kern.c new file mode 100644 index 0000000000..20d009e2d2 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/exhandler_kern.c @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021, Oracle and/or its affiliates. */ + +#include "vmlinux.h" + +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> +#include <bpf/bpf_core_read.h> + +char _license[] SEC("license") = "GPL"; + +unsigned int exception_triggered; +int test_pid; + +/* TRACE_EVENT(task_newtask, + * TP_PROTO(struct task_struct *p, u64 clone_flags) + */ +SEC("tp_btf/task_newtask") +int BPF_PROG(trace_task_newtask, struct task_struct *task, u64 clone_flags) +{ + int pid = bpf_get_current_pid_tgid() >> 32; + struct callback_head *work; + void *func; + + if (test_pid != pid) + return 0; + + /* To verify we hit an exception we dereference task->task_works->func. + * If task work has been added, + * - task->task_works is non-NULL; and + * - task->task_works->func is non-NULL also (the callback function + * must be specified for the task work. + * + * However, for a newly-created task, task->task_works is NULLed, + * so we know the exception handler triggered if task_works is + * NULL and func is NULL. + */ + work = task->task_works; + func = work->func; + /* Currently verifier will fail for `btf_ptr |= btf_ptr` * instruction. + * To workaround the issue, use barrier_var() and rewrite as below to + * prevent compiler from generating verifier-unfriendly code. + */ + barrier_var(work); + if (work) + return 0; + barrier_var(func); + if (func) + return 0; + exception_triggered++; + return 0; +} |