diff options
Diffstat (limited to 'tools/testing/selftests/bpf/progs/task_ls_recursion.c')
-rw-r--r-- | tools/testing/selftests/bpf/progs/task_ls_recursion.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/task_ls_recursion.c b/tools/testing/selftests/bpf/progs/task_ls_recursion.c new file mode 100644 index 000000000000..f1853c38aada --- /dev/null +++ b/tools/testing/selftests/bpf/progs/task_ls_recursion.c @@ -0,0 +1,90 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021 Facebook */ + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +#ifndef EBUSY +#define EBUSY 16 +#endif + +char _license[] SEC("license") = "GPL"; +int nr_del_errs = 0; +int test_pid = 0; + +struct { + __uint(type, BPF_MAP_TYPE_TASK_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, long); +} map_a SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_TASK_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, long); +} map_b SEC(".maps"); + +SEC("fentry/bpf_local_storage_update") +int BPF_PROG(on_update) +{ + struct task_struct *task = bpf_get_current_task_btf(); + long *ptr; + + if (!test_pid || task->pid != test_pid) + return 0; + + ptr = bpf_task_storage_get(&map_a, task, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + /* ptr will not be NULL when it is called from + * the bpf_task_storage_get(&map_b,...F_CREATE) in + * the BPF_PROG(on_enter) below. It is because + * the value can be found in map_a and the kernel + * does not need to acquire any spin_lock. + */ + if (ptr) { + int err; + + *ptr += 1; + err = bpf_task_storage_delete(&map_a, task); + if (err == -EBUSY) + nr_del_errs++; + } + + /* This will still fail because map_b is empty and + * this BPF_PROG(on_update) has failed to acquire + * the percpu busy lock => meaning potential + * deadlock is detected and it will fail to create + * new storage. + */ + ptr = bpf_task_storage_get(&map_b, task, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + if (ptr) + *ptr += 1; + + return 0; +} + +SEC("tp_btf/sys_enter") +int BPF_PROG(on_enter, struct pt_regs *regs, long id) +{ + struct task_struct *task; + long *ptr; + + task = bpf_get_current_task_btf(); + if (!test_pid || task->pid != test_pid) + return 0; + + ptr = bpf_task_storage_get(&map_a, task, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + if (ptr && !*ptr) + *ptr = 200; + + ptr = bpf_task_storage_get(&map_b, task, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + if (ptr && !*ptr) + *ptr = 100; + return 0; +} |