bpf/progs/task_local_storage.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /* Copyright (c) 2021 Facebook */
0003
0004 #include "vmlinux.h"
0005 #include <bpf/bpf_helpers.h>
0006 #include <bpf/bpf_tracing.h>
0007
0008 char _license[] SEC("license") = "GPL";
0009
0010 struct {
0011     __uint(type, BPF_MAP_TYPE_TASK_STORAGE);
0012     __uint(map_flags, BPF_F_NO_PREALLOC);
0013     __type(key, int);
0014     __type(value, long);
0015 } enter_id SEC(".maps");
0016
0017 #define MAGIC_VALUE 0xabcd1234
0018
0019 pid_t target_pid = 0;
0020 int mismatch_cnt = 0;
0021 int enter_cnt = 0;
0022 int exit_cnt = 0;
0023
0024 SEC("tp_btf/sys_enter")
0025 int BPF_PROG(on_enter, struct pt_regs *regs, long id)
0026 {
0027     struct task_struct *task;
0028     long *ptr;
0029
0030     task = bpf_get_current_task_btf();
0031     if (task->pid != target_pid)
0032         return 0;
0033
0034     ptr = bpf_task_storage_get(&enter_id, task, 0,
0035                    BPF_LOCAL_STORAGE_GET_F_CREATE);
0036     if (!ptr)
0037         return 0;
0038
0039     __sync_fetch_and_add(&enter_cnt, 1);
0040     *ptr = MAGIC_VALUE + enter_cnt;
0041
0042     return 0;
0043 }
0044
0045 SEC("tp_btf/sys_exit")
0046 int BPF_PROG(on_exit, struct pt_regs *regs, long id)
0047 {
0048     struct task_struct *task;
0049     long *ptr;
0050
0051     task = bpf_get_current_task_btf();
0052     if (task->pid != target_pid)
0053         return 0;
0054
0055     ptr = bpf_task_storage_get(&enter_id, task, 0,
0056                    BPF_LOCAL_STORAGE_GET_F_CREATE);
0057     if (!ptr)
0058         return 0;
0059
0060     __sync_fetch_and_add(&exit_cnt, 1);
0061     if (*ptr != MAGIC_VALUE + exit_cnt)
0062         __sync_fetch_and_add(&mismatch_cnt, 1);
0063     return 0;
0064 }