23316a366e
Commitf269099a7e("tools/bpf: add a selftest for bpf_get_current_cgroup_id() helper") added a test for bpf_get_current_cgroup_id() helper. The bpf program is attached to tracepoint syscalls/sys_enter_nanosleep and will record the cgroup id if the tracepoint is hit. The test program creates a cgroup and attachs itself to this cgroup and expects that the test program process cgroup id is the same as the cgroup_id retrieved by the bpf program. In a light system where no other processes called nanosleep syscall, the test case can pass. In a busy system where many different processes can hit syscalls/sys_enter_nanosleep tracepoint, the cgroup id recorded by bpf program may not match the test program process cgroup_id. This patch fixed an issue by communicating the test program pid to bpf program. The bpf program only records cgroup id if the current task pid is the same as passed-in pid. This ensures that the recorded cgroup_id is for the cgroup within which the test program resides. Fixes:f269099a7e("tools/bpf: add a selftest for bpf_get_current_cgroup_id() helper") Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
41 lines
918 B
C
41 lines
918 B
C
// SPDX-License-Identifier: GPL-2.0
|
|
// Copyright (c) 2018 Facebook
|
|
|
|
#include <linux/bpf.h>
|
|
#include "bpf_helpers.h"
|
|
|
|
struct bpf_map_def SEC("maps") cg_ids = {
|
|
.type = BPF_MAP_TYPE_ARRAY,
|
|
.key_size = sizeof(__u32),
|
|
.value_size = sizeof(__u64),
|
|
.max_entries = 1,
|
|
};
|
|
|
|
struct bpf_map_def SEC("maps") pidmap = {
|
|
.type = BPF_MAP_TYPE_ARRAY,
|
|
.key_size = sizeof(__u32),
|
|
.value_size = sizeof(__u32),
|
|
.max_entries = 1,
|
|
};
|
|
|
|
SEC("tracepoint/syscalls/sys_enter_nanosleep")
|
|
int trace(void *ctx)
|
|
{
|
|
__u32 pid = bpf_get_current_pid_tgid();
|
|
__u32 key = 0, *expected_pid;
|
|
__u64 *val;
|
|
|
|
expected_pid = bpf_map_lookup_elem(&pidmap, &key);
|
|
if (!expected_pid || *expected_pid != pid)
|
|
return 0;
|
|
|
|
val = bpf_map_lookup_elem(&cg_ids, &key);
|
|
if (val)
|
|
*val = bpf_get_current_cgroup_id();
|
|
|
|
return 0;
|
|
}
|
|
|
|
char _license[] SEC("license") = "GPL";
|
|
__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */
|