From 23316a366e1654e4ad05817c6075bc1019efb30a Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Wed, 6 Jun 2018 09:12:44 -0700 Subject: [PATCH] tools/bpf: fix selftest get_cgroup_id_user Commit f269099a7e7a ("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: f269099a7e7a ("tools/bpf: add a selftest for bpf_get_current_cgroup_id() helper") Signed-off-by: Yonghong Song Signed-off-by: Daniel Borkmann --- tools/testing/selftests/bpf/get_cgroup_id_kern.c | 14 +++++++++++++- tools/testing/selftests/bpf/get_cgroup_id_user.c | 12 ++++++++++-- 2 files changed, 23 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/get_cgroup_id_kern.c b/tools/testing/selftests/bpf/get_cgroup_id_kern.c index 2cf8cb23f209..014dba10b8a5 100644 --- a/tools/testing/selftests/bpf/get_cgroup_id_kern.c +++ b/tools/testing/selftests/bpf/get_cgroup_id_kern.c @@ -11,12 +11,24 @@ struct bpf_map_def SEC("maps") cg_ids = { .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 key = 0; + __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(); diff --git a/tools/testing/selftests/bpf/get_cgroup_id_user.c b/tools/testing/selftests/bpf/get_cgroup_id_user.c index ea19a42e5894..e8da7b39158d 100644 --- a/tools/testing/selftests/bpf/get_cgroup_id_user.c +++ b/tools/testing/selftests/bpf/get_cgroup_id_user.c @@ -50,13 +50,13 @@ int main(int argc, char **argv) const char *probe_name = "syscalls/sys_enter_nanosleep"; const char *file = "get_cgroup_id_kern.o"; int err, bytes, efd, prog_fd, pmu_fd; + int cgroup_fd, cgidmap_fd, pidmap_fd; struct perf_event_attr attr = {}; - int cgroup_fd, cgidmap_fd; struct bpf_object *obj; __u64 kcgid = 0, ucgid; + __u32 key = 0, pid; int exit_code = 1; char buf[256]; - __u32 key = 0; err = setup_cgroup_environment(); if (CHECK(err, "setup_cgroup_environment", "err %d errno %d\n", err, @@ -81,6 +81,14 @@ int main(int argc, char **argv) cgidmap_fd, errno)) goto close_prog; + pidmap_fd = bpf_find_map(__func__, obj, "pidmap"); + if (CHECK(pidmap_fd < 0, "bpf_find_map", "err %d errno %d\n", + pidmap_fd, errno)) + goto close_prog; + + pid = getpid(); + bpf_map_update_elem(pidmap_fd, &key, &pid, 0); + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%s/id", probe_name); efd = open(buf, O_RDONLY, 0); -- 2.30.2