Subject: Re: [PATCH v13 4/4] tools/testing/selftests/bpf: Add self-tests for new helper.

From: Carlos Antonio Neira Bustos <[email-masked]>
Date: Wed, 9 Oct 2019 13:44:04 -0300

On Wed, Oct 09, 2019 at 09:26:32AM -0700, Andrii Nakryiko wrote:
> On Wed, Oct 9, 2019 at 8:29 AM Carlos Neira <[email-masked]> wrote:
> >
> > Self tests added for new helper
> >
> > Signed-off-by: Carlos Neira <[email-masked]>
> > ---
> >  tools/testing/selftests/bpf/bpf_helpers.h     |  4 +
> >  .../bpf/prog_tests/get_ns_current_pid_tgid.c  | 85 +++++++++++++++++++
> >  .../bpf/progs/get_ns_current_pid_tgid_kern.c  | 53 ++++++++++++
> >  3 files changed, 142 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/get_ns_current_pid_tgid.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/get_ns_current_pid_tgid_kern.c
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
> > index 54a50699bbfd..16261b23e011 100644
> > --- a/tools/testing/selftests/bpf/bpf_helpers.h
> > +++ b/tools/testing/selftests/bpf/bpf_helpers.h
> > @@ -233,6 +233,10 @@ static int (*bpf_send_signal)(unsigned sig) = (void *)BPF_FUNC_send_signal;
> >  static long long (*bpf_tcp_gen_syncookie)(struct bpf_sock *sk, void *ip,
> >                                           int ip_len, void *tcp, int tcp_len) =
> >         (void *) BPF_FUNC_tcp_gen_syncookie;
> > +static unsigned long long (*bpf_get_ns_current_pid_tgid)(struct bpf_pidns_info *nsinfo,
> > +               unsigned int buf_size) =
> > +       (void *) BPF_FUNC_get_ns_current_pid_tgid;
> > +
> 
> This is obsolete as of two days ago :) We now generate this
> automatically from the bpf.h's documentation (which is currently
> broken for your helper, I replied on respective patch). So please pull
> latest bpf-next and rebase.
> 
> >
> >  /* llvm builtin functions that eBPF C program may use to
> >   * emit BPF_LD_ABS and BPF_LD_IND instructions
> > diff --git a/tools/testing/selftests/bpf/prog_tests/get_ns_current_pid_tgid.c b/tools/testing/selftests/bpf/prog_tests/get_ns_current_pid_tgid.c
> > new file mode 100644
> > index 000000000000..a7bff0ef6677
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/get_ns_current_pid_tgid.c
> > @@ -0,0 +1,85 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2019 Carlos Neira [email-masked] */
> > +#include <test_progs.h>
> > +#include <sys/stat.h>
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +#include <unistd.h>
> > +#include <sys/syscall.h>
> > +
> > +void test_get_ns_current_pid_tgid(void)
> > +{
> > +       const char *probe_name = "syscalls/sys_enter_nanosleep";
> > +       const char *file = "get_ns_current_pid_tgid_kern.o";
> > +       int ns_data_map_fd, duration = 0;
> > +       struct perf_event_attr attr = {};
> > +       int err, efd, prog_fd, pmu_fd;
> > +       __u64 ino, dev, id, nspid;
> > +       struct bpf_object *obj;
> > +       struct stat st;
> > +       __u32 key = 0;
> > +       char buf[256];
> > +
> > +       err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
> > +       if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
> > +               return;
> > +
> > +       ns_data_map_fd = bpf_find_map(__func__, obj, "ns_data_map");
> > +       if (CHECK_FAIL(ns_data_map_fd < 0))
> > +               goto close_prog;
> > +
> > +       pid_t tid = syscall(SYS_gettid);
> > +       pid_t pid = getpid();
> > +
> > +       id = (__u64) tid << 32 | pid;
> > +       bpf_map_update_elem(ns_data_map_fd, &key, &id, 0);
> > +
> > +       if (stat("/proc/self/ns/pid", &st))
> 
> CHECK() or CHECK_FAIL() ?
> 
> > +               goto close_prog;
> > +
> > +       dev = st.st_dev;
> > +       ino = st.st_ino;
> > +       key = 1;
> > +       bpf_map_update_elem(ns_data_map_fd, &key, &dev, 0);
> > +       key = 2;
> > +       bpf_map_update_elem(ns_data_map_fd, &key, &ino, 0);
> > +
> > +       snprintf(buf, sizeof(buf),
> > +                "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> > +       efd = open(buf, O_RDONLY, 0);
> > +       read(efd, buf, sizeof(buf));
> > +       close(efd);
> > +       attr.config = strtol(buf, NULL, 0);
> > +       attr.type = PERF_TYPE_TRACEPOINT;
> > +       attr.sample_type = PERF_SAMPLE_RAW;
> > +       attr.sample_period = 1;
> > +       attr.wakeup_events = 1;
> > +
> > +       pmu_fd = syscall(__NR_perf_event_open, &attr, getpid(), -1, -1, 0);
> > +       if (CHECK_FAIL(pmu_fd < 0))
> > +               goto cleanup;
> > +
> > +       err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
> > +       if (CHECK_FAIL(err))
> > +               goto cleanup;
> > +
> > +       err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> > +       if (CHECK_FAIL(err))
> > +               goto cleanup;
> 
> 
> All this attaching boilerplate is now obsolete as well, stick to
> bpf_program__attach_tracepoint(). But even better, use RAW_TRACEPOINT.
> 
> > +
> > +       /* trigger some syscalls */
> > +       sleep(1);
> > +       key = 3;
> > +       err = bpf_map_lookup_elem(ns_data_map_fd, &key, &nspid);
> > +       if (CHECK_FAIL(err))
> > +               goto cleanup;
> > +
> > +       if (CHECK(id != nspid, "Compare user pid/tgid vs. bpf pid/tgid",
> > +                 "Userspace pid/tgid %llu EBPF pid/tgid %llu\n", id, nspid))
> > +               goto cleanup;
> > +
> > +cleanup:
> > +       close(pmu_fd);
> > +close_prog:
> > +       bpf_object__close(obj);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/get_ns_current_pid_tgid_kern.c b/tools/testing/selftests/bpf/progs/get_ns_current_pid_tgid_kern.c
> > new file mode 100644
> > index 000000000000..3659aaa7c71f
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/get_ns_current_pid_tgid_kern.c
> > @@ -0,0 +1,53 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2019 Carlos Neira [email-masked] */
> > +
> > +#include <linux/bpf.h>
> > +#include "bpf_helpers.h"
> > +
> > +struct {
> > +       __uint(type, BPF_MAP_TYPE_ARRAY);
> > +       __uint(max_entries, 4);
> > +       __type(key, __u32);
> > +       __type(value, __u64);
> > +} ns_data_map SEC(".maps");
> > +
> > +
> > +SEC("tracepoint/syscalls/sys_enter_nanosleep")
> > +int trace(void *ctx)
> > +{
> > +       __u64 *val, *inum, *dev, nspidtgid, *expected_pid;
> > +       struct bpf_pidns_info nsdata;
> > +       __u32 key = 1;
> > +
> > +       dev = bpf_map_lookup_elem(&ns_data_map, &key);
> > +       if (!dev)
> > +               return 0;
> > +       key = 2;
> > +       inum = bpf_map_lookup_elem(&ns_data_map, &key);
> > +       if (!inum)
> > +               return 0;
> > +
> > +       nsdata.dev = *dev;
> > +       nsdata.inum = *inum;
> > +
> > +       if (bpf_get_ns_current_pid_tgid(&nsdata, sizeof(struct bpf_pidns_info)))
> > +               return 0;
> > +
> > +       nspidtgid = (__u64)nsdata.tgid << 32 | nsdata.pid;
> > +       key = 0;
> > +       expected_pid = bpf_map_lookup_elem(&ns_data_map, &key);
> > +
> > +       if (!expected_pid || *expected_pid != nspidtgid)
> > +               return 0;
> > +
> > +       key = 3;
> > +       val = bpf_map_lookup_elem(&ns_data_map, &key);
> 
> Please, use global data for this, will make this BPF program much
> shorter, cleaner, and up to the point. See recent patch by Daniel T.
> Lee, or some of the tests I added (e.g.,
> progs/test_core_reloc_kernel.c)
> 
> > +
> > +       if (val)
> > +               *val = nspidtgid;
> > +
> > +       return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > +__u32 _version SEC("version") = 1;
> 
> You can drop version now (recent stuff), it's not required by libbpf anymore.
> 
> > --
> > 2.20.1
> >
Thanks for checking this out!, I'll rebase to current bpf-next and
checkout progs/test_core_reloc_kernel.c.

Bests