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Message-ID: <20190925203334.GA26832@frodo.byteswizards.com>
Date: Wed, 25 Sep 2019 17:33:34 -0300
From: Carlos Antonio Neira Bustos <cneirabustos@...il.com>
To: Yonghong Song <yhs@...com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
"brouer@...hat.com" <brouer@...hat.com>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v11 4/4] tools/testing/selftests/bpf: Add
self-tests for new helper.
On Wed, Sep 25, 2019 at 04:07:09PM +0000, Yonghong Song wrote:
>
>
> On 9/24/19 8:20 AM, Carlos Neira wrote:
> > Self tests added for new helper
> >
> > Signed-off-by: Carlos Neira <cneirabustos@...il.com>
> > ---
> > tools/testing/selftests/bpf/Makefile | 2 +-
> > tools/testing/selftests/bpf/bpf_helpers.h | 3 +
> > .../selftests/bpf/progs/test_pidns_kern.c | 71 ++++++++
> > tools/testing/selftests/bpf/test_pidns.c | 152 ++++++++++++++++++
> > 4 files changed, 227 insertions(+), 1 deletion(-)
> > create mode 100644 tools/testing/selftests/bpf/progs/test_pidns_kern.c
> > create mode 100644 tools/testing/selftests/bpf/test_pidns.c
> >
> > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > index 7f3196af1ae4..d86b28aa8f44 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -28,7 +28,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
> > test_sock test_btf test_sockmap get_cgroup_id_user test_socket_cookie \
> > test_cgroup_storage test_select_reuseport test_section_names \
> > test_netcnt test_tcpnotify_user test_sock_fields test_sysctl test_hashmap \
> > - test_btf_dump test_cgroup_attach xdping
> > + test_btf_dump test_cgroup_attach xdping test_pidns
>
> Could you fold test_pidns into test_progs?
>
> >
> > BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
> > TEST_GEN_FILES = $(BPF_OBJ_FILES)
> > diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
> > index 6c4930bc6e2e..03d0e15ae29f 100644
> > --- a/tools/testing/selftests/bpf/bpf_helpers.h
> > +++ b/tools/testing/selftests/bpf/bpf_helpers.h
> > @@ -231,6 +231,9 @@ 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 int (*bpf_get_ns_current_pid_tgid)(__u32 dev, __u64 inum) =
> > + (void *) BPF_FUNC_get_ns_current_pid_tgid;
> > +
> >
> > /* 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/progs/test_pidns_kern.c b/tools/testing/selftests/bpf/progs/test_pidns_kern.c
> > new file mode 100644
> > index 000000000000..96cb707db3ee
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_pidns_kern.c
> > @@ -0,0 +1,71 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2018 Carlos Neira cneirabustos@...il.com
>
> 2019
>
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of version 2 of the GNU General Public
> > + * License as published by the Free Software Foundation.
>
> You do not need the above statement, which is covered by
> "SPDX-License-Identifier: GPL-2.0".
>
> > + */
> > +
> > +#include <linux/bpf.h>
> > +#include "bpf_helpers.h"
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_ARRAY);
> > + __uint(max_entries, 1);
> > + __type(key, __u32);
> > + __type(value, __u64);
> > +} ns_inum_map SEC(".maps");
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_ARRAY);
> > + __uint(max_entries, 1);
> > + __type(key, __u32);
> > + __type(value, __u32);
> > +} ns_dev_map SEC(".maps");
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_ARRAY);
> > + __uint(max_entries, 1);
> > + __type(key, __u32);
> > + __type(value, __u32);
> > +} pidmap SEC(".maps");
>
> Can we make the value __u64 to include
> both pid and tid to compare both?
>
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_ARRAY);
> > + __uint(max_entries, 1);
> > + __type(key, __u32);
> > + __type(value, __u64);
> > +} ns_pid_map SEC(".maps");
> > +
> >
>
> The above four one-element maps are perfectly examples
> to use static global variables which are supported
> by the kernel.
>
> You can take a look at the patch
> https://patchwork.ozlabs.org/patch/1081014/
> which shows how user space can modify the map
> values. In the future, we could have a better
> interface to read/update those static variable
> values.
>
> > +
> > +SEC("tracepoint/syscalls/sys_enter_nanosleep")
> > +int trace(void *ctx)
> > +{
> > + __u32 key = 0, *expected_pid, *dev;
>
> expected_pid => __u64 *?
>
> > + __u64 *val, *inum, nspid;
> > + __u32 pid;
> > +
> > + dev = bpf_map_lookup_elem(&ns_dev_map, &key);
> > + if (!dev)
> > + return 0;
> > +
> > + inum = bpf_map_lookup_elem(&ns_inum_map, &key);
> > + if (!inum)
> > + return 0;
> > +
> > + nspid = bpf_get_ns_current_pid_tgid(*dev, *inum);
> > + expected_pid = bpf_map_lookup_elem(&pidmap, &key);
> > +
> > + if (!expected_pid || *expected_pid != nspid)
> > + return 0;
> > +
> > + val = bpf_map_lookup_elem(&ns_pid_map, &key);
> > + if (val)
> > + *val = nspid;
> > +
> > + return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > +__u32 _version SEC("version") = 1;
> > diff --git a/tools/testing/selftests/bpf/test_pidns.c b/tools/testing/selftests/bpf/test_pidns.c
> > new file mode 100644
> > index 000000000000..088f8025f2bf
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/test_pidns.c
> > @@ -0,0 +1,152 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2018 Carlos Neira cneirabustos@...il.com
>
> 2019
>
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of version 2 of the GNU General Public
> > + * License as published by the Free Software Foundation.
>
> ditto. you do not need the above statement.
>
> > + */
> > +
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <syscall.h>
> > +#include <unistd.h>
> > +#include <linux/perf_event.h>
> > +#include <sys/ioctl.h>
> > +#include <sys/time.h>
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +
> > +#include <linux/bpf.h>
> > +#include <bpf/bpf.h>
> > +#include <bpf/libbpf.h>
> > +
> > +#include "cgroup_helpers.h"
> > +#include "bpf_rlimit.h"
> > +
> > +#define CHECK(condition, tag, format...) ({ \
> > + int __ret = !!(condition); \
> > + if (__ret) { \
> > + printf("%s:FAIL:%s ", __func__, tag); \
> > + printf(format); \
> > + } else { \
> > + printf("%s:PASS:%s\n", __func__, tag); \
> > + } \
> > + __ret; \
> > +})
> > +
> > +static int bpf_find_map(const char *test, struct bpf_object *obj,
> > + const char *name)
> > +{
> > + struct bpf_map *map;
> > +
> > + map = bpf_object__find_map_by_name(obj, name);
> > + if (!map)
> > + return -1;
> > + return bpf_map__fd(map);
>
> The 'test' argument is not used here.
> Also, we have bpf_object__find_map_fd_by_name() API, you can
> use it and you do not need this function.
>
> > +}
> > +
> > +
> > +int main(int argc, char **argv)
> > +{
> > + int pidmap_fd, ns_inum_map_fd, ns_dev_map_fd, ns_pid_map_fd;
> > + const char *probe_name = "syscalls/sys_enter_nanosleep";
> > + const char *file = "test_pidns_kern.o";
> > + int err, bytes, efd, prog_fd, pmu_fd;
> > + struct perf_event_attr attr = {};
> > + struct bpf_object *obj;
> > + __u32 nspid = 0;
> > + __u32 key = 0, pid;
> > + int exit_code = 1;
>
> to make it reverse Christmas tree style?
>
> > + struct stat st;
> > + char buf[256];
> > +
> > + err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
> > + if (CHECK(err, "bpf_prog_load", "err %d errno %d\n", err, errno))
> > + goto cleanup_cgroup_env;
> > +
> > + ns_dev_map_fd = bpf_find_map(__func__, obj, "ns_dev_map");
> > + if (CHECK(ns_dev_map_fd < 0, "bpf_find_map", "err %d errno %d\n",
> > + ns_dev_map_fd, errno))
> > + goto close_prog;
> > +
> > + ns_inum_map_fd = bpf_find_map(__func__, obj, "ns_inum_map");
> > + if (CHECK(ns_inum_map_fd < 0, "bpf_find_map", "err %d errno %d\n",
> > + ns_inum_map_fd, errno))
> > + goto close_prog;
> > +
> > + ns_pid_map_fd = bpf_find_map(__func__, obj, "ns_pid_map");
> > + if (CHECK(ns_pid_map_fd < 0, "bpf_find_map", "err %d errno %d\n",
> > + ns_pid_map_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);
>
> maybe
> id = (__u64) getpid() << 32 | gettid();
> bpf_map_update_elem(pidmap_fd, &key, &id, 0);
>
> In your original above kernel code, you actually compare user space pid
> to kernel tid, which is okay for this program as it is the main thread
> and tid == pid, but the mechanism is wrong.
>
> > +
> > + if (stat("/proc/self/ns/pid", &st))
> > + goto close_prog;
> > +
> > + bpf_map_update_elem(ns_inum_map_fd, &key, &st.st_ino, 0);
> > + bpf_map_update_elem(ns_dev_map_fd, &key, &st.st_dev, 0);
> > +
> > +
> > + snprintf(buf, sizeof(buf),
> > + "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> > + efd = open(buf, O_RDONLY, 0);
> > + if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
> > + goto close_prog;
> > + bytes = read(efd, buf, sizeof(buf));
> > + close(efd);
> > + if (CHECK(bytes <= 0 || bytes >= sizeof(buf), "read",
> > + "bytes %d errno %d\n", bytes, errno))
> > + goto close_prog;
> > +
> > + 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(pmu_fd < 0, "perf_event_open", "err %d errno %d\n", pmu_fd,
> > + errno))
> > + goto close_prog;
> > +
> > + err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
> > + if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n", err,
> > + errno))
> > + goto close_pmu;
> > +
> > + err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> > + if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n", err,
> > + errno))
> > + goto close_pmu;
>
> The whole thing above related to tracepoint can be simplified. Please
> see prog_tests/stacktrace_map.c.
>
> > +
> > + /* trigger some syscalls */
> > + sleep(1);
> > +
> > + err = bpf_map_lookup_elem(ns_pid_map_fd, &key, &nspid);
> > + if (CHECK(err, "bpf_map_lookup_elem", "err %d errno %d\n", err, errno))
> > + goto close_pmu;
> > +
> > + if (CHECK(nspid != pid, "compare nspid vs pid",
> > + "kern nspid %u user pid %u", nspid, pid))
> > + goto close_pmu;
> > +
> > + exit_code = 0;
> > + printf("%s:PASS\n", argv[0]);
> > +
> > +close_pmu:
> > + close(pmu_fd);
> > +close_prog:
> > + bpf_object__close(obj);
> > +cleanup_cgroup_env:
> > + return exit_code;
> > +}
> >
Thanks Yonghong,
I'll correct these issues on v12.
Bests
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