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    Subject[PATCH bpf-next v9 2/5] selftests/bpf: Test cgroup_iter.
    From
    Add a selftest for cgroup_iter. The selftest creates a mini cgroup tree
    of the following structure:

    ROOT (working cgroup)
    |
    PARENT
    / \
    CHILD1 CHILD2

    and tests the following scenarios:

    - invalid cgroup fd.
    - pre-order walk over descendants from PARENT.
    - post-order walk over descendants from PARENT.
    - walk of ancestors from PARENT.
    - process only a single object (i.e. PARENT).
    - early termination.

    Acked-by: Yonghong Song <yhs@fb.com>
    Acked-by: Andrii Nakryiko <andrii@kernel.org>
    Signed-off-by: Hao Luo <haoluo@google.com>
    ---
    .../selftests/bpf/prog_tests/btf_dump.c | 2 +-
    .../selftests/bpf/prog_tests/cgroup_iter.c | 224 ++++++++++++++++++
    tools/testing/selftests/bpf/progs/bpf_iter.h | 7 +
    .../testing/selftests/bpf/progs/cgroup_iter.c | 39 +++
    4 files changed, 271 insertions(+), 1 deletion(-)
    create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
    create mode 100644 tools/testing/selftests/bpf/progs/cgroup_iter.c

    diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
    index 84c1cfaa2b02..a1bae92be1fc 100644
    --- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c
    +++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
    @@ -764,7 +764,7 @@ static void test_btf_dump_struct_data(struct btf *btf, struct btf_dump *d,

    /* union with nested struct */
    TEST_BTF_DUMP_DATA(btf, d, "union", str, union bpf_iter_link_info, BTF_F_COMPACT,
    - "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},.cgroup = (struct){.order = (__u32)1,.cgroup_fd = (__u32)1,},}",
    + "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},.cgroup = (struct){.order = (enum bpf_cgroup_iter_order)BPF_ITER_SELF_ONLY,.cgroup_fd = (__u32)1,},}",
    { .cgroup = { .order = 1, .cgroup_fd = 1, }});

    /* struct skb with nested structs/unions; because type output is so
    diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
    new file mode 100644
    index 000000000000..38958c37b9ce
    --- /dev/null
    +++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
    @@ -0,0 +1,224 @@
    +// SPDX-License-Identifier: GPL-2.0
    +/* Copyright (c) 2022 Google */
    +
    +#include <test_progs.h>
    +#include <bpf/libbpf.h>
    +#include <bpf/btf.h>
    +#include "cgroup_iter.skel.h"
    +#include "cgroup_helpers.h"
    +
    +#define ROOT 0
    +#define PARENT 1
    +#define CHILD1 2
    +#define CHILD2 3
    +#define NUM_CGROUPS 4
    +
    +#define PROLOGUE "prologue\n"
    +#define EPILOGUE "epilogue\n"
    +
    +static const char *cg_path[] = {
    + "/", "/parent", "/parent/child1", "/parent/child2"
    +};
    +
    +static int cg_fd[] = {-1, -1, -1, -1};
    +static unsigned long long cg_id[] = {0, 0, 0, 0};
    +static char expected_output[64];
    +
    +static int setup_cgroups(void)
    +{
    + int fd, i = 0;
    +
    + for (i = 0; i < NUM_CGROUPS; i++) {
    + fd = create_and_get_cgroup(cg_path[i]);
    + if (fd < 0)
    + return fd;
    +
    + cg_fd[i] = fd;
    + cg_id[i] = get_cgroup_id(cg_path[i]);
    + }
    + return 0;
    +}
    +
    +static void cleanup_cgroups(void)
    +{
    + int i;
    +
    + for (i = 0; i < NUM_CGROUPS; i++)
    + close(cg_fd[i]);
    +}
    +
    +static void read_from_cgroup_iter(struct bpf_program *prog, int cgroup_fd,
    + int order, const char *testname)
    +{
    + DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
    + union bpf_iter_link_info linfo;
    + struct bpf_link *link;
    + int len, iter_fd;
    + static char buf[128];
    + size_t left;
    + char *p;
    +
    + memset(&linfo, 0, sizeof(linfo));
    + linfo.cgroup.cgroup_fd = cgroup_fd;
    + linfo.cgroup.order = order;
    + opts.link_info = &linfo;
    + opts.link_info_len = sizeof(linfo);
    +
    + link = bpf_program__attach_iter(prog, &opts);
    + if (!ASSERT_OK_PTR(link, "attach_iter"))
    + return;
    +
    + iter_fd = bpf_iter_create(bpf_link__fd(link));
    + if (iter_fd < 0)
    + goto free_link;
    +
    + memset(buf, 0, sizeof(buf));
    + left = ARRAY_SIZE(buf);
    + p = buf;
    + while ((len = read(iter_fd, p, left)) > 0) {
    + p += len;
    + left -= len;
    + }
    +
    + ASSERT_STREQ(buf, expected_output, testname);
    +
    + /* read() after iter finishes should be ok. */
    + if (len == 0)
    + ASSERT_OK(read(iter_fd, buf, sizeof(buf)), "second_read");
    +
    + close(iter_fd);
    +free_link:
    + bpf_link__destroy(link);
    +}
    +
    +/* Invalid cgroup. */
    +static void test_invalid_cgroup(struct cgroup_iter *skel)
    +{
    + DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
    + union bpf_iter_link_info linfo;
    + struct bpf_link *link;
    +
    + memset(&linfo, 0, sizeof(linfo));
    + linfo.cgroup.cgroup_fd = (__u32)-1;
    + opts.link_info = &linfo;
    + opts.link_info_len = sizeof(linfo);
    +
    + link = bpf_program__attach_iter(skel->progs.cgroup_id_printer, &opts);
    + ASSERT_ERR_PTR(link, "attach_iter");
    + bpf_link__destroy(link);
    +}
    +
    +/* Specifying both cgroup_fd and cgroup_id is invalid. */
    +static void test_invalid_cgroup_spec(struct cgroup_iter *skel)
    +{
    + DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
    + union bpf_iter_link_info linfo;
    + struct bpf_link *link;
    +
    + memset(&linfo, 0, sizeof(linfo));
    + linfo.cgroup.cgroup_fd = (__u32)cg_fd[PARENT];
    + linfo.cgroup.cgroup_id = (__u64)cg_id[PARENT];
    + opts.link_info = &linfo;
    + opts.link_info_len = sizeof(linfo);
    +
    + link = bpf_program__attach_iter(skel->progs.cgroup_id_printer, &opts);
    + ASSERT_ERR_PTR(link, "attach_iter");
    + bpf_link__destroy(link);
    +}
    +
    +/* Preorder walk prints parent and child in order. */
    +static void test_walk_preorder(struct cgroup_iter *skel)
    +{
    + snprintf(expected_output, sizeof(expected_output),
    + PROLOGUE "%8llu\n%8llu\n%8llu\n" EPILOGUE,
    + cg_id[PARENT], cg_id[CHILD1], cg_id[CHILD2]);
    +
    + read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
    + BPF_ITER_DESCENDANTS_PRE, "preorder");
    +}
    +
    +/* Postorder walk prints child and parent in order. */
    +static void test_walk_postorder(struct cgroup_iter *skel)
    +{
    + snprintf(expected_output, sizeof(expected_output),
    + PROLOGUE "%8llu\n%8llu\n%8llu\n" EPILOGUE,
    + cg_id[CHILD1], cg_id[CHILD2], cg_id[PARENT]);
    +
    + read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
    + BPF_ITER_DESCENDANTS_POST, "postorder");
    +}
    +
    +/* Walking parents prints parent and then root. */
    +static void test_walk_ancestors_up(struct cgroup_iter *skel)
    +{
    + /* terminate the walk when ROOT is met. */
    + skel->bss->terminal_cgroup = cg_id[ROOT];
    +
    + snprintf(expected_output, sizeof(expected_output),
    + PROLOGUE "%8llu\n%8llu\n" EPILOGUE,
    + cg_id[PARENT], cg_id[ROOT]);
    +
    + read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
    + BPF_ITER_ANCESTORS_UP, "ancestors_up");
    +
    + skel->bss->terminal_cgroup = 0;
    +}
    +
    +/* Early termination prints parent only. */
    +static void test_early_termination(struct cgroup_iter *skel)
    +{
    + /* terminate the walk after the first element is processed. */
    + skel->bss->terminate_early = 1;
    +
    + snprintf(expected_output, sizeof(expected_output),
    + PROLOGUE "%8llu\n" EPILOGUE, cg_id[PARENT]);
    +
    + read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
    + BPF_ITER_DESCENDANTS_PRE, "early_termination");
    +
    + skel->bss->terminate_early = 0;
    +}
    +
    +/* Waling self prints self only. */
    +static void test_walk_self_only(struct cgroup_iter *skel)
    +{
    + snprintf(expected_output, sizeof(expected_output),
    + PROLOGUE "%8llu\n" EPILOGUE, cg_id[PARENT]);
    +
    + read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
    + BPF_ITER_SELF_ONLY, "self_only");
    +}
    +
    +void test_cgroup_iter(void)
    +{
    + struct cgroup_iter *skel = NULL;
    +
    + if (setup_cgroup_environment())
    + return;
    +
    + if (setup_cgroups())
    + goto out;
    +
    + skel = cgroup_iter__open_and_load();
    + if (!ASSERT_OK_PTR(skel, "cgroup_iter__open_and_load"))
    + goto out;
    +
    + if (test__start_subtest("cgroup_iter__invalid_cgroup"))
    + test_invalid_cgroup(skel);
    + if (test__start_subtest("cgroup_iter__invalid_cgroup_spec"))
    + test_invalid_cgroup_spec(skel);
    + if (test__start_subtest("cgroup_iter__preorder"))
    + test_walk_preorder(skel);
    + if (test__start_subtest("cgroup_iter__postorder"))
    + test_walk_postorder(skel);
    + if (test__start_subtest("cgroup_iter__ancestors_up_walk"))
    + test_walk_ancestors_up(skel);
    + if (test__start_subtest("cgroup_iter__early_termination"))
    + test_early_termination(skel);
    + if (test__start_subtest("cgroup_iter__self_only"))
    + test_walk_self_only(skel);
    +out:
    + cgroup_iter__destroy(skel);
    + cleanup_cgroups();
    + cleanup_cgroup_environment();
    +}
    diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h
    index e9846606690d..c41ee80533ca 100644
    --- a/tools/testing/selftests/bpf/progs/bpf_iter.h
    +++ b/tools/testing/selftests/bpf/progs/bpf_iter.h
    @@ -17,6 +17,7 @@
    #define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used
    #define bpf_iter__sockmap bpf_iter__sockmap___not_used
    #define bpf_iter__bpf_link bpf_iter__bpf_link___not_used
    +#define bpf_iter__cgroup bpf_iter__cgroup___not_used
    #define btf_ptr btf_ptr___not_used
    #define BTF_F_COMPACT BTF_F_COMPACT___not_used
    #define BTF_F_NONAME BTF_F_NONAME___not_used
    @@ -40,6 +41,7 @@
    #undef bpf_iter__bpf_sk_storage_map
    #undef bpf_iter__sockmap
    #undef bpf_iter__bpf_link
    +#undef bpf_iter__cgroup
    #undef btf_ptr
    #undef BTF_F_COMPACT
    #undef BTF_F_NONAME
    @@ -141,6 +143,11 @@ struct bpf_iter__bpf_link {
    struct bpf_link *link;
    };

    +struct bpf_iter__cgroup {
    + struct bpf_iter_meta *meta;
    + struct cgroup *cgroup;
    +} __attribute__((preserve_access_index));
    +
    struct btf_ptr {
    void *ptr;
    __u32 type_id;
    diff --git a/tools/testing/selftests/bpf/progs/cgroup_iter.c b/tools/testing/selftests/bpf/progs/cgroup_iter.c
    new file mode 100644
    index 000000000000..de03997322a7
    --- /dev/null
    +++ b/tools/testing/selftests/bpf/progs/cgroup_iter.c
    @@ -0,0 +1,39 @@
    +// SPDX-License-Identifier: GPL-2.0
    +/* Copyright (c) 2022 Google */
    +
    +#include "bpf_iter.h"
    +#include <bpf/bpf_helpers.h>
    +#include <bpf/bpf_tracing.h>
    +
    +char _license[] SEC("license") = "GPL";
    +int terminate_early = 0;
    +u64 terminal_cgroup = 0;
    +
    +static inline u64 cgroup_id(struct cgroup *cgrp)
    +{
    + return cgrp->kn->id;
    +}
    +
    +SEC("iter/cgroup")
    +int cgroup_id_printer(struct bpf_iter__cgroup *ctx)
    +{
    + struct seq_file *seq = ctx->meta->seq;
    + struct cgroup *cgrp = ctx->cgroup;
    +
    + /* epilogue */
    + if (cgrp == NULL) {
    + BPF_SEQ_PRINTF(seq, "epilogue\n");
    + return 0;
    + }
    +
    + /* prologue */
    + if (ctx->meta->seq_num == 0)
    + BPF_SEQ_PRINTF(seq, "prologue\n");
    +
    + BPF_SEQ_PRINTF(seq, "%8llu\n", cgroup_id(cgrp));
    +
    + if (terminal_cgroup == cgroup_id(cgrp))
    + return 1;
    +
    + return terminate_early ? 1 : 0;
    +}
    --
    2.37.1.595.g718a3a8f04-goog
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