selftests/bpf: Add a test for open coded kmem_cache iter

The new subtest runs with bpf_prog_test_run_opts() as a syscall prog.
It iterates the kmem_cache using bpf_for_each loop and count the number
of entries.  Finally it checks it with the number of entries from the
regular iterator.

  $ ./vmtest.sh -- ./test_progs -t kmem_cache_iter
  ...
  #130/1   kmem_cache_iter/check_task_struct:OK
  #130/2   kmem_cache_iter/check_slabinfo:OK
  #130/3   kmem_cache_iter/open_coded_iter:OK
  #130     kmem_cache_iter:OK
  Summary: 1/3 PASSED, 0 SKIPPED, 0 FAILED

Also simplify the code by using attach routine of the skeleton.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20241030222819.1800667-2-namhyung@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index b0668f29f7b394eb5294b6c9cade28fc1b17265a..cd8ecd39c3f3c68d40c6e3e1465b42ed66537027 100644 (file)
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -582,4 +582,10 @@ extern int bpf_wq_set_callback_impl(struct bpf_wq *wq,
                unsigned int flags__k, void *aux__ign) __ksym;
 #define bpf_wq_set_callback(timer, cb, flags) \
        bpf_wq_set_callback_impl(timer, cb, flags, NULL)
+
+struct bpf_iter_kmem_cache;
+extern int bpf_iter_kmem_cache_new(struct bpf_iter_kmem_cache *it) __weak __ksym;
+extern struct kmem_cache *bpf_iter_kmem_cache_next(struct bpf_iter_kmem_cache *it) __weak __ksym;
+extern void bpf_iter_kmem_cache_destroy(struct bpf_iter_kmem_cache *it) __weak __ksym;
+
 #endif

diff --git a/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c b/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
index 848d8fc9171fae45484510bd8ce0192a87c6d9dd..8e13a3416a21d2e9bd9c47f518ac91918c7f8b5f 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
@@ -68,12 +68,27 @@ static void subtest_kmem_cache_iter_check_slabinfo(struct kmem_cache_iter *skel)
        fclose(fp);
 }
 
+static void subtest_kmem_cache_iter_open_coded(struct kmem_cache_iter *skel)
+{
+       LIBBPF_OPTS(bpf_test_run_opts, topts);
+       int err, fd;
+
+       /* No need to attach it, just run it directly */
+       fd = bpf_program__fd(skel->progs.open_coded_iter);
+
+       err = bpf_prog_test_run_opts(fd, &topts);
+       if (!ASSERT_OK(err, "test_run_opts err"))
+               return;
+       if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
+               return;
+
+       /* It should be same as we've seen from the explicit iterator */
+       ASSERT_EQ(skel->bss->open_coded_seen, skel->bss->kmem_cache_seen, "open_code_seen_eq");
+}
+
 void test_kmem_cache_iter(void)
 {
-       DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
        struct kmem_cache_iter *skel = NULL;
-       union bpf_iter_link_info linfo = {};
-       struct bpf_link *link;
        char buf[256];
        int iter_fd;
 
@@ -81,16 +96,12 @@ void test_kmem_cache_iter(void)
        if (!ASSERT_OK_PTR(skel, "kmem_cache_iter__open_and_load"))
                return;
 
-       opts.link_info = &linfo;
-       opts.link_info_len = sizeof(linfo);
-
-       link = bpf_program__attach_iter(skel->progs.slab_info_collector, &opts);
-       if (!ASSERT_OK_PTR(link, "attach_iter"))
+       if (!ASSERT_OK(kmem_cache_iter__attach(skel), "skel_attach"))
                goto destroy;
 
-       iter_fd = bpf_iter_create(bpf_link__fd(link));
+       iter_fd = bpf_iter_create(bpf_link__fd(skel->links.slab_info_collector));
        if (!ASSERT_GE(iter_fd, 0, "iter_create"))
-               goto free_link;
+               goto destroy;
 
        memset(buf, 0, sizeof(buf));
        while (read(iter_fd, buf, sizeof(buf) > 0)) {
@@ -105,11 +116,11 @@ void test_kmem_cache_iter(void)
                subtest_kmem_cache_iter_check_task_struct(skel);
        if (test__start_subtest("check_slabinfo"))
                subtest_kmem_cache_iter_check_slabinfo(skel);
+       if (test__start_subtest("open_coded_iter"))
+               subtest_kmem_cache_iter_open_coded(skel);
 
        close(iter_fd);
 
-free_link:
-       bpf_link__destroy(link);
 destroy:
        kmem_cache_iter__destroy(skel);
 }

diff --git a/tools/testing/selftests/bpf/progs/kmem_cache_iter.c b/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
index e775d5cd99fca579695dbceaee02d4866f638aaa..b9c8f9457492209999dadbb35b6b21db84a73444 100644 (file)
--- a/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
+++ b/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
@@ -3,6 +3,7 @@
 #include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
+#include "bpf_experimental.h"
 
 char _license[] SEC("license") = "GPL";
 
@@ -32,6 +33,7 @@ extern struct kmem_cache *bpf_get_kmem_cache(u64 addr) __ksym;
 /* Result, will be checked by userspace */
 int task_struct_found;
 int kmem_cache_seen;
+int open_coded_seen;
 
 SEC("iter/kmem_cache")
 int slab_info_collector(struct bpf_iter__kmem_cache *ctx)
@@ -84,3 +86,23 @@ int BPF_PROG(check_task_struct)
                task_struct_found = -2;
        return 0;
 }
+
+SEC("syscall")
+int open_coded_iter(const void *ctx)
+{
+       struct kmem_cache *s;
+
+       bpf_for_each(kmem_cache, s) {
+               struct kmem_cache_result *r;
+
+               r = bpf_map_lookup_elem(&slab_result, &open_coded_seen);
+               if (!r)
+                       break;
+
+               if (r->obj_size != s->size)
+                       break;
+
+               open_coded_seen++;
+       }
+       return 0;
+}