The test traverses all slab caches using the kmem_cache_iter and check
if current task's pointer is from "task_struct" slab cache.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
.../bpf/prog_tests/kmem_cache_iter.c | 64 ++++++++++++++++++
tools/testing/selftests/bpf/progs/bpf_iter.h | 7 ++
.../selftests/bpf/progs/kmem_cache_iter.c | 66 +++++++++++++++++++
3 files changed, 137 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
create mode 100644 tools/testing/selftests/bpf/progs/kmem_cache_iter.c
diff --git a/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c b/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
new file mode 100644
index 0000000000000000..3965e2924ac82d91
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Google */
+
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <bpf/btf.h>
+#include "kmem_cache_iter.skel.h"
+
+static void test_kmem_cache_iter_check_task(struct kmem_cache_iter *skel)
+{
+ LIBBPF_OPTS(bpf_test_run_opts, opts,
+ .flags = 0, /* run it with the current task */
+ );
+ int prog_fd = bpf_program__fd(skel->progs.check_task_struct);
+
+ /* get task_struct and check it if's from a slab cache */
+ bpf_prog_test_run_opts(prog_fd, &opts);
+
+ /* the BPF program should set 'found' variable */
+ ASSERT_EQ(skel->bss->found, 1, "found task_struct");
+}
+
+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[1024];
+ int iter_fd;
+
+ skel = kmem_cache_iter__open_and_load();
+ 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"))
+ goto destroy;
+
+ iter_fd = bpf_iter_create(bpf_link__fd(link));
+ if (!ASSERT_GE(iter_fd, 0, "iter_create"))
+ goto free_link;
+
+ memset(buf, 0, sizeof(buf));
+ while (read(iter_fd, buf, sizeof(buf) > 0)) {
+ /* read out all contents */
+ printf("%s", buf);
+ }
+
+ /* next reads should return 0 */
+ ASSERT_EQ(read(iter_fd, buf, sizeof(buf)), 0, "read");
+
+ test_kmem_cache_iter_check_task(skel);
+
+ close(iter_fd);
+
+free_link:
+ bpf_link__destroy(link);
+destroy:
+ kmem_cache_iter__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h
index c41ee80533ca219a..3305dc3a74b32481 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter.h
+++ b/tools/testing/selftests/bpf/progs/bpf_iter.h
@@ -24,6 +24,7 @@
#define BTF_F_PTR_RAW BTF_F_PTR_RAW___not_used
#define BTF_F_ZERO BTF_F_ZERO___not_used
#define bpf_iter__ksym bpf_iter__ksym___not_used
+#define bpf_iter__kmem_cache bpf_iter__kmem_cache___not_used
#include "vmlinux.h"
#undef bpf_iter_meta
#undef bpf_iter__bpf_map
@@ -48,6 +49,7 @@
#undef BTF_F_PTR_RAW
#undef BTF_F_ZERO
#undef bpf_iter__ksym
+#undef bpf_iter__kmem_cache
struct bpf_iter_meta {
struct seq_file *seq;
@@ -165,3 +167,8 @@ struct bpf_iter__ksym {
struct bpf_iter_meta *meta;
struct kallsym_iter *ksym;
};
+
+struct bpf_iter__kmem_cache {
+ struct bpf_iter_meta *meta;
+ struct kmem_cache *s;
+} __attribute__((preserve_access_index));
diff --git a/tools/testing/selftests/bpf/progs/kmem_cache_iter.c b/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
new file mode 100644
index 0000000000000000..3f6ec15a1bf6344c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Google */
+
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define SLAB_NAME_MAX 256
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(key_size, sizeof(void *));
+ __uint(value_size, SLAB_NAME_MAX);
+ __uint(max_entries, 1024);
+} slab_hash SEC(".maps");
+
+extern struct kmem_cache *bpf_get_kmem_cache(__u64 addr) __ksym;
+
+/* result, will be checked by userspace */
+int found;
+
+SEC("iter/kmem_cache")
+int slab_info_collector(struct bpf_iter__kmem_cache *ctx)
+{
+ struct seq_file *seq = ctx->meta->seq;
+ struct kmem_cache *s = ctx->s;
+
+ if (s) {
+ char name[SLAB_NAME_MAX];
+
+ /*
+ * To make sure if the slab_iter implements the seq interface
+ * properly and it's also useful for debugging.
+ */
+ BPF_SEQ_PRINTF(seq, "%s: %u\n", s->name, s->object_size);
+
+ bpf_probe_read_kernel_str(name, sizeof(name), s->name);
+ bpf_map_update_elem(&slab_hash, &s, name, BPF_NOEXIST);
+ }
+
+ return 0;
+}
+
+SEC("raw_tp/bpf_test_finish")
+int BPF_PROG(check_task_struct)
+{
+ __u64 curr = bpf_get_current_task();
+ struct kmem_cache *s;
+ char *name;
+
+ s = bpf_get_kmem_cache(curr);
+ if (s == NULL) {
+ found = -1;
+ return 0;
+ }
+
+ name = bpf_map_lookup_elem(&slab_hash, &s);
+ if (name && !bpf_strncmp(name, 11, "task_struct"))
+ found = 1;
+ else
+ found = -2;
+
+ return 0;
+}
--
2.46.1.824.gd892dcdcdd-googOn Tue, Oct 1, 2024 at 11:55 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> +++ b/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
> @@ -0,0 +1,66 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2024 Google */
> +
> +#include "bpf_iter.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#define SLAB_NAME_MAX 256
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_HASH);
> + __uint(key_size, sizeof(void *));
> + __uint(value_size, SLAB_NAME_MAX);
> + __uint(max_entries, 1024);
> +} slab_hash SEC(".maps");
> +
> +extern struct kmem_cache *bpf_get_kmem_cache(__u64 addr) __ksym;
> +
> +/* result, will be checked by userspace */
> +int found;
> +
> +SEC("iter/kmem_cache")
> +int slab_info_collector(struct bpf_iter__kmem_cache *ctx)
> +{
> + struct seq_file *seq = ctx->meta->seq;
> + struct kmem_cache *s = ctx->s;
> +
> + if (s) {
> + char name[SLAB_NAME_MAX];
> +
> + /*
> + * To make sure if the slab_iter implements the seq interface
> + * properly and it's also useful for debugging.
> + */
> + BPF_SEQ_PRINTF(seq, "%s: %u\n", s->name, s->object_size);
> +
> + bpf_probe_read_kernel_str(name, sizeof(name), s->name);
> + bpf_map_update_elem(&slab_hash, &s, name, BPF_NOEXIST);
> + }
> +
> + return 0;
> +}
> +
> +SEC("raw_tp/bpf_test_finish")
> +int BPF_PROG(check_task_struct)
> +{
> + __u64 curr = bpf_get_current_task();
> + struct kmem_cache *s;
> + char *name;
> +
> + s = bpf_get_kmem_cache(curr);
> + if (s == NULL) {
> + found = -1;
> + return 0;
> + }
> +
> + name = bpf_map_lookup_elem(&slab_hash, &s);
> + if (name && !bpf_strncmp(name, 11, "task_struct"))
> + found = 1;
> + else
> + found = -2;
> +
> + return 0;
> +}
The test is a bit too simple.
Could you add a more comprehensive test that also demonstrates
the power of such a slab iterator?
Like progs/bpf_iter_task_vmas.c provides output equivalent to
cat proc/pid/maps
and progs/bpf_iter_tcp6.c dumps equivalent output to
cat /proc/net/tcp6
Would be great to have a selftest that is equivalent to
cat /proc/slabinfo
(or at least close enough)
That will give more confidence that the interface works as intended.
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