The test traverses all slab caches using the kmem_cache_iter and save
the data into slab_result array map. And check if current task's
pointer is from "task_struct" slab cache using bpf_get_kmem_cache().
Also compare the result array with /proc/slabinfo if available (when
CONFIG_SLUB_DEBUG is on). Note that many of the fields in the slabinfo
are transient, so it only compares the name and objsize fields.
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
.../bpf/prog_tests/kmem_cache_iter.c | 115 ++++++++++++++++++
tools/testing/selftests/bpf/progs/bpf_iter.h | 7 ++
.../selftests/bpf/progs/kmem_cache_iter.c | 95 +++++++++++++++
3 files changed, 217 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..848d8fc9171fae45
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c
@@ -0,0 +1,115 @@
+// 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"
+
+#define SLAB_NAME_MAX 32
+
+struct kmem_cache_result {
+ char name[SLAB_NAME_MAX];
+ long obj_size;
+};
+
+static void subtest_kmem_cache_iter_check_task_struct(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 */
+ ASSERT_OK(bpf_prog_test_run_opts(prog_fd, &opts), "prog_test_run");
+
+ /* The BPF program should set 'found' variable */
+ ASSERT_EQ(skel->bss->task_struct_found, 1, "task_struct_found");
+}
+
+static void subtest_kmem_cache_iter_check_slabinfo(struct kmem_cache_iter *skel)
+{
+ FILE *fp;
+ int map_fd;
+ char name[SLAB_NAME_MAX];
+ unsigned long objsize;
+ char rest_of_line[1000];
+ struct kmem_cache_result r;
+ int seen = 0;
+
+ fp = fopen("/proc/slabinfo", "r");
+ if (fp == NULL) {
+ /* CONFIG_SLUB_DEBUG is not enabled */
+ return;
+ }
+
+ map_fd = bpf_map__fd(skel->maps.slab_result);
+
+ /* Ignore first two lines for header */
+ fscanf(fp, "slabinfo - version: %*d.%*d\n");
+ fscanf(fp, "# %*s %*s %*s %*s %*s %*s : %[^\n]\n", rest_of_line);
+
+ /* Compare name and objsize only - others can be changes frequently */
+ while (fscanf(fp, "%s %*u %*u %lu %*u %*u : %[^\n]\n",
+ name, &objsize, rest_of_line) == 3) {
+ int ret = bpf_map_lookup_elem(map_fd, &seen, &r);
+
+ if (!ASSERT_OK(ret, "kmem_cache_lookup"))
+ break;
+
+ ASSERT_STREQ(r.name, name, "kmem_cache_name");
+ ASSERT_EQ(r.obj_size, objsize, "kmem_cache_objsize");
+
+ seen++;
+ }
+
+ ASSERT_EQ(skel->bss->kmem_cache_seen, seen, "kmem_cache_seen_eq");
+
+ fclose(fp);
+}
+
+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;
+
+ 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");
+
+ if (test__start_subtest("check_task_struct"))
+ subtest_kmem_cache_iter_check_task_struct(skel);
+ if (test__start_subtest("check_slabinfo"))
+ subtest_kmem_cache_iter_check_slabinfo(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..1cff8c7772683caf
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/kmem_cache_iter.c
@@ -0,0 +1,95 @@
+// 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 32
+
+struct kmem_cache_result {
+ char name[SLAB_NAME_MAX];
+ long obj_size;
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(key_size, sizeof(void *));
+ __uint(value_size, SLAB_NAME_MAX);
+ __uint(max_entries, 1);
+} slab_hash SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(key_size, sizeof(int));
+ __uint(value_size, sizeof(struct kmem_cache_result));
+ __uint(max_entries, 1024);
+} slab_result SEC(".maps");
+
+extern void bpf_rcu_read_lock(void) __ksym;
+extern void bpf_rcu_read_unlock(void) __ksym;
+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;
+
+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;
+ struct kmem_cache_result *r;
+ int idx;
+
+ if (s) {
+ /* 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->size);
+
+ idx = kmem_cache_seen;
+ r = bpf_map_lookup_elem(&slab_result, &idx);
+ if (r == NULL)
+ return 0;
+
+ kmem_cache_seen++;
+
+ /* Save name and size to match /proc/slabinfo */
+ bpf_probe_read_kernel_str(r->name, sizeof(r->name), s->name);
+ r->obj_size = s->size;
+
+ if (!bpf_strncmp(r->name, 11, "task_struct"))
+ bpf_map_update_elem(&slab_hash, &s, r->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;
+
+ bpf_rcu_read_lock();
+
+ s = bpf_get_kmem_cache(curr);
+ if (s == NULL) {
+ task_struct_found = -1;
+ bpf_rcu_read_unlock();
+ return 0;
+ }
+
+ name = bpf_map_lookup_elem(&slab_hash, &s);
+ if (name && !bpf_strncmp(name, 11, "task_struct"))
+ task_struct_found = 1;
+ else
+ task_struct_found = -2;
+
+ bpf_rcu_read_unlock();
+ return 0;
+}
--
2.47.0.rc1.288.g06298d1525-goog
