On Fri, Sep 27, 2024 at 11:41:33AM -0700, Namhyung Kim wrote:
> 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@xxxxxxxxxx>
> ---
> .../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..814bcc453e9f3ccd
> --- /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 = BPF_F_TEST_RUN_ON_CPU,
> + );
> + 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");
Hmm.. I'm seeing a failure with found being -1, which means ...
> +}
> +
> +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;
... it cannot find a kmem_cache for the current task. This program is
run by bpf_prog_test_run_opts() with BPF_F_TEST_RUN_ON_CPU. So I think
the curr should point a task_struct in a slab cache.
Am I missing something?
Thanks,
Namhyung
> + }
> +
> + 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-goog
>
