Commit a496d0cd authored by Namhyung Kim's avatar Namhyung Kim Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add a test for kmem_cache_iter 



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: default avatarNamhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20241010232505.1339892-4-namhyung@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent a992d7a3

tools/testing/selftests/bpf/prog_tests/kmem_cache_iter.c

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+115 −0
Original line number Diff line number Diff line 
// 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);

}

tools/testing/selftests/bpf/progs/bpf_iter.h

+7 −0
Original line number Diff line number Diff line
@@ -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));

tools/testing/selftests/bpf/progs/kmem_cache_iter.c

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Original line number Diff line number Diff line 
// 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 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;



	s = bpf_get_kmem_cache(curr);

	if (s == NULL) {

		task_struct_found = -1;

		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;

	return 0;

}