[PATCH bpf-next 2/2] selftests/bpf: Add a local kptr test with no special fields

Yonghong Song
2023-08-23T22:56:26Z

Add a local kptr test with no special fields in the struct. Without the
previous patch, the following warning will hit:

[ 44.683877] WARNING: CPU: 3 PID: 485 at kernel/bpf/syscall.c:660 bpf_obj_free_fields+0x220/0x240
[ 44.684640] Modules linked in: bpf_testmod(OE)
[ 44.685044] CPU: 3 PID: 485 Comm: kworker/u8:5 Tainted: G OE 6.5.0-rc5-01703-g260d855e9b90 #248
[ 44.685827] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 44.686693] Workqueue: events_unbound bpf_map_free_deferred
[ 44.687297] RIP: 0010:bpf_obj_free_fields+0x220/0x240
[ 44.687775] Code: e8 55 17 1f 00 49 8b 74 24 08 4c 89 ef e8 e8 14 05 00 e8 a3 da e2 ff e9 55 fe ff ff 0f 0b e9 4e fe ff
ff 0f 0b e9 47 fe ff ff <0f> 0b e8 d9 d9 e2 ff 31 f6 eb d5 48 83 c4 10 5b 41 5c e
[ 44.689353] RSP: 0018:ffff888106467cb8 EFLAGS: 00010246
[ 44.689806] RAX: 0000000000000000 RBX: ffff888112b3a200 RCX: 0000000000000001
[ 44.690433] RDX: 0000000000000000 RSI: dffffc0000000000 RDI: ffff8881128ad988
[ 44.691094] RBP: 0000000000000002 R08: ffffffff81370bd0 R09: 1ffff110216231a5
[ 44.691643] R10: dffffc0000000000 R11: ffffed10216231a6 R12: ffff88810d68a488
[ 44.692245] R13: ffff88810767c288 R14: ffff88810d68a400 R15: ffff88810d68a418
[ 44.692829] FS: 0000000000000000(0000) GS:ffff8881f7580000(0000) knlGS:0000000000000000
[ 44.693484] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 44.693964] CR2: 000055c7f2afce28 CR3: 000000010fee4002 CR4: 0000000000370ee0
[ 44.694513] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 44.695102] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 44.695747] Call Trace:
[ 44.696001] <TASK>
[ 44.696183] ? __warn+0xfe/0x270
[ 44.696447] ? bpf_obj_free_fields+0x220/0x240
[ 44.696817] ? report_bug+0x220/0x2d0
[ 44.697180] ? handle_bug+0x3d/0x70
[ 44.697507] ? exc_invalid_op+0x1a/0x50
[ 44.697887] ? asm_exc_invalid_op+0x1a/0x20
[ 44.698282] ? btf_find_struct_meta+0xd0/0xd0
[ 44.698634] ? bpf_obj_free_fields+0x220/0x240
[ 44.699027] ? bpf_obj_free_fields+0x1e2/0x240
[ 44.699414] array_map_free+0x1a3/0x260
[ 44.699763] bpf_map_free_deferred+0x7b/0xe0
[ 44.700154] process_one_work+0x46d/0x750
[ 44.700523] worker_thread+0x49e/0x900
[ 44.700892] ? pr_cont_work+0x270/0x270
[ 44.701224] kthread+0x1ae/0x1d0
[ 44.701516] ? kthread_blkcg+0x50/0x50
[ 44.701860] ret_from_fork+0x34/0x50
[ 44.702178] ? kthread_blkcg+0x50/0x50
[ 44.702508] ret_from_fork_asm+0x11/0x20
[ 44.702880] </TASK>

With the previous patch, there is no warnings.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
.../bpf/prog_tests/local_kptr_stash.c | 25 ++++++++++++++++-
.../selftests/bpf/progs/local_kptr_stash.c | 28 +++++++++++++++++++
2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/local_kptr_stash.c b/tools/testing/selftests/bpf/prog_tests/local_kptr_stash.c
index 158616c94658..4225108b8e4d 100644
--- a/tools/testing/selftests/bpf/prog_tests/local_kptr_stash.c
+++ b/tools/testing/selftests/bpf/prog_tests/local_kptr_stash.c
@@ -27,6 +27,27 @@ static void test_local_kptr_stash_simple(void)
local_kptr_stash__destroy(skel);
}

+static void test_local_kptr_stash_simple_2(void)
+{
+ LIBBPF_OPTS(bpf_test_run_opts, opts,
+ .data_in = &pkt_v4,
+ .data_size_in = sizeof(pkt_v4),
+ .repeat = 1,
+ );
+ struct local_kptr_stash *skel;
+ int ret;
+
+ skel = local_kptr_stash__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "local_kptr_stash__open_and_load"))
+ return;
+
+ ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.stash_rb_nodes_2), &opts);
+ ASSERT_OK(ret, "local_kptr_stash_add_nodes run");
+ ASSERT_OK(opts.retval, "local_kptr_stash_add_nodes retval");
+
+ local_kptr_stash__destroy(skel);
+}
+
static void test_local_kptr_stash_unstash(void)
{
LIBBPF_OPTS(bpf_test_run_opts, opts,
@@ -59,8 +80,10 @@ static void test_local_kptr_stash_fail(void)

void test_local_kptr_stash(void)
{
- if (test__start_subtest("local_kptr_stash_simple"))
+ if (test__start_subtest("local_kptr_stash_simple_yes_special_field"))
test_local_kptr_stash_simple();
+ if (test__start_subtest("local_kptr_stash_simple_no_special_field"))
+ test_local_kptr_stash_simple_2();
if (test__start_subtest("local_kptr_stash_unstash"))
test_local_kptr_stash_unstash();
if (test__start_subtest("local_kptr_stash_fail"))
diff --git a/tools/testing/selftests/bpf/progs/local_kptr_stash.c b/tools/testing/selftests/bpf/progs/local_kptr_stash.c
index 06838083079c..4de548c31aab 100644
--- a/tools/testing/selftests/bpf/progs/local_kptr_stash.c
+++ b/tools/testing/selftests/bpf/progs/local_kptr_stash.c
@@ -14,10 +14,16 @@ struct node_data {
struct bpf_rb_node node;
};

+struct node_data2 {
+ long key;
+ long data;
+};
+
struct map_value {
struct prog_test_ref_kfunc *not_kptr;
struct prog_test_ref_kfunc __kptr *val;
struct node_data __kptr *node;
+ struct node_data2 __kptr *node2;
};

/* This is necessary so that LLVM generates BTF for node_data struct
@@ -66,6 +72,28 @@ long stash_rb_nodes(void *ctx)
return create_and_stash(0, 41) ?: create_and_stash(1, 42);
}

+SEC("tc")
+long stash_rb_nodes_2(void *ctx)
+{
+ struct map_value *mapval;
+ struct node_data2 *res;
+ int idx = 0;
+
+ mapval = bpf_map_lookup_elem(&some_nodes, &idx);
+ if (!mapval)
+ return 1;
+
+ res = bpf_obj_new(typeof(*res));
+ if (!res)
+ return 1;
+ res->key = 41;
+
+ res = bpf_kptr_xchg(&mapval->node2, res);
+ if (res)
+ bpf_obj_drop(res);
+ return 0;
+}
+
SEC("tc")
long unstash_rb_node(void *ctx)
{
--
2.34.1