selftests/bpf: Add test for bpf_list_{front,back}

This patch adds the "list_peek" test to use the new
bpf_list_{front,back} kfunc.

The test_{front,back}* tests ensure that the return value
is a non_own_ref node pointer and requires the spinlock to be held.

Suggested-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> # check non_own_ref marking
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20250506015857.817950-9-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c
index 77d07e0a4a55c56a20eefa99ab2f3f12f3ef4aca..5266c70228631bceb2b1ced16df4c9448848371c 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/linked_list.c
+++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c
@@ -7,6 +7,7 @@
 
 #include "linked_list.skel.h"
 #include "linked_list_fail.skel.h"
+#include "linked_list_peek.skel.h"
 
 static char log_buf[1024 * 1024];
 
@@ -805,3 +806,8 @@ void test_linked_list(void)
        test_linked_list_success(LIST_IN_LIST, true);
        test_linked_list_success(TEST_ALL, false);
 }
+
+void test_linked_list_peek(void)
+{
+       RUN_TESTS(linked_list_peek);
+}

diff --git a/tools/testing/selftests/bpf/progs/linked_list_peek.c b/tools/testing/selftests/bpf/progs/linked_list_peek.c
new file mode 100644 (file)
index 0000000..264e81b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_list_peek.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "bpf_experimental.h"
+
+struct node_data {
+       struct bpf_list_node l;
+       int key;
+};
+
+#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+private(A) struct bpf_spin_lock glock;
+private(A) struct bpf_list_head ghead __contains(node_data, l);
+
+#define list_entry(ptr, type, member) container_of(ptr, type, member)
+#define NR_NODES 16
+
+int zero = 0;
+
+SEC("syscall")
+__retval(0)
+long list_peek(void *ctx)
+{
+       struct bpf_list_node *l_n;
+       struct node_data *n;
+       int i, err = 0;
+
+       bpf_spin_lock(&glock);
+       l_n = bpf_list_front(&ghead);
+       bpf_spin_unlock(&glock);
+       if (l_n)
+               return __LINE__;
+
+       bpf_spin_lock(&glock);
+       l_n = bpf_list_back(&ghead);
+       bpf_spin_unlock(&glock);
+       if (l_n)
+               return __LINE__;
+
+       for (i = zero; i < NR_NODES && can_loop; i++) {
+               n = bpf_obj_new(typeof(*n));
+               if (!n)
+                       return __LINE__;
+               n->key = i;
+               bpf_spin_lock(&glock);
+               bpf_list_push_back(&ghead, &n->l);
+               bpf_spin_unlock(&glock);
+       }
+
+       bpf_spin_lock(&glock);
+
+       l_n = bpf_list_front(&ghead);
+       if (!l_n) {
+               err = __LINE__;
+               goto done;
+       }
+
+       n = list_entry(l_n, struct node_data, l);
+       if (n->key != 0) {
+               err = __LINE__;
+               goto done;
+       }
+
+       l_n = bpf_list_back(&ghead);
+       if (!l_n) {
+               err = __LINE__;
+               goto done;
+       }
+
+       n = list_entry(l_n, struct node_data, l);
+       if (n->key != NR_NODES - 1) {
+               err = __LINE__;
+               goto done;
+       }
+
+done:
+       bpf_spin_unlock(&glock);
+       return err;
+}
+
+#define TEST_FB(op, dolock)                                    \
+SEC("syscall")                                                 \
+__failure __msg(MSG)                                           \
+long test_##op##_spinlock_##dolock(void *ctx)                  \
+{                                                              \
+       struct bpf_list_node *l_n;                              \
+       __u64 jiffies = 0;                                      \
+                                                               \
+       if (dolock)                                             \
+               bpf_spin_lock(&glock);                          \
+       l_n = bpf_list_##op(&ghead);                            \
+       if (l_n)                                                \
+               jiffies = bpf_jiffies64();                      \
+       if (dolock)                                             \
+               bpf_spin_unlock(&glock);                        \
+                                                               \
+       return !!jiffies;                                       \
+}
+
+#define MSG "call bpf_list_{{(front|back).+}}; R0{{(_w)?}}=ptr_or_null_node_data(id={{[0-9]+}},non_own_ref"
+TEST_FB(front, true)
+TEST_FB(back, true)
+#undef MSG
+
+#define MSG "bpf_spin_lock at off=0 must be held for bpf_list_head"
+TEST_FB(front, false)
+TEST_FB(back, false)
+#undef MSG
+
+char _license[] SEC("license") = "GPL";