selftests/bpf: Add overwrite mode test for BPF ring buffer

Add overwrite mode test for BPF ring buffer. The test creates a BPF ring
buffer in overwrite mode, then repeatedly reserves and commits records
to check if the ring buffer works as expected both before and after
overwriting occurs.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20251018035738.4039621-3-xukuohai@huaweicloud.com

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 7437c325179e47b3fd427ce637b7ef2bfcb10dd7..64997fa47053274a0c3fada5d3e2a1515cb272d1 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -499,7 +499,8 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h               \
 
 LSKELS := fexit_sleep.c trace_printk.c trace_vprintk.c map_ptr_kern.c  \
        core_kern.c core_kern_overflow.c test_ringbuf.c                 \
-       test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c
+       test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c    \
+       test_ringbuf_overwrite.c
 
 LSKELS_SIGNED := fentry_test.c fexit_test.c atomics.c
 

diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
index d1e4cb28a72c6bbb87b3cc1b216d5634fffb6736..64520684d2cb9bef0521c25cbda653debb52b637 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
@@ -17,6 +17,7 @@
 #include "test_ringbuf_n.lskel.h"
 #include "test_ringbuf_map_key.lskel.h"
 #include "test_ringbuf_write.lskel.h"
+#include "test_ringbuf_overwrite.lskel.h"
 
 #define EDONE 7777
 
@@ -497,6 +498,68 @@ cleanup:
        test_ringbuf_map_key_lskel__destroy(skel_map_key);
 }
 
+static void ringbuf_overwrite_mode_subtest(void)
+{
+       unsigned long size, len1, len2, len3, len4, len5;
+       unsigned long expect_avail_data, expect_prod_pos, expect_over_pos;
+       struct test_ringbuf_overwrite_lskel *skel;
+       int page_size = getpagesize();
+       int err;
+
+       skel = test_ringbuf_overwrite_lskel__open();
+       if (!ASSERT_OK_PTR(skel, "skel_open"))
+               return;
+
+       size = page_size;
+       len1 = page_size / 2;
+       len2 = page_size / 4;
+       len3 = size - len1 - len2 - BPF_RINGBUF_HDR_SZ * 3;
+       len4 = len3 - 8;
+       len5 = len3; /* retry with len3 */
+
+       skel->maps.ringbuf.max_entries = size;
+       skel->rodata->LEN1 = len1;
+       skel->rodata->LEN2 = len2;
+       skel->rodata->LEN3 = len3;
+       skel->rodata->LEN4 = len4;
+       skel->rodata->LEN5 = len5;
+
+       skel->bss->pid = getpid();
+
+       err = test_ringbuf_overwrite_lskel__load(skel);
+       if (!ASSERT_OK(err, "skel_load"))
+               goto cleanup;
+
+       err = test_ringbuf_overwrite_lskel__attach(skel);
+       if (!ASSERT_OK(err, "skel_attach"))
+               goto cleanup;
+
+       syscall(__NR_getpgid);
+
+       ASSERT_EQ(skel->bss->reserve1_fail, 0, "reserve 1");
+       ASSERT_EQ(skel->bss->reserve2_fail, 0, "reserve 2");
+       ASSERT_EQ(skel->bss->reserve3_fail, 1, "reserve 3");
+       ASSERT_EQ(skel->bss->reserve4_fail, 0, "reserve 4");
+       ASSERT_EQ(skel->bss->reserve5_fail, 0, "reserve 5");
+
+       ASSERT_EQ(skel->bss->ring_size, size, "check_ring_size");
+
+       expect_avail_data = len2 + len4 + len5 + 3 * BPF_RINGBUF_HDR_SZ;
+       ASSERT_EQ(skel->bss->avail_data, expect_avail_data, "check_avail_size");
+
+       ASSERT_EQ(skel->bss->cons_pos, 0, "check_cons_pos");
+
+       expect_prod_pos = len1 + len2 + len4 + len5 + 4 * BPF_RINGBUF_HDR_SZ;
+       ASSERT_EQ(skel->bss->prod_pos, expect_prod_pos, "check_prod_pos");
+
+       expect_over_pos = len1 + BPF_RINGBUF_HDR_SZ;
+       ASSERT_EQ(skel->bss->over_pos, expect_over_pos, "check_over_pos");
+
+       test_ringbuf_overwrite_lskel__detach(skel);
+cleanup:
+       test_ringbuf_overwrite_lskel__destroy(skel);
+}
+
 void test_ringbuf(void)
 {
        if (test__start_subtest("ringbuf"))
@@ -507,4 +570,6 @@ void test_ringbuf(void)
                ringbuf_map_key_subtest();
        if (test__start_subtest("ringbuf_write"))
                ringbuf_write_subtest();
+       if (test__start_subtest("ringbuf_overwrite_mode"))
+               ringbuf_overwrite_mode_subtest();
 }

diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c b/tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c
new file mode 100644 (file)
index 0000000..ff4aa67
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2025. Huawei Technologies Co., Ltd */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+       __uint(type, BPF_MAP_TYPE_RINGBUF);
+       __uint(map_flags, BPF_F_RB_OVERWRITE);
+} ringbuf SEC(".maps");
+
+int pid;
+
+const volatile unsigned long LEN1;
+const volatile unsigned long LEN2;
+const volatile unsigned long LEN3;
+const volatile unsigned long LEN4;
+const volatile unsigned long LEN5;
+
+long reserve1_fail = 0;
+long reserve2_fail = 0;
+long reserve3_fail = 0;
+long reserve4_fail = 0;
+long reserve5_fail = 0;
+
+unsigned long avail_data = 0;
+unsigned long ring_size = 0;
+unsigned long cons_pos = 0;
+unsigned long prod_pos = 0;
+unsigned long over_pos = 0;
+
+SEC("fentry/" SYS_PREFIX "sys_getpgid")
+int test_overwrite_ringbuf(void *ctx)
+{
+       char *rec1, *rec2, *rec3, *rec4, *rec5;
+       int cur_pid = bpf_get_current_pid_tgid() >> 32;
+
+       if (cur_pid != pid)
+               return 0;
+
+       rec1 = bpf_ringbuf_reserve(&ringbuf, LEN1, 0);
+       if (!rec1) {
+               reserve1_fail = 1;
+               return 0;
+       }
+
+       rec2 = bpf_ringbuf_reserve(&ringbuf, LEN2, 0);
+       if (!rec2) {
+               bpf_ringbuf_discard(rec1, 0);
+               reserve2_fail = 1;
+               return 0;
+       }
+
+       rec3 = bpf_ringbuf_reserve(&ringbuf, LEN3, 0);
+       /* expect failure */
+       if (!rec3) {
+               reserve3_fail = 1;
+       } else {
+               bpf_ringbuf_discard(rec1, 0);
+               bpf_ringbuf_discard(rec2, 0);
+               bpf_ringbuf_discard(rec3, 0);
+               return 0;
+       }
+
+       rec4 = bpf_ringbuf_reserve(&ringbuf, LEN4, 0);
+       if (!rec4) {
+               reserve4_fail = 1;
+               bpf_ringbuf_discard(rec1, 0);
+               bpf_ringbuf_discard(rec2, 0);
+               return 0;
+       }
+
+       bpf_ringbuf_submit(rec1, 0);
+       bpf_ringbuf_submit(rec2, 0);
+       bpf_ringbuf_submit(rec4, 0);
+
+       rec5 = bpf_ringbuf_reserve(&ringbuf, LEN5, 0);
+       if (!rec5) {
+               reserve5_fail = 1;
+               return 0;
+       }
+
+       for (int i = 0; i < LEN3; i++)
+               rec5[i] = 0xdd;
+
+       bpf_ringbuf_submit(rec5, 0);
+
+       ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
+       avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
+       cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
+       prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
+       over_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_OVERWRITE_POS);
+
+       return 0;
+}