From: Xu Kuohai <xukuohai@huawei.com>
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>
---
tools/testing/selftests/bpf/Makefile | 3 +-
.../selftests/bpf/prog_tests/ringbuf.c | 64 ++++++++++++
.../bpf/progs/test_ringbuf_overwrite.c | 98 +++++++++++++++++++
3 files changed, 164 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f00587d4ede6..43d133bf514d 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -498,7 +498,8 @@ 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 d1e4cb28a72c..5264af1dc768 100644
--- 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 +498,67 @@ static void ringbuf_map_key_subtest(void)
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 err;
+
+ skel = test_ringbuf_overwrite_lskel__open();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+
+ size = 0x1000;
+ len1 = 0x800;
+ len2 = 0x400;
+ len3 = size - len1 - len2 - BPF_RINGBUF_HDR_SZ * 3; /* 0x3e8 */
+ len4 = len3 - 8; /* 0x3e0 */
+ 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 +569,6 @@ 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
index 000000000000..ff4aa67ddacc
--- /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;
+}
--
2.43.0On Fri, Oct 17, 2025 at 9:04 PM Xu Kuohai <xukuohai@huaweicloud.com> wrote:
>
> From: Xu Kuohai <xukuohai@huawei.com>
>
> 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>
> ---
> tools/testing/selftests/bpf/Makefile | 3 +-
> .../selftests/bpf/prog_tests/ringbuf.c | 64 ++++++++++++
> .../bpf/progs/test_ringbuf_overwrite.c | 98 +++++++++++++++++++
> 3 files changed, 164 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index f00587d4ede6..43d133bf514d 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -498,7 +498,8 @@ 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 d1e4cb28a72c..5264af1dc768 100644
> --- 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 +498,67 @@ static void ringbuf_map_key_subtest(void)
> 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 err;
> +
> + skel = test_ringbuf_overwrite_lskel__open();
> + if (!ASSERT_OK_PTR(skel, "skel_open"))
> + return;
> +
> + size = 0x1000;
this will fail on architecture with page size != 4KB, I adjusted this
to use page_size, len1 to page_size / 2 and len2 to page_size / 4
> + len1 = 0x800;
> + len2 = 0x400;
> + len3 = size - len1 - len2 - BPF_RINGBUF_HDR_SZ * 3; /* 0x3e8 */
> + len4 = len3 - 8; /* 0x3e0 */
> + len5 = len3; /* retry with len3 */
> +
[...]
On 10/28/2025 10:47 AM, Andrii Nakryiko wrote:
> On Fri, Oct 17, 2025 at 9:04 PM Xu Kuohai <xukuohai@huaweicloud.com> wrote:
>>
>> From: Xu Kuohai <xukuohai@huawei.com>
>>
>> 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>
>> ---
>> tools/testing/selftests/bpf/Makefile | 3 +-
>> .../selftests/bpf/prog_tests/ringbuf.c | 64 ++++++++++++
>> .../bpf/progs/test_ringbuf_overwrite.c | 98 +++++++++++++++++++
>> 3 files changed, 164 insertions(+), 1 deletion(-)
>> create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c
>>
>> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
>> index f00587d4ede6..43d133bf514d 100644
>> --- a/tools/testing/selftests/bpf/Makefile
>> +++ b/tools/testing/selftests/bpf/Makefile
>> @@ -498,7 +498,8 @@ 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 d1e4cb28a72c..5264af1dc768 100644
>> --- 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 +498,67 @@ static void ringbuf_map_key_subtest(void)
>> 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 err;
>> +
>> + skel = test_ringbuf_overwrite_lskel__open();
>> + if (!ASSERT_OK_PTR(skel, "skel_open"))
>> + return;
>> +
>> + size = 0x1000;
>
> this will fail on architecture with page size != 4KB, I adjusted this
> to use page_size, len1 to page_size / 2 and len2 to page_size / 4
>
Ah, good catch, thanks for fixing it!
>> + len1 = 0x800;
>> + len2 = 0x400;
>> + len3 = size - len1 - len2 - BPF_RINGBUF_HDR_SZ * 3; /* 0x3e8 */
>> + len4 = len3 - 8; /* 0x3e0 */
>> + len5 = len3; /* retry with len3 */
>> +
>
> [...]
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