The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com --- .../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{ - const unsigned char *s1 = m1; - const unsigned char *s2 = m2; - int i, delta = 0; - - for (i = 0; i < len; i++) { - delta = s1[i] - s2[i]; - if (delta || s1[i] == 0 || s2[i] == 0) - break; - } - return delta; -}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \ - _cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \ + _cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \ if (_cmp != 0) { \ bpf_printk("(%d) got %s", _cmp, _str); \ bpf_printk("(%d) expected %s", _cmp, \
On Thu, 2025-11-06 at 05:14 +0900, Hoyeon Lee wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
Acked-by: Eduard Zingerman eddyz87@gmail.com
[...]
On Wed, Nov 5, 2025 at 12:14 PM Hoyeon Lee hoyeon.lee@suse.com wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
.../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{
const unsigned char *s1 = m1;const unsigned char *s2 = m2;int i, delta = 0;for (i = 0; i < len; i++) {delta = s1[i] - s2[i];if (delta || s1[i] == 0 || s2[i] == 0)break;}return delta;-}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
_cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \
Though it's equivalent, the point of the test is to be heavy for the verifier with open coded __strncmp().
pw-bot: cr
On Wed, 2025-11-05 at 14:45 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 12:14 PM Hoyeon Lee hoyeon.lee@suse.com wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
.../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{
const unsigned char *s1 = m1;const unsigned char *s2 = m2;int i, delta = 0;for (i = 0; i < len; i++) {delta = s1[i] - s2[i];if (delta || s1[i] == 0 || s2[i] == 0)break;}return delta;-}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
_cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \Though it's equivalent, the point of the test is to be heavy for the verifier with open coded __strncmp().
pw-bot: cr
I double checked that before acking, the test was added as a part of [1]. So it seems to be focused on bpf_snprintf_btf(), not on scalability. And it's not that heavy in terms of instructions budget:
File Program Verdict Insns States ----------------------- ----------------------- ------- ----- ------ netif_receive_skb.bpf.o trace_netif_receive_skb success 18152 629
[1] https://lore.kernel.org/bpf/1601292670-1616-5-git-send-email-alan.maguire@or...
On Wed, Nov 5, 2025 at 2:52 PM Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-11-05 at 14:45 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 12:14 PM Hoyeon Lee hoyeon.lee@suse.com wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
.../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{
const unsigned char *s1 = m1;const unsigned char *s2 = m2;int i, delta = 0;for (i = 0; i < len; i++) {delta = s1[i] - s2[i];if (delta || s1[i] == 0 || s2[i] == 0)break;}return delta;-}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
_cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \Though it's equivalent, the point of the test is to be heavy for the verifier with open coded __strncmp().
pw-bot: cr
I double checked that before acking, the test was added as a part of [1]. So it seems to be focused on bpf_snprintf_btf(), not on scalability. And it's not that heavy in terms of instructions budget:
File Program Verdict Insns States
netif_receive_skb.bpf.o trace_netif_receive_skb success 18152 629
Is this before or after? What is the % decrease in insn_processed? I'd like to better understand the impact of the change.
On Wed, 2025-11-05 at 15:33 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 2:52 PM Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-11-05 at 14:45 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 12:14 PM Hoyeon Lee hoyeon.lee@suse.com wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
.../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{
const unsigned char *s1 = m1;const unsigned char *s2 = m2;int i, delta = 0;for (i = 0; i < len; i++) {delta = s1[i] - s2[i];if (delta || s1[i] == 0 || s2[i] == 0)break;}return delta;-}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
_cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \Though it's equivalent, the point of the test is to be heavy for the verifier with open coded __strncmp().
pw-bot: cr
I double checked that before acking, the test was added as a part of [1]. So it seems to be focused on bpf_snprintf_btf(), not on scalability. And it's not that heavy in terms of instructions budget:
File Program Verdict Insns States
netif_receive_skb.bpf.o trace_netif_receive_skb success 18152 629
Is this before or after? What is the % decrease in insn_processed? I'd like to better understand the impact of the change.
That's before, after the change it is as follows:
File Program Verdict Insns States ----------------------- ----------------------- ------- ----- ------ netif_receive_skb.bpf.o trace_netif_receive_skb success 4353 235 ----------------------- ----------------------- ------- ----- ------
So, the overall impact is 18K -> 4K instructions processed.
On Wed, Nov 5, 2025 at 3:38 PM Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-11-05 at 15:33 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 2:52 PM Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-11-05 at 14:45 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 12:14 PM Hoyeon Lee hoyeon.lee@suse.com wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
.../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{
const unsigned char *s1 = m1;const unsigned char *s2 = m2;int i, delta = 0;for (i = 0; i < len; i++) {delta = s1[i] - s2[i];if (delta || s1[i] == 0 || s2[i] == 0)break;}return delta;-}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
_cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \Though it's equivalent, the point of the test is to be heavy for the verifier with open coded __strncmp().
pw-bot: cr
I double checked that before acking, the test was added as a part of [1]. So it seems to be focused on bpf_snprintf_btf(), not on scalability. And it's not that heavy in terms of instructions budget:
File Program Verdict Insns States
netif_receive_skb.bpf.o trace_netif_receive_skb success 18152 629
Is this before or after? What is the % decrease in insn_processed? I'd like to better understand the impact of the change.
That's before, after the change it is as follows:
File Program Verdict Insns States
netif_receive_skb.bpf.o trace_netif_receive_skb success 4353 235
So, the overall impact is 18K -> 4K instructions processed.
It's large enough impact for the verifier. I agree that the test was mainly focusing on testing bpf_snprintf_btf(), but it has a nice side effect by testing bounded loops too. I prefer to keep it as-is.
On Thu, Nov 6, 2025 at 8:43 AM Alexei Starovoitov alexei.starovoitov@gmail.com wrote:
On Wed, Nov 5, 2025 at 3:38 PM Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-11-05 at 15:33 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 2:52 PM Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-11-05 at 14:45 -0800, Alexei Starovoitov wrote:
On Wed, Nov 5, 2025 at 12:14 PM Hoyeon Lee hoyeon.lee@suse.com wrote:
The netif_receive_skb BPF program used in snprintf_btf test still uses a custom __strncmp. This is unnecessary as the bpf_strncmp helper is available and provides the same functionality.
This commit refactors the test to use the bpf_strncmp helper, removing the redundant custom implementation.
Signed-off-by: Hoyeon Lee hoyeon.lee@suse.com
.../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c index 9e067dcbf607..186b8c82b9e6 100644 --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c @@ -31,19 +31,6 @@ struct { __type(value, char[STRSIZE]); } strdata SEC(".maps");
-static int __strncmp(const void *m1, const void *m2, size_t len) -{
const unsigned char *s1 = m1;const unsigned char *s2 = m2;int i, delta = 0;for (i = 0; i < len; i++) {delta = s1[i] - s2[i];if (delta || s1[i] == 0 || s2[i] == 0)break;}return delta;-}
#if __has_builtin(__builtin_btf_type_id) #define TEST_BTF(_str, _type, _flags, _expected, ...) \ @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) &_ptr, sizeof(_ptr), _hflags); \ if (ret) \ break; \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
_cmp = bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedval); \Though it's equivalent, the point of the test is to be heavy for the verifier with open coded __strncmp().
pw-bot: cr
I double checked that before acking, the test was added as a part of [1]. So it seems to be focused on bpf_snprintf_btf(), not on scalability. And it's not that heavy in terms of instructions budget:
File Program Verdict Insns States
netif_receive_skb.bpf.o trace_netif_receive_skb success 18152 629
Is this before or after? What is the % decrease in insn_processed? I'd like to better understand the impact of the change.
That's before, after the change it is as follows:
File Program Verdict Insns States
netif_receive_skb.bpf.o trace_netif_receive_skb success 4353 235
So, the overall impact is 18K -> 4K instructions processed.
It's large enough impact for the verifier. I agree that the test was mainly focusing on testing bpf_snprintf_btf(), but it has a nice side effect by testing bounded loops too. I prefer to keep it as-is.
Thanks for the clarification.
Removing the open-coded __strncmp would drop the bounded-loop coverage that this test currently provides (as a side effect), and that stress on the verifier is still valuable.
I'll drop this patch. Thank you all for the discussion and review.
linux-kselftest-mirror@lists.linaro.org
-
Alexei Starovoitov -
Eduard Zingerman -
Hoyeon Lee