1. Patchew
  2. linux
  3. [PATCHv3 bpf-next 0/5] libbpf: Make optimized uprobes backward compatible
  4. View patch

[PATCHv3 bpf-next 4/5] selftests/bpf: Add test for checking correct nop of optimized usdt

Jiri Olsa posted 5 patches 2 days, 8 hours ago
[PATCHv3 bpf-next 4/5] selftests/bpf: Add test for checking correct nop of optimized usdt
Posted by Jiri Olsa 2 days, 8 hours ago 
Adding test that attaches bpf program on usdt probe in 2 scenarios;

- attach program on top of usdt_1, which is single nop instruction,
  so the probe stays on nop instruction and is not optimized.

- attach program on top of usdt_2 which is probe defined on top
  of nop,nop5 combo, so the probe is placed on top of nop5 and
  is optimized.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/testing/selftests/bpf/.gitignore        |  2 +
 tools/testing/selftests/bpf/Makefile          |  3 +-
 tools/testing/selftests/bpf/prog_tests/usdt.c | 85 +++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_usdt.c |  9 ++
 tools/testing/selftests/bpf/usdt_1.c          | 18 ++++
 tools/testing/selftests/bpf/usdt_2.c          | 16 ++++
 6 files changed, 132 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/usdt_1.c
 create mode 100644 tools/testing/selftests/bpf/usdt_2.c

diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
index a3ea98211ea6..bfdc5518ecc8 100644
--- a/tools/testing/selftests/bpf/.gitignore
+++ b/tools/testing/selftests/bpf/.gitignore
@@ -47,3 +47,5 @@ verification_cert.h
 *.BTF
 *.BTF_ids
 *.BTF.base
+usdt_1
+usdt_2
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c6bf4dfb1495..306949162a5b 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -749,7 +749,8 @@ TRUNNER_EXTRA_SOURCES := test_progs.c		\
 			 $(VERIFY_SIG_HDR)		\
 			 flow_dissector_load.h	\
 			 ip_check_defrag_frags.h	\
-			 bpftool_helpers.c
+			 bpftool_helpers.c	\
+			 usdt_1.c usdt_2.c
 TRUNNER_LIB_SOURCES := find_bit.c
 TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read				\
 		       $(OUTPUT)/liburandom_read.so			\
diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c
index f4be5269fa90..6daed3dfa75b 100644
--- a/tools/testing/selftests/bpf/prog_tests/usdt.c
+++ b/tools/testing/selftests/bpf/prog_tests/usdt.c
@@ -247,6 +247,89 @@ static void subtest_basic_usdt(bool optimized)
 #undef TRIGGER
 }
 
+#ifdef __x86_64__
+extern void usdt_1(void);
+extern void usdt_2(void);
+
+/* nop, nop5 */
+static unsigned char nop1_nop5_combo[6] = { 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 };
+static unsigned char nop1[6] = { 0x90 };
+
+static void *find_instr(void *fn, unsigned char *instr, size_t cnt)
+{
+	int i;
+
+	for (i = 0; i < 10; i++) {
+		if (!memcmp(instr, fn + i, cnt))
+			return fn + i;
+	}
+	return NULL;
+}
+
+static void subtest_optimized_attach(void)
+{
+	struct test_usdt *skel;
+	__u8 *addr_1, *addr_2;
+
+	/* usdt_1 USDT probe has single nop instruction */
+	addr_1 = find_instr(usdt_1, nop1_nop5_combo, 6);
+	if (!ASSERT_NULL(addr_1, "usdt_1_find_nop1_nop5_combo"))
+		return;
+
+	addr_1 = find_instr(usdt_1, nop1, 1);
+	if (!ASSERT_OK_PTR(addr_1, "usdt_1_find_nop1"))
+		return;
+
+	/* usdt_1 USDT probe has nop,nop5 instructions combo */
+	addr_2 = find_instr(usdt_2, nop1_nop5_combo, 6);
+	if (!ASSERT_OK_PTR(addr_2, "usdt_2_find_nop1_nop5_combo"))
+		return;
+
+	skel = test_usdt__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_usdt__open_and_load"))
+		return;
+
+	/*
+	 * Attach program on top of usdt_1 which is single nop probe,
+	 * so the probe won't get optimized.
+	 */
+	skel->links.usdt_executed = bpf_program__attach_usdt(skel->progs.usdt_executed,
+						     0 /*self*/, "/proc/self/exe",
+						     "optimized_attach", "usdt_1", NULL);
+	if (!ASSERT_OK_PTR(skel->links.usdt_executed, "bpf_program__attach_usdt"))
+		goto cleanup;
+
+	usdt_1();
+	usdt_1();
+
+	/* nop is on addr_1 address */
+	ASSERT_EQ(*addr_1, 0xcc, "int3");
+	ASSERT_EQ(skel->bss->executed, 2, "executed");
+
+	bpf_link__destroy(skel->links.usdt_executed);
+
+	/*
+	 * Attach program on top of usdt_2 which is probe defined on top
+	 * of nop1,nop5 combo, so the probe gets optimized on top of nop5.
+	 */
+	skel->links.usdt_executed = bpf_program__attach_usdt(skel->progs.usdt_executed,
+						     0 /*self*/, "/proc/self/exe",
+						     "optimized_attach", "usdt_2", NULL);
+	if (!ASSERT_OK_PTR(skel->links.usdt_executed, "bpf_program__attach_usdt"))
+		goto cleanup;
+
+	usdt_2();
+	usdt_2();
+
+	/* nop5 is on addr_2 + 1 address */
+	ASSERT_EQ(*(addr_2 + 1), 0xe8, "call");
+	ASSERT_EQ(skel->bss->executed, 4, "executed");
+
+cleanup:
+	test_usdt__destroy(skel);
+}
+#endif
+
 unsigned short test_usdt_100_semaphore SEC(".probes");
 unsigned short test_usdt_300_semaphore SEC(".probes");
 unsigned short test_usdt_400_semaphore SEC(".probes");
@@ -516,6 +599,8 @@ void test_usdt(void)
 #ifdef __x86_64__
 	if (test__start_subtest("basic_optimized"))
 		subtest_basic_usdt(true);
+	if (test__start_subtest("optimized_attach"))
+		subtest_optimized_attach();
 #endif
 	if (test__start_subtest("multispec"))
 		subtest_multispec_usdt();
diff --git a/tools/testing/selftests/bpf/progs/test_usdt.c b/tools/testing/selftests/bpf/progs/test_usdt.c
index a78c87537b07..6911868cdf67 100644
--- a/tools/testing/selftests/bpf/progs/test_usdt.c
+++ b/tools/testing/selftests/bpf/progs/test_usdt.c
@@ -138,4 +138,13 @@ int usdt_sib(struct pt_regs *ctx)
 	return 0;
 }
 
+int executed;
+
+SEC("usdt")
+int usdt_executed(struct pt_regs *ctx)
+{
+	executed++;
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/usdt_1.c b/tools/testing/selftests/bpf/usdt_1.c
new file mode 100644
index 000000000000..4f06e8bcf58b
--- /dev/null
+++ b/tools/testing/selftests/bpf/usdt_1.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#if defined(__x86_64__)
+
+/*
+ * Include usdt.h with defined USDT_NOP macro to use single
+ * nop instruction.
+ */
+#define USDT_NOP .byte 0x90
+#include "usdt.h"
+
+__attribute__((aligned(16)))
+void usdt_1(void)
+{
+	USDT(optimized_attach, usdt_1);
+}
+
+#endif
diff --git a/tools/testing/selftests/bpf/usdt_2.c b/tools/testing/selftests/bpf/usdt_2.c
new file mode 100644
index 000000000000..789883aaca4c
--- /dev/null
+++ b/tools/testing/selftests/bpf/usdt_2.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#if defined(__x86_64__)
+
+/*
+ * Include usdt.h with default nop,nop5 instructions combo.
+ */
+#include "usdt.h"
+
+__attribute__((aligned(16)))
+void usdt_2(void)
+{
+	USDT(optimized_attach, usdt_2);
+}
+
+#endif
-- 
2.53.0
Re: [PATCHv3 bpf-next 4/5] selftests/bpf: Add test for checking correct nop of optimized usdt
Posted by Andrii Nakryiko 1 day, 19 hours ago 
On Wed, Feb 11, 2026 at 12:49 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding test that attaches bpf program on usdt probe in 2 scenarios;
>
> - attach program on top of usdt_1, which is single nop instruction,
>   so the probe stays on nop instruction and is not optimized.
>
> - attach program on top of usdt_2 which is probe defined on top
>   of nop,nop5 combo, so the probe is placed on top of nop5 and
>   is optimized.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/testing/selftests/bpf/.gitignore        |  2 +
>  tools/testing/selftests/bpf/Makefile          |  3 +-
>  tools/testing/selftests/bpf/prog_tests/usdt.c | 85 +++++++++++++++++++
>  tools/testing/selftests/bpf/progs/test_usdt.c |  9 ++
>  tools/testing/selftests/bpf/usdt_1.c          | 18 ++++
>  tools/testing/selftests/bpf/usdt_2.c          | 16 ++++
>  6 files changed, 132 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/usdt_1.c
>  create mode 100644 tools/testing/selftests/bpf/usdt_2.c
>
> diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
> index a3ea98211ea6..bfdc5518ecc8 100644
> --- a/tools/testing/selftests/bpf/.gitignore
> +++ b/tools/testing/selftests/bpf/.gitignore
> @@ -47,3 +47,5 @@ verification_cert.h
>  *.BTF
>  *.BTF_ids
>  *.BTF.base
> +usdt_1
> +usdt_2
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index c6bf4dfb1495..306949162a5b 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -749,7 +749,8 @@ TRUNNER_EXTRA_SOURCES := test_progs.c               \
>                          $(VERIFY_SIG_HDR)              \
>                          flow_dissector_load.h  \
>                          ip_check_defrag_frags.h        \
> -                        bpftool_helpers.c
> +                        bpftool_helpers.c      \
> +                        usdt_1.c usdt_2.c
>  TRUNNER_LIB_SOURCES := find_bit.c
>  TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read                          \
>                        $(OUTPUT)/liburandom_read.so                     \
> diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c
> index f4be5269fa90..6daed3dfa75b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/usdt.c
> +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c
> @@ -247,6 +247,89 @@ static void subtest_basic_usdt(bool optimized)
>  #undef TRIGGER
>  }
>
> +#ifdef __x86_64__
> +extern void usdt_1(void);
> +extern void usdt_2(void);
> +
> +/* nop, nop5 */
> +static unsigned char nop1_nop5_combo[6] = { 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 };
> +static unsigned char nop1[6] = { 0x90 };
> +
> +static void *find_instr(void *fn, unsigned char *instr, size_t cnt)
> +{
> +       int i;
> +
> +       for (i = 0; i < 10; i++) {
> +               if (!memcmp(instr, fn + i, cnt))
> +                       return fn + i;
> +       }
> +       return NULL;
> +}
> +
> +static void subtest_optimized_attach(void)
> +{
> +       struct test_usdt *skel;
> +       __u8 *addr_1, *addr_2;
> +
> +       /* usdt_1 USDT probe has single nop instruction */
> +       addr_1 = find_instr(usdt_1, nop1_nop5_combo, 6);
> +       if (!ASSERT_NULL(addr_1, "usdt_1_find_nop1_nop5_combo"))
> +               return;
> +
> +       addr_1 = find_instr(usdt_1, nop1, 1);
> +       if (!ASSERT_OK_PTR(addr_1, "usdt_1_find_nop1"))
> +               return;
> +
> +       /* usdt_1 USDT probe has nop,nop5 instructions combo */
> +       addr_2 = find_instr(usdt_2, nop1_nop5_combo, 6);
> +       if (!ASSERT_OK_PTR(addr_2, "usdt_2_find_nop1_nop5_combo"))
> +               return;
> +
> +       skel = test_usdt__open_and_load();
> +       if (!ASSERT_OK_PTR(skel, "test_usdt__open_and_load"))
> +               return;
> +
> +       /*
> +        * Attach program on top of usdt_1 which is single nop probe,
> +        * so the probe won't get optimized.
> +        */
> +       skel->links.usdt_executed = bpf_program__attach_usdt(skel->progs.usdt_executed,
> +                                                    0 /*self*/, "/proc/self/exe",
> +                                                    "optimized_attach", "usdt_1", NULL);
> +       if (!ASSERT_OK_PTR(skel->links.usdt_executed, "bpf_program__attach_usdt"))
> +               goto cleanup;
> +
> +       usdt_1();
> +       usdt_1();
> +
> +       /* nop is on addr_1 address */
> +       ASSERT_EQ(*addr_1, 0xcc, "int3");
> +       ASSERT_EQ(skel->bss->executed, 2, "executed");
> +
> +       bpf_link__destroy(skel->links.usdt_executed);
> +
> +       /*
> +        * Attach program on top of usdt_2 which is probe defined on top
> +        * of nop1,nop5 combo, so the probe gets optimized on top of nop5.
> +        */
> +       skel->links.usdt_executed = bpf_program__attach_usdt(skel->progs.usdt_executed,
> +                                                    0 /*self*/, "/proc/self/exe",
> +                                                    "optimized_attach", "usdt_2", NULL);
> +       if (!ASSERT_OK_PTR(skel->links.usdt_executed, "bpf_program__attach_usdt"))
> +               goto cleanup;
> +
> +       usdt_2();
> +       usdt_2();
> +
> +       /* nop5 is on addr_2 + 1 address */
> +       ASSERT_EQ(*(addr_2 + 1), 0xe8, "call");
> +       ASSERT_EQ(skel->bss->executed, 4, "executed");
> +
> +cleanup:
> +       test_usdt__destroy(skel);
> +}
> +#endif
> +
>  unsigned short test_usdt_100_semaphore SEC(".probes");
>  unsigned short test_usdt_300_semaphore SEC(".probes");
>  unsigned short test_usdt_400_semaphore SEC(".probes");
> @@ -516,6 +599,8 @@ void test_usdt(void)
>  #ifdef __x86_64__
>         if (test__start_subtest("basic_optimized"))
>                 subtest_basic_usdt(true);
> +       if (test__start_subtest("optimized_attach"))
> +               subtest_optimized_attach();
>  #endif
>         if (test__start_subtest("multispec"))
>                 subtest_multispec_usdt();
> diff --git a/tools/testing/selftests/bpf/progs/test_usdt.c b/tools/testing/selftests/bpf/progs/test_usdt.c
> index a78c87537b07..6911868cdf67 100644
> --- a/tools/testing/selftests/bpf/progs/test_usdt.c
> +++ b/tools/testing/selftests/bpf/progs/test_usdt.c
> @@ -138,4 +138,13 @@ int usdt_sib(struct pt_regs *ctx)
>         return 0;
>  }
>
> +int executed;
> +
> +SEC("usdt")
> +int usdt_executed(struct pt_regs *ctx)
> +{
> +       executed++;

did you try capturing pt_reg's ip value and validating it?


> +       return 0;
> +}
> +
>  char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/usdt_1.c b/tools/testing/selftests/bpf/usdt_1.c
> new file mode 100644
> index 000000000000..4f06e8bcf58b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/usdt_1.c
> @@ -0,0 +1,18 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#if defined(__x86_64__)
> +
> +/*
> + * Include usdt.h with defined USDT_NOP macro to use single
> + * nop instruction.
> + */
> +#define USDT_NOP .byte 0x90
> +#include "usdt.h"
> +
> +__attribute__((aligned(16)))
> +void usdt_1(void)
> +{
> +       USDT(optimized_attach, usdt_1);
> +}
> +
> +#endif
> diff --git a/tools/testing/selftests/bpf/usdt_2.c b/tools/testing/selftests/bpf/usdt_2.c
> new file mode 100644
> index 000000000000..789883aaca4c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/usdt_2.c
> @@ -0,0 +1,16 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#if defined(__x86_64__)
> +
> +/*
> + * Include usdt.h with default nop,nop5 instructions combo.
> + */
> +#include "usdt.h"
> +
> +__attribute__((aligned(16)))
> +void usdt_2(void)
> +{
> +       USDT(optimized_attach, usdt_2);
> +}
> +
> +#endif
> --
> 2.53.0
>
Re: [PATCHv3 bpf-next 4/5] selftests/bpf: Add test for checking correct nop of optimized usdt
Posted by Jiri Olsa 1 day, 3 hours ago 
On Wed, Feb 11, 2026 at 01:45:24PM -0800, Andrii Nakryiko wrote:

SNIP

> > diff --git a/tools/testing/selftests/bpf/progs/test_usdt.c b/tools/testing/selftests/bpf/progs/test_usdt.c
> > index a78c87537b07..6911868cdf67 100644
> > --- a/tools/testing/selftests/bpf/progs/test_usdt.c
> > +++ b/tools/testing/selftests/bpf/progs/test_usdt.c
> > @@ -138,4 +138,13 @@ int usdt_sib(struct pt_regs *ctx)
> >         return 0;
> >  }
> >
> > +int executed;
> > +
> > +SEC("usdt")
> > +int usdt_executed(struct pt_regs *ctx)
> > +{
> > +       executed++;
> 
> did you try capturing pt_reg's ip value and validating it?

ok, it's easy to add that check

jirka
Re: [PATCHv3 bpf-next 4/5] selftests/bpf: Add test for checking correct nop of optimized usdt
Posted by bot+bpf-ci@kernel.org 2 days, 8 hours ago 
> diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c
> --- a/tools/testing/selftests/bpf/prog_tests/usdt.c
> +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c

[ ... ]

> +static void subtest_optimized_attach(void)
> +{
> +	struct test_usdt *skel;
> +	__u8 *addr_1, *addr_2;
> +
> +	/* usdt_1 USDT probe has single nop instruction */
> +	addr_1 = find_instr(usdt_1, nop1_nop5_combo, 6);
> +	if (!ASSERT_NULL(addr_1, "usdt_1_find_nop1_nop5_combo"))
> +		return;
> +
> +	addr_1 = find_instr(usdt_1, nop1, 1);
> +	if (!ASSERT_OK_PTR(addr_1, "usdt_1_find_nop1"))
> +		return;
> +
> +	/* usdt_1 USDT probe has nop,nop5 instructions combo */
> +	addr_2 = find_instr(usdt_2, nop1_nop5_combo, 6);

This comment says "usdt_1" but the code operates on "usdt_2". Should this
say "usdt_2 USDT probe has nop,nop5 instructions combo" to match the code?


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21898612624

AI-authorship-score: low
AI-authorship-explanation: The code follows standard kernel selftest patterns with natural commit message style, and the copy-paste comment error is a characteristically human mistake.
issues-found: 1
issue-severity-score: low
issue-severity-explanation: Comment/code mismatch in test file where comment says usdt_1 but code operates on usdt_2; does not affect test functionality.

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