From: Jiri Olsa <jolsa@kernel.org>
To: Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>
Subject: [PATCHv4 bpf-next 4/5] selftests/bpf: Add test for checking correct nop of optimized usdt
Date: Fri, 20 Feb 2026 11:42:19 +0100 [thread overview]
Message-ID: <20260220104220.634154-5-jolsa@kernel.org> (raw)
In-Reply-To: <20260220104220.634154-1-jolsa@kernel.org>
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 | 92 +++++++++++++++++++
tools/testing/selftests/bpf/progs/test_usdt.c | 12 +++
tools/testing/selftests/bpf/usdt_1.c | 18 ++++
tools/testing/selftests/bpf/usdt_2.c | 16 ++++
6 files changed, 142 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 6776158f1f3e..23857d17fc5b 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..69759b27794d 100644
--- a/tools/testing/selftests/bpf/prog_tests/usdt.c
+++ b/tools/testing/selftests/bpf/prog_tests/usdt.c
@@ -247,6 +247,96 @@ static void subtest_basic_usdt(bool optimized)
#undef TRIGGER
}
+#ifdef __x86_64__
+extern void usdt_1(void);
+extern void usdt_2(void);
+
+static unsigned char nop1[1] = { 0x90 };
+static unsigned char nop1_nop5_combo[6] = { 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 };
+
+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_2 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;
+
+ skel->bss->expected_ip = (unsigned long) addr_1;
+
+ /*
+ * 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();
+
+ /* int3 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);
+
+ /* we expect the nop5 ip */
+ skel->bss->expected_ip = (unsigned long) addr_2 + 1;
+
+ /*
+ * 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();
+
+ /* nop stays on addr_2 address */
+ ASSERT_EQ(*addr_2, 0x90, "nop");
+
+ /* call 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 +606,8 @@ 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..f00cb52874e0 100644
--- a/tools/testing/selftests/bpf/progs/test_usdt.c
+++ b/tools/testing/selftests/bpf/progs/test_usdt.c
@@ -138,4 +138,16 @@ int usdt_sib(struct pt_regs *ctx)
return 0;
}
+#ifdef __TARGET_ARCH_x86
+int executed;
+unsigned long expected_ip;
+
+SEC("usdt")
+int usdt_executed(struct pt_regs *ctx)
+{
+ if (expected_ip == ctx->ip)
+ executed++;
+ return 0;
+}
+#endif
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
next prev parent reply other threads:[~2026-02-20 10:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-20 10:42 [PATCHv4 bpf-next 0/5] libbpf: Make optimized uprobes backward compatible Jiri Olsa
2026-02-20 10:42 ` [PATCHv4 bpf-next 1/5] libbpf: Add uprobe syscall feature detection Jiri Olsa
2026-02-20 10:42 ` [PATCHv4 bpf-next 2/5] libbpf: Add support to detect nop,nop5 instructions combo for usdt probe Jiri Olsa
2026-02-20 11:24 ` bot+bpf-ci
2026-02-21 12:00 ` David Laight
2026-02-22 14:32 ` Jiri Olsa
2026-02-20 10:42 ` [PATCHv4 bpf-next 3/5] selftests/bpf: Emit nop,nop5 instructions combo for x86_64 arch Jiri Olsa
2026-02-20 10:42 ` Jiri Olsa [this message]
2026-02-20 10:42 ` [PATCHv4 bpf-next 5/5] selftests/bpf: Add usdt trigger bench Jiri Olsa
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