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Message-ID: <20251117083551.517393-5-jolsa@kernel.org>
Date: Mon, 17 Nov 2025 09:35:51 +0100
From: Jiri Olsa <jolsa@...nel.org>
To: Andrii Nakryiko <andrii@...nel.org>
Cc: bpf@...r.kernel.org,
linux-kernel@...r.kernel.org,
Song Liu <songliubraving@...com>,
Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>
Subject: [PATCH bpf-next 4/4] selftests/bpf: Add test for checking correct nop of optimized usdt
Adding test that attaches bpf program on usdt probe in 2 scenarios;
- attach program on top of usdt_1 which is standard nop probe
incidentally followed by nop5. The usdt probe does not have
extra data in elf note record, so we expect the probe to land
on the first nop without being optimized.
- attach program on top of usdt_2 which is probe defined on top
of nop,nop5 combo. The extra data in the elf note record and
presence of upeobe syscall ensures that the probe is placed
on top of nop5 and optimized.
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
tools/testing/selftests/bpf/.gitignore | 2 +
tools/testing/selftests/bpf/Makefile | 7 +-
tools/testing/selftests/bpf/prog_tests/usdt.c | 82 +++++++++++++++++++
tools/testing/selftests/bpf/progs/test_usdt.c | 9 ++
tools/testing/selftests/bpf/usdt_1.c | 14 ++++
tools/testing/selftests/bpf/usdt_2.c | 13 +++
6 files changed, 126 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 be1ee7ba7ce0..89f480729a6b 100644
--- a/tools/testing/selftests/bpf/.gitignore
+++ b/tools/testing/selftests/bpf/.gitignore
@@ -45,3 +45,5 @@ xdp_synproxy
xdp_hw_metadata
xdp_features
verification_cert.h
+usdt_1
+usdt_2
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 34ea23c63bd5..4a21657e45f7 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -733,6 +733,10 @@ $(VERIFICATION_CERT) $(PRIVATE_KEY): $(VERIFY_SIG_SETUP)
$(VERIFY_SIG_HDR): $(VERIFICATION_CERT)
$(Q)xxd -i -n test_progs_verification_cert $< > $@
+ifeq ($(SRCARCH),$(filter $(SRCARCH),x86))
+USDTX := usdt_1.c usdt_2.c
+endif
+
# Define test_progs test runner.
TRUNNER_TESTS_DIR := prog_tests
TRUNNER_BPF_PROGS_DIR := progs
@@ -754,7 +758,8 @@ TRUNNER_EXTRA_SOURCES := test_progs.c \
json_writer.c \
$(VERIFY_SIG_HDR) \
flow_dissector_load.h \
- ip_check_defrag_frags.h
+ ip_check_defrag_frags.h \
+ $(USDTX)
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..a8ca2920c009 100644
--- a/tools/testing/selftests/bpf/prog_tests/usdt.c
+++ b/tools/testing/selftests/bpf/prog_tests/usdt.c
@@ -247,6 +247,86 @@ 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 nop15[6] = { 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 };
+
+static void *find_nop15(void *fn)
+{
+ int i;
+
+ for (i = 0; i < 10; i++) {
+ if (!memcmp(nop15, fn + i, 5))
+ return fn + i;
+ }
+ return NULL;
+}
+
+static void subtest_optimized_attach(void)
+{
+ struct test_usdt *skel;
+ __u8 *addr_1, *addr_2;
+
+ addr_1 = find_nop15(usdt_1);
+ if (!ASSERT_OK_PTR(addr_1, "find_nop15"))
+ return;
+
+ addr_2 = find_nop15(usdt_2);
+ if (!ASSERT_OK_PTR(addr_2, "find_nop15"))
+ 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 standard nop probe
+ * incidentally followed by nop5. The usdt probe does not have
+ * extra data in elf note record, so we expect the probe to land
+ * on the first nop without being 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 nop,nop5 combo. The extra data in the elf note record and
+ * presence of uprobe syscall ensures that the probe is placed
+ * on top of nop5 and optimized.
+ */
+ 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 +596,8 @@ 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..0e00702b1701
--- /dev/null
+++ b/tools/testing/selftests/bpf/usdt_1.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Include usdt.h with defined USDT_NOP macro will switch
+ * off the extra info in usdt probe.
+ */
+#define USDT_NOP .byte 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00
+#include "usdt.h"
+
+__attribute__((aligned(16)))
+void usdt_1(void)
+{
+ USDT(optimized_attach, usdt_1);
+}
diff --git a/tools/testing/selftests/bpf/usdt_2.c b/tools/testing/selftests/bpf/usdt_2.c
new file mode 100644
index 000000000000..fcb7417a1953
--- /dev/null
+++ b/tools/testing/selftests/bpf/usdt_2.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Include usdt.h with the extra info in usdt probe and
+ * nop/nop5 combo for usdt attach point.
+ */
+#include "usdt.h"
+
+__attribute__((aligned(16)))
+void usdt_2(void)
+{
+ USDT(optimized_attach, usdt_2);
+}
--
2.51.1
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