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 <[email protected]>

Author: olsajiri

tools/testing/selftests/bpf/.gitignore

@@ -45,3 +45,5 @@ xdp_synproxy
 xdp_hw_metadata
 xdp_features
 verification_cert.h
+usdt_1
+usdt_2

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			\

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();

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";

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);
+}

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);
+}