On Wed, Aug 6, 2025 at 7:35 PM Jiawei Zhao phoenix500526@163.com wrote:
When using GCC on x86-64 to compile an usdt prog with -O1 or higher optimization, the compiler will generate SIB addressing mode for global array and PC-relative addressing mode for global variable, e.g. "1@-96(%rbp,%rax,8)" and "-1@4+t1(%rip)".
In this patch:
- add usdt_o2 test case to cover SIB addressing usdt argument spec handling logic
Signed-off-by: Jiawei Zhao phoenix500526@163.com
tools/testing/selftests/bpf/Makefile | 8 +++ .../selftests/bpf/prog_tests/usdt_o2.c | 71 +++++++++++++++++++ .../selftests/bpf/progs/test_usdt_o2.c | 37 ++++++++++ 3 files changed, 116 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/usdt_o2.c create mode 100644 tools/testing/selftests/bpf/progs/test_usdt_o2.c
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 910d8d6402ef..68cf6a9cf05f 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -759,6 +759,14 @@ TRUNNER_BPF_BUILD_RULE := $$(error no BPF objects should be built) TRUNNER_BPF_CFLAGS := $(eval $(call DEFINE_TEST_RUNNER,test_maps))
+# Use -O2 optimization to generate SIB addressing usdt argument spec +# Only apply on x86 architecture where SIB addressing is relevant +ifeq ($(ARCH), x86) +$(OUTPUT)/usdt_o2.test.o: CFLAGS:=$(subst O0,O2,$(CFLAGS)) +$(OUTPUT)/cpuv4/usdt_o2.test.o: CFLAGS:=$(subst O0,O2,$(CFLAGS)) +$(OUTPUT)/no_alu32/usdt_o2.test.o: CFLAGS:=$(subst O0,O2,$(CFLAGS)) +endif
Have you considered using GCC's __attribute__((optimize("O2"))) attribute. It seems like Clang doesn't have support for something like that, but we'll still have this covered in BPF CI for GCC-built selftests. Then I'd just add this as another subtest to existing usdt tests.
Can you please try that?
# Define test_verifier test runner. # It is much simpler than test_maps/test_progs and sufficiently different from # them (e.g., test.h is using completely pattern), that it's worth just diff --git a/tools/testing/selftests/bpf/prog_tests/usdt_o2.c b/tools/testing/selftests/bpf/prog_tests/usdt_o2.c new file mode 100644 index 000000000000..f04b756b3640 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/usdt_o2.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2025 Jiawei Zhao phoenix500526@163.com. */ +#include <test_progs.h>
+#define _SDT_HAS_SEMAPHORES 1 +#include "../sdt.h" +#include "test_usdt_o2.skel.h"
+int lets_test_this(int);
+#define test_value 0xFEDCBA9876543210ULL +#define SEC(name) __attribute__((section(name), used))
+static volatile __u64 array[1] = {test_value}; +unsigned short test_usdt1_semaphore SEC(".probes");
Is semaphore essential to this test?
+static __always_inline void trigger_func(void) +{
/* Base address + offset + (index * scale) */if (test_usdt1_semaphore) {for (volatile int i = 0; i <= 0; i++)STAP_PROBE1(test, usdt1, array[i]);}+}
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