On 8/6/25 2:24 AM, Jiawei Zhao 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@xxxxxxx>
---
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
I tried your selftest with gcc14 and llvm20 in my environment. See below:
llvm20:
Displaying notes found in: .note.stapsdt
Owner Data size Description
stapsdt 0x0000002f NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt1
Location: 0x00000000000003ac, Base: 0x0000000000000000, Semaphore: 0x0000000000000000
Arguments: 8@-64(%rbp)
gcc14:
Displaying notes found in: .note.stapsdt
Owner Data size Description
stapsdt 0x00000034 NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt1
Location: 0x0000000000000334, Base: 0x0000000000000000, Semaphore: 0x0000000000000000
Arguments: 8@array(,%rax,8)
llvm20 and gcc14 generate different usdt patterns. '8@-64(%rbp)' already supports so
with SIB support, the test should pass CI, I think.
+
# 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@xxxxxxx>. */
+#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");
+
+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]);
+ }
+}
+
+static void basic_sib_usdt(void)
+{
+ LIBBPF_OPTS(bpf_usdt_opts, opts);
+ struct test_usdt_o2 *skel;
+ struct test_usdt_o2__bss *bss;
+ int err;
+
+ skel = test_usdt_o2__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+
+ bss = skel->bss;
+ bss->my_pid = getpid();
+
+ err = test_usdt_o2__attach(skel);
+ if (!ASSERT_OK(err, "skel_attach"))
+ goto cleanup;
+
+ /* usdt1 won't be auto-attached */
+ opts.usdt_cookie = 0xcafedeadbeeffeed;
+ skel->links.usdt1 = bpf_program__attach_usdt(skel->progs.usdt1,
+ 0 /*self*/, "/proc/self/exe",
+ "test", "usdt1", &opts);
+ if (!ASSERT_OK_PTR(skel->links.usdt1, "usdt1_link"))
+ goto cleanup;
+
+ trigger_func();
+
+ ASSERT_EQ(bss->usdt1_called, 1, "usdt1_called");
+ ASSERT_EQ(bss->usdt1_cookie, 0xcafedeadbeeffeed, "usdt1_cookie");
+ ASSERT_EQ(bss->usdt1_arg_cnt, 1, "usdt1_arg_cnt");
+ ASSERT_EQ(bss->usdt1_arg, test_value, "usdt1_arg");
+ ASSERT_EQ(bss->usdt1_arg_ret, 0, "usdt1_arg_ret");
+ ASSERT_EQ(bss->usdt1_arg_size, sizeof(array[0]), "usdt1_arg_size");
+
+cleanup:
+ test_usdt_o2__destroy(skel);
+}
+
+
+
+void test_usdt_o2(void)
+{
+ basic_sib_usdt();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_usdt_o2.c b/tools/testing/selftests/bpf/progs/test_usdt_o2.c
new file mode 100644
index 000000000000..14602aa54578
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_usdt_o2.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/usdt.bpf.h>
+
+int my_pid;
+
+int usdt1_called;
+u64 usdt1_cookie;
+int usdt1_arg_cnt;
+int usdt1_arg_ret;
+u64 usdt1_arg;
+int usdt1_arg_size;
+
+SEC("usdt")
+int usdt1(struct pt_regs *ctx)
+{
+ long tmp;
+
+ if (my_pid != (bpf_get_current_pid_tgid() >> 32))
+ return 0;
+
+ __sync_fetch_and_add(&usdt1_called, 1);
+
+ usdt1_cookie = bpf_usdt_cookie(ctx);
+ usdt1_arg_cnt = bpf_usdt_arg_cnt(ctx);
+
+ usdt1_arg_ret = bpf_usdt_arg(ctx, 0, &tmp);
+ usdt1_arg = (u64)tmp;
+ usdt1_arg_size = bpf_usdt_arg_size(ctx, 0);
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
