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Thu, 14 Aug 2025 02:00:58 -0700 (PDT) Received: from krava ([2a02:8308:a00c:e200::31e0]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45a1c6e336csm13777865e9.16.2025.08.14.02.00.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Aug 2025 02:00:57 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 14 Aug 2025 11:00:55 +0200 To: Jiawei Zhao Cc: andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, shuah@kernel.org, yonghong.song@linux.dev, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next v8 2/2] selftests/bpf: Add an usdt_o2 test case in selftests to cover SIB handling logic Message-ID: References: <20250814064504.103401-1-phoenix500526@163.com> <20250814064504.103401-3-phoenix500526@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250814064504.103401-3-phoenix500526@163.com> On Thu, Aug 14, 2025 at 06:45:04AM +0000, 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 hi, on my setup (gcc15) the test generates ust register argument: stapsdt 0x0000002a NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt1 Location: 0x00000000007677ce, Base: 0x00000000035bc728, Semaphore: 0x0000000000000000 Arguments: 8@%rax 7677c6: 48 8b 04 c5 20 49 9c mov 0x39c4920(,%rax,8),%rax 7677cd: 03 7677ce: 90 nop I'm not sure if there's reliable solution to generate SIB argument from gcc, maybe we could generate all in assembly, but that might get complicated jirka > > Signed-off-by: Jiawei Zhao > --- > tools/testing/selftests/bpf/Makefile | 1 + > .../selftests/bpf/prog_tests/usdt_o2.c | 69 +++++++++++++++++++ > .../selftests/bpf/progs/test_usdt_o2.c | 37 ++++++++++ > 3 files changed, 107 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 4863106034df..24ff1a329625 100644 > --- a/tools/testing/selftests/bpf/Makefile > +++ b/tools/testing/selftests/bpf/Makefile > @@ -760,6 +760,7 @@ TRUNNER_BPF_BUILD_RULE := $$(error no BPF objects should be built) > TRUNNER_BPF_CFLAGS := > $(eval $(call DEFINE_TEST_RUNNER,test_maps)) > > + > # 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..f02dcf5188ab > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/usdt_o2.c > @@ -0,0 +1,69 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2025 Jiawei Zhao . */ > +#include > + > +#include "../sdt.h" > +#include "test_usdt_o2.skel.h" > + > +#if defined(__GNUC__) && !defined(__clang__) > +__attribute__((optimize("O2"))) > +#endif > + > +#define test_value 0xFEDCBA9876543210ULL > +#define SEC(name) __attribute__((section(name), used)) > + > +int lets_test_this(int); > +static volatile __u64 array[1] = {test_value}; > + > +static __always_inline void trigger_func(void) > +{ > + /* Base address + offset + (index * scale) */ > + 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 > +#include > + > +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"; > -- > 2.43.0 > >