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(unknown []) by gzsmtp4 (Coremail) with SMTP id PygvCgBHfPRQa6loSD0TAQ--.40650S4; Sat, 23 Aug 2025 15:18:45 +0800 (CST) From: Jiawei Zhao To: ast@kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, yonghong.song@linux.dev, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v15 2/2] selftests/bpf: Enrich subtest_basic_usdt case in selftests to cover SIB handling logic Date: Sat, 23 Aug 2025 07:18:39 +0000 Message-ID: <20250823071839.1191350-3-phoenix500526@163.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250823071839.1191350-1-phoenix500526@163.com> References: <20250823071839.1191350-1-phoenix500526@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: PygvCgBHfPRQa6loSD0TAQ--.40650S4 X-Coremail-Antispam: 1Uf129KBjvJXoWxKF15Cry3JFW7ZFWkWw4DArb_yoWxGFyUpa ykZ34ftFy5t3WxGw4xJr4jqw4rKFn2yrW5AFZrXry2yrWkGrs7Xrn7K3W3KFnIqaykX3W5 ArZ0kan5tw4xXF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jg8n5UUUUU= X-CM-SenderInfo: pskrv0dl0viiqvswqiywtou0bp/1tbiFBqyiGipaC035AAAsj Content-Type: text/plain; charset="utf-8" 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: - enrich subtest_basic_usdt test case to cover SIB addressing usdt argument= spec handling logic Signed-off-by: Jiawei Zhao --- tools/testing/selftests/bpf/prog_tests/usdt.c | 62 ++++++++++++++++++- tools/testing/selftests/bpf/progs/test_usdt.c | 32 ++++++++++ 2 files changed, 92 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/= selftests/bpf/prog_tests/usdt.c index 9057e983cc54..4b264f7d3324 100644 --- a/tools/testing/selftests/bpf/prog_tests/usdt.c +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c @@ -10,6 +10,26 @@ =20 int lets_test_this(int); =20 +#if defined(__x86_64__) || defined(__i386__) +/* + * SIB (Scale-Index-Base) addressing format: + * "size@(base_reg, index_reg, scale)" + * - 'size' is the size in bytes of the array element, and its sign indica= tes + * whether the type is signed (negative) or unsigned (positive). + * - 'base_reg' is the register holding the base address, normally rdx or = edx + * - 'index_reg' is the register holding the index, normally rax or eax + * - 'scale' is the scaling factor (typically 1, 2, 4, or 8), which matche= s the + * size of the element type. + * + * For example, for an array of 'short' (signed 2-byte elements), the SIB = spec would be: + * - size: -2 (negative because 'short' is signed) + * - scale: 2 (since sizeof(short) =3D=3D 2) + * The resulting SIB format: "-2@(%%rdx,%%rax,2)" + */ +static volatile short array[] =3D {-1, -2, -3, -4}; +#define USDT_SIB_ARG_SPEC -2@(%%rdx,%%rax,2) +#endif + static volatile int idx =3D 2; static volatile __u64 bla =3D 0xFEDCBA9876543210ULL; static volatile short nums[] =3D {-1, -2, -3, -4}; @@ -25,6 +45,10 @@ unsigned short test_usdt0_semaphore SEC(".probes"); unsigned short test_usdt3_semaphore SEC(".probes"); unsigned short test_usdt12_semaphore SEC(".probes"); =20 +#if defined(__x86_64__) || defined(__i386__) +unsigned short test_usdt_sib_semaphore SEC(".probes"); +#endif + static void __always_inline trigger_func(int x) { long y =3D 42; =20 @@ -40,12 +64,27 @@ static void __always_inline trigger_func(int x) { } } =20 +#if defined(__x86_64__) || defined(__i386__) +static void trigger_sib_spec(void) +{ + /* Base address + offset + (index * scale) */ + /* Force SIB addressing with inline assembly */ + asm volatile( + STAP_PROBE_ASM(test, usdt_sib, USDT_SIB_ARG_SPEC) + : + : "d"(array), "a"(0) + : "memory" + ); +} +#endif + static void subtest_basic_usdt(void) { LIBBPF_OPTS(bpf_usdt_opts, opts); struct test_usdt *skel; struct test_usdt__bss *bss; int err, i; + const __u64 expected_cookie =3D 0xcafedeadbeeffeed; =20 skel =3D test_usdt__open_and_load(); if (!ASSERT_OK_PTR(skel, "skel_open")) @@ -59,20 +98,29 @@ static void subtest_basic_usdt(void) goto cleanup; =20 /* usdt0 won't be auto-attached */ - opts.usdt_cookie =3D 0xcafedeadbeeffeed; + opts.usdt_cookie =3D expected_cookie; skel->links.usdt0 =3D bpf_program__attach_usdt(skel->progs.usdt0, 0 /*self*/, "/proc/self/exe", "test", "usdt0", &opts); if (!ASSERT_OK_PTR(skel->links.usdt0, "usdt0_link")) goto cleanup; =20 +#if defined(__x86_64__) || defined(__i386__) + opts.usdt_cookie =3D expected_cookie; + skel->links.usdt_sib =3D bpf_program__attach_usdt(skel->progs.usdt_sib, + 0 /*self*/, "/proc/self/exe", + "test", "usdt_sib", &opts); + if (!ASSERT_OK_PTR(skel->links.usdt_sib, "usdt_sib_link")) + goto cleanup; +#endif + trigger_func(1); =20 ASSERT_EQ(bss->usdt0_called, 1, "usdt0_called"); ASSERT_EQ(bss->usdt3_called, 1, "usdt3_called"); ASSERT_EQ(bss->usdt12_called, 1, "usdt12_called"); =20 - ASSERT_EQ(bss->usdt0_cookie, 0xcafedeadbeeffeed, "usdt0_cookie"); + ASSERT_EQ(bss->usdt0_cookie, expected_cookie, "usdt0_cookie"); ASSERT_EQ(bss->usdt0_arg_cnt, 0, "usdt0_arg_cnt"); ASSERT_EQ(bss->usdt0_arg_ret, -ENOENT, "usdt0_arg_ret"); ASSERT_EQ(bss->usdt0_arg_size, -ENOENT, "usdt0_arg_size"); @@ -156,6 +204,16 @@ static void subtest_basic_usdt(void) ASSERT_EQ(bss->usdt3_args[1], 42, "usdt3_arg2"); ASSERT_EQ(bss->usdt3_args[2], (uintptr_t)&bla, "usdt3_arg3"); =20 +#if defined(__x86_64__) || defined(__i386__) + trigger_sib_spec(); + ASSERT_EQ(bss->usdt_sib_called, 1, "usdt_sib_called"); + ASSERT_EQ(bss->usdt_sib_cookie, expected_cookie, "usdt_sib_cookie"); + ASSERT_EQ(bss->usdt_sib_arg_cnt, 1, "usdt_sib_arg_cnt"); + ASSERT_EQ(bss->usdt_sib_arg, nums[0], "usdt_sib_arg"); + ASSERT_EQ(bss->usdt_sib_arg_ret, 0, "usdt_sib_arg_ret"); + ASSERT_EQ(bss->usdt_sib_arg_size, sizeof(nums[0]), "usdt_sib_arg_size"); +#endif + cleanup: test_usdt__destroy(skel); } diff --git a/tools/testing/selftests/bpf/progs/test_usdt.c b/tools/testing/= selftests/bpf/progs/test_usdt.c index 096488f47fbc..63db72253316 100644 --- a/tools/testing/selftests/bpf/progs/test_usdt.c +++ b/tools/testing/selftests/bpf/progs/test_usdt.c @@ -107,4 +107,36 @@ int BPF_USDT(usdt12, int a1, int a2, long a3, long a4,= unsigned a5, return 0; } =20 + +int usdt_sib_called; +u64 usdt_sib_cookie; +int usdt_sib_arg_cnt; +int usdt_sib_arg_ret; +u64 usdt_sib_arg; +int usdt_sib_arg_size; + +/* + * usdt_sib is only tested on x86-related architectures, so it requires + * manual attach since auto-attach will panic tests under other architectu= res + */ +SEC("usdt") +int usdt_sib(struct pt_regs *ctx) +{ + long tmp; + + if (my_pid !=3D (bpf_get_current_pid_tgid() >> 32)) + return 0; + + __sync_fetch_and_add(&usdt_sib_called, 1); + + usdt_sib_cookie =3D bpf_usdt_cookie(ctx); + usdt_sib_arg_cnt =3D bpf_usdt_arg_cnt(ctx); + + usdt_sib_arg_ret =3D bpf_usdt_arg(ctx, 0, &tmp); + usdt_sib_arg =3D (short)tmp; + usdt_sib_arg_size =3D bpf_usdt_arg_size(ctx, 0); + + return 0; +} + char _license[] SEC("license") =3D "GPL"; --=20 2.43.0