From nobody Sun Feb 8 13:27:15 2026 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.2]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8B0C324467F; Thu, 14 Aug 2025 06:45:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.2 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755153938; cv=none; b=qOj99pTC4Oa4niKHvPmgfJh6IftIvKy3C1vYXGNbI6S9sG5nFa6rQPGMmxqpx0xDFGIkksWJm1PBjM3fZYqN648hNAGhYDhC/AO0vYeipauJTST67U3RWKju17/C45nwg1/qJG8RB0io2yeA74T5YoDSTXFZI5kRaT4PdNw8Z40= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755153938; c=relaxed/simple; bh=GqGmvapcqj9zCgiVIWLXB/BD3psZXJmQZX3DZ9pVLjY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F1hyV8LA3vQJSNl7ljSEcPAKCkrTm/gGJsctWgkNT+rLjIhHscIwAg+cdtzpocfb2AnevOMncWex4dnNC448MVjzo+RIZNmFP0j2I4zMgHeicvnUIeCZOH0OFyAYDyST0HVJN24AKZf+jlLkxpkN40HtDJ4HlNDDtwsYMlPG2q0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=CxwKuzwX; arc=none smtp.client-ip=220.197.31.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="CxwKuzwX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=vA JZWIBZ/GMlJcKm2t6cSG7u1EC34nHt8lN2Xu8aVjE=; b=CxwKuzwXyECzP8vlX4 6f5i2omQytvl4q0uX/zVneqKH9Ih/+M/ncGJ+/E5TeNMhiMyU6Z5i6ecVeJquZpw 2d+Azb8uHzj6lh12lyMvhmj5YMdFzxC42thNjmwuz/IuiS4oimyzPOznEEXVHo7m q7EsFMS3MlkINzo7La0ojtAXM= Received: from phoenix.. (unknown []) by gzga-smtp-mtada-g0-2 (Coremail) with SMTP id _____wCHVEjxhZ1oTQ2nBQ--.36242S3; Thu, 14 Aug 2025 14:45:08 +0800 (CST) From: Jiawei Zhao To: andrii@kernel.org Cc: 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: [PATCH bpf-next v8 1/2] libbpf: fix USDT SIB argument handling causing unrecognized register error Date: Thu, 14 Aug 2025 06:45:03 +0000 Message-ID: <20250814064504.103401-2-phoenix500526@163.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250814064504.103401-1-phoenix500526@163.com> References: <20250814064504.103401-1-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: _____wCHVEjxhZ1oTQ2nBQ--.36242S3 X-Coremail-Antispam: 1Uf129KBjvJXoWxtryfArWkXF4kJr48Zr1fJFb_yoW3WFy3pa 109r9ayry8Jr4SvF4fX3WFya43CFs7Gr4rAr1kta4YvFWxWr4UXrySkF1Ykrn8Ka47tF43 XF4YqrWxCa47Zr7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07j7PEfUUUUU= X-CM-SenderInfo: pskrv0dl0viiqvswqiywtou0bp/xtbBgBapiGidhbQFfQAAsL Content-Type: text/plain; charset="utf-8" On x86-64, USDT arguments can be specified using Scale-Index-Base (SIB) addressing, e.g. "1@-96(%rbp,%rax,8)". The current USDT implementation in libbpf cannot parse this format, causing `bpf_program__attach_usdt()` to fail with -ENOENT (unrecognized register). This patch fixes this by implementing the necessary changes: - add correct handling for SIB-addressed arguments in `bpf_usdt_arg`. - add adaptive support to `__bpf_usdt_arg_type` and `__bpf_usdt_arg_spec` to represent SIB addressing parameters. Signed-off-by: Jiawei Zhao --- tools/lib/bpf/usdt.bpf.h | 55 ++++++++++++++++++++++++++++++++++-- tools/lib/bpf/usdt.c | 61 ++++++++++++++++++++++++++++++++++++---- 2 files changed, 109 insertions(+), 7 deletions(-) diff --git a/tools/lib/bpf/usdt.bpf.h b/tools/lib/bpf/usdt.bpf.h index 2a7865c8e3fe..f6bb7d6e4f9a 100644 --- a/tools/lib/bpf/usdt.bpf.h +++ b/tools/lib/bpf/usdt.bpf.h @@ -34,13 +34,31 @@ enum __bpf_usdt_arg_type { BPF_USDT_ARG_CONST, BPF_USDT_ARG_REG, BPF_USDT_ARG_REG_DEREF, + BPF_USDT_ARG_SIB, }; =20 +/* + * To preserve overall layout and avoid growing this struct while adding S= IB + * extras, we keep 4 bytes worth of space after val_off: + * + * - arg_type is stored as a single byte (values from enum below) + * - idx_packed is a 16-bit field packing idx_reg_off (high 12 bits) + * and scale shift (low 4 bits, i.e., scale =3D 1 << shift) + * - reserved is one spare byte for future use + * + * This keeps the offset of reg_off identical to the historical layout + * (val_off:8 + 4 bytes here), ensuring backwards/forwards compatibility f= or + * non-SIB modes that only rely on val_off/arg_type/reg_off/... offsets. + */ struct __bpf_usdt_arg_spec { /* u64 scalar interpreted depending on arg_type, see below */ __u64 val_off; /* arg location case, see bpf_usdt_arg() for details */ - enum __bpf_usdt_arg_type arg_type; + __u8 arg_type; + /* packed: [15:4] idx_reg_off, [3:0] scale_shift */ + __u16 idx_packed; + /* reserved for future use, keeps reg_off offset stable */ + __u8 reserved; /* offset of referenced register within struct pt_regs */ short reg_off; /* whether arg should be interpreted as signed value */ @@ -52,6 +70,10 @@ struct __bpf_usdt_arg_spec { char arg_bitshift; }; =20 +/* Helpers to (un)pack SIB extras from idx_packed without relying on bitfi= elds. */ +#define USDT_IDX_OFF(packed) ((packed) >> 4) +#define USDT_IDX_SCALE_SHIFT(packed) ((packed) & 0x000f) + /* should match USDT_MAX_ARG_CNT in usdt.c exactly */ #define BPF_USDT_MAX_ARG_CNT 12 struct __bpf_usdt_spec { @@ -149,8 +171,9 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, lo= ng *res) { struct __bpf_usdt_spec *spec; struct __bpf_usdt_arg_spec *arg_spec; - unsigned long val; + unsigned long val, idx; int err, spec_id; + int idx_off =3D 0, scale =3D 0; =20 *res =3D 0; =20 @@ -202,6 +225,34 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, l= ong *res) return err; #if __BYTE_ORDER__ =3D=3D __ORDER_BIG_ENDIAN__ val >>=3D arg_spec->arg_bitshift; +#endif + break; + case BPF_USDT_ARG_SIB: + /* Arg is in memory addressed by SIB (Scale-Index-Base) mode + * (e.g., "-1@-96(%rbp,%rax,8)" in USDT arg spec). Register + * is identified like with BPF_USDT_ARG_SIB case, the offset + * is in arg_spec->val_off, the scale factor is in arg_spec->scale. + * Firstly, we fetch the base register contents and the index + * register contents from pt_regs. Secondly, we multiply the + * index register contents by the scale factor, then add the + * base address and the offset to get the final address. Finally, + * we do another user-space probe read to fetch argument value + * itself. + */ + idx_off =3D USDT_IDX_OFF(arg_spec->idx_packed); + scale =3D 1UL << USDT_IDX_SCALE_SHIFT(arg_spec->idx_packed); + err =3D bpf_probe_read_kernel(&val, sizeof(val), (void *)ctx + arg_spec-= >reg_off); + if (err) + return err; + err =3D bpf_probe_read_kernel(&idx, sizeof(idx), (void *)ctx + idx_off); + if (err) + return err; + err =3D bpf_probe_read_user(&val, sizeof(val), + (void *)val + idx * scale + arg_spec->val_off); + if (err) + return err; +#if __BYTE_ORDER__ =3D=3D __ORDER_BIG_ENDIAN__ + val >>=3D arg_spec->arg_bitshift; #endif break; default: diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c index 3373b9d45ac4..0a6499f654fc 100644 --- a/tools/lib/bpf/usdt.c +++ b/tools/lib/bpf/usdt.c @@ -200,12 +200,15 @@ enum usdt_arg_type { USDT_ARG_CONST, USDT_ARG_REG, USDT_ARG_REG_DEREF, + USDT_ARG_SIB, }; =20 /* should match exactly struct __bpf_usdt_arg_spec from usdt.bpf.h */ struct usdt_arg_spec { __u64 val_off; - enum usdt_arg_type arg_type; + __u8 arg_type; /* enum value stored as u8 */ + __u16 idx_packed; /* [15:4]=3Didx_reg_off, [3:0]=3Dscale_shift */ + __u8 reserved; /* keep reg_off offset stable */ short reg_off; bool arg_signed; char arg_bitshift; @@ -214,6 +217,10 @@ struct usdt_arg_spec { /* should match BPF_USDT_MAX_ARG_CNT in usdt.bpf.h */ #define USDT_MAX_ARG_CNT 12 =20 +/* Helpers to (un)pack SIB extras from idx_packed without relying on bitfi= elds. */ +#define BPF_USDT_IDX_PACK(idx_off, scale_shift) \ + ((__u16)(((__u16)((idx_off) & 0x0fff)) << 4) | (__u16)((scale_shift) & 0x= 000f)) + /* should match struct __bpf_usdt_spec from usdt.bpf.h */ struct usdt_spec { struct usdt_arg_spec args[USDT_MAX_ARG_CNT]; @@ -1283,11 +1290,54 @@ static int calc_pt_regs_off(const char *reg_name) =20 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_ar= g_spec *arg, int *arg_sz) { - char reg_name[16]; - int len, reg_off; - long off; + char reg_name[16] =3D {0}, idx_reg_name[16] =3D {0}; + int len, reg_off, idx_reg_off, scale =3D 1; + long off =3D 0; + __u16 scale_shift; + + if (sscanf(arg_str, " %d @ %ld ( %%%15[^,] , %%%15[^,] , %d ) %n", + arg_sz, &off, reg_name, idx_reg_name, &scale, &len) =3D=3D 5 || + sscanf(arg_str, " %d @ ( %%%15[^,] , %%%15[^,] , %d ) %n", + arg_sz, reg_name, idx_reg_name, &scale, &len) =3D=3D 4 || + sscanf(arg_str, " %d @ %ld ( %%%15[^,] , %%%15[^)] ) %n", + arg_sz, &off, reg_name, idx_reg_name, &len) =3D=3D 4 || + sscanf(arg_str, " %d @ ( %%%15[^,] , %%%15[^)] ) %n", + arg_sz, reg_name, idx_reg_name, &len) =3D=3D 3 + ) { + /* + * Scale Index Base case: + * 1@-96(%rbp,%rax,8) + * 1@(%rbp,%rax,8) + * 1@-96(%rbp,%rax) + * 1@(%rbp,%rax) + */ + arg->arg_type =3D USDT_ARG_SIB; + arg->val_off =3D off; =20 - if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n", arg_sz, &off, reg_name,= &len) =3D=3D 3) { + reg_off =3D calc_pt_regs_off(reg_name); + if (reg_off < 0) + return reg_off; + arg->reg_off =3D reg_off; + + idx_reg_off =3D calc_pt_regs_off(idx_reg_name); + if (idx_reg_off < 0) + return idx_reg_off; + /* pack idx_reg_off and scale shift (scale in {1,2,4,8}) */ + if (scale =3D=3D 1) + scale_shift =3D 0; + else if (scale =3D=3D 2) + scale_shift =3D 1; + else if (scale =3D=3D 4) + scale_shift =3D 2; + else if (scale =3D=3D 8) + scale_shift =3D 3; + else { + pr_warn("usdt: invalid SIB scale %d, expected 1,2,4,8; defaulting to 1\= n", scale); + return -EINVAL; + } + arg->idx_packed =3D BPF_USDT_IDX_PACK(idx_reg_off, scale_shift); + } else if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n", + arg_sz, &off, reg_name, &len) =3D=3D 3) { /* Memory dereference case, e.g., -4@-20(%rbp) */ arg->arg_type =3D USDT_ARG_REG_DEREF; arg->val_off =3D off; @@ -1306,6 +1356,7 @@ static int parse_usdt_arg(const char *arg_str, int ar= g_num, struct usdt_arg_spec } else if (sscanf(arg_str, " %d @ %%%15s %n", arg_sz, reg_name, &len) =3D= =3D 2) { /* Register read case, e.g., -4@%eax */ arg->arg_type =3D USDT_ARG_REG; + /* register read has no memory offset */ arg->val_off =3D 0; =20 reg_off =3D calc_pt_regs_off(reg_name); --=20 2.43.0 From nobody Sun Feb 8 13:27:15 2026 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.4]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0F95625EFBE; Thu, 14 Aug 2025 07:01:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.4 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755154870; cv=none; b=dwQG6w+D5653higroa4yBbwtv7sOcc12YSEwini72gCnl/cMlyn9eEi9LYpVAEvdLchQeL7u5CFeiI0y7oCyULHSCgRBilvRn3d3HBkqSPgw4czW9FargFHaGn/ntqu7PJjzDlxm5VpNbutPoXeAO5oTCiGWJmq1OzN1UqR6KMk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755154870; c=relaxed/simple; bh=l4RpZEZEyFuGtuV7W4a26EQUDXnqU+r9rXYOKFw33+U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F4GxBmW4HL5iod7Hnw067+SvoyXbuacjcHUHnIgHJdKNBERSkr8djGlr/3KAKdt7drPVw0WOMNLCm+aYKdyN1BDkGgQiJAmhbHp8VzTjLMoaf6T/Ea+VH85GQGo4kCZAOkkFDC2WOyd91LZZCwzhqTWUcp/CjVhliH2lRM6okxY= ARC-Authentication-Results: i=1; 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(unknown []) by gzga-smtp-mtada-g0-2 (Coremail) with SMTP id _____wCHVEjxhZ1oTQ2nBQ--.36242S4; Thu, 14 Aug 2025 14:45:08 +0800 (CST) From: Jiawei Zhao To: andrii@kernel.org Cc: 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: [PATCH bpf-next v8 2/2] selftests/bpf: Add an usdt_o2 test case in selftests to cover SIB handling logic Date: Thu, 14 Aug 2025 06:45:04 +0000 Message-ID: <20250814064504.103401-3-phoenix500526@163.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250814064504.103401-1-phoenix500526@163.com> References: <20250814064504.103401-1-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: _____wCHVEjxhZ1oTQ2nBQ--.36242S4 X-Coremail-Antispam: 1Uf129KBjvJXoWxWw4ktF4fAF15uFyUZw1UKFg_yoWrtrW5pa 48X348KFWIqF13K3Wftr4Utr4rKanayrW8JFykXryavr48JryIqr1xKr17tasxG395XF1r A39xtan8Gr48JaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07j2PfQUUUUU= X-CM-SenderInfo: pskrv0dl0viiqvswqiywtou0bp/xtbBawWpiGidggVa6QAAsO 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: - add usdt_o2 test case to cover SIB addressing usdt argument spec handling logic 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 :=3D $$(error no BPF objects sho= uld be built) TRUNNER_BPF_CFLAGS :=3D $(eval $(call DEFINE_TEST_RUNNER,test_maps)) =20 + # 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/testi= ng/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] =3D {test_value}; + +static __always_inline void trigger_func(void) +{ + /* Base address + offset + (index * scale) */ + for (volatile int i =3D 0; i <=3D 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 =3D test_usdt_o2__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open")) + return; + + bss =3D skel->bss; + bss->my_pid =3D getpid(); + + err =3D test_usdt_o2__attach(skel); + if (!ASSERT_OK(err, "skel_attach")) + goto cleanup; + + /* usdt1 won't be auto-attached */ + opts.usdt_cookie =3D 0xcafedeadbeeffeed; + skel->links.usdt1 =3D 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/testi= ng/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 !=3D (bpf_get_current_pid_tgid() >> 32)) + return 0; + + __sync_fetch_and_add(&usdt1_called, 1); + + usdt1_cookie =3D bpf_usdt_cookie(ctx); + usdt1_arg_cnt =3D bpf_usdt_arg_cnt(ctx); + + usdt1_arg_ret =3D bpf_usdt_arg(ctx, 0, &tmp); + usdt1_arg =3D (u64)tmp; + usdt1_arg_size =3D bpf_usdt_arg_size(ctx, 0); + + return 0; +} + +char _license[] SEC("license") =3D "GPL"; --=20 2.43.0