From patchwork Thu Feb 20 21:59:03 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ihor Solodrai X-Patchwork-Id: 13984534 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-174.mta1.migadu.com (out-174.mta1.migadu.com [95.215.58.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 990AD1EA7ED for ; Thu, 20 Feb 2025 21:59:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.174 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740088755; cv=none; b=SE6HCk927jg6CBbGya7a+wT253r/ndrLDnf/bFGxfTaO+W2Rpn8zP6Z/R1tWnywyW/SbxktypGkahBTk1XaEW+sBS8NPcP0GI/+Jg3hAiG6Ejpz5OLgp5D7LpgPVSPh9cSiJBUE/S0DyAu6mdE4aD3bU+rJ8QEjj0qfPIoiLsMo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740088755; c=relaxed/simple; bh=TOSygrza++He//qOVXcaQpNcfyAdM7kTtBs6knGw4V0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=fCz/kZsEn7ufH4uPzhNFa75zpViM/8pEpv7UoJMzE9IeJQfvY85HugbwGvj+83tQScvxmfLD5B7FbrywD+nYIO/rWYUxWKEsnhHj75zEs95pfAU+Wz/f+li/nMnKHGA0/tLd/2EHmuOO2uc6TH4PC4jQzXVUFYUj/2U8dQqbnOQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Ld4ima8g; arc=none smtp.client-ip=95.215.58.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Ld4ima8g" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1740088751; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=iZpJAulZucENFx39QcwmM0fgkw6mFhtqV9TUBtKQwFM=; b=Ld4ima8gcFsPO4psRhxF5xJPxiYA9JvMjoPw8sEZjIubdY8e52YhzHkwIPDVL+iTuyP3WB uL8SkOkWLAQZoJYixddbqyIqrLYVY26T/7CXLY7MnHCDnjDuTtFcixrI2BdswA7F/9qaES aV8LOV4eCQzBBveAx4iCVC9LW2Jt1+A= From: Ihor Solodrai To: bpf@vger.kernel.org Cc: andrii@kernel.org, ast@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, mykolal@fb.com, kernel-team@meta.com Subject: [PATCH bpf-next 1/2] libbpf: implement bpf_usdt_arg_size BPF function Date: Thu, 20 Feb 2025 13:59:03 -0800 Message-ID: <20250220215904.3362709-1-ihor.solodrai@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net Information about USDT argument size is implicitly stored in __bpf_usdt_arg_spec, but currently it's not accessbile to BPF programs that use USDT. Implement bpf_sdt_arg_size() that returns the size of an USDT argument in bytes. Factor out __bpf_usdt_arg_spec() routine from bpf_usdt_arg(). It searches for arg_spec given ctx and arg_num. Suggested-by: Andrii Nakryiko Signed-off-by: Ihor Solodrai --- tools/lib/bpf/usdt.bpf.h | 59 ++++++++++++++++++++++++++++++++-------- 1 file changed, 47 insertions(+), 12 deletions(-) diff --git a/tools/lib/bpf/usdt.bpf.h b/tools/lib/bpf/usdt.bpf.h index b811f754939f..6041271c5e4e 100644 --- a/tools/lib/bpf/usdt.bpf.h +++ b/tools/lib/bpf/usdt.bpf.h @@ -108,19 +108,12 @@ int bpf_usdt_arg_cnt(struct pt_regs *ctx) return spec->arg_cnt; } -/* Fetch USDT argument #*arg_num* (zero-indexed) and put its value into *res. - * Returns 0 on success; negative error, otherwise. - * On error *res is guaranteed to be set to zero. - */ -__weak __hidden -int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res) +/* Validate ctx and arg_num, if ok set arg_spec pointer */ +static __always_inline +int __bpf_usdt_arg_spec(struct pt_regs *ctx, __u64 arg_num, struct __bpf_usdt_arg_spec **arg_spec) { struct __bpf_usdt_spec *spec; - struct __bpf_usdt_arg_spec *arg_spec; - unsigned long val; - int err, spec_id; - - *res = 0; + int spec_id; spec_id = __bpf_usdt_spec_id(ctx); if (spec_id < 0) @@ -136,7 +129,49 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res) if (arg_num >= spec->arg_cnt) return -ENOENT; - arg_spec = &spec->args[arg_num]; + *arg_spec = &spec->args[arg_num]; + + return 0; +} + +/* Returns the size in bytes of the #*arg_num* (zero-indexed) USDT argument. + * Returns negative error if argument is not found or arg_num is invalid. + */ +static __always_inline +int bpf_usdt_arg_size(struct pt_regs *ctx, __u64 arg_num) +{ + struct __bpf_usdt_arg_spec *arg_spec; + int err; + + err = __bpf_usdt_arg_spec(ctx, arg_num, &arg_spec); + if (err) + return err; + + /* arg_spec->arg_bitshift = 64 - arg_sz * 8 + * so: arg_sz = (64 - arg_spec->arg_bitshift) / 8 + * Do a bitshift instead of a division to avoid + * "unsupported signed division" error. + */ + return (64 - arg_spec->arg_bitshift) >> 3; +} + +/* Fetch USDT argument #*arg_num* (zero-indexed) and put its value into *res. + * Returns 0 on success; negative error, otherwise. + * On error *res is guaranteed to be set to zero. + */ +__weak __hidden +int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res) +{ + struct __bpf_usdt_arg_spec *arg_spec; + unsigned long val; + int err; + + *res = 0; + + err = __bpf_usdt_arg_spec(ctx, arg_num, &arg_spec); + if (err) + return err; + switch (arg_spec->arg_type) { case BPF_USDT_ARG_CONST: /* Arg is just a constant ("-4@$-9" in USDT arg spec).