From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 6E15B79FD; Thu, 19 Dec 2024 01:08:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734570502; cv=none; b=mEaNUZmHGrij9uq3iLfYwV7WbDrLVfH0Ji7LZVnPgXTXVgIRsXKuXb2TUlm4qjYZg8s1N1hkNNPybkrVZTsZzEWsm4byaNXgLTZMLfPJCmD8M8hdC1RVduJo8scIGahWJgyPrGM6NMMA4dilIgVG+nodaQI3SvFPJ6UQmI9ji/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734570502; c=relaxed/simple; bh=QZ4z8fjBWTcf3il0BH2jZzxoBzP4WVaws/GscSyURNg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cLxe98G0Kn9OibYR3thxzRBIsUjQeJOxyPK1wT/0h6Dp2Y8saQdOLxkPpbSTxw1lyMQEYcPeLuXyfS68A7KsnJ2bUqtHnyUpxjeW8ayIg3oVJeu1KKItMJYAw1mEwA0Xjn1z7Yz8PoSVvRnh6qFLoQaM+OJ3WX+ILVwrmsGABQc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ENhMPHg1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ENhMPHg1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4319CC4CECD; Thu, 19 Dec 2024 01:08:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1734570501; bh=QZ4z8fjBWTcf3il0BH2jZzxoBzP4WVaws/GscSyURNg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ENhMPHg1VrFPFSGz+vbM+Yh2LPcDCSGXGLo2vJ7olQhZxsVUBfCCcEBBVx4BdS9EI 1RWVEfDicylpJ/qx61nzEWglLLvZtKowJKVgGFDlsrMWjsAswRKD9ah2C7hBUQXGja UK6v7YEPWNbrcoU0831kDW+FOqnM6j1ewhPk4VJjAPnX+jfwaueGedgo0D0DxoG8qm /KXRE8sU+jmmd+rlXImGOh/voD6ZKhIL9jxt7x7AAIUepf2y+IMKzvuJ3/CZrK8GlO tdAjgWXi0hKLeCVnqt5pVrdu+wJgfG2J4GSjxgowirDuCu0Olf5HndT28PPwt8Rslp qXAIGE92iWIlw== Date: Wed, 18 Dec 2024 17:08:19 -0800 From: Namhyung Kim To: Ian Rogers Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Kan Liang , Sun Haiyong , Yanteng Si , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/5] perf synthetic-events: Ensure features are aligned Message-ID: References: <20241216232459.427642-1-irogers@google.com> <20241216232459.427642-4-irogers@google.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=utf-8 Content-Disposition: inline In-Reply-To: <20241216232459.427642-4-irogers@google.com> On Mon, Dec 16, 2024 at 03:24:57PM -0800, Ian Rogers wrote: > Features like hostname have arbitrary size and break the assumed > 8-byte alignment of perf events. Pad all feature events until 8-byte > alignment is restored. But it seems write_hostname() and others use do_write_string() which handles the padding already. thanks, Namhyung > > Rather than invent a new mechanism, reuse write_padded but pass an > empty buffer as what to write. As no alignment may be necessary, > update write_padded to be tolerant of 0 as a count and count_aligned > value. > > Signed-off-by: Ian Rogers > --- > tools/perf/util/header.c | 7 ++++--- > tools/perf/util/synthetic-events.c | 2 ++ > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index 03e43a9894d4..d10703090e83 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -168,11 +168,12 @@ int write_padded(struct feat_fd *ff, const void *bf, > size_t count, size_t count_aligned) > { > static const char zero_buf[NAME_ALIGN]; > - int err = do_write(ff, bf, count); > + int err = count > 0 ? do_write(ff, bf, count) : 0; > > - if (!err) > + if (!err && count_aligned > count) { > + assert(count_aligned - count < sizeof(zero_buf)); > err = do_write(ff, zero_buf, count_aligned - count); > - > + } > return err; > } > > diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c > index f8ac2ac2da45..ee6e9c2fb11b 100644 > --- a/tools/perf/util/synthetic-events.c > +++ b/tools/perf/util/synthetic-events.c > @@ -2401,6 +2401,8 @@ int perf_event__synthesize_features(const struct perf_tool *tool, struct perf_se > pr_debug("Error writing feature\n"); > continue; > } > + write_padded(&ff, /*bf=*/NULL, /*count=*/0, > + /*count_aligned=*/PERF_ALIGN(ff.offset, sizeof(u64)) - ff.offset); > /* ff.buf may have changed due to realloc in do_write() */ > fe = ff.buf; > memset(fe, 0, sizeof(*fe)); > -- > 2.47.1.613.gc27f4b7a9f-goog >