From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B53EC0044C for ; Sun, 4 Nov 2018 02:13:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8EBE2082E for ; Sun, 4 Nov 2018 02:13:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="VBqTM++/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B8EBE2082E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728691AbeKDL03 (ORCPT ); Sun, 4 Nov 2018 06:26:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:32868 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726994AbeKDL03 (ORCPT ); Sun, 4 Nov 2018 06:26:29 -0500 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0F32F2082E; Sun, 4 Nov 2018 02:13:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541297598; bh=2pBmTKr0Mj1DuT8q6LHwX+3/bG8sIGECYp3R7Cj0Uxs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=VBqTM++/badxD22KpL0Tyv1mT2ozKUWLF7LWrSrJI3O/er8ADwuchaNvHOt2J5Kfd 9o8twUIdVL0w/yI5Y/DOplC9BL4w3L9S58gH7qB7Fh+O6xz3dqcEUPN1Zf0tYElpqX oQew0BHJwcXkzq1gZVi57v+fBGizZ49InmUb/M/k= Date: Sun, 4 Nov 2018 11:13:15 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] tracing/kprobes: Avoid parsing symbol+offset when updating arguments Message-Id: <20181104111315.c065079b88477e62bedc127d@kernel.org> In-Reply-To: <20181103134317.68873bd8@vmware.local.home> References: <20181103205448.15b667077e0b72fcd6147239@kernel.org> <154126101356.14912.1379688281618914741.stgit@devbox> <20181103134317.68873bd8@vmware.local.home> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 3 Nov 2018 13:43:16 -0400 Steven Rostedt wrote: > On Sun, 4 Nov 2018 01:03:34 +0900 > Masami Hiramatsu wrote: > > > Introduce symbol_offset data structure for avoiding symbol+offset > > parsing when updating arguments. > > > > For kprobe events, "@symbol+offset" is supported, that requires > > to be updated when new module is loaded because @symbol address > > can be solved at that point. Currently kprobe events saves > > the "symbol+offset" string and parse it repeatedly, but that > > is inefficient. > > Do we care if it's inefficient? It's only done on module load and at > the beginning. That's far from a fast path. > > If anything, the original solution saves memory, which is a bigger > concern than speed in this case. OK, and original one saves lines too. Please drop it :) Thank you, > > -- Steve > > > > This introduces symbol_offset data structure which can save the > > offset and symbol separated, so that we don't need to parse it > > anymore. > > > > Signed-off-by: Masami Hiramatsu > > --- > > kernel/trace/trace_probe.c | 49 +++++++++++++++++++++++++------------------- > > kernel/trace/trace_probe.h | 7 +++++- > > 2 files changed, 34 insertions(+), 22 deletions(-) > > > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > > index bd30e9398d2a..0a3af7d6e133 100644 > > --- a/kernel/trace/trace_probe.c > > +++ b/kernel/trace/trace_probe.c > > @@ -201,6 +201,26 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t, > > return ret; > > } > > > > +static struct symbol_offset *allocate_symbol_offset(char *sym_offs_str) > > +{ > > + int ret; > > + long offset = 0; > > + struct symbol_offset *sof; > > + > > + ret = traceprobe_split_symbol_offset(sym_offs_str, &offset); > > + if (ret) > > + return ERR_PTR(ret); > > + > > + sof = kzalloc(sizeof(struct symbol_offset) + strlen(sym_offs_str) + 1, > > + GFP_KERNEL); > > + if (!sof) > > + return ERR_PTR(-ENOMEM); > > + > > + sof->offset = offset; > > + strcpy(sof->symbol, sym_offs_str); > > + return sof; > > +} > > + > > /* Recursive argument parser */ > > static int > > parse_probe_arg(char *arg, const struct fetch_type *type, > > @@ -253,9 +273,9 @@ parse_probe_arg(char *arg, const struct fetch_type *type, > > > > /* Preserve symbol for updating */ > > code->op = FETCH_NOP_SYMBOL; > > - code->data = kstrdup(arg + 1, GFP_KERNEL); > > - if (!code->data) > > - return -ENOMEM; > > + code->symoffs = allocate_symbol_offset(arg + 1); > > + if (IS_ERR(code->symoffs)) > > + return PTR_ERR(code->symoffs); > > if (++code == end) > > return -E2BIG; > > > > @@ -483,7 +503,7 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size, > > if (ret) { > > for (code = tmp; code < tmp + FETCH_INSN_MAX; code++) > > if (code->op == FETCH_NOP_SYMBOL) > > - kfree(code->data); > > + kfree(code->symoffs); > > } > > kfree(tmp); > > > > @@ -513,7 +533,7 @@ void traceprobe_free_probe_arg(struct probe_arg *arg) > > > > while (code && code->op != FETCH_OP_END) { > > if (code->op == FETCH_NOP_SYMBOL) > > - kfree(code->data); > > + kfree(code->symoffs); > > code++; > > } > > kfree(arg->code); > > @@ -525,31 +545,18 @@ void traceprobe_free_probe_arg(struct probe_arg *arg) > > int traceprobe_update_arg(struct probe_arg *arg) > > { > > struct fetch_insn *code = arg->code; > > - long offset; > > - char *tmp; > > - char c; > > - int ret = 0; > > > > while (code && code->op != FETCH_OP_END) { > > if (code->op == FETCH_NOP_SYMBOL) { > > if (code[1].op != FETCH_OP_IMM) > > return -EINVAL; > > > > - tmp = strpbrk(code->data, "+-"); > > - if (tmp) > > - c = *tmp; > > - ret = traceprobe_split_symbol_offset(code->data, > > - &offset); > > - if (ret) > > - return ret; > > - > > code[1].immediate = > > - (unsigned long)kallsyms_lookup_name(code->data); > > - if (tmp) > > - *tmp = c; > > + (unsigned long)kallsyms_lookup_name( > > + code->symoffs->symbol); > > if (!code[1].immediate) > > return -ENOENT; > > - code[1].immediate += offset; > > + code[1].immediate += code->symoffs->offset; > > } > > code++; > > } > > diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h > > index 974afc1a3e73..942424d05427 100644 > > --- a/kernel/trace/trace_probe.h > > +++ b/kernel/trace/trace_probe.h > > @@ -103,6 +103,11 @@ enum fetch_op { > > FETCH_NOP_SYMBOL, /* Unresolved Symbol holder */ > > }; > > > > +struct symbol_offset { > > + long offset; > > + char symbol[]; > > +}; > > + > > struct fetch_insn { > > enum fetch_op op; > > union { > > @@ -117,7 +122,7 @@ struct fetch_insn { > > unsigned char rshift; > > }; > > unsigned long immediate; > > - void *data; > > + struct symbol_offset *symoffs; > > }; > > }; > > > -- Masami Hiramatsu