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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C861C05051 for ; Tue, 8 Aug 2023 17:47:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231634AbjHHRrO (ORCPT ); Tue, 8 Aug 2023 13:47:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234898AbjHHRpw (ORCPT ); Tue, 8 Aug 2023 13:45:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5BD79AD149; Tue, 8 Aug 2023 09:20:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 314BF62493; Tue, 8 Aug 2023 10:20:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12030C433C7; Tue, 8 Aug 2023 10:20:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691490057; bh=3D8UlFaQhT9sb59ACbUa5dShagqWM3haJ/9jO2RNvK4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=jzT3dAbhEjiZBW7Dluo41cuVp4S/mvEjxsBDpyQB6jAJfcz9vFfLHpcTjMUf4pHRB BpFpxbUHqdgB1in+UDTXMXptX5Ok7LAHuHO8NqMSdnRk9Z4F9dVdJse1XjA0G382Rp OkuK7nw8evOoQ/606MpZuZgsqPhFetNfNeEQmbp/rCr+SMqb+W7U7mP73cqNDUI8L2 ceTpHRgVJCUajztU5xIPvHiIp9e3ZHXxsD3PJEOAHorzAcHTW/X0oXG0KIUsmVMglt 3NBxz+LMy8nEZgkdxu33HXBFFmHQ9C3Yo3bhfdRy5WyB9ALb0h+dh+AFAfmz7hrE8y EnKi2PRm3w6ZA== Date: Tue, 8 Aug 2023 19:20:51 +0900 From: Masami Hiramatsu (Google) To: Jiri Olsa Cc: Alexei Starovoitov , Steven Rostedt , Florent Revest , linux-trace-kernel@vger.kernel.org, LKML , Martin KaFai Lau , bpf , Sven Schnelle , Alexei Starovoitov , Arnaldo Carvalho de Melo , Daniel Borkmann , Alan Maguire , Mark Rutland , Peter Zijlstra , Thomas Gleixner Subject: Re: [RFC PATCH v2 6/6] bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled Message-Id: <20230808192051.ef24cfae1532f9e7779bae43@kernel.org> In-Reply-To: References: <169139090386.324433.6412259486776991296.stgit@devnote2> <169139097360.324433.2521527070503682979.stgit@devnote2> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org On Tue, 8 Aug 2023 00:08:11 +0200 Jiri Olsa wrote: > On Mon, Aug 07, 2023 at 03:49:33PM +0900, Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) > > > > Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is > > converted from ftrace_regs by ftrace_partial_regs(), thus some registers > > may always returns 0. But it should be enough for function entry (access > > arguments) and exit (access return value). > > > > Signed-off-by: Masami Hiramatsu (Google) > > --- > > kernel/trace/bpf_trace.c | 22 +++++++++------------- > > 1 file changed, 9 insertions(+), 13 deletions(-) > > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > index 99c5f95360f9..0725272a3de2 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -2460,7 +2460,7 @@ static int __init bpf_event_init(void) > > fs_initcall(bpf_event_init); > > #endif /* CONFIG_MODULES */ > > > > -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > > +#ifdef CONFIG_FPROBE > > struct bpf_kprobe_multi_link { > > struct bpf_link link; > > struct fprobe fp; > > @@ -2482,6 +2482,8 @@ struct user_syms { > > char *buf; > > }; > > > > +static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs); > > + > > static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt) > > { > > unsigned long __user usymbol; > > @@ -2623,13 +2625,14 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx) > > > > static int > > kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, > > - unsigned long entry_ip, struct pt_regs *regs) > > + unsigned long entry_ip, struct ftrace_regs *fregs) > > { > > struct bpf_kprobe_multi_run_ctx run_ctx = { > > .link = link, > > .entry_ip = entry_ip, > > }; > > struct bpf_run_ctx *old_run_ctx; > > + struct pt_regs *regs; > > int err; > > > > if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) { > > @@ -2639,6 +2642,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, > > > > migrate_disable(); > > rcu_read_lock(); > > + regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs)); > > you did check for !regs when returned from ftrace_get_regs, why don't we need > to check it in here? both ftrace_partial_regs and ftrace_get_regs call > arch_ftrace_get_regs on x86 Good catch! I think ftrace_partial_regs must not return NULL (unless getting invalid parameter, e.g. fregs == NULL). > > also also I can't find the place ensuring fregs->regs.cs != 0 for FL_SAVE_REGS > flag as stated in arch_ftrace_get_regs, any hint? Oops, I misread that part. Maybe ftrace_partial_regs must forcibly return ftrace_regs::regs if HAVE_PT_REGS_COMPAT_FTRACE_REGS=y because it does not care the regs is partial or not. Thank you! > > thanks, > jirka > > > > old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx); > > err = bpf_prog_run(link->link.prog, regs); > > bpf_reset_run_ctx(old_run_ctx); > > @@ -2656,13 +2660,9 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip, > > void *data) > > { > > struct bpf_kprobe_multi_link *link; > > - struct pt_regs *regs = ftrace_get_regs(fregs); > > - > > - if (!regs) > > - return 0; > > > > link = container_of(fp, struct bpf_kprobe_multi_link, fp); > > - kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs); > > + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs); > > return 0; > > } > > > > @@ -2672,13 +2672,9 @@ kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip, > > void *data) > > { > > struct bpf_kprobe_multi_link *link; > > - struct pt_regs *regs = ftrace_get_regs(fregs); > > - > > - if (!regs) > > - return; > > > > link = container_of(fp, struct bpf_kprobe_multi_link, fp); > > - kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs); > > + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs); > > } > > > > static int symbols_cmp_r(const void *a, const void *b, const void *priv) > > @@ -2918,7 +2914,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr > > kvfree(cookies); > > return err; > > } > > -#else /* !CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > > +#else /* !CONFIG_FPROBE */ > > int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > > { > > return -EOPNOTSUPP; > > -- Masami Hiramatsu (Google)