From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 CB9372117 for ; Mon, 31 Jul 2023 08:07:55 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6EB711B8 for ; Mon, 31 Jul 2023 01:07:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1690790873; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=uSQ6W5Zoa0gBagmi/y4T86ZEvZFNbTljOVuJZIYMvgo=; b=Oajc7IVXCe++Pr6shKndVqFTG/wwjV+YHBpSPxvsUNQtkJ8FYjMDYV6/Tfi8Px4K53tVni hjpisVBAWw16gLm+YPyJB41cAAMOXnzR1SDGMS32el4hdMSkkDWRTTAqSivCtcaWuRoEoL aUeDdfTKWktjnhfGg+rbMJfa4kwcN1Y= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-412-2Wf4NzK3MCaTVosRuM4RZA-1; Mon, 31 Jul 2023 04:07:50 -0400 X-MC-Unique: 2Wf4NzK3MCaTVosRuM4RZA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 508981C07248; Mon, 31 Jul 2023 08:07:50 +0000 (UTC) Received: from astarta.redhat.com (unknown [10.39.194.45]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 72D7EC57964; Mon, 31 Jul 2023 08:07:49 +0000 (UTC) From: Yauheni Kaliuta To: Yonghong Song Cc: bpf@vger.kernel.org, andrii@kernel.org, ast@kernel.org Subject: Re: [PATCH bpf-next v2] tracing: perf_call_bpf: use struct trace_entry in struct syscall_tp_t References: <33b93245-6740-e2e7-3a2a-6a9375d7ddc4@linux.dev> <20230728142740.483431-1-ykaliuta@redhat.com> <225ed430-dfd1-bf0b-8481-58f5f0d3f7eb@linux.dev> Date: Mon, 31 Jul 2023 11:07:48 +0300 In-Reply-To: <225ed430-dfd1-bf0b-8481-58f5f0d3f7eb@linux.dev> (Yonghong Song's message of "Fri, 28 Jul 2023 09:44:20 -0700") Message-ID: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL, SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Hi, Yonghong! >>>>> On Fri, 28 Jul 2023 09:44:20 -0700, Yonghong Song wrote: > On 7/28/23 7:27 AM, Yauheni Kaliuta wrote: >> bpf tracepoint program uses struct trace_event_raw_sys_enter as >> argument where trace_entry is the first field. Use the same instead >> of unsigned long long since if it's amended (for example by RT >> patch) it accesses data with wrong offset. >> Signed-off-by: Yauheni Kaliuta >> --- >> v2: >> - remove extra BUILD_BUG_ON >> - add structure alignement >> --- >> kernel/trace/trace_syscalls.c | 12 ++++++++---- >> 1 file changed, 8 insertions(+), 4 deletions(-) >> diff --git a/kernel/trace/trace_syscalls.c >> b/kernel/trace/trace_syscalls.c >> index 942ddbdace4a..b7139f8f4ce8 100644 >> --- a/kernel/trace/trace_syscalls.c >> +++ b/kernel/trace/trace_syscalls.c >> @@ -555,12 +555,15 @@ static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *re >> struct syscall_trace_enter *rec) >> { >> struct syscall_tp_t { >> - unsigned long long regs; >> + struct trace_entry ent; >> unsigned long syscall_nr; >> unsigned long args[SYSCALL_DEFINE_MAXARGS]; >> - } param; >> + } __aligned(8) param; >> int i; >> + BUILD_BUG_ON(sizeof(param.ent) < sizeof(void *)); > Considering we used 'unsigned long long regs' before, should > the above BUILD_BUG_ON should be > BUILD_BUG_ON(sizeof(param.ent) < sizeof(long long)); > ? Since the pointer's value is assigned I agree with Alexei (in the thread [1]) to use void *. >> + >> + /* __bpf_prog_run() requires *regs as the first parameter */ > This comment is not correct. > static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog, > const void *ctx, > bpf_dispatcher_fn dfunc) > { > ... > } > The first parameter is 'prog'. > Also there is no __bpf_prog_run() referenced in this function > so this comment may confuse readers. So I suggest removing > this comment. The same for perf_call_bpf_exit() below. Again, in [1] we agreed that it's better to have the comment since it's even more confusing. Could you help to formulate it? "__bpf_prog_run() requires *regs as the first argument for bpf prog" or something? But yes, I can remove it of course. >> *(struct pt_regs **)¶m = regs; >> param.syscall_nr = rec->nr; >> for (i = 0; i < sys_data->nb_args; i++) >> @@ -657,11 +660,12 @@ static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *reg >> struct syscall_trace_exit *rec) >> { >> struct syscall_tp_t { >> - unsigned long long regs; >> + struct trace_entry ent; >> unsigned long syscall_nr; >> unsigned long ret; >> - } param; >> + } __aligned(8) param; >> + /* __bpf_prog_run() requires *regs as the first parameter */ >> *(struct pt_regs **)¶m = regs; >> param.syscall_nr = rec->nr; >> param.ret = rec->ret; [1] https://lore.kernel.org/bpf/xunyjzy64q9b.fsf@redhat.com/T/#u -- WBR, Yauheni Kaliuta